Bess Touch Hole

[Loyalist Dave]

OK some more on the restored Japanese Bess project.

I scrounged a very good condition Jap Bess lock..., Thanks be to God, :bow:

All the other hardware too, so I'm "in business". The stock will need a bunch of work and some crafty hiding of Acragalss when I repair the wood, but that's not the main problem.

When I placed the replacement lock into the stock..., the touch hole is so low on the barrel, it's below the lock pan. So I'm going to need to install a touch hole liner, only higher up on the barrel flat for the touch hole, AND I'm going to have to do it so the liner hole when drilled and tapped, consumes the original hole installed by whoever built this gun as a kit. :cursing:

(I mean the guy probably had to really mess with the pan on the original lock to make this thing work). :shake:

I think any of the standard touch hole liners will work in raising up the actual hole location BUT it still may be very low in the pan. So the Question is, does anybody sell a liner without the touch hole pre-drilled, so I can install the undrilled liner, and then drill the hole perhaps a teeny tiny bit higher..., off center from the insert but closer to the right position in relation to the pan? I can't find such a product online. I VERY much prefer using a prefab product rather than making one myself.

LD

 

[Col. Batguano]

I think what you are describing is a plug.

Why don't you just drill out the hole, tap it, screw a bolt in place, peen it, braze it, and file it smooth both inside and out? Then you can put in a liner where it SHOULD be and not worry about it. I would think a # 4 bolt and tap would do it, and almost for sure a # 6 would. Those are pretty small taps and bolts.

Just consult with the machinists here about using the right sorts of tap and bolt to get the maximum amount of thread bearing contact.

Before you do that though, I would get the largest vent liner I could find, and see if there is a location that would work AND take out the older misplaced hole. My hunch is that it's a wee bit on the low side though. But remember, flint locks are amazingly tolerant as to vent hole location, so long as they're somewhere above the bottom of the pan.

 

[dave_person]

Hi Dave,
I am not aware of anyone selling undrilled liners however, it would be very simple to by a large steel flat head screw the diameter you need with perhaps 5/16-24 or 1/4 28 threads,cutt off the extra threads, drill and tap the hole, counter sink it a little, and install the screw. File the head flush with the barrel so it also gets rid of the slot and then drill the touch hole where it needs to be. If you don't mind it showing, you could use stainless steel.

dave

 

[Zonie]

All that is needed to make your undrilled "liner" is a bolt or screw with suitable threads.

Assuming your barrel does not have a vent liner in it, and assuming you know where the center of the new liner should be, measure the distance from the new center to the most distant edge of the existing vent hole.

Multiply this distance by 2.
The answer will be the smallest thread diameter thread that will work.

It will most likely not be a standard screw thread size so look for a standard, fine pitch thread that is larger.
Buy a suitable tap drill, tap and bolt or screw and your all set.

When you drill the new hole for the threads, the existing vent hole will try to make the drill "walk" so it possible, first drill the new hole with a small drill bit that will not interfere with the existing vent hole.
This new, small hole will help to guide the tap drill at the right location, keeping it from wandering off (walking) as it removes the existing vent hole.

Tap drill thru the barrel wall, thread the hole, cut off a length of the threaded end of the screw and install it.


Drill the new vent hole thru the new vent liner.

I would use a standard mild steel bolt so after it was finished, it would match the barrel in appearance. (If the barrel is brown, a mild steel liner can easily be browned. If the barrel is bright, the new liner should match without doing anything.)

I also wouldn't bother with trying to counterbore or countersink the inside of the liner like most new liners are made.

The Bess used a fairly large vent hole and it should work fine without the extra work of messing with the inside of the liner.

A good way of holding the threaded stock, screw or bolt so you can cut it off and file the ends square is to buy a nut with a matching thread.

Screw the bolt/screw/stock into the nut and clamp the nut in a vise.

The vise will crush the nuts threads into the screw threads and hold it firmly in place while you work on it.
Relaxing the vise pressure on the nut will release the cut off screw, leaving the threads in new condition.

 

[Artificer]

Dave,

I don't know how much you know about choosing the correct size drill bit for a threaded hole, so if you already know this please disregard.

Many drill bit charts give you the size drill bit to use, BUT may or may not give you the percentage of threads for the size drill bit used. For this kind of application, you want a 75 percent thread and NOT a 60 or 50 percent thread, the latter two for looser tolerance for common bolts and screws. BTW, a 100 percent thread is only 10 percent stronger than a 75 percent thread, but is THREE times more difficult to tap and is not needed in this application.

Here is a drill chart that will help you choose the correct size drill bit for a 75 percent thread. http://www.shender4.com/thread_chart.htm

I can still hear the strict advice of older and much more experienced Machinist Instructors from the early 1970'a telling me the thinner the material you want to thread, the more threads per inch you should use for strength. So while 1/4 x 28 TPI is a good thread for thicker walled rifle barrels, I personally would choose a 1/4 x 32 TPI bolt for this application.

