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Gallery, Projects and General => How do I?? => Topic started by: PekkaNF on August 20, 2013, 12:27:34 PM

Title: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 20, 2013, 12:27:34 PM
I got two 10 mm dia 300 mm lenght gun drills. They are well used and sharpened probably to a last useful point. These are for practice.

I would like to learn how to drill holes on spindles. Nothing very exotic and demanding - I only have some tempering steel rod tough.

I have found bewildering amount of info on web, but I'm having hard time finding a practical starting point. Somehow I find plenty of diagrams and then stuff that is such hardcore that I'm having really hard time assesing relevancy.

Wanted: Good practical approach how-to punch deep holes in a domesticated lathe.

Tall order?

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: awemawson on August 20, 2013, 01:17:53 PM
Start by boring a hole that is accurately concentric, on size, and accommodates a sleeve that is a snug fit on the shaft of your gun  drill. Go at it with the gun drill slowly with plenty of lubricant and withdrawals for swarf clearance.



..... or so I am told .......
Title: Re: Deep hole drilling 101 on lathe?
Post by: NeoTech on August 20, 2013, 01:43:48 PM
I made a gundrill out of a spade bit,  then used a short hole drill and made a concentric sleeve that sat on the "outside" of the stock to be bored. So that the inner index wouldnt be messed up or you need to cut the oversized part for the sleeve off. But if i think about it i was prob. cheap and bought just enough barrel material. Errgh.. roundstock... Guns is illegal in sweden. ;D
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 20, 2013, 02:37:59 PM
Guns are legal here and I have some of them. No interest of making any, because life is short to learn everything and permits and reviews are a hassle.

But I have in making some small auxiliary spidles and some grinding spindles... serious case of  :proj:

Most stuff needs hole for drawbolt, nice concentric hole would be nice on high speed (hobby high speed) spindles.

Never thought too much about drilling on the lathe, until broke too many drills in one seating trying to punch holes on tempering steel shaft...that still haunts me.

I'm going to drill start hole, ream it and start there. I also can find cutting oil pressure and demand charts, also some feed info. Also pictures of various setups (most professional and outside of my equipment and reach). I can afford breaking two gun drills before learning or giving up. :bang:

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: chipenter on August 20, 2013, 03:27:42 PM
I replaced my lathe spindle and made a d bit 16mm dia , the only problem was heat build up as it got hot it would bind in the hole , and it heated up faster than it cooled .


Jeff
Title: Re: Deep hole drilling 101 on lathe?
Post by: unc1esteve on August 20, 2013, 09:37:54 PM
Links to gun drilling

http://www.practicalmachinist.com/vb/general/gun-drilling-lathe-192962/

http://www.chaski.org/homemachinist/viewtopic.php?f=10&t=90457
Title: Re: Deep hole drilling 101 on lathe?
Post by: unc1esteve on August 20, 2013, 09:44:24 PM
You Tube

   


   


   


Title: Re: Deep hole drilling 101 on lathe?
Post by: unc1esteve on August 20, 2013, 09:49:04 PM
Information on barrel drilling

http://www.bgfta.org/files/akraba/INSTUMENTS/28543407-Guns-Mi-Thing-and-Tool-Making-Bible-by-h-Hoffman.pdf
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 21, 2013, 03:25:14 AM
Thank you very much Steve,

That PDF was very much spot on info I was lookking for. I probably could not find it, because I was bypassing all stuff about guns - because I'm not making one. Logical or not, but that was pretty much I should have been lookking. Drilling lubrication holes on marine diesels is not easily converted to garage level application.

The info I got made me feel better. My application should be whole lot more simple, because I need whole lot shorter hole and I'm not going to load this one. This is going to be interesting  :coffee: reading some time and then a little bit of application  :zap:

The only thing I'm worried about is the spindle material. I have very little free machining leaded steel (and dimater is too small) and pretty much the only right size material I have is mystery tempering steel that eats my convetional drills...although turns beatifully with inserts.

But one step a time.

Thank you,
Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: PeterE on August 21, 2013, 10:17:48 AM
Would it be possible to grind a masonry (concrete) drill to a suitable angle and use that together with a suitable sleeve? In that case you get a carbide tip that well can handle tough stainless.

BR

/Peter
Title: Re: Deep hole drilling 101 on lathe?
Post by: Lew_Merrick_PE on August 21, 2013, 11:16:11 AM
Pekka,

A true gun barrel drill is designed to drill extremely deep holes with very tight tolerances on diameter and straightness.  The business end actually burnishes the bore and has enough contact area (diameter X length) to keep if running straight and true.  They usually contact around 270° of the hole's periphery to achieve this.  The primary "secret" of a gun barrel drill is that the point is located exactly on 1/4 of the diameter such that the side-acting cutting forces are balanced.

