Boring a 15 mm hole 240mm long

Hello all. I'm making another flintlock pistol but my main problem is the barrel, it's 240mm long with a 15mm hole through to the end, the outside will be tapered. The last pistol I made I used a 25mm pipe and cut the taper then silver solder the joint, It looks OK but it's not what I want to do. I also tried to make the barrel in three parts, silver soldered them together and machined the tapered, but that was not successful. I have a 9x20 lathe, any idea how I can make the barrel, it's a pistol to be non firing, the most difficult part to make is the barrel.

Thanks Bob

If its just for replica purposes. Could you drill the hole partially? It doesn't need to extend the full length of the barrel being a muzzle loader?

Failing that drill from both ends under sized then you can make a boring bar to fit between centres and clamp the part on the tool post using the travel of the Saddle to move the part. You'd probably need very light cuts and maybe a steady of some sort for the bar.

Hope that helps

Gaz

Edited By Gaz on 07/07/2023 11:43:21

You can drill the stock with one end in the chuck, and the outer portion in a steady. The important part is to get the start of the hole correct. Drill as close to 15 as you can, and then use a reamer. Use a longer piece than you want to finish with. Then using a centre at each end, turn the outside true to the hole.

Or you can get a 15mm gundrill, do a start drill, bore to size, then start with the gun drill. You don't have to have high pressure coolant to use a gundrill. You can peck and retract clear the hole, then drill a little more. Just try to gauge the feedrate at around 1 thou per rev feedrate.

Neil

As it's a replica, accuracy is not that critical. Any boring bar is going to be flimsy at the hole lengths indicated. There are plenty of extra long series drills available but if you only have your lathe I can't see you doing it in one go. As already suggested though, may be possible drilling in halfway from either end. Again, as it's a replica, if they don't accurately meet in the middle it won't be the end of the world.

Mike

Plus one for the gun drill but the other alternative is a D bit. Make it yourself and if used in a floating holder should be parallel .

There is an affordable 150 long 15mm gun drill on Ebay at the moment -

Use this to drill from each end to get your required depth ?

You would need to bore a short close fitting 15mm recess into the end of the bar to centre the gun drill initially as they are not self centering (proper gun drilling machines use a hardened bush held against the end of the part to centre the drill) , but they drill very straight. Best used with through coolant (messy ! ) but air would probably work to blow the chips out - the method my last employment used gun drilling graphite.

Nigel B.

with a 9 x 20 lathe there are not many options,suggest get a 15 mm drill turn down 25 mm of the shank to 11 mm ten get a length of round bar possibly silver steel 12 mm dia drill the silver steel down the cetre for 30mm so that the drill shank fits,drill and pin the two gether so that you have a 15mm drill with longer thinner shank as it would be difficult to hold a long drill in the tailstock with oly 20 inch bed available,hold the thin shank in the lathe toolholder/toolpost and drill down the gun barrel as far as you can go,then wind the carriage back and slide the drill shank out of the toolholder and drill a bit further into the barrel until and keep progressing the drill forward until the desired depth is achieved,

I drilled the bore in my 1/10 scale 24 pounder Naval gun with the cascabel in the chuck and the 3-point steady behind the muzzle-swell astragal. It probably would have been better to bore it before turning the outer profile, but it's certainly good enough as is.

I centre drilled to start, then drilled 1/2" or 13mm as deep as a standard jobber drill would go, then finished with a 9/16" slot drill of which I'd turned and threaded the shank (they're softish, machinable HSS behind the cutting lips), with two (or maybe three - it was 20 years ago and I can't remember now) silver steel extension rods threaded to fit together, because the quill travel on the Myford Speed 10 I then had was only about 2 1/2". Because the slot drill cuts on the full length of the land, the hole was effectively bored at the start, and went to scale length.

Last time I had a stick of 9/16" silver steel it fit neatly down the bore with very little slop, so the result was clearly as round, straight, parallel and to size as could reasonably be expected.

To avoid any legal issues, I didn't drill the touchhole.

Edited By Mick B1 on 07/07/2023 17:59:05

Thanks for the replies. As its a replica the replies state theirs no need for a straight through bore. My uncle made a flintlock many years ago and my first effort is not up to his standards, he did make it at work so must of made the barrel bore in one go, his gun all works but has no charge hole so safe. My first effort is not up to his standards but the lock works perfectly, the hardest parts was the pan and frizzen to make. This is a photo of my uncle's gun my first effort is under flintlock in my albums. A nice cannon Mick made its a shame you can't try it out, but the law won't allow it,it's odd that you can buy all the ingredients and make gunpowder, two really as charcoal is easy to come by.

Bob