Author Topic: Deep hole drilling 101 on lathe?  (Read 35007 times)

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #25 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.


Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #26 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

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #27 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

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #28 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

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #29 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.


Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #30 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

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #31 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:
« Last Edit: July 02, 2014, 09:24:24 AM by shaddr3 »

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #32 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

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #33 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 I may need to use two belts to gear it down enough.

Offline Jonny

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Re: Deep hole drilling 101 on lathe?
« Reply #34 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.

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #35 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

Offline vintageandclassicrepairs

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Re: Deep hole drilling 101 on lathe?
« Reply #36 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

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #37 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.

Offline Jonny

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Re: Deep hole drilling 101 on lathe?
« Reply #38 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.

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #39 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

Offline Jonny

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Re: Deep hole drilling 101 on lathe?
« Reply #40 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.

Offline rowbare

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Re: Deep hole drilling 101 on lathe?
« Reply #41 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

Offline PekkaNF

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Re: Deep hole drilling 101 on lathe?
« Reply #42 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

Offline shaddr3

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Re: Deep hole drilling 101 on lathe?
« Reply #43 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.