It seems like overkill for a drawbar clearance hole to my way of thinking.  I drill 30:1 (depth:diameter) holes with fair regularity using only bell hanger twist drill bits.  So long as I keep the cutting edges sharp, I can drill such holes with no more than .010 inch (0.25 mm) wander when making gas passages that are typically .094 inch (2.4 mm) diameter X 3.75 inches (95.25 mm) deep in Rc 35-40 4130 steel.

???
Title: Re: Deep hole drilling 101 on lathe?
Post by: PeterE on August 21, 2013, 02:59:46 PM
Pekka,

How deep is the hole you want to drill? If you look into my thread about the pin vice I show that I drilled a 3 mm hole 90 mm deep and it came out well centered in the other end. I did that using a combination of center drill, ordinary jobbers drill and an extra long jobbers drill.

To be fairly safe I used new drills to be sure the points were correct.

/Peter
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 21, 2013, 03:08:33 PM
hank you.

Actually with that material I have tried many methods. Peck drilling  was no-go, work hardening does not work well..Some resharpened SDS long masonry bits worked somewhat, but after it started to chatter, tip chipped and rest you know. Some HSS-co twist drills seem to work and the short trough cooled drill was the only one that worked fine. I would be fine with 25x, if can drill on one go.

So trough cooled twist drill or something else...then gun drills wandered my way 20€ apiece and I tought that it might be worth of finding out...I need pressure pump, holder and such anyways.

There are some other drawbacks and unknowns on this gun drills anyway, like if I read it right that it is not ideal if the material tends to make long continuous curly swarf and that is what I have.

Still some  :coffee: to go.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: unc1esteve on August 21, 2013, 04:56:53 PM
Pekka,
My need for deep holes was several.  A #46 hole one and one half inch deep and a .2180 hole 13 inches deep.  I had bought a metal bench that had an old Atlas lathe attached to it.  Missing parts, needed a lot of work.  I was going to use the bed for something else until I took a close look at it.  It was in good shape so I took it apart, replaced the missing parts, cleaned, repaired and painted it.

I added a variable speed DC motor and changed the pulleys to achieve 4000 rpm.  I checked with Timken, the maximum rpm for the bearings with oil is 7200 rpm.  I added a variable DC motor to the lead screw so I could slow down the feed rate.  I made a collet system to replace the chuck.  (This was also deep hole drilling.  Step drilled from both ends, then reamed).

I made a pressure vessel to supply air and coolant like the Sterling unit.  I then added a high pressure pump from a small pressure washer to increase the coolant pressure.

I purchased some carbide 'v' with a through coolant hole from EBay.  I bought some 'v' tubing from Drill Masters.

I hard soldered a gun drill the length I needed, 18 inches.  Ground it to size on the lathe and the T&C G.

Hooked everything up and that is where I stopped.  I have a few details to finish.  I have not made a test hole as of yet, other things got in the way.  One thing I am having trouble with is to keep the solder out of the coolant hole.  I purchased some anti-flux and have been doing some reading.

The material I am drilling is 4140.  I am going to purchase some stress proof before I continue so I can see which is better.  I believe the stress proof will be.

The long, curly swarf is to be avoided.  It will jamb and destroy the gun drill.  The higher the rpm, the slower the feed rate, the smaller the chip, the more success.

Long term project.
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 22, 2013, 01:33:34 AM
Good work you have done with your drilling machine.

Thank you, you gave me some really good info.

My needs and drills are not that long, the two drills I have are 10 mm dia and about 350 mm or so, to make 300 mm long hole max. Should have done my reading first :doh: Pressure of the cutting oil didn't surprice me, but rpm of the blank did. Alhough I have one extra lathe body to experiment....but do I want to use time and effort to do it? Great learning experiment no doubt.

I read deep drilling parts of the linkked PDF and had some hard time trying to figure out tables and other numerical values that were missing units. Like "500 lbs" sounds to me more like force and not pressure....One table had oil volume, but not units etc....but reading the text of someone doing the production did give some pointters. Later on there was really nice chapter about drilling and reamin and plenty of general machining info. Halfway of the manual many pictures seem to be missing, but that is no problem here.

I'm going to track down the orginal drill makers data for this drill to see recommendations, that should give me pretty good idea viability of my idea.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: PeterE on August 22, 2013, 12:59:25 PM
Interesting subject this.

