Siler tumbler fit question

[Chrisweiler]

I dissembled my left hand Siler for stock fitting/finishing etc. The tumbler seems to have a loose fit in the lockplate. Is this normal? Inner diameter of the tumbler hole run's around .312" on my caliper. Outer diameter of the tumbler where it enters the plate is around .310". The lock functions fine and smoothly enough, just curiosity. 

[Mark Elliott]

I think a .002" tolerance is just fine.   There is no way the plate alone will keep the tumbler from tilting unless the fit is too tight to turn freely.  The purpose of the bridle is to stabilize the tumbler and keep it on axis.   The tumbler should be free enough to fall without a mainspring on the weight of the cock alone.   That pretty much dictates a .001-002" gap.
 

[Bob Roller]

I think a .002" tolerance is just fine.   There is no way the plate alone will keep the tumbler from tilting unless the fit is too tight to turn freely.  The purpose of the bridle is to stabilize the tumbler and keep it on axis.   The tumbler should be free enough to fall without a mainspring on the weight of the cock alone.   That pretty much dictates a .001-002" gap.
 

Right on target,Mark. I will add that bridle screw(s) should be checked to make sure that
the mechanism is running true. If NOT,it can do damage to the tumbler hole in the plate.
I have seen this on one of may Hawken caplocks years ago.

Bob Roller

[flehto]

For the small  dias on a tumber and their corresponding holes in the lock plate and bridle, I think .002 "slop" is excessive.  Perhaps it's my thinking as a tool and diemaker. but slip fit clearances are commensurate /w the dias. .002 clearance might be suitable for a shaft and hole of say 4" dia., but for the very small dias of  tumbler shafts, the clearances should be in .0001s......Fred

[Chrisweiler]

Thanks for the input all.

Bob at what point would you say it's excessive? When the locks all together the cock is snug as far as side to side play. So the bridal is doing its job.

The gentleman helping me build the rifle said that with the Walt Cain locks he always used the tumbler was always very tightly fit in the lock plate, made me ask the question

[okieboy]

 One primary question in this discussion (no offense meant toward Chrisweiler) is, how good are the calipers that are generating these measurements? Have they been gage block calibrated for both inside and outside measuring? And how good is Chris at using (the old machinist's feel) them? It seems possible that the slop Chris feels might be more than what his calipers tell him. Measuring tools not measuring accurately is why manufacturing shops devote resources to calibration. Checking  that measuring tools had up to date calibration stickers was a major audit item at the shop I worked at. So it is possible that Chris's measured .002" could actually be .003" or .004". 
 Fred's point about clearance varying with diameter is very good. But clearances also vary with price point production levels; expensive individually hand made locks have tighter clearances than less expensive production locks.
 Just thoughts.

[Chrisweiler]

These calibers are on the cheaper end ($30), and digital. Good enough for pistol cartridge reloading. My method for measuring inner and outer diameter was to take a measurement, record, set
Down calipers, then measure again. Five times total for average. The slop is more noticeable by feel vs actual measurement. Figured it just supported my question to add in some actual numbers.

[Bob Roller]

These calibers are on the cheaper end ($30), and digital. Good enough for pistol cartridge reloading. My method for measuring inner and outer diameter was to take a measurement, record, set
Down calipers, then measure again. Five times total for average. The slop is more noticeable by feel vs actual measurement. Figured it just supported my question to add in some actual numbers.

Small hole gauges and micrometers calibrated in 0001's works for me.

Bob Roller

[Bob Roller]

Thanks for the input all.

Bob at what point would you say it's excessive? When the locks all together the cock is snug as far as side to side play. So the bridal is doing its job.

The gentleman helping me build the rifle said that with the Walt Cain locks he always used the tumbler was always very tightly fit in the lock plate, made me ask the question

Walter Cain was a FINE lock and trigger maker. I was speaking  of sdrews in the bridle working loose and
letting the tumble tip a little. It takes but little to elongate the tumbler hole in the plate.Maybe a case hardened plate would hold up better but checking the internal lock screws is a sure way to see what is happening.

Bob Roller

[bob in the woods]

We are talking about a standard production run Siler , right ??    Considering the quality of the finished product, they're still a deal.  Any tighter tolerances , and I expect you'd double the price, with little if any effect on performance. 

[ddoyle]

My left hand silers are in that range, I kind of considered them the bench mark of perfection. My L&R left hand locks fit orders of magnitude looser and that is a looser fit with the axles still un-turned, unpolished and as cast. Once the axles are made round and lightly polished things positively rattle.  Make the tumbler hole in the plate round and you could throw a cat thru the gap. No problem though just buy some starret ball gauges, some expensive bronze, a collet chuck or 3 and spend a winter practicing making and trashing bushings  and eventually all will be mostly right

The great thing about a Siler from the Chambers shop is you know it is either right or will be made right. Bargain. You pay your money once.

[Jim Chambers]

If you will check our competitor's tolerances I believe you will find we build far more precision in our locks than any others.  Having said that, we could certainly hold the diameters to much closer tolerances if we hand fitted the parts to each individual lock.  It's just a matter of how much are you guys willing to pay for more precision.  Some guys already think we charge too much for our locks.  What would they think if we held tolerances to .0001 and doubled or tripled the price of our locks?  Any takers?

