Problem building a lock from castings………HELP! [Fixed - Thanks!]

[Robert Wolfe]

I got this early Dutch lock from TRS and have been slowly putting it together. (Note: I am a lock building novice, this is number 2.) I installed the mainspring but it interferes with itself before getting to full cock – see pics.

Did I need to screw the mainspring higher on the lock plate? I can take it a little bit higher by filing off the tit above the screw but not a bunch (16th inch?). Higher than that and it will interfere with the pan. What am I missing?

Thanks in advance.



Cock down


Half cock


Almost full cock. Arrow shows there the mainspring interferes with itself.

[Bob Roller]

File a radius around the screw head and that MIGHT give the room needed to get to fully cocked.I noticed the mainspring at low point is almost off the tumbler or appears to be so,I have never tried a lock from a kit and can't speak from experience.Now that I have changed glasses I think the hole where the upper limb stud goes thru is a bit too high and it can be plugged and redrilled to lower the front of the spring and change the geometry of the whole thing and get the spring where it belongs including the fired cock down/fired.One more thing as Lt.Columbo used to say.The cock is NOW too far back in that lower picture and the full cock looks like anther safety.I wonder if this sin't a case of mismatched parts.
Bob Roller

[DavidC]

Is there a small key and keyway preventing you from rotating the spring slightly? It needs a slight counterclockwise rotation but that looks like it will cause the tumbler to hit inside of the radius at the spring top rather than the very edge.

[Bob Roller]

File a radius around the screw head and that MIGHT give the room needed to get to fully cocked.I noticed the mainspring at low point is almost off the tumbler or appears to be so,I have never tried a lock from a kit and can't speak from experience.Now that I have changed glasses I think the hole where the upper limb stud goes thru is a bit too high and it can be plugged and redrilled to lower the front of the spring and change the geometry of the whole thing and get the spring where it belongs including the fired cock down/fired.
Bob Roller

[D. Taylor Sapergia]

In your last photo, it appears that you may be able to remove a bit of metal from the lower edge of the screw boss of the mainspring, and even a little of the screw's head to allow the cock to rotate just a little more.  Don't file anything off the spring's arms.  But you may need to file out the hook just a bit for the tumbler's foot.

[rich pierce]

What do folks think of moving the mainspring to the right a smidge?  Not likely to solve the issue?

[kutter]

If you file out the tumbler a little so the spring isn't lifted as high , I think the front point of the tunbler notch will still push the spring up too high at full cock.
You can't cut that front point down any as it now just barely engages the spring hook when the hammer is at rest.


I would  remove the spring, plug the hole in the plate for the attachment screw.
File off some of the matrl on the spring above the screw hole so the spring attachmnet point sits higher.
Also plugging and redrilling for the stud on the side of the spring arm as well. Lowering that stud placement bringing the leaf down.
Readjusting the two positions  you can place the spring exactly where it will function w/o interference.

[Robert Wolfe]

Thanks for all the great advice. I think I have it licked using several approaches suggested:
1.   I plugged the stud hole and lowered it a bit to change the angle of the lower limb of the mainspring.
2.   I took some more off the lower edge of the screw boss to pick up a little more room.
3.   I had to take a little out of the mainspring hook to clear the tumbler’s foot at full cock.
4.   And finally, I had to file out a little of the full cock notch to get the sear to drop in cleanly.

Here are pics with the adjustments. Look OK?

[RAT]

Has anyone thought of simply creating a new full cock notch in the tumbler? The existing notch seems pretty deep. That's going to give you one really long/heavy trigger pull. For someone with welding skill  (not me) the notch could be filled and re-filed. I have a Jack Brooks gun where he brazed a piece of steel into the notch and re-cut it.

[rich pierce]

Looks solved!  Win!

[Robert Wolfe]

Rich, that is one of the great things about this site. Ask and ye shall receive wisdom from on high.

[Bob Gerard]

Congratulations on correcting the issue! Boy that cock really goes far back. One heck of a throw!

[Robert Wolfe]

Thanks Bob. It is a beast of a lock. I suspect it won't set any speed records!

[smart dog]

Hi Bob,
I cannot help but believe that lock is going to catch at half cock when fired unless the trigger pull is very heavy.  A way to mitigate that if you can is to measure the distance from the center of the tumbler or center of rotation, to the lip of the half cock notch and also measure that distance to the lip of the full cock notch. Ideally, without a fly detent, you want those distances to be equal or better, the distance to half cock being a little less. That way the distance your finger pressure must hold the sear away from the lip of the full cock notch when fired is sufficient to keep the sear clear of the  half cock notch as the tumbler rotates forward during firing.

dave

[Robert Wolfe]

Thanks Smartdog - I will check this out. I have only released the cock from full cock softly in my hand so far as the frizzen and top jaw are not in place yet. I will come back around to this as I get the lock fully put together.

Thanks again. There are way more nuances to lock construction than one would think.  I have been spoiled by Chamber's locks over the years.