ALSO, when you go to mark the center of the new hole where you want to drill, you should use a good center punch with a nice/sharp point and hammer to mark the position of the hole. Also, because the Brown Bess barrel is round, I would use a "Center Bit" to begin drilling the hole, so it is far less likely to run off center. Then finish the hole with the correct size drill bit for the 75 percent thread from the chart above.

Though I would use a little more expensive center bit than these, the following link is an example of a center bit set. Drill slowly with a light touch with these and make sure you choose the size center bit where the initial cutting end of each end of the center bit is the same size or slightly SMALLER than the drill bit you will use to drill the hole completely through the barrel wall.
https://www.harborfreight.com/center-drill-countersink-set-5-pc-60381.html

Hope this helps.

Gus

 

[Zonie]

I think that thread tap drill chart is good enough to keep so I "Print Screen"'ed it and pasted it into a photo which I saved as a jpg file.

I couldn't get all of the chart but by reducing the screen picture size by holding my keyboard Control button and hitting the - (minus) button I shrunk the image size down so I could get up to the 7/16-28 thread.

(I am running an old Windows XP).
Thanks for the link.

 

[Artificer]

Jim,

Glad you liked it and you are most welcome.

In 1974, I was given an old copy of the Morse Tool company's, Machinist's practical guide and have come close to almost wearing it out lately, especially the tap and die section. There is an amazing amount of information a home machinist can use in the little pocket guide and some of the above information came straight out of that pocket guide. I wish I could have found a link to the tap/drill chart in that guide on the internet.

Today, though, I might opt instead for the Machinist's guide for taps and especially if all I was doing was working with taps.

If anyone is interested in these pocket sized practical guides, here is a link to them.
http://www.penntoolco.com/morse-pocket-size-machinist-guides/

Gus

 

[Artificer]

Dave,

One more thing on drilling the barrel for tapping. Since the barrel is round and that makes it easier for a drill bit to wander, I would highly recommend you get a brand new drill bit in the size you need to drill the hole for the threads. I always do that when tapping a new hole in something as important as this, to ensure the drill bit is sharp and far less likely to wander, even with center punching and center drilling to begin the hole.

Gus

 

[B.Habermehl]

Just my two cents, first I would permanently plug the original hole. Drill and tap the hole with smallest size possible. Degrease thoroughly, flux both the machine screw and the tapped hole. Heat from inside the bore, and sweat solder the screw in place. The solder will follow the heat and wick into the thread. Now that the old hole will not cause trouble with the new touch hole liners drilling and tapping. I would suggest utilizing a chambers white lightning liner 5/16 or 3/8 if necessary. As long as the new touch hole is above the bottom of the pan it should work OK. The object is with the old hole filled with steel you can pilot drill your liners hole with out it drawing the drill bit from your intended location. Of course your plan to consume the old hole location is best.

 

[M. De Land]

I not only use a center drill to start any hole I can I also use a tap guide when ever possible.
Both will save you no end to grief and make both tools last much longer.
A round barrel tap, hand held tap guide is easy to use and works like a miracle.

 

[Loyalist Dave]

Why don't you just drill out the hole, tap it, screw a bolt in place, peen it, braze it, and file it smooth both inside and out? Then you can put in a liner where it SHOULD be and not worry about it. I would think a # 4 bolt and tap would do it, and almost for sure a # 6 would. Those are pretty small taps and bolts.

WOW you guys are the best. Sure I can do that, I have a good quality tap and die set, and a good drill press. I have reworked bad screw holes and such on used locks to success.

I was just thinking that I'd simply close by tapping and installing a screw, silver solder it, and then redrill a plain, standard factory Bess touch hole. I was concerned that perhaps it might be too close to the original..., making my repair weak, so I though "touch hole liner" would be the trick. :wink: Hence my question...

Sorry, I should've mentioned my concerns in my OP. So with so many of the more experienced of you suggesting that course of action, I measured the distance from where the touch hole is, to where it should be..., it's more "off" than I had realized at first from just eyeballing it. :shocked2: So..., I think now, that a proper filling, followed by drilling a new hole will work and be safe. IF the owner want's a touch hole liner, then I'll do that.

Thanks again gentlemen. :hatsoff:

LD

 

[Col. Batguano]

Yeah, even if it shows a little, as you stated, it's below the bottom of the pan, so it shouldn't be a really big deal. It'll be more important to get it filed smooth on the inside so jags and patches don't catch on it, and level on the outside so the lock bolster seats tightly.

As stated previously, a finer thread on the plug will give you a better bearing surface and positive seal. Your barrel wall is pretty thin relatively speaking, so more threads will be better. Upsetting the plug with peening, brazing etc. will help it remain permanent. But in the end, it's really not that much different than a vent liner that way.

 

[Artificer]

Dave,

I think drilling/tapping for a bolt just big enough to completely cover the old hole and soldering that in as a plug, then simply drilling a new vent hole is the way to go as well. Kudo's to Colonel Batguano for mentioning cleaning up the inside as well as the outside of the barrel.

I would advise against adding a vent liner until/unless the owner burns out the new touch hole you are going to drill. No need to do that now and it just adds more expense/time to the project.

Gus