Just a question, why not step-drill? I mean that one starts with say 6 mm for 50 mm or so, change to a 10 mm and drill 40 mm, then chjange back to the 6 mm who now get guidance from the 10 mm long 6 mm hole, but is not affected by the 40 mm long larger distance. That way I guess that the load on the thinner drill becomes much less and the problem with heating is lowered.

Also by changing drills there will be a natural time for cooling both the workpiece and the drills.

Then the last question; Why not drill to a bit under final size and then bore the rest? That will of course demand that your lathe is long enough  :palm:

BR

/Peter
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 23, 2013, 02:14:15 AM
The crux of the mater here is that I don't have available easy maching material to make spindles with holes. This material is bit of trouble. On the other hand is's nice to make axles and such. External turing works fine. The touble is only with internal turning or drilling a (relatively) long hole. I have tried several methods with warying decrees of success.

I have got this temprering steel bars from 12 to 25 mm dia and I can buy larger ones in cut length. I have a nice 40 mm dia and 30 cm long for one project. The good (and very important news for me it is that there is plenty of it and I can get always some more). The trouble is that I find it very hard to find anything easier to machine bar here. There are some mystery metals on junk yard and I have bought several bars these mysteries and after a little while I have found out why they were reject. Best gues machined beautifully, but had some inclusions on it. Broke a insert very few minutes....some were gummy and some bent after turnig them then bet other way when drilled. Some turned ugly no matter you tried...

It's 34CrNiMo6 to me, these are other names for same stuff (or close)
4340
817M40
En24
 
Some of the bars are rolled some bright, but all are in tempered state.

Very nice for external turning and works fine for short drilling (I have drills that eat this no problemo).

BUT: This material tends to make very long stringy swarf and it is workhardening and pretty tough. Therefore any peck drilling does not work. I get few pecks pretty ok and then one that will squal like pig.

Also smaller the drill, nastier it get's do drill long hole. It is easier to get a 10 mm 160 mm long drill than 6 mm 160 mm long drill that takes the beatting. Although I must say that if I had a 6 mm drill of 200 to 300 long that would make a pilot hole I would be very happy to use one and then feed 15 bar coolant trough it and use cheaper long 8 to 10 mm drill for final hole. Pretty good indication of this how drills are rated often something like 3xD or 5xD that means that lenght is 3 or 5 times the diameter.

It's pretty nicely explained here:
http://www.unisig.com/gundrilling-education/deep-hole-drilling.php
http://www.unisig.com/drilling-videos/deep-hole-drilling-101-video.php

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: unc1esteve on August 23, 2013, 08:56:03 AM
Pekka,

Do you have an hydraulic cylinder repair shop near by?  The cut offs and bent pieces
in the rubbish can make good project material.  The bars are usually 1045.
The chrome turns off with carbide tools.  You can also purchase new material
but in larger sizes than 13mm.  It seems you need stress proof steel.

http://www.homemadetools.net/deep-hole-drill?gce=tab50&utm_expid=57824293-7&utm_referrer=https%3A%2F%2Fwww.google.com%2F

http://www.practicalmachinist.com/vb/search.php?searchid=1484507

http://bbs.homeshopmachinist.net/search.php?searchid=763358
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on August 23, 2013, 02:47:37 PM
Pekka,

Do you have an hydraulic cylinder repair shop near by?  The cut offs and bent pieces
in the rubbish can make good project material.  The bars are usually 1045......

THANKS! I was really thinking hard to find right kind of second hand material...never thought of hydraulic cylinder rods. I can find the material used or even "new". I'll check it first weekday. Hmm....what kind of material is the tube? I'm going to check one junkyard and find one to test.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: NeoTech on August 23, 2013, 03:38:33 PM
Was more kinda in the lines of this i was talking about.. the "drillhead" holding the spade bit can be mounted onto a thinner rod for making it longer, guides and strong materials is needed though. Unless you are just making a short hole. =)

Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on June 27, 2014, 10:07:28 AM
I joined the forums mainly because of this thread, and found quite a few more interesting threads. I apologize for bringing up an old thread, but wanted to know how this project went. I found unc1esteve's email to ask him about his progress.
I'm trying to attempt the same with my lathe. I'm looking at a bore diameter of .4375" at 36.5:1 in 6061 aluminum.
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on June 27, 2014, 12:18:06 PM
I haven't got much further, BUT this week local machine tool shop is a sale on MT taper trough cooled extra long spiral drills. My holiday just started...I'm planning to go there, buy few drills and give it a try.

I'm wondering would side feed (after the MT-taper) or trough MT-taper.

