Thread: Deep hole drilling. MT5 - ER32

Joes thread on hollow bar has bought up a question I've been working towards and before I offer to help Joe I thought I better be sure I can do it first.

I've been making an MT5 to ER32 adaptor with built in draw bar. Why not use pipe? where is a challenge in that? and I had 36mm bar that come with some big nuts
The time has come to drill a clearance hole for the work piece. Now to drill all the way through is 500mm. Anybody drilled a hole this deep in a lathe? I have some very long small drills that could drill a pilot hole and a reduced shank 20mm drill that I could make an extension bar for. Or would it be better to try with the 20mm? I think as the work is turning and not the drill I should end up with a pretty striaght hole?

Should I give up and drill 100mm deep and call it good? How often would you want an ER chuck with 500mm hanging out the back? Of course if I dont drill all the way through I may was well have just used threaded rod as the draw bar
Made a mount for my dia grinder for the MT5, that worked great... makes my Waldown grinder look pretty crappy so I'll have to have more of a play with that.

Stuart

[QUOTE=Stustoys;167049
I've been making an MT5 to ER32 adaptor with built in draw bar. Why not use pipe? where is a challenge in that? and I had 36mm bar that come with some big nuts
The time has come to drill a clearance hole for the work piece. Now to drill all the way through is 500mm. Anybody drilled a hole this deep in a lathe? I have some very long small drills that could drill a pilot hole and a reduced shank 20mm drill that I could make an extension bar for. Or would it be better to try with the 20mm? I think as the work is turning and not the drill I should end up with a pretty striaght hole?

Should I give up and drill 100mm deep and call it good? How often would you want an ER chuck with 500mm hanging out the back? Of course if I dont drill all the way through I may was well have just used threaded rod as the draw bar
Stuart[/QUOTE]

Stuart,

Not 500, but 320, for a knock-out bar hole for the new 2MT headstock spindle I made for my wood lathe. I worked from both ends, and started each end with an 8mm hole which I bored to 3/8 about 25 mm deep to make sure the drill would start true, then drilled as deep as I could with a brand new good quality normal 3/8 drill. I then switched to a home made long shank 3/8 drill with OAL of 270mm. It started out as a reduced shank new 3/8" drill, with the reduced shank loctited into a slightly undersize MS extension.

Possibly more by good luck than good judgement, the two holes lined up almost exactly when they met up in the middle of the 1" diameter headstock spindle. I can't see why, if the drills are properly ground and started accurately initially, this procedure would not give a similar result for an extra 90 mm of depth each end. This should provide a reasonable pilot hole for, say a 22mm drill.

Re "why not use use pipe" - well, why not other than the challenge? I used a piece of conduit with a 22mm bore which is completely satisfactory, and is an easy way to obtain a clearance hole (see photo). I think it is worth having the through hole - I have used mine a couple of times, and it can be very convenient.

If I were to do it again, I would probably have the female thread inside the 5MT adapter and the male thread on the hollow drawbar though.

Regards,

Frank

Hi Stuart,
Of course there was a really easy way around this one.....make a collet chuck to suit your spindle nose.
I have never had success drilling deep holes, the bit has always wondered off center. But I have never drilled such deep holes with large bits either.
What are you grinding in that 3rd last pic? And where are you getting your wheels from?

Cheers,
Ew

Hi Stuart,

I have some gun drills that will drill a long straight hole, they have a weird off center cutting tip, maybe you could copy something like that.

I tried to find a good picture of what they look like... not a good picture but... might give some idea?



Regards
Ray

Hi Frank,
I'll answer the easy ones and think about the rest while I head out to get some goodies.

Hi Ewan,
Were you drilling the holes in a lathe? I'm thinking its easier for things to wander when the drill is turning, not so easy when the work is turning(not sure about that one)
You had to bring it up....... Why not make a collet chuck to suit my spindle? Well I did, I used the axle out of a Navara to make an adaptor from a backing plate, to a flange mount ER32 chuck. all ground and everything. The adaptor is wonderful.... shame the chuck has about 0.1mm runout

The third last picture??? its the adaptor?? the first grinding pass after roughing the blue area is the MT5.
You mean why am I grinding there?
Well, cuz I can, it looks pretty, I need the practice.(don't confuse pretty with size. it tapers about 0.0025" if I remember correctly, but I haven't check since I reground it with the die grinder) but mostly because the ring in the next picture is a tight press fit in the back of the spindle and is a sliding fit to the outside of the adaptor. The theory being that the thread isnt used alignment.

My grinding wheels for the dia grind are dirty cheap things that came with a $50 flex shaft dia grinder. They seem to hold up pretty well. For the big one they are wheels I have had around here waiting for a grinder to use them on. They are for tool steel but I dont think thats the problem.

Hi Ray,
I'd thought of making some sort of gun drill but.. I think gun drills need pressured coolant.(they cant be used with a pilot hole right?)
I've been thinking about some sort of boring bar with a sized section on it that can be changed but swarf is an issue and I'm not sure it would get me any straighter then a twist drill.



I have plenty of bar maybe I should try drilling a test piece? Seems a waste, but I think I might just cry if I have to start over lol.

Stuart

Yep on the lathe. Although in my mms right now I don't see the difference as to which is turning. Either way the comparative movements are the same.....
That .1mm clicks now, you commented about it in another thread. Why not regrind the er taper true with the die grinder? You can always take a bit off its nose of the tapers dis gets too big.
I'm havimg trouble sourcing wheels. My local place doesn't have any and tells me they would probably have to get them from o/s. EBay shows up a few internal wheels but I haven't spent enough time looking for externals (5" x 3/4 bore)

Cheers,
Ew

It's an interesting subject - drilling long holes accurately.