[ddoyle]

Jim,

It is a dam shame that people will not pay the extra for an even better product. IMHO locks should be a 500 dollar item, barrels the same (with quality to match) and let the chips fall where they may for wood and furniture. We seem to have raced to the bottom with abandon.

we'd all be better off saving and scrimping to buy one or two first quality guns then we are with safes full of 'good enough' guns. 

That said I am not really sure where you would find room to improve anything on the locks that I have from your shop? Keep up the good work you make the competition look pretty bad

[David R. Pennington]

I have never had an issue with a Chambers lock, did have one from another maker once that had tons of slop in the tumbler hole, I turned a little bronze bushing and refitted tumbler shaft.

[oldtravler61]

Worked in a machine shop almost 40years. Over half that in Quality Control. Number one it doesn't take any longer to do it right than it does to do it wrong. What adds to precise work. Is the quality of the cutting tools, the metal being used excetra. As for Jim Chambers locks. Have three. Never ever had a problem. An yes the guns are fired alot. An lastly he stands behind his products.

[David Rase]

I have only assembled a few locks.  The ones I have done I drill the lock plate and bridle and then turn the tumbler axle diameter's to a zero clearance fit.  I then use diamond lapping compound and lap the fit until it frees up.  After I remove the lapping compound I add a drop of oil to check the fit for any hang ups or tight spots.  You must have enough clearance for lubricant.
David 

[little joe]

A friend asked me to post this as he has no computer. Locks and bbls at 500 apeice he would not be using 6-8 Chambers locks and Rice bbls per year.  Have Bob Roller do you a lock and you will have the  best in the business however it will cost more.

[Bob Roller]

If you will check our competitor's tolerances I believe you will find we build far more precision in our locks than any others.  Having said that, we could certainly hold the diameters to much closer tolerances if we hand fitted the parts to each individual lock.  It's just a matter of how much are you guys willing to pay for more precision.  Some guys already think we charge too much for our locks.  What would they think if we held tolerances to .0001 and doubled or tripled the price of our locks?  Any takers?

Jim ,
"Some guys think we charge too much for our locks". I think they are part of a fading crowd from years ago that think that ANYthing made for a muzzle loader MUST be well made and CHEEP. Remember last Fall at Friendship when I told you "I won't pay anybody to buy my work" and you thought it was a good saying.Use it. You have a fine product and great displays of it and NO reason to reduce prices that I can see.

Bob Roller

[bob in the woods]

Look back to my post. It was totally in line with what Jim Chambers said. What wasn't mentioned is that the locks as is are totally functional and dependable as is .  Like I said, there are always those who want the next level up...just because. That's fine if they are willing to spend the $ , but there are some folks out there who offer lock tuning services and charge accordingly. The honest truth is that I can't afford to pay much more for the components I use, because I can't pass along the extra cost.

[Chrisweiler]

Personally my chambers lock is very well fitted and smooth in operation. forget offhand what the difference in a kit vs. assembled lock is, but for a beginning flintlock builder it's WELL worth it. My questions about tolerances stem more from a desire to learn and generally curiosity about the locks operation. The lock didn't need anything done with it from a functionality standpoint, but of course there's always that desire to see if you can tweak something for better performance. I bought a chambers lock because my understanding is that they are the standard by which others are measured and had no contacts for custom built/tuned locks. I am in no way disappointed with how my money was spent. Keep in mind you've got a new builder here (and a younger than average one) so dumb questions will arise.

[Bob Roller]

Personally my chambers lock is very well fitted and smooth in operation. forget offhand what the difference in a kit vs. assembled lock is, but for a beginning flintlock builder it's WELL worth it. My questions about tolerances stem more from a desire to learn and generally curiosity about the locks operation. The lock didn't need anything done with it from a functionality standpoint, but of course there's always that desire to see if you can tweak something for better performance. I bought a chambers lock because my understanding is that they are the standard by which others are measured and had no contacts for custom built/tuned locks. I am in no way disappointed with how my money was spent. Keep in mind you've got a new builder here (and a younger than average one) so dumb questions will arise.

Chrisweiler,
The ONLY dumb questions are the ones that don't get asked.

Bob Roller

[retired fella]

I own 2 Silers the last I built from a Chamber's kit.  I wanted the feel of what I was putting into my build.  Really straight forward stuff.  The only problem I had was the fly kept " jumping like a flea" around the workbench.  Probably added 3 hours to the build trying to find the !@*%&@ thing (happened several times).  Even with the aggregation I would do it again.  Jim, you do good stuff.

[ddoyle]

The ones I have done I drill the lock plate and bridle and then turn the tumbler axle diameter's to a zero clearance fit.  I then use diamond lapping compound and lap the fit until it frees up.  After I remove the lapping compound I add a drop of oil to check the fit for any hang ups or tight spots.  You must have enough clearance for lubricant.

Thanks for posting this, I think you might have saved me.

[Jim Chambers]

When I build a lock to go in one of my fancy custom rifles I do basically what David said above.  I turn the tumbler axles oversize and then carefully polish them so they are a very tight slip fit in their respective holes.  I do basically the same for fitting all the parts in those locks.  It is not unusual for me to spend a week on that one lock.  I could build locks the same way for you guys who want more quality in a lock, but I doubt many of you would want to pay me a week's salary for a lock.
Keep in mind, for those of you who want to try your hand at making a lock to your specifications and save a bunch of money, we still sell the Siler locks in kit form.  We're more than happy to sell you all the parts.

[thimble rig]

I have 6 different styles of chambers locks.Ive never has a problem with any of them.I do want to try one of the kits though.I think that would be a good project to try.