Jump to content


Photo
- - - - -

Inspecting And Testing 1928 Thompson Locking Slots


  • Please log in to reply
13 replies to this topic

#1 dalbert

dalbert

    Website Owner

  • Admin
  • 4571 posts
  • Gender:Male
  • Location:Ohio

Posted 26 December 2010 - 12:19 PM

All,

First, I need to sincerely apologize to PK for it taking me so long to post this. We communicated about a tutorial on this topic over a year and a half ago, and I was ready to post it, and then I got sidetracked and forgot about it. The recent thread about cracked West Hurley receivers prompted me to remember it, because some of the same pictures were used. A link will also be added to the pinned Thompson Reference Post at the top of the board.

I want to thank PK for putting this together. The material is copyrighted by Paul Krogh - Diamond K, and the text is displayed as pictures to discourage use on other sites.





Supporting Pictures:





Cracked WH Receiver Pictures:





David Albert
dalbert@sturmgewehr.com


  • 0

#2 Sig

Sig

    Respected Member and Board Benefactor

  • Moderator
  • 1652 posts
  • Gender:Male

Posted 26 December 2010 - 04:42 PM

seem to remember a post about abuse and receiver cracks
  • 0

#3 The1930sRust

The1930sRust

    Respected Member and Board Donor

  • Moderator
  • 1939 posts
  • Gender:Male
  • Location:Confederate, Kentucky
  • Interests:Thompsons, obviously. Proud West Hurley 1928 and Savage M1 owner, cave explorer, and KSP trooper (retired). Also interested in 1920-1930 American history. I appreciate all Thompson models and their owners.

Posted 30 January 2013 - 07:35 AM

Should be pinned or linked someplace at the top perhaps?
  • 0

#4 mike in pa

mike in pa

    Regular Member

  • Regular Group
  • 201 posts
  • Gender:Male
  • Location:ne P.A.

Posted 30 January 2013 - 09:58 PM

seem to remember a post about abuse and receiver cracks


Cracked receivers were usually caused by speed bolts or by removing the Blish lock ears.
  • 0

#5 Chief762

Chief762

    Long Time RKI Member

  • Board Benefactor
  • 268 posts
  • Gender:Male
  • Location:Louisiana
  • Interests:Old Mustangs, single-cam Harleys, good Scotch whisky and US gold coins. Oh, and Thompsons.

Posted 30 January 2013 - 10:24 PM

I visited my Westie yesterday at the dealers, and he was nice enough to let my use his bench and some tools. I stripped the gun and really examined the lock slots. They looked like the Bridgeport receiver pictured in PK's examples. No off angled cut on either side. I didn't do the "dime" test, tho. It's a 1979 mfg date gun, and maybe it's one that got done right on a Wednsday, rather than a Friday/Monday gun. We'll (dealer & me) shoot it next month and I'll post some interior photos.
Chief
  • 0

#6 reconbob

reconbob

    Technical Expert

  • Board Benefactor
  • 2418 posts
  • Gender:Male

Posted 02 February 2013 - 07:57 PM

PK - You are the expert on the WH locking slots. So I am asking the expert - is the
cracking of the WH receiver cause-and-effect with the improperly machined H-lock slots?
How many cracked WH receivers have you actually seen so far - 25? 50? More? This would
be of interest because one could weigh the odds of his receiver cracking.
Do you think it is possible that the receivers could be cracking because of the soft
steel used for these receivers regardless of the locking slots? Have you ever seen
a WH receiver with correct locking slots but still with a cracked rear? Put another way,
do you think that any WH receiver will eventually fail as shown in your photos?
As you know we manufacture 100% receivers here and I have a special gage I made
to measure the position of the locking slots we machine in the receiver. Every chance
I get I use the gage to check original or WH guns. I have encountered a couple of WH's
where the slots are correctly formed but are way off (0.05"-0.06") in terms of front/rear location.
The owners say the guns shoot perfectly and there is (so far) no sign of any damage to
them. Do you think that even though guns like this work and shoot ok that they are headed
for a problem?

