Deep hole drilling 101 on lathe?

Gallery, Projects and General > How do I??

<< < (7/9) > >>

PekkaNF:
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

shaddr3:
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:

PekkaNF:
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

shaddr3:
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.

Jonny:
How deep are these holes and diameter.

Various ways to do it with normal twist drills accurately.

Navigation

 Message Index

Go to full version