Making a 100% Jenks lock copy

[dd832]

Back again, this time making (attempting to anyway) a full size Jenks mule ear lock. Here's a photo of the Jenks lock mechanism:



and a photo of the stripped lock plate interior:


I started off machining a mild steel plate that was 3/8" x 1-1/4" x 7" long to .280" thick and making through slots in the plate to insert 2 vertical plates that hold the hammer & sear.


The metal is peened over on the front of the lock and machined off and filed flush with the plate.


here's both vertical plates inserted & peened over:


That's enough photos for this part, I'll start another to show more.
Mike

 

[dd832]

So this is the next portion, an interior photo of the two plates installed on the lock:


Here's a photo of the plate after machining & filing the peened material off:


So the next step is to machine between the vertical plates to .306" to allow the hammer to enter the slot. Also have to widened the slot to .306" in the plate. The distance between the 2 vertical plates is about .265" right now, is there is a small amount of material to come off...slowly. The slot is .748" (I think) long and there are two beveled areas on the lock, one in the back of the plate and a small one in the front of the plate that lets the hammer rotate forward.

Until next time.
Mike

 

[Metalshaper]

Wow,
never knew anyone else, that had an interest in the Jenks? Have talked to guys who own originals and they say the trigger/ sear bar combination creates an
horrible trigger pull.. ( heavy with lots of drag ) pictured are a few of the parts I've made for one.

Respect Always
Metalshaper/Jonathan

 

[dd832]

Metalshaper, the sear engagement is very deep but the sear releases easily from full cock. In the second photo I posted you can see the wear marks on the sear arm from the trigger pushing up against it. (all my photos are thumbnails & will enlarge when you click on them) The trigger is a standard trigger arrangement and probably would have been lighter if the trigger pushed vertically against the sear rather than pushing up from underneath. The trigger pull isn't horrible at all but is heavier than I like. I think if the full cock engagement wasn't so deep it would be lighter, but that probably isn't ideal in a military weapon.

Mike

 

[Metalshaper]

fair enough? I have never handled an original so I'll defer to you on how the lock works. I was just commenting on what I had been told by owners/shooter of originals? maybe their guns were not that great? Are you making a copy, "just because"? or to save the original?? I'll leave you to it, Nice work btw!

Respect Always
Metalshaper/Jonathan

 

[dd832]

Thanks Metalshaper!
I'm attempting to make a copy of the lock because when the Jenks was being released for review an officer stated that the breech loading system was a waste of time & the carbine could be loaded just as fast from the muzzle. So Jenks made a muzzle loading version of his carbine. I have a small photo of this version, but we'll see how this lock goes first.
Mike

 

[springfield art]

Back again, this time making (attempting to anyway) a full size Jenks mule ear lock. Here's a photo of the Jenks lock mechanism:
View attachment 133357
View attachment 133358

and a photo of the stripped lock plate interior:
View attachment 133359

I started off machining a mild steel plate that was 3/8" x 1-1/4" x 7" long to .280" thick and making through slots in the plate to insert 2 vertical plates that hold the hammer & sear.
View attachment 133360

The metal is peened over on the front of the lock and machined off and filed flush with the plate.
View attachment 133361

here's both vertical plates inserted & peened over:
View attachment 133362

That's enough photos for this part, I'll start another to show more.
Mike

Machinists rock!

 

[dd832]

I have never handled an original so I'll defer to you on how the lock works. I was just commenting on what I had been told by owners/shooter of originals? maybe their guns were not that great?

Here's a photo of the lock at full cock, you can see the notch is quite deep and adds to the heavy trigger pull (click on the photo to enlarge):

 

[dd832]

Well I gave up on making the lockplate out of 3 pieces and built one out of a piece of 1"x 2" x 16" scrap bar. I cut the bar to 7" long and the made a long cut to narrow the bar down to about 1-5/16" wide. Then I cut off a piece that was about 3-1/4" long x 5/8"thick and another piece that was about 1-1/2" long by 1/2" thick. After I machined it (hours doing this) it sort of looked like this:

and looked this from the front:


I've got the hammer about 85% done today and it fits in the lock plate:


So this is where we are today:


So now I have to drill the lock plate for the nipple hole and figure out how to locate the hammer pin. One the hammer pin is set the hammer will sit with the nose of the hammer in the nipple hole. On the original plate they tapered the plate from the top to the bottom so the pivot pin screw head will fit (you can see this in the photo from my reply number 8). I didn't do this, I just relieved the plate for the pivot screw instead, you can see the relief area in the 1st & 3rd photos of this tread.

Well that's all for today. More shenanigans & swearing tomorrow. Mike

 

[dd832]

Worked on the hammer some more and fitted the hammer pivot pin:


Mike

 

[dd832]

More progress today:


Mike

 

[Metalshaper]

Mike,

Jonathan here, what caliber are you gonna end up with? where are you sourcing your barrel?