Bob

  • 0

#7 mnshooter

mnshooter

    Long Time RKI Member

  • Board Donor
  • 1962 posts
  • Gender:Male
  • Location:Minnesota

Posted 02 February 2013 - 09:26 PM

If fortunate enough to have one of the Hurley's with properly formed but misplaced blish slots as described above, would it be feasible to make a blish lock with offset ears to provide the correct bolt position?
Not even sure if the correct alloy is available, but that machine work is pretty straightforward, or at worst still easier than the slot rebuild. Easier said than done?
  • 0

#8 PK.

PK.

    Technical Expert

  • Board Benefactor
  • 1569 posts
  • Gender:Male
  • Location:CO, USA
  • Interests:Full time gunsmith who loves Thompsons, 35+ years experience.

Posted 05 February 2013 - 11:31 AM

Good questions Bob, I will endeavor to answer below. Another poster noted that often speed bolts and “de-eared” locks were responsible for cracked receivers and this is quite true, but I note that I have repaired cracked receivers on one owners gun that had never seen such adulterated parts and I have no reason to doubt them.

In all of this one has to ask the question; how much risk do I want to take with my investment? Cracked receivers are only one of a long list of maladies the WH gun can be troubled with, but that doesn't mean they aren't worth owning, and shooting. A correct WH can be just as satisfying and long lasting as any other TSMG.

Q: is the cracking of the WH receiver cause-and-effect with the improperly machined H-lock slots? A: WH receivers suffer from a plethora of malformed features that may or may not contribute to this problem; the lock slot abnormalities are a significant contributor.

Q: How many cracked WH receivers have you actually seen so far - 25? 50? More? A: I couldn't say without digging out years of records. In my practice I wouldn't say I’ve encountered a large percentage, but enough to be noteworthy. I try to get them before they are so damaged.

Q: Do you think it is possible that the receivers could be cracking because of the soft steel used for these receivers regardless of the locking slots? A: Without a doubt, the steel used is part of the problem. Properly hardened steel is much stronger and able to withstand the impact forces better. The TSMG was designed around the use of a hardened steel receiver, but even a gun with such will eventually be damaged if used without a functioning lock.

Q: Have you ever seen a WH receiver with correct locking slots but still with a cracked rear? A: I’ve never seen a WH 28 with properly machined locking slots. I do not believe that if all the pertinent interfaces are correct that receiver cracking will be a problem.

Q: Do you think that any WH receiver will eventually fail as shown in your photos? A: No. Not if it’s to specification.

Q: I have encountered a couple of WH's where the slots are correctly formed but are way off (0.05"-0.06") in terms of front/rear location. The owners say the guns shoot perfectly and there is (so far) no sign of any damage to them. Do you think that even though guns like this work and shoot ok that they are headed for a problem? A: The TSMG design is very good, and I have seen many guns that worked perfectly while eating themselves alive in a variety of ways. When they stop you usually have a lot of work to do. Every WH is a unique firearm.
  • 1

#9 newtommygunner

newtommygunner

    Regular Member

  • Board Benefactor
  • 455 posts
  • Gender:Male
  • Location:new orleans
  • Interests:guns, boats, ultralights, girls, horses, old cars

Posted 05 February 2013 - 11:46 AM

Tks for all the good info. Bob asked some great Q's and Paul gave some great answers. Mike
  • 0

#10 james m

james m

    RKI Member

  • Regular Group
  • 873 posts

Posted 05 February 2013 - 01:47 PM

The "28" used as a rental at SGC started out as one of the Philadelphia Ordnance 80 % receivers which was hogged out so a bolt could be installed. They had no way of machining the Blish lock slots and, since this was prior to Philadelphia Ordnace do so, they omitted them and cut the ears off the Blish lock. The last I knew the receiver hadn't crack(about 1 year ago) but the gun was hell on actuators. I had to replace the actuator more than once and I expect this was due to no bolt retardation. I suspect the gun was running at arounf 800 rounds per minute.
Jim
  • 0

