The trail is getting cold. It's not easy making Thompson parts

[reconbob]

     The trail is getting cold... the knowledge, the skill, and the tools and machines to make

Thompson parts that were once commonplace, are now rare or completely gone.

    I came across a new manufacture "Colt" style cocking knob for the semi autos. The knurling

is not a diamond knurl, but by generated by some type of "sawtooth" cutter which does not create

a diamond knurl, just mush.

    I have no doubt that whoever made these did the best they could, and they consider the product

to be Colt quality. 

Bob

M1921 Colt actuator with diamond knurl

New manufacture "Colt" knob with sawtooth knurl

  

[TSMGguy]

Sad.

[TD.]

I don't know anything about the Thompson semi-automatic carbines, but I do know that cocking knob still looks much better than the original corn-cob type that is featured on many of the older West Hurley semi-auto carbines. 

What we need is someone to manufacture a Colt Style 1921 actuator with the pear shape between the cocking ears and with expansive knurling. Doug Richardson made a beautiful display 1921 style actuator with excellent knurling (although not a perfect match of the Colt era knurling). Unfortunately, Doug would not modify the original Colt era design so the cocking ears would not break off after repeated use. Maybe someone will copy Doug's design but strengthen the cocking ears. 

Hint, hint, hint...reconbob 😉

[StrangeRanger]

43 minutes ago, TD. said:

I don't know anything about the Thompson semi-automatic carbines, but I do know that cocking knob still looks much better than the original corn-cob type that is featured on many of the older West Hurley semi-auto carbines. 

What we need is someone to manufacture a Colt Style 1921 actuator with the pear shape between the cocking ears and with expansive knurling. Doug Richardson made a beautiful display 1921 style actuator with excellent knurling (although not a perfect match of the Colt era knurling). Unfortunately, Doug would not modify the original Colt era design so the cocking ears would not break off after repeated use. Maybe someone will copy Doug's design but strengthen the cocking ears. 

Hint, hint, hint...reconbob 😉

Wasn't someone (Ben Edwards??) planning on making a '21 actuator clone with strengthened ears?

[reconbob]

        I have been working in what little spare time I have on an original quality, original specification

M1921 actuator. My plan of attack is to first figure out how to machine the ball knob. The pear shaped

sighting slot is easy - that is straight up-and-down machining. The knurl is no problem, other than you

can't get the original 32 lines per inch knurls, and so have to use 36 line per inch knurls. Even the 36 line

knurls are $850 a set.

      But even though I have the original tooling from Doug, I have not been able to hollow out the ball 

as called for on the original drawing. I won't go into boring detail, but I think I have figured this part out.

Once the ball knob is figured out then I will work on complete actuators, although I plan on doing Colt

M1928 actuators first (I have the original drawing) and then converting them by machining away the body.

     I may have mentioned - Doug did not make his actuators. He provided special tooling but the actuators

were made by two other shops out in LA. I checked to see if they would make more, in one shop the guy had

passed away, in the other they remembered the job and wanted no parts of it.

     Way back I talked to Doug about his actuators and he knew about the problem with the ears breaking

off. He offered to make them stronger, but said that everybody he talked to wanted them to be exactly like

the original, so that is how he made them.

Bob

[Merry Ploughboy]

2 hours ago, reconbob said:

        I have been working in what little spare time I have on an original quality, original specification

M1921 actuator. My plan of attack is to first figure out how to machine the ball knob. The pear shaped

sighting slot is easy - that is straight up-and-down machining. The knurl is no problem, other than you

can't get the original 32 lines per inch knurls, and so have to use 36 line per inch knurls. Even the 36 line

knurls are $850 a set.

      But even though I have the original tooling from Doug, I have not been able to hollow out the ball 

as called for on the original drawing. I won't go into boring detail, but I think I have figured this part out.

Once the ball knob is figured out then I will work on complete actuators, although I plan on doing Colt

M1928 actuators first (I have the original drawing) and then converting them by machining away the body.

     I may have mentioned - Doug did not make his actuators. He provided special tooling but the actuators

were made by two other shops out in LA. I checked to see if they would make more, in one shop the guy had

passed away, in the other they remembered the job and wanted no parts of it.

     Way back I talked to Doug about his actuators and he knew about the problem with the ears breaking

off. He offered to make them stronger, but said that everybody he talked to wanted them to be exactly like

the original, so that is how he made them.

Bob

Thanks for the status report.  And a nice pun there, also [I bolded it so it would stand out].