Respect Always
Metalshaper/Jonathan

 

[dd832]

Mike,
Jonathan here, what caliber are you gonna end up with? where are you sourcing your barrel?
Respect Always
Metalshaper/Jonathan

Don't know right now, I haven't finished the lock yet.

Anyway, I have to make the main spring again. I thinned out the leaf too much & it keeps bending. I heated & tempered it twice yesterday and I got nothing to show for it. The sear spring seems okay, but the main spring just bends. I've been cooling it in ATF fluid, but doesn't seem to work. Maybe I'll try water next time? The spring should look more like the original in reply #8.

Back to the shop for now. Mike

 

[Metalshaper]

I heat my springs to a cherry red/low orange <Non magnetic > and quench in cooking oil. Clean that all up
and it goes into my Lee production pot, set on the lower end of the temp range. I submerge the piece and let it set to soak.
when it's done the molten lead should just slide right off and leave you with very lil cleanup. nice and robin egg blue, until
I polish them back..

at least that's how I've managed to get it to work??? My buds tell me I tend to make rather robust springs

Respect Always
Metalshaper/Jonathan

 

[dd832]

I heat my springs to a cherry red/low orange <Non magnetic > and quench in cooking oil. Clean that all up
and it goes into my Lee production pot, set on the lower end of the temp range. I submerge the piece and let it set to soak.
when it's done the molten lead should just slide right off and leave you with very lil cleanup. nice and robin egg blue, until
I polish them back..
Respect Always
Metalshaper/Jonathan

I do the same thing as you. I heat the spring to cherry red and dunk in ATF & this time into water right after. Then soak in lead for 8-9 minutes that is 750* hot. I've done this before and never had any problems. This time the spring can be bent, so it's not hardening properly.

I'm making a new spring out of different material and we'll see how it goes.

When you say robins egg blue which color are you talking about, 650* or 730*?


Mike

 

[Metalshaper]

When you say robins egg blue which color are you talking about, 650* or 730*? >>>>

other direction on your visual actually, it's kind of what would be right in the 625-630* range..
by color, to my eye, 590 is too cool and 650 is a bit on the high end.. Depending on the steel either might be fine??
730 is way too high for the 1075 and 1095 stock i've been using??

I learned temp colors blacksmithing.. and just by visual referencing.. so I may be off compared to others?

Respect Always
Jonathan

I should get a good IR gun or thermometer and see what my Lead pot is set at when I temper..

 

[dd832]

Well it is done - the mainspring that is. I heated it with my acetylene torch, quenched it in ATF & water and tempered it in my Lee 20 lb. pot. I tempered it twice in the lead pot. I used my Lyman digital thermometer to check the lead temp. But anyway it looks OK and time will tell.
This is what it looks like now:



So tomorrow I'll trim the sear nose & cut notches in the hammer. Then I'll machine the plate thickness to the final dimension & trim to the final shape. Then parts will be hardened.
Mike

 

[Metalshaper]

Mike,

your killing me what was the temp of your lead???? just curious and what "color" did you see?
Shop lights are notoriously yellow, so in my shop I try to gauge color under old style light bulbs
or go outside... the new spring looks like its a bit thicker!!

Respect Always
Metalshaper/Jonathan

 

[dd832]

your killing me what was the temp of your lead???? just curious and what "color" did you see?
Shop lights are notoriously yellow, so in my shop I try to gauge color under old style light bulbs
or go outside... the new spring looks like its a bit thicker!!
Respect Always
Metalshaper/Jonathan

I put the mainspring in the lead pot twice. The first time the lead was 625-635*, the second time the lead was about 640*. Both times were about 10-12 minutes dunked into the lead. The color of the steel was about the 440* in the color chart above ( in fluorescent lights) when I pulled it out.

The mainspring pretty much duplicates the thickness & curve of the original spring. I'm pleased with the results.
Mike

 

[dd832]

Made good progress today. First I trimmed the sear to length and worked on cutting the half-cock & full cock notches in the hammer. After hours of filing I finally got the lock to hold at full and half cock.

So now it's trimming the rectangular lock plate to shape. I traced the lock outline onto card stock and cut it out. Then I traced the outline on to the lock plate. But how to cut it out? I cut a 3/4" board to the same size as the lock plate and cut an area out for the two vertical plates. Then to the bandsaw and after a rough cut it looks like this:


After some milling and 8" disk sander work it looks like this:


The wood base helps a lot when using the disk sander, not only in control but also shields your fingers from the heat some.

And last a shot of the lock at full cock:


Tomorrow more lock plate shaping.
Mike