#11 reconbob

reconbob

    Technical Expert

  • Board Benefactor
  • 2418 posts
  • Gender:Male

Posted 06 February 2013 - 08:53 AM

Paul - Thanks for the thoughtful and detailed response!
A Phila Ord receiver is going be either 4130 or 4140 steel. Either alloy is much stronger and tougher that what I believe to be the leaded steel that the WH's are made from.

Bob
  • 0

#12 The1930sRust

The1930sRust

    Respected Member and Board Donor

  • Moderator
  • 1939 posts
  • Gender:Male
  • Location:Confederate, Kentucky
  • Interests:Thompsons, obviously. Proud West Hurley 1928 and Savage M1 owner, cave explorer, and KSP trooper (retired). Also interested in 1920-1930 American history. I appreciate all Thompson models and their owners.

Posted 06 February 2013 - 09:19 AM

For what it is worth, when I had my WH radiologically tested back in 2008 for cracks, they tested the steel. The composition of the receiver and trigger frame was "Carbon steel 12L14 0.28". Fe 99.73% Mn 0.27%
  • 0

#13 TD.

TD.

    Respected Member

  • Board Benefactor
  • 3132 posts
  • Gender:Male

Posted 06 February 2013 - 09:52 AM

A: The TSMG design is very good, and I have seen many guns that worked perfectly while eating themselves alive in a variety of ways. When they stop you usually have a lot of work to do. Every WH is a unique firearm.


I have been on this Board for several years. There is one member whose posts I do not ignore: PK. One reason is because I own a 1928 West Hurley. After changing out some parts and the installation of a Richardson barrel, my WH was as described above. I was having second thoughts about spending the money with PK. to re-manufacture a Thompson that was working great. What cemented the deal was the cracking of a 28 WH receiver owned by a friend of mine that did not use any of the Speed Bolt crap sold years ago. I knew if his receiver could crack, mine could too. He did shoot his WH more often than I do but mine was no safe queen.

I took the plunge and have been very pleased with PK.’s craftsmanship. My WH is simply beautiful. Dan Block’s wood was the finishing touch! I am serious when I say I need a Colt shooter to go with my presentation grade WH.

One of my WH’s many problems was an oversized pilot hole in the rear of the receiver. PK. fixed this problem by installing a custom manufactured oversized buffer pilot. He returned my original first variation Savage buffer pilot. He pointed out how my Savage buffer pilot was wearing on one side of the rod, almost to the point where it ruined the part. This was but one of the problems my WH was experiencing as it was eating itself alive every time I pulled the trigger. If you have a WH I strongly suggest you reserve a place in PK.’s queue and shoot your WH sparingly until PK. can re-manufacture it to proper specifications. Another thought is to purchase a .22 caliber conversion kit from Merle to enjoy that full-auto feeling without worrying about cracking the back out of your receiver.
  • 0

#14 buzz

buzz

    RKI Member

  • Regular Group
  • 2059 posts
  • Gender:Male

Posted 23 September 2014 - 04:44 PM

What an interesting thread.

 

Rust, it's great that you had your WH steel tested, that explains a lot about these WHs cracking.

 

12L14 steel is carbon steel with lead in it to greatly enhance the machinability, but it also reduces the strength and toughness of the steel.

 

Toughness is the ability to absorb energy without fracturing (cracking).

 

They use it for parts where a lot of machining is done but high strength is not required, like light duty machine screws or parts for light duty consumer products like garbage disposals.

 

4130 & 4140, on the other hand, are general purpose chromoly alloy steel used for applications where fatigue resisance, toughness and surface hardness is called for, like crankshafts and piston rods.


Edited by buzz, 23 September 2014 - 04:46 PM.

  • 1