Deep hole drilling in the lathe

hi, all! Got some info here: you can do barrel drilling and reaming in a lathe that's got at least 13 x 36 capacity and at least 2 HP with a 1 3/8 spindle hole. A company in VT makes and sells gun drills and reamers utilizing a mist coolant system of 100 to 120 psi. The mist system runs about $1150 and the drills that they make run around $100+ but any gun drill will work. There is a modification to the lathe in that the feed rate cannot exceed .0005 per rev. This is extremely critical using this system. The company is Sterling Gun Drills and they are on line. Hope this helps anyone wanting to make their own barrels. thanks, John

rifler99 said:

hi, all! Got some info here: you can do barrel drilling and reaming in a lathe that's got at least 13 x 36 capacity and at least 2 HP with a 1 3/8 spindle hole. A company in VT makes and sells gun drills and reamers utilizing a mist coolant system of 100 to 120 psi. The mist system runs about $1150 and the drills that they make run around $100+ but any gun drill will work. There is a modification to the lathe in that the feed rate cannot exceed .0005 per rev. This is extremely critical using this system. The company is Sterling Gun Drills and they are on line. Hope this helps anyone wanting to make their own barrels. thanks, John

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That misting system seems a bit pricey. I wonder how complicated it really is. I'm guessing there's a reservoir pump that mixes a certain amount into the air feed to get the right type of mist. Just wondering why such a seemingly simple system would be over a grand.

Sterling have been in the deephole drill business for a long time..(assuming the name hasnt been sold to an ebayist)....but I dont see how 120 psi could flush out chips.Bore length comes into the problem,and for pistol bores ,probably OK.....but if you want to do ,say 22 bore and 25" long then?...The other issue is that you must also have a device for sharpening that will maintain geometry....mist coolant may also involve a costly friction modified cutting fluid.

Here's my Sterling at work. This is at .0005 feed rate. The mist pump is air operated, which has a booster cylinder in it to boost the pressure somewhere over 150. As you can see, the chips come out with no problem.
Gun drilling on engine lathe - YouTube

Thanks for sharing this. I never thought air could work.

FWIW, I just added a pressure washer pump, for high pressure coolant, to my CNC lathe and its now a gundrill machine.

Well,that explains both issues.....Yes the near cheapest HP pump is a pressure washer.It can easily handle chemical base coolants,but oily coolants may damage the internals.....Filtering out swarf is simplified by super strong magnets ....in fact making a steel fragment filter from these is very useful on any machine or engine.I picked up on the hydraulic pump in my crane truck,before the pump disintegrated on the job,wrecking the crane seals.

Fellas,

I'm quite taken by your progress. I've heard that a pressure cleaner can be used for coolant. Being that they operate on 1200 psi+. Are you guys regulating your pressure ???. Does this have any long term affect on the pressure cleaner ????

What brand of coolant are you using ???

Danjon also does deep hole drills and reamers that will finish to size and finish in one pass.

I have the Guy Lataurd/Bill Webb video/booklet and it had occurred to me that Webb's machine is duplicating what an existing lathe would do.

The challenge would be to speed the spindle up (to 2,650 rpm) and slow the carriage down (to about 1/2" - 3/4" per minute - drilling) and after that it's pretty much the fluid/coolant system and gearing for rifling ( a gear train on a quadrant that engages with the lathes rack makes sense to me. A very small driving gear and a very large driven gear in the gearbox should achieve the required carriage speed and changing pulleys on the motor should achieve adequate spindle speeds.

I'd be interested to see pictures of your setups if you can/will post them. Youtube footage of them in action is even better.

Cliff Labounty's book is also very good on reboring/rifling and the various machines involved.

There is also good information in Hoffmann's writings. I believe (??) that Hoffman uses an adapted lathe to drill and ream without undue stresses/damage to the machine.

4140 of the grade suitable for barrels is easily obtained but has anyone had any success sourcing 416 series stainless ????

Great to see there is other people out there that are interested in making rifle barrels.

Yep, There`s more than one to do this, I got a star .50 gundrill from eBay, new for $75 so I can drill .50 barrels. When I got it I found it had two oil holes in the tip but drilled hole ok, but only got 100 psi oil pressure so now upgrading to two oil pumps for more oil flow.

I've heard that a pressure cleaner can be used for coolant. Being that they operate on 1200 psi+. Are you guys regulating your pressure ???. Does this have any long term affect on the pressure cleaner ????

What brand of coolant are you using ???

twobobbwana said:

I've heard that a pressure cleaner can be used for coolant. Being that they operate on 1200 psi+. Are you guys regulating your pressure ???. Does this have any long term affect on the pressure cleaner ????

What brand of coolant are you using ???

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I just use a pressure washer pump as is. It does have a relief valve as part of the pump. My setup is not for long term production. A pressure gauge and relief valve would be a good idea. A regular high pressure coolant system would be needed if doing production runs.

I use hangsterfers S500 at 8% for this.

Karl T,

Thank you for your reply.

I think it's time for me to "nut up" and give this ago. "What could possibly go wrong ??"

If I went to a place and asked for hangsterfers S500 here they'd probably refer me to a chemist.

Does the fluid have to be anything more than coolant ???

GGaskill,

thank you for this information.

In short it seems soluble oil is what is required.

"4140 of the grade suitable for barrels is easily obtained but has anyone had any success sourcing 416 series stainless ????"

416 is as common as dirt. Used for pump shafts and rods on reciprocating pumps. Have you tried to buy it?

The 4140 that barrelmakers use is not exactly the same stuff you buy off the shelf. It is made to drill, ream and rifle easier. I suspect the SS versions are the same.

tcmidget,

I've asked around about 416 series stainless and never got a favourable reply.

I will ask about their pump shaft material. Thank you.

Doug W,

Boehler, here in Australia, will quote me the exact same 4140 that they supply to three of the barrel makers here. It's not even expensive.

So it looks like they're talking about the right stuff.

This is hobby barrel making so I'm are not in mass probation, I've found that using water soluble oil as a cutting fluid for barrel drilling and reaming is no good, I have Fuchs Ecocool 400, when reaming I could not get any cut from the reamer and just about got it stuck in the barrel. So changed to oil and lots of chips and a nice clean cut from the reamer. With the barrel hole drilling I use oil as my pump is a car power steering one, this is just me of cause . I wounder if a water blaster pump would work with the soluble oil, sure get a lot of pressure .

twobobbwana said:

Doug W,

Boehler, here in Australia, will quote me the exact same 4140 that they supply to three of the barrel makers here. It's not even expensive.

So it looks like they're talking about the right stuff.

Click to expand...

Good!

I have a small stash of 4140 from a premium barrel maker, it is the rejects. Wandering bore, jammed in reamers etc. I use it to make bushings, it is nice to have a hole already through it.
I find it machines and finishes way better than typical 4140 prehard or annealed, and it always seems to crack if welded, even with preheat whereas typical 4140 doesn't.

The steel used is specially doped for free machining and button rifling.Which is how the US govt is able to restrict "barrel steel" under ITAR.

People, I am interested in drilling a 36 cal barrel for an Under-hammer black powder rifle. I always hear people say you got to use a gun drill with fluid coolant drills to clear the chips. Question how did they do it in the early days of machining. I'm not talking about hammered on a mandrel I'm talking drilling and reaming. If you get the right bit and clear your tool every 1/4 inch or so why not. Slow yes but still why not. I have an atlas lathe with a 3/4 through hole so a small caliber is my limit. I am going to try it.