Also I have been making half assed effort trying to find better material.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on June 27, 2014, 01:20:00 PM
What is your longitudinal feed on your lathe?
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on June 27, 2014, 01:49:21 PM
What is your longitudinal feed on your lathe?

Uuh...Tail is on manual crankking...pretty well when swarf looks right, but that is really not acceptable because tail stock stroke is way too short.

On cross slide I have normal lathe feeds. I have got some results with spiral drill when feed is 0,10 - 0.15 mm/r.

Tempering steel is very nice for shaft/spindle, but it's pretty hard in tempered state, work hardens and produces very long swarf - hard to drill well. Turns really nice with lot of speed with carbide though.

What are you making? Milling, drilling or grinding spindle?

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: David Jupp on June 27, 2014, 02:21:23 PM
For really deep hole drilling, the cutting bit is revolved as well as the work, and lots of lubricant fed to the drill tip to flush out the swarf.  I'm aware of a shop in Austria that can drill to 17m  for hole size around 2", but that does come down a lot as the hole size reduces.
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on June 27, 2014, 02:48:39 PM
You are using a gun drill in the tailstock or a different type of bit? I was told gun drills needs to be fed at a consistent rate and NEVER reversed while spindle is in motion.
I'm building a machine that makes snow in the winter when temperatures allow, trying to build an all in one unit design. I plan on using a gun drill that will fit in a boring bar holder. Modifying my lead screw as my lowest feed rate is .004", and i'm aiming for .0005" (Which is the norm for gun drilling). Spinning at 2000rpm, it should cut 1"IPM.

You're right David. A machinist that used to work for Beretta many years ago told me it's best to rotate your bit in the opposite direction of the spindle as this will help keep the bit straight and also increase your desired SFM. In my case my material is aluminum, which my sfm is much higher while trying to avoid chip welding on my bit.

Right now i'm focusing on the best method for the lead screw.

Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on June 28, 2014, 07:24:26 AM
I'm not planning to use the standard tail stock for any deep hole drilling, everything wrong with it.

I am planning to try out trough cooled twist drill first. Less pressure requirement and more relaxed feed requirements.

My primary lathe is not good for anything more demanding. It's only about 150 kg 500w single phase motor.

If that does not work plan b is to start toying with piece of crap capstan lathe I have. It has no tail stock, chuck is crap and lead screw is missing. It weights close to 1000 kg and has a gearbox plus about 4 hp 3 phase motor. Spindle speed goes up to 2400 rpm. I.E. it is perfect base for lathe/vertical drilling machine. But plenty of work for few holes....

You probably have found this thread:
http://www.practicalmachinist.com/vb/general/gun-drilling-lathe-192962/

Some parameters:
http://www.sterlinggundrills.com/printer-friendly/gundrilling-guidelines.pdf
http://www.sterlinggundrills.com/speed_and_feed_charts.shtml

interesting picture here:
http://www.practicalmachinist.com/vb/general/shop-made-tool-pics-201261/index5.html#post1400560

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on June 30, 2014, 11:44:46 AM
Not sure if this ever going to be much use of anybody or I get anywhere, but I lets see.

I bought three long spiral drills stubby ones are 8,5 and 9 mm diameter and just over 100 mm long. The long one is 10 mm diameter and business lenght is 185 mm. Local toolshop was selling them out, these were smallest ones they had.

Exact drill types are (if anybody is interested):
STOCK 71553 DIN 341 V70-IK Ø8,5 x 250/100 mm
STOCK 71553 DIN 341 V70-IK Ø9,0 x 257/107 mm
STOCK 71567 DIN 1870 V63-IK Ø10,0 x 335/185 mm

All are MT2 taper shank with side coolant feed. They are trough cooled. Just close enough to work with tempered steel, but not much room for error.

The side coolant feed is cylindrical ground surface, very close to 24 mm OD and 30 mm length. Should not be very hard to make coolant mount (inducer?) to it.

Bit more lost with coolant pump requirements. I see sealed collets advertized for cylindrical shank and up to 1000 psi (about 60 bars) that probably gives some indication of max required pressure.

I wonder if those drill operated transfer pumps could be used to test or do I need to source a car motor oil pump or small gear pump (hydraulic pump) for it.

There is some more work to do, so don't expect any results tomorrow (or next week:).

On this picture I'm gloating my spending on local tool shop. They had some guide dog calibers for sale and they said that they really don't suck really that much. I like that kind of sales talk.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 01, 2014, 04:26:31 PM
I have been googling and calculating stuff, it all starts to look achievable. Not too easy, but not outright impossible either.