[68coupe]

10 hours ago, TD. said:

I don't know anything about the Thompson semi-automatic carbines, but I do know that cocking knob still looks much better than the original corn-cob type that is featured on many of the older West Hurley semi-auto carbines. 

What we need is someone to manufacture a Colt Style 1921 actuator with the pear shape between the cocking ears and with expansive knurling. Doug Richardson made a beautiful display 1921 style actuator with excellent knurling (although not a perfect match of the Colt era knurling). Unfortunately, Doug would not modify the original Colt era design so the cocking ears would not break off after repeated use. Maybe someone will copy Doug's design but strengthen the cocking ears. 

Hint, hint, hint...reconbob 😉

The newer Kahr's have those "Cheese Grater" charging knobs, too. It must be considerably cheaper to produce, as that seems to be their business model. "Make 'em as cheap as we can, so we can to make the most profit". Mine, purchased at least a decade ago has the nicer one. Some run fine out of the box, others need quite a bit of tuning. West Hurleys had a better reputation, however slight. There is a board member making replacements for the cheese graters (Shameless plug). They look pretty close to mine. The knurling is done well, and nothing like knob in that ghastly photo in the first post.

Karl, 68coupe

[DARIVS]

They are much easier to make.  To knurl a ball shape on my lathe, I have to reposition the knurling tool at several angles to knurl an arc across the curved surface of the ball.  It takes time, patience, and care to do, and you don't want to cross knurl and make a double impression on the metal after you change the position of the tool.  So, when James offered to sell properly shaped parts with the knurling for only $65.00, it was a no brainer to buy one.

[Motorcar]

Bob,

I have one of Doug's semi auto '21 style actuators on my PK'ed semi. When I spoke to Doug about it many years ago he made no mention of it being a "display" piece or not serviceable in any way. His catalog had them as a direct replacement.  Have you found them to have a high failure rate or dangerous in any way?

[reconbob]

     This is a good question. It is often mentioned that one of the ears on the knob on

a M1921 actuator can break off. But how many actually have? The only guns left are 

those in the registry. Is that 1000? more? less? If it's 1000 have 50 actuators broken?

100?

     I have one of Doug's actuators with a broken ear. But on his actuators the hollowing

out of the ball is deeper (in an up/down direction) than on an original Colt actuator,

causing an even thinner cross section making the ear more likely to break off.

Bob

[Centrifugal Arms]

I have a Richardson 21 actuator that both ears broke off (in the same magazine) about a week ago… I was less than thrilled with myself for using it that day. It had been fired very little too.  I will post pictures if there is any interest.

Edited May 17 by Centrifugal Arms

[Motorcar]

It was a '27 semi auto Richardson similar to the one I posted above or a full size Richardson '21 full auto actuator?

He produced both, I imagine he did the ears and depth the same for either.

[TD.]

Great question reconbob. I have no idea regarding the failure rate of Colt era or Richardson actuators. That said, I have seen enough broken ones over the years to know it is a problem. A nice 1921 Colt actuator is $1500 plus in today's market when you can find one. Why take the chance. I do know from speaking with Doug years ago that he had to replace a number of his broken actuators. I actually had one break on me when dumping a L drum. If Colt era actuators were a hardy piece, there would be no need for anyone to make a replacement given the number of Form 10 Thompson guns that were cut up years ago. Original actuators would be plentiful. I have also seen a number of NAVY Colt's with USGI 1928 actuators. It appears this variation also had issues in the past. 

I believe the safest route for Colt owners with shooter grade guns in 1921 style is to use a cut-down USGI 1928 actuator with one of PK's hybrid 1921/1928 buffer pilots. If just running 1928 internals, a USGI actuator with a polyurethane buffer disc is the way to go. Those with my Amateur's Guide book can turn to pages 88 and 89 to see the results of using an original Colt era actuator at the range. Don't be that guy!  

[jirahice]

I think I recognize that actuator.

I have no idea the requirements of machining tungsten, but a heavy 1928 profile tunsgsten actuator would be interesting. I've always thought it would be amazing to have a Thompson that fired at the rate of an M3. In the same vein as the Mac 10/11 CFW tungsten bolts. 

[Merry Ploughboy]

7 hours ago, jirahice said:

I think I recognize that actuator.

I have no idea the requirements of machining tungsten, but a heavy 1928 profile tunsgsten actuator would be interesting. I've always thought it would be amazing to have a Thompson that fired at the rate of an M3. In the same vein as the Mac 10/11 CFW tungsten bolts. 

A heavier (e.g., tungsten alloy) actuator would cause very premature Blish lock piece breakage.  Even with the current weight, the Blish lock piece does occasionally break.

MHO, YMMV. etc.