Question on fitting cock and tumbler stops.

[Artificer]

From the Journal of Historical Armsmaking Technology, Volume I, I came across this note: 

“The cock is fitted to the tumbler so that it comes to rest on the top edge of the plate as the tumbler rotates against the stop on the bridle.  This double stop reduces the pressure either must bear, and prevents the mainspring from slipping off the foot of the tumbler due to the wear or battering of either stop.”

Folks, since you all told me I was overworking fitting frizzens to pans, I thought I had better ask a question about this as I might overwork it otherwise as well. 

I’m assuming they used lamp black to see if both parts were contacting the stops at more or less the same time?  Since I’m not sure how exactly that can be done to get both parts to contact evenly, is it better for the edge of the cock that contacts the top of the plate to take the greater amount of  pressure?   

Thank you,
Gus

[Blacksmoke]

Gus:   I usually have to silver solder an "anvil" or "stop" on the upper portion of the bridle for the tumbler to  come in contact with at the same time as the cock lip contacks the the lock plate.  The bridle stop is continually dressed till both cock and tumbler contact their respective stops at the same time.  Hence the shock of the mainspring is absorbed and spread over a wider area.      That's how I do it,     Hugh Toenjes

[Artificer]

Gus:   I usually have to silver solder an "anvil" or "stop" on the upper portion of the bridle for the tumbler to  come in contact with at the same time as the cock lip contacks the the lock plate.  The bridle stop is continually dressed till both cock and tumbler contact their respective stops at the same time.  Hence the shock of the mainspring is absorbed and spread over a wider area.      That's how I do it,     Hugh Toenjes

Thanks Hugh,

Not sure if I would have thought of that and that would be easier than welding up the shoulder of the cock or something else. 

Gus

[Jim Kibler]

In the few locks I've made, I've set them up so the tumbler stops with the cock.  That being said, I'm not sure how critical this really is.  Given the huge number of production locks that do not have a positive tumbler stop surely we would have heard about tumbler failures if this was a necesity.  There are a whole list of other features that I'd worry about before this.  It's certainly something that can only help though.

[Curtis]

Gus,

On the lock in my current build, the cock would strike the plate before the tumbler would stop.  In order to get them to stop at the same instant I simply relieved the shelf on the cock (that strikes the plate) with a file.  When doing this you have to keep in mind that the angle of the shelf will change slightly as the cock rotates further.  I hope this makes sense the way I typed it.....

[B Shipman]

After more than 30 yrs. of experience, the first stop should be the hammer on the plate. File the hammer stop so that it hits inboard of the edge of the plate avoiding the edge of the plate being smashed. There is far more meat here than on a relativaly fragile internal bridal.  Ideally the internal stop should be close so that wear and tear will engage the bridal as well. When is the last time someone has broken a Siler hammer or any Chambers lock hammer. Not an issue.

[LynnC]

To be honest, I've been using them just the way they left Mr Chambers shop and no problems.
I like Bill Shipmans idea of filing the cock stop so as to strike inboard and not on the corner of the plate.................Lynn

[westbj2]

Bill's advise is correct as usual.  The cock shoulder has ample material to withstand the pressure/shock of the mainspring especially if both parts are case hardened.  I have never seen a cock broken in that area. 
More common on antique locks is to see the tumbler axle broken off at or near the surface of the lockplate.  In this case the bridal stop should be fitted to prevent the main spring from coming off the tumbler and potentially break out the bottom of the lock mortise.
Jim Westberg

[mattdog]

I set up all of my locks to stop via the stop on the baa ck of the cock.  I do not want the tumbler banging into the bridle.  The bridle is held by two 8-32 screws and if they get bent then they will allow the bridle to bind on the tumbler axle causing more problems.

In my humble opinion the tumbler stop is only to hold the main spring in place when the cock is not on the lock. 

One more thing: by removing material from the back of the cock you can regulate how far the cock rotates to get the flint pointing into the pan where you want it.  Be careful when doing this so that you don't get so much rotation that the main spring can slip off the tumbler.  If the tumbler stop is doing it's job then this can't happen. 

[P.W.Berkuta]

I also do this on "cap locks" but leave a aprox 0.010 - 0.015 gap to crush the percussion cap  .

Gus:   I usually have to silver solder an "anvil" or "stop" on the upper portion of the bridle for the tumbler to  come in contact with at the same time as the cock lip contacks the the lock plate.  The bridle stop is continually dressed till both cock and tumbler contact their respective stops at the same time.  Hence the shock of the mainspring is absorbed and spread over a wider area.      That's how I do it,     Hugh Toenjes

[Artificer]

A sincere and hearty THANK YOU to everyone who answered.  Your comments took most of the guesswork out of it for me and gave a LOT of good info.  Matter of fact, I wish I had thought of asking the question when I rebuilt an original 1836 Waters and Johnson Flintlock Pistol lock a few years ago. 

I have worked on both repro and and modern flintlock locks, but most of that has been military locks with maybe only a dozen original flint rifle and pistol locks for the International Muzzleloading crowd.  Most of the locks I've worked on have been 1840's - 1860's percussion locks.  Funny thing there is I have seen cracked/broken repro and original percussion military hammers.  That may have been due to poor metalurgy or improper heat treating though.

Since the force of the mainspring applied to the cock is also "spent" or used up a good deal with the flint scraping the frizzen, I can see how they got away with more refined cocks and see the points you have been making. 


Thank you again,
Gus

[Blacksmoke]

Bill Shipman:   In My 39 yrs. of muzzle loading experience I've had two Siler cocks break right at stop - I've also seen a number of old originals break there as well.   It might take 50 yrs. of lock use before a failure occurs  , so I believe in a little prevention if at all possible.    Today's investment castings are not always as solid as they should be.   Also there is the problem of the mainspring slipping off of the tumbler if the cock does break.  There goes your lock mortise!  More thoughts to ponder,   Hugh Toenjes

[flintriflesmith]

I set up all of my locks to stop via the stop on the baa ck of the cock.  I do not want the tumbler banging into the bridle.  The bridle is held by two 8-32 screws and if they get bent then they will allow the bridle to bind on the tumbler axle causing more problems. 

Bridles on the some of the better original locks also had a re-enforcing pin that was integral to the top part of the bridle and extended into the lock plate. This is shown and discussed on page 50 of JHAT Volume I (where this thread started). Many also had the front of the bridle butt against the shoulder of the lock plate bolster.
Some of the 1750-70 convex English locks, with the long sear springs that hide the screw under the cock, were set up so the tumbler could be stopped by the sear spring and had a thin extension on the tumbler that would pass over the sear screw and also come to rest on the bridle.
Gary

[Pete G.]

I'm not real enthusiastic about the tumbler smacking the bridal because in reality it is putting the force on the bridal screw, and with a lever arm at that. It is a lot of force on a small screw, threaded into a shallow hole in a soft lock plate.