The best source of information would be how they drill and bore rifle barrels.

I expect they would have to support the drill very close to the end of the steel stock (tube in a fixed steady ?), but you would still have to contend with runout as the drill bores through the stock.

I haven't read up on this so I'm only summising.

Once the initial hole has gone through, I imagine they would then use a rod to centre in the stock (full length) and then use that as a guide for a tubular boring bar.

Once again this is all conjecture, but you would need a fixed centre line to get accuracy.

All specialized equipment.

If I was doing this job it would be a case of pass the pipe please.

Rob

Aren't long holes drilled with the work 'and' the drill turning. And no, not in the same direction
Or am I an idiot again. I just thought I saw that somewhere.

Phil

This is a subject I know very little about.

I do know that runout and drill canting is an issue when boring long holes in stuff - been there, done that.

You've only got to see how the gas and telcos drill in at 30 odd degrees to bore horizontally under roads etc to realize there's more to this than meets the eye.

The little bit I have read on this (rifle barrel making) indicates that they draw the cutter through the barrel, rather than pushing it through, to eliminate bending and deflection of the cutter shaft.

Interesting subject.

Rob

Gun drill as per RayG's post.
Easy with the right gear.

Hi Ewan,
I'm imagining there is some sort of self centering force when the work is rotated.... not sure though.
A regrind might happen, not sure I thought about that..... mostly thought about grinding the back wich would have made the adaptor useless........I doubt a little run out of the thread would worry the collet?

3/4" bore? for the waldown?

Hi Rob,
They use specail drills and as Phil says turn both the work and the drill(though I dont know why).
As far as "pulling the cutter" are you sure you arent thinking about doing the rifling?(though there are at least 3 ways to rifle a barrel)

Hi Phil,
I'd been told about rotating the drills as well but I cant think of a way to do it with the torque required.



I'm thinking a test hole is in order.. or maybe some googling. I like Franks idea of boring the start to be sure you get a good start.

Stuart

ejector drilling is the norm either twin tube (Big stuff) Single tube (middle stuff) Gun drill (little stuff) you smart boys should be able to work out how a 105 mm field gun is made with a 85 mm ejector drill I made a couple of hundred of them at the ordnance factory Maribyrnong funny place now long gone where we actually made something for defence in this country llink with the best piccies

Premier Deep Hole Drilling Limited - The Deep Hole Drilling Process

Yep always spin the work never the tool its a bugger trying to work 30 thou out of a 30,000 dollar barrel billet cause some smart engineer challenged the norm

By the way why not use dom boiler tube / its really nice stuff to use available from Ian stansfield smith / interlloy smooth true to within a thou and available in 6 metre lengths

Bruce

Trust Stuart to come up with a problem none of us know much about. Well, with such great company, I'm willing to chuck in my 2/- worth as well.
A story before I'm called away (ie; caught on the Forum!), A (nameless) Defence Contractor was supposed to breath 'new fatigue life' into the centre section (the bit where the wings attach) of the Macchi trainer - they were required to bore long holes with a single drill operation - then ream the holes (to remove stress raisers) to finished size. They didn't have a drill long enough, so they drilled from both ends. You guessed it - they didn't 'always' meet true nor 'line bored' and therefore couldn't be reamed - so they over-bored them. This was all discovered after recovering an aircraft from about 300m of water off Newcastle. One wing had snapped off and the pilot was killed. So (long) line boring is important - right Stuart?
Having read the ideas above, another method could be to select some regular steel tubing (say 12mm OD), bore an initial 12mm hole to a depth where one is comfortable with the accuracy. Take another 12mm drill and grind the shank and most of the flutes to the ID (say ~9mm) of the tube. Leave about 20mm of the 12mm tip of the drill intact and cut a 'substantial' slot across the shank end. Use the 12mm tube over the reduced shank of the drill so that it acts as a guide (in the true part of the bore so far). Bore until 50% through the 'true section' - add longer sleeves and drive the drill with an old flat blade screwdriver shank (in the slot cut in the drill shank.
Concept is the use the initial trueness of the bore to keep the (modified) drill nice & straight - like an oil well. I should make another hi-qual sketch I think.

Yours in Mad Ideas, Daryl

If one has money, a modern "gun drill" like in Ray's pic is certainly nice.

But there were guns long before such modern highly specialized gun drills existed. They used simple D-bits, as one can grind from a length of silver steel..... (maybe this is why in some parts of the world round silver steel rod is also called "drill rod"?). Simple D bits do not have an internal channel (or two) for oil to aid chip removal. So with a simple homemade D-bit one is busy sliding the tailstock back and forth and back and forth.... to clear chips. But one may eventually end up with a long straight hole.

Originally Posted by cba_melbourne

If one has money, a modern "gun drill" like in Ray's pic is certainly nice.

But there were guns long before such modern highly specialized gun drills existed. They used simple D-bits, as one can grind from a length of silver steel..... (maybe this is why in some parts of the world round silver steel rod is also called "drill rod"?). Simple D bits do not have an internal channel (or two) for oil to aid chip removal. So with a simple homemade D-bit one is busy sliding the tailstock back and forth and back and forth.... to clear chips. But one may eventually end up with a long straight hole.

Yes this method also has merit if you are at about 3/8 to 1/2 dia above that spade bits come into play also a modern d bit head can be used on a reduced shank with appropriate support pads and pumped coolant

D bits in big dias cause too much drag and frictional working rigging up the pumped coolant supply will be critical