Lock bolt misalignment

[tmdreb]

I have an India Pattern Bess repro that is, appropriately enough, made in India. I bought it after someone else had very competently converted it to percussion. I am now in the process of attempting to fit it with an intact flint lock that was also made in India. I bought the replacement lock knowing full well there would be fitting issues due to the handmade reproductions not possessing interchangeable parts. Yes, I'm also aware I need to install a vent liner.

I've done enough inletting to where the new lock can be placed in the stock just fine. The problem is that the only way the upper (rear) bolt will thread into the lock is if the lock sits well below the space designed for it, leaving a rather large gap. It seems that this is due to the alignment of the threads in the lock.

When I thread a bolt into the same hole of the original lock off the gun, the bolt seems to approach from an angle slightly lower than perpendicular. On the new lock, the opposite seems to be true.

Is there any somewhat simple way to correct this?

 

[Zonie]

If I understand this correctly, the rear lock bolt hole is located higher than the lock bolt in the old lock was and the lock bolt hole in the new lock is canted somewhat upward?

The real problem as I see it is that the sideplate for the lockbolts is already installed so it can't be moved.

That being the case, the only thing I can think of is to use the existing hole in the sideplate as a starting place and run a clearance sized drill bit thru the stock, aiming somewhat high towards the new holes location.
I'm not sure about a Bess but you may have to enlarge the clearance hole thru the rear of the breech plug with a file if the old bolt went thru it.

This should clean the wood out of the way for the bolt leaving the canted hole as the remaining problem.

If the rear lock bolt won't screw into the new locks threaded hole thru its newly enlarged clearance hole you could obtain a (probably) metric tap of the correct thread size and pitch and install it thru the sideplate and the stock engaging the end with the offending hole.
(Before doing this, be sure to run the tap into the existing hole. It should enter and screw thru the lockplate using finger pressure only. If it doesn't screw easily into the lockplates hole it probably is the wrong size or pitch tap.)

Then, carefully turn the tap to re-chase the locks thread. Because this is going to put a high strain on the tap and taps break easily go slow, use thread cutting oil in the locks hole and back out the tap 1 turn to clear the chips for every 1/2 turn in that its cutting.

Yes, this will create an oversize thread in the lock.
No, I wouldn't recommend doing this if there was a better way.

At least, after recutting the threads while the tap is being guided you will have something that you can install the lock bolt into.

On the positive side, the lock bolt(s) only job is to keep the lock in the stock. They aren't subjected to any real stress because the locks mortice takes the load from cocking it.

 

[tmdreb]

Thanks!

First off, I'll clarify that the hole in the new lockplate seems to be just barely higher than in the old one. The hole through the stock is clear, and the bolt would fit in just fine if it wouldn't enter and exit the stock at an angle.

I'm finding this somewhat difficult to describe, so please bear with me if I don't get it just right.

Using a tap in the manner you described is the thought that had come to me in recent days, but as I'd never done anything like this, I didn't know if it was a workable plan.

Thanks again! I've got a standard tap and die set already. If it doesn't fit, I'll get a metric set and get to work on this.

 

[Keb]

Like Zonie, I am not quite sure of the problem. If the hole can't be "wobbled" out to accept the screw, moving the hole in the lock plate is an option. You can plug the lock plate hole by using a larger steel screw. Drill & tap for a larger screw. Lock tite the screw in the oversized hole and work it back flush with the surface of the lock plate. Then using a clearance drill for the lock screw, spot the hole location through the stock into the lock plate. Remove the plate & drill the hole with the tap drill. Put the lock plate back in the mortice & tap the new thread through the gun using the existing clearance hole for your location.

 

[matt denison]

I would do exactly what Keb says. Plug the hole in your lock plate and start out fresh with a hole where it belongs.

L.Dog

 

[Zonie]

I would only consider plugging the existing hole if it was mis-located far enough away from the needed hole that the new hole wouldn't interfere with the plugged hole.

For instance, if a #8 (.164 dia.) screw was being used and it was less than .080 from where the new hole was going to be tapped I would not plug it and redrill the new hole.

Also, I need to say that if this screw was highly loaded like a tang bolt can be I wouldn't suggest that the existing hole be "retapped" at the new angle as I did a couple of posts up.
This solution should only be considered for lightly loaded screws.

 

[tmdreb]

Maybe I didn't describe the issue so poorly after all. I really like and appreciate all the suggestions.

I believe what I'll try is retapping the existing hole, and if that fails, I'll plug it and make a new one.

You gentlemen have all been very kind and helpful. Thanks again to all for your wisdom.