I have to work on three fronts:

1) Coolant inducer. This I think is easy one. Lot like that:
http://www.carbideanddiamondtooling.com/thumbnail.asp?file=assets/images/yg1usa/spadedrills/spade_drill_rci.jpg&maxx=750&maxy=0

2) MT2 taper holder. I do have a MT2 taper holder for the cross slide. I am not 100% sure it will be able to hold drilling forces and bit unclear how to put drill bit absolutely straight without test bar. Maybe between spotted pilot hole on the bar under drilling and MT2 holder end on tail stock?
* I can gear down correct machine feed on cross slide no problem.
* Probably really should build a separate tool holder for drills.

Plan B: to build a separate tail stock from scratch to allow 300 mm of feed. I have a TR16*4 mm acme rod + nut + geared 24 VDC servomotor, but no electronics.

maybe something like this:
http://www.practicalmachinist.com/vb/attachments/f26/77378d1369344103-schaublin-capstan-handle-tailstock-20130302_110946.jpg

Or like in capstan lathe - like capstan lathe ram. It all looks pretty doable. some serious work thoug. Something like this:
http://static.wixstatic.com/media/999e2a_e754617990544f3acc20dda4e9e08855.jpg_srz_620_360_85_22_0.50_1.20_0.00_jpg_srz

3) High pressure coolant pump. I probably need 20-40 bar pressure and low flow. Just have figure out what kind of madmodder pump I am looking for? Oil transfer pump? Car engine oil pump, small hydraulic pump?

Ideas?

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on July 02, 2014, 12:02:10 AM
Pekka,
I really want to see you accomplish your goal, and like yourself i've spent hours on end over the past two months figuring the best method as well. Local machine shops want to charge as much just for ONE drilling than the entire costs of parts and materials of TWO finished units.

I came across a post on practical machinist months back where someone had built an adapter that connects their carriage to their tail-stock, which may work if you can adjust your lead screw to your needs. Attached is a picture and documentation of Sterling's suggestion for mounting the gun drill bit to the cross slide. I'm also skeptical about using a tool holder on such a long bore, but their adapter suggestion is much more rigid.

If you already have the servomotor and want to utilize it further down the road, they sell off the shelf controllers for nearly pennies to adjust the speeds via a dial/potentiometer. I've just been worried about setting mine (stepper motor) up on my lead screw and not being powerful enough for my feed rate, slowing it down. Stalling can also damage the motor. So i've been having trouble calculating the best torque motor for the task.

I myself have been trying to determine the best pump to use. A high pressure coolant pump would require a complete enclosure around your material, with a reservoir & filtering system. I have several high pressure pumps but unfortunately are 2.5gpm-13gpm. I did build a pump setup years ago with a Hypro dual piston pump, which I think go as low as 1.5gpm and 34bar, still too high of a flow rate. It had a hollow shaft so I direct connected to a 3/4hp electric motor. I'm sure you've already seen the post on practical about a member using an automotive power steering pump instead of buying Sterling's Spraymist system. Though i'm pretty sure average PS Pumps are 2.5gpm+. Check out http://unist.com/ they have a product very similar to Sterling's but a couple hundred dollars cheaper. They also offered me a 30 day trial. Still $900 for a system  :bang: not quit in my budget. Unist's system along with their lubricants (which are 100% green) can be operated without any extra coolant exiting the bore so no mess.

I really like those drills you picked up, any ideas on US suppliers that sell them?

I hope this helps, as i'm new to this as well. I'm still waiting on unc1esteve's response.

Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 02, 2014, 07:05:33 AM
Thank you for couragement.

I had tought on putting the tailstock on tow. It's pretty standard on some (russian) lathes and I saw it on austrian hobbylathe (Klippfeld GmbH). But the tailstock on my lathe is too short and rikety for it.

I have been thinking a little of building a bridge to bypass that cross slide. I don't think it will have much positive function on drilling operation.

Thank you for the power steering pump idea. I have to look if I can dig something up fast. I didn't find the thread on practicalmachinist. Maybe a wrong search word?

You have a whole lot bigger hurdle ahead. Gun drilling needs a whole lot more on coolant pressure and is more critical on feed. Haven't tried that but talked some years back on machinist that did some oil holes and such.

I would not worry too much about the power feed demand (on small drill diameters least) feed is slow and you have a huge mechanical advantage.Unless you want fast rapids....

I have been playing on drill power calculators and it looks like 8,5 mm drill needs about 200-300w of pure power to punch trough alloyed steel bar on table feeds and speed. Needs something like 4 Nm of torque and 700N of feed force.

