Drilling a Deep Hole

[BronxFigs]

Planning to turn a Black Powder, cannon barrel on lathe. Depending on the size of the steel that is available, the 1.00" - 1.250" diameter bore will be approximately 15"-18" deep. OAL of barrel: approximately 22" breech to muzzle.

I am willing to buy a Long Boy extra-length, drill just to do this job, and was wondering how long the fluted section on the drill should be? The longer the fluted section, the more expensive the drill. Also, is a Silver and Deming style drill an option? I suppose I could always fabricate a drill extension.

So, what's the easiest way to get a deep hole with a reasonably smooth finish? Work will be chucked and supported by a steady rest...drill will be held in the tail stock. I plan on just taking light pecks with the drill, using of plenty of cutting fluid, and then clearing out the chips often....very often. I don't care how long it takes to drill this hole, but I'd like it to be close to center and not wander.

Also, is a pilot hole and step drilling necessary, or, can I just center drill and go in with the full size drill?

I need some options. Thanks for any suggestions.


Frank

 

[dnalot]

Years ago a friend gave me a 1" black powder cannon. He had shatered some windows with it and his wife wanted it gone. So I took it out behind the house and put 3 tablespoons of black powder in it and a paper wad. Long story short I blew out all the windows on the back side of the house and a few along one side. Lucky for me I wasn't married at the time so I got to keep the cannon. Out in the woods I loaded it with a 1/4 pound of 1/8" lead pellets and took the bark and all the leaves of the trees leaving a pattern about 10 feet wide.

So you wand to be way far away from windows when you fire it.

Mark T

 

[purpleknif]

Depeds on what yo got to push the drill with. Where I work we would use an ejector drill in a boring mill and do it in one pass.

 

[Woodster]

It would probably be cheaper to get it gun drilled by professionals. On a gun drilling machine, the work piece and drill counter rotate to keep the hole true. Gun drills are carbide tipped, straight single flute and through lubricant. When drilling deep holes, you need to use a drill with through coolant/lubricant holes and use high pressure flood lubricant delivered straight to the tip to lubricate/ cool and flush the swarf. Not easy to do in the home workshop!
I work for a Gun drilling company (as a CNC turner) in the UK and would only cost about £50 to drill AND hone something like that.

Tip : If you want the hole to be perfectly true, drill the hole 1st, mount workpiece on newly turned mandrel and hold using tailstock pressure only. Take very light skim cuts to clean up as much O/D as you need to chuck on and get a DTI on. When you chuck up to turn the O/D you know your hole is true to the skim turn at the chuck end so you can indicate the hole and the turn to ensure perfect concentricity.

 

[deverett]

Have a look at this series of articles on rifle barrel making. You may be able to pick up some tips.
http://www.riflebarrels.com/articles/barrel_making.htm

Have had that link bookmarked for yonks - can't remember why though!

Dave
The Emerald Isle

 

[BronxFigs]

Thanks for the comments, links and suggestions.


Frank

 

[bb218]

Why not use some DOM seamless schedule 120 pipe ? I have made black powder shotgun barrels from schedule 80 seamless pipe only had to turn the OD, with no issues.

Might be hard to find a short length but would save a lot of work.

Mike

 

[MachineTom]

It first depends on the size machine you are drilling with. An 18" Monarch or a SB9. A mini lathe will not do it.

So a 36" bed length, I step drill, 1/4" go about 2" deep, follow with a 1/2 or so, only drill 1 1/2 " deep, now back to the 1/4 another 2 ". The idea is that clearing the chips is the time consuming part of the process, if there is space fot chip you can keep drilling, but once the flutes have chips jammed up, no drilling happens. So by following the 1/4 with the 1/2the always is somewhere for the chips to go.

After the 1/2 hole is 3" deep go to the 1" size and follow about 1 1/2 " behind the 1/2. Do not try to drill with a single 1/4 or 1/2 full depth, bad results will happen,

Gun Drill

results

 

[BronxFigs]

Thanks bb218-

The DOM, seamless tube schedule 120 would solve my hole (bore) problems. It should be plenty strong for occasional salute. I suppose I could then turn the breech end, trunnions, etc. and press these sections onto the heavy-walled, seamless tube with installed breech plug. Considering the total weight of the 5.00" diameter breech section, and the blank loads, this construction should be OK for blank loads.

MachineTom-

Appreciate the step by step suggestions for drilling a deep hole. Chip removal, and slow, incremental, step drilling is essential. Many thanks.



Frank

 

[Swifty]

I've drilled deep holes in the lathe before with long series drills for water ways on injection moulds, I set the saddle as a stop for the tailstock, drill a short way, then drag the whole tailstock back to clear the chips. Push the tailstock back against the saddle, clamp it, and continue to drill the hole by winding the quill forward. This saves winding the quill back all the time to clear the chips. Once you get in a rhythm with it, it is surprisingly quick.

Paul.

 

[Entropy455]

I built my cannon long before I picked up my big lathe – thus there’s no fancy turning work.

The barrel is 1028 mild steel seamless tubing (7” OD x 3” ID). The breach plug contains an inner radius to relieve the stress riser, and the breach was welded to the barrel using 7018 rod, with a 100% penetration joint. It took about 15 pounds of welding rod to attach the breach.

Even with my 10-foot lathe, if I ever build another cannon, purchasing thick-wall tubing is the only way to go. . . As welding a breach plug is super easy, and boring a deep hole is not - - - just one man’s opinion. . . .

I fire my cannon on the forth (blanks only) using bread as packing. I normally fire it out over a large body of water – mainly to ensure no one walks in front of it accidently – as the combustion gasses alone can easily cut a man in half. My cannon rattles windows hard over 1/2 mile away. Fortunately I’ve never broken a window –yet - - - because I’m nowhere near one. . . . This picture was taken at my local gun range.

 

[MachineTom]

DOM tubing is drawn so that bore will not be very regular in size. You need to bore/ream the DOM to get a constant size then turn a liner for a snug fit.

The cannons pictured in my previous post are breech loaded, with 10GA Blanks.
They are 8 drams (one ounce) of BP, have not broken any windows, and I'm surrounded by homes.But everyone knows when its fired.

 

[BronxFigs]

Thanks for all the feed back. I appreciate your interest. Reading through all the suggestions have helped me solve some of my problems. My inclination is to just buy a properly made barrel....but I can't afford the prices, nor, can I find just what I want. So....lathe and scrap steel is the way that I will go. Besides, I'd rather make the barrel myself.

I am now going to look around for some local sources for seamless tubing and price this material. It might be the way to go, and be cheaper in the long run to just use a section of seamless tubing and shrink/press fit the larger diameter breech section, including the trunnions, onto barrel. Of course, the seamless will have a welded breech-plug. The completed barrel will be mounted on a wooden naval carriage.

Frank

 

[MachineTom]

One of the barrels I've made was threaded to the breech, using a 16 tpi x 2,250. The connection was made to line up with the trunnions, so that a 3/8 SHCS which holds the trunnions on would thread into barrel connection, eliminating any chance of the barrel unscrewing from the breech. This I did before I bought the second lathe shown in the previous photo with the gun drill. It also saves material as the forward section was 2.375, and the rear 2.75 D.

If you weld the sections together, and don't paint the barrel, the weld will likely be a shade different than the base metal. Where threading as I did the joint is invisible because it was done at a reinforcing band edge. Just counter bore .100 or so deep, the D of the extension barrel. You should make the threads at least 1" or more in length, and good mating surfaces between the breech and barrel.You need to have good torque on the tube when tightened, not jammed threads.