Those still needs factoring with mechanical and electrical efficiencies before we are talking about motor speeds and powers.

http://www.kennametal.com/en/resources/calculators/holemaking-calculators/torque-thrust-power.html

8,5 mm dia drill, feed 0,12 mm/r and cutting speed 14 m/min as table values from manufacturer for tough steels.

Screenshots from source values, some results here as text:


n Spindle speed: 524.2751 1/min
Qz Metal removal rate: 3.57 cm3/min
Vf Unit per minute: 62.91 mm/min
Tc Time in cut: 95.37 sec.


Your Results
Mc / Md Torque: 2.978 Nm
Ff Thrust (Feed Force): 679 N
Pc Power: 0.16 kilowatt

I don't know where to get those german made drils from usa, but I'm pretty sure there are similar ones. And anyways gun drills seem to be really really plentifull there!

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on July 02, 2014, 08:38:53 AM
Now that I think about it, the guy who made the power steering up coolant system also made a manifold where the coolant is introduced into the air. I'll try to find it later today but he did not go into any specifics about the build. I think you could use a bypass regulator typically found on a pressure washer, and at the manifold you would have some sort of needle valve to adjust the passage smaller, less coolant. Any over pressures would be diverted back into your reservoir via the bypass port.

*EDIT*
Pekka, check this thread out http://www.practicalmachinist.com/vb/gunsmithing/you-carn-t-make-barrels-lathe-275071/ , look for homebrew's posts. Pretty neat how he has a capture system for the coolant. Never thought about slowing down my feed with pulleys  :bang:
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 03, 2014, 03:14:31 PM
Thank you.

Is there a English language calculator for mechanical drive? I used one Finnish one, but like to verify it and show results here.

Excuse my French Finnish:
http://www.mekanex.se/ber/fi-vridmom_skruvdrift.shtml#

Does it transalates?
https://translate.google.fi/translate?hl=fi&sl=fi&tl=en&u=http%3A%2F%2Fwww.mekanex.se%2Fber%2Ffi-vridmom_skruvdrift.shtml%23

Badly. Anyways this calculates rotary power, torque and rpm (for a mechanical drive) that is needed to produce a linear force with ballscrew or acme screw.

I'm using values above
Ff Thrust (Feed Force for drilling): 679 N
Vf Unit per minute: 62.91 mm/min -> 1,05 mm/s! This is the drill spindle/chuck linear speed from spindle rpm and feed

TR16*4 (OD 16 mm acme screw with 4 mm lead) would result about 0,42 efficiency when lubricated.

So, it looks like those values will result in fairly modest feed motor requirements : About 1 Nm of torque at 16 rpm. To me it looks like:
* Pretty hefty stepper motor if directly coupled. Rapids would be pretty impressive.
* But even small stepper would produce that if geared down.
* Any small geared AC/DC servo would produce it and provide good rapids.
* I have small geared 24 VDC motor that nominally produces 18 rpm. I could use it it check this.

How does it sounds? Did I got mechanical drive close enough so far?

I'm calculating here only horizontal feed force of the acme screw to produce table feeds and speeds for 8,5 mm drill.
I'm not counting here acceleration etc. dynamic forces - they are not yet priority and not very interesting on steady feed. Friction will be interesting but I'm not sure if I should try to estimate it or measure after construction?

I may have found a suitable pump: Small hydraulic gear pump. I cleaned it. I'm planning to test it. First simple bucket test (short, reservoir is only 2-3 litres) but to test pressure I would need some unions.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on July 04, 2014, 09:28:27 AM
Pekka,
Unfortunately I am unable to help with your equations, maybe someone with a bit more knowledgeable background can help. Unc1esteve emailed me and will be responding soon about his progress.

As far as your gear pump, find a suitable container you can fill and time it while also adding a pressure gauge to determine your flow rate. Sounds to me it should work well. If the pressure is too high then add a bypass valve that runs from your output to your input.

When I mentioned never thinking about pulleys I just never thought of adding a pulley in the gear assembly, instead I was focusing on adding the motor at the end of the lead screw. However, homebrew has a larger lathe, I don't have as much room. An alternative to a motor i'm considering using timing belt/pulley to use instead of the gears so I won't need a motor. I found this site that has a large selection of timing belt pulleys available. http://www.misumiusa.com/rotary-motion/timing-pulley/?mkwid=sS9ouPlAQ&pcrid=39687221020&kw=timing%20belt%20pulley&mt=p&utm_source=google&utm_medium=cpc&utm_term=timing%20belt%20pulley&utm_content=39687221020&utm_campaign=GS_Misumi_US_EN_P_PRD_RPT_TimingPulley&lisid=lisid_google_111107_S9ouPlAQ (http://www.misumiusa.com/rotary-motion/timing-pulley/?mkwid=sS9ouPlAQ&pcrid=39687221020&kw=timing%20belt%20pulley&mt=p&utm_source=google&utm_medium=cpc&utm_term=timing%20belt%20pulley&utm_content=39687221020&utm_campaign=GS_Misumi_US_EN_P_PRD_RPT_TimingPulley&lisid=lisid_google_111107_S9ouPlAQ) I may need to use two belts to gear it down enough.
Title: Re: Deep hole drilling 101 on lathe?
Post by: Jonny on July 04, 2014, 11:10:57 AM
How deep are these holes and diameter.

Various ways to do it with normal twist drills accurately.
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 04, 2014, 02:51:37 PM
How deep are these holes and diameter.

Various ways to do it with normal twist drills accurately.

Hi. I'm having no problem until 5xD. There is 7xD carbide trough cooled drills, but now I need some holes min 10xD. With trough cooled drill. NO PECK DRILLING. Have to go in one go. Material is 1.7225. 42CrMo4. 4142 on a good day, but I have mostly 36NICrMo16, 1.6773, 1050. Now I admit that it does not sound much, but give war a change! With industrial machines, industrial drills and industrial prices. My next drill to break is bit over 40€ a piece on sale.

I would be really happy to hear how others have done this.

shaddr3 here is making probably slightly longer and smoother hole on slightly easier mater (least I hope).

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: vintageandclassicrepairs on July 04, 2014, 04:27:29 PM
Hi All,
Regarding a high pressure pump what about using the motor and pump from a domestic oil burner,
They have a built in bypass pressure control valve  ????

Just a thought
John
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on July 04, 2014, 08:46:12 PM
My maximum depth hole is 35.5xD BLIND, and my minimum depth hole is 16xD BLIND in 6061 Aluminum hex bar. Going to be difficult to center the hex but I plan on using 6 point socket with three set screws to hold the material in a steady center with roller finger bearings. Measured my material and play in socket, found .005 so .0025 on each edge, may shim three sides. Machine a small groove in the socket for the finger bearings. Smoothness isn't so much as important as straightness but I don't have strict tolerances. My hole is a water passage, with 2xD holes drilled perpendicular joining the passage. My blind deep hole just needs a 7/16" NPT thread on bore entry.
Title: Re: Deep hole drilling 101 on lathe?
Post by: Jonny on July 07, 2014, 12:12:41 PM
Pekka ive only done it a few times for production items.
From memory 170mm long x finished 12mm dia hole, no runout permissible using a Colchester 50" Triumpth, about 30 off.

Last time a one off on Harrison 140 12 years ago, two holes parallel 1/2" through and a 5/8" through with M28.5x 1.25 screwcut lower down. All need to be parallel.

Extend a finishing reamer and a slightly smaller drill by brazing or silver soldering. Normal hss decent twist drill.
May have used a centre drill but cant guarantee, just drill in with coolant around 8.5+mm dia as far as you can get think about 5mm max depth before pulling out to clear swarf.  Any further heat gets in to the part gradually getting worse and worse coolant or not. So dril a little, remove and repeat.
At this point with flimsy machine or out of square you may need to bore out to next drill used so it centres.
No boring out on both machines here just went on to larger extended drill and ploughed all the way through, often drawing drill out to clear swarf and that's the key.
Dropped speed to around 60rpm plenty of coolant and reamed out to final size, no boring nothing.
170mm long took about 22 mins job done, hard part is the initial smaller hole.
1/2" and 5/8" silver steel poking through showed runout of 0.03mm, I was half expecting 3mm.

Material shouldn't be a problem.
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 08, 2014, 05:13:45 AM
.....
Extend a finishing reamer and a slightly smaller drill by brazing or silver soldering. Normal hss decent twist drill.
May have used a centre drill but cant guarantee, just drill in with coolant around 8.5+mm dia as far as you can get think about 5mm max depth before pulling out to clear swarf.  Any further heat gets in to the part gradually getting worse and worse coolant or not. So dril a little, remove and repeat.
.....

Material shouldn't be a problem.

This material is problem. Wonderful for shafts, turns easy with carbide inserts (real ones, indian/chinese will break), compared to this one 42 CrMo4 (Moc 410) is soft and really nice. I may need to resort that. This is hardened and tempered, approx.1000 N/mm2 of tensile strength.

I measured some I had (took them work, they have a hardness tester):
25 mm 365 HB -> n. 1220 N/mm2
20 mm 342 HB
16 mm 206 HB -> n. 700 N/mm2


This will not drill with HSS and even HSSCO5 is very marginal. See:
http://www.acerosboehler.com.ar/english/files/downloads/V155DE.pdf

Because this is work hardening and hard peck drilling will not work. You have to make hole on one go. Sawrf is long, most of the time it is one long continous swarf until you speed up over 100 m/min (carbide insert). I have dried. Dormer HSS A002 10mm dia will last one or few holes max. 66 mm deep. D8mm Dormer HSCO (A777)  425 rpm is a bit better, but both will break if stopped even once (peck drilling).

I may need to resort lower strength material. But it has it's own set of problems.

I know there is are different steels on same spesification and I know there is just right steel which will do and machine well, but I can't buy few 6 m bars of as a private customer, should buy few tons of it and have a company.

Not much progress on this front yet, but I have a lead of small amount of nearly ideal steel bars AND I might get ex industrial small drilling unit with pneumatic 700N feed on reasonable price. ER 20 collet though....no trough coolant on that one.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: Jonny on July 09, 2014, 07:39:30 PM
I tried a few A002 and A777 plus others from Dormer last year, they don't last long perhaps 1/8 a decent drill of a few years back.
I sill have a fondness for most Titex, not far behind are Hertel on all materials in general.
Some of the best drills found to date Oon hard stuff are the Titex 3 flute but i wouldn't like going more than 5D.

Know exactly what you mean its a rarity I break a drill but now going through a phase 4 in about 1 1/2 weeks, no warning.
Often I see a drill work great then start to flex like a banana

If jobs work hardening its getting hot due to friction and will get worse if carry on.
Some breakages or hard going can be contributed to the swarf not evacuating and why I mentioned keep drawing the drill out to clear the swarf.

Never used gun drills but don't they use high pressure thru coolant forcing swarf out.
Title: Re: Deep hole drilling 101 on lathe?
Post by: rowbare on July 10, 2014, 02:58:59 PM
Pekka,

Since you are building companion spindles, you might find the book "Workshop Practice Series no 27 Spindles" a good read. It is inexpensive and the author goes through the construction of several different spindles.

bob
Title: Re: Deep hole drilling 101 on lathe?
Post by: PekkaNF on July 10, 2014, 04:52:33 PM
Pekka,

Since you are building companion spindles, you might find the book "Workshop Practice Series no 27 Spindles" a good read. It is inexpensive and the author goes through the construction of several different spindles.

bob

Thanks. I read it often. I got lot some time ago and it's been both inspiration and frustration. The only of spindle only book I now for amateur and it has lot to recommend. Definately worth of the money and time spent studying it. It has it's own mindset. I some of the choices are very good. I's based on inch measurements and materials. Some choices and dimensions are outright weird, not sure is some "metric" size bearings are available at all, some material and threads are weird like M7 and many design considerations are based on myford measurements, which is fine if you got one. One part has three threads cut on it. All different dpi. Some measurements are nominal bar (material) size. Some opinions are given, not explained.

But if anybody would be building spindles, I would recommend it. Specially, if you like imperial units, withworth thread and have Myford lathe.

Pretty much only two more common design comes into my mind: Quorn spindle and Harold Hall WPS#34 has one pretty nice design.

Does anybody know a design of a internal grinding spindle with long quill and double AC bearings at both ends?

I bought a little of hollow bar. Have to check how it turns, but it would save a lot of boring for the shell. Also got some free machining steel of 22 mm diameter (hex bar). Drilling it should be a dream. I am not sure how well it would fare, if feels really soft for a shaft and tensile strength looks bad. But it machines overly easy maybe it´s weakness will be compensated more easily reached (possibly more accurate) dimensions. Anyway, reaming leaded steel is nice, offering a taper reamer on tempered steel is not.

Pekka
Title: Re: Deep hole drilling 101 on lathe?
Post by: shaddr3 on August 20, 2014, 11:32:00 AM
 :update: on my progress. My 7.25" x 7/16" bore was done with the tailstock. It was brutal, took forever to keep removing for chip evacuation. My method using 6 point sockets (with set screws) to hold the aluminum hex stock worked out great. A few weeks later after getting the 25cfm air compressor setup I dived into the 11.25" x 7/16" bore using a through coolant bit held by a 3/4" boring bar holder on the QCTP. I purchased a cheap pneumatic air tool oiler, filled it with WD40 for my lubricant. I predrilled a 3" x 7/16" hole to center my through coolant bit. I was surprised it worked so well, and how the swarf was evacuated out of the hole. I still plan on buying an actual gun drill and modifying my lead screw once a few prototypes are finished.