doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Slot Lineup on Screws

In a effort to keep the slot lineup on all screws in correct lineup, I need a question answered before I go any further on a project I am into at this time. I am making some firing pins and screw-in bushings for an old Elsie I acquired, that these pieces had been cracked and broken, when someon attempted to remove them because of a broken firing pin. So, before I cut the screw slots in the new bushings, which way should I make them face...Parallel to the landing or perpendicular to it?

thanks
binko

The ones I have are perpendicular and I also have an 1897 Grade 3 that has tiny copper screws locking them in perpendicular also.
I don't know if you know but the firing pins were made out of chrome vanadium (SAE 6150).

These, pins and bushings, will be made of grade 8 alloy. I think that will be sufficient for strength. Do you have an opinion?

binko

Binko,
If you mean you will make them from a grade 8 bolt, that should work o.k.. But, there are better choices if you have the ability to heat treat and/or have access to other materials. Grade 8 refers only to the tensile strength (150,000 psi in this case, equating to about 40 RC hardness) and the alloy remains somewhat optional to the manufacturer. Cheap grade 8 bolts will be made from low alloy steel with moderate carbon content to get it to harden during heat treat. Fracture and fatigue characteristics of a hardwarestore grade 8 won't likely come close to an aircraft quality grade 8 bolt. There are other specs to control aircraft bolts that specify these other characteristics.

Nevertheless, a common grade 8 bolt is better than a piece of mild steel for what you're doing. The 40 RC hardness is about as soft as you may be able to get away with. On a low usage gun, it should be fine. On a Perazzi target gun that will see tens of thousands of rounds, it'd be a temporary fix for the firing pins.

I don't think I would try to make the bushings from Grade 8 bolt steel. They were made out of soft steel with 32 threads to the inch and I thnk you will have trouble threading the Grade 8 material.

I was able to acquire, from an industrial bolt supplier, 4 cap screws in grade 8, 32 threads to the inch, which had been a special order for a chemical plant here in the BR area. Normal availability was only 24 TPI, so I jumped on them. My other option was to make them out of mild steel and harden them with "Kasenit", but I was afraid of them becoming to brittle?

decisions
binko

A grade 8 shouldn't be soft steel, it should be about high 30's or low 40's RC, which is pretty hard but not brittle by any means. About like a bolt action reciever from Rem or a little harder. The bushings will be fine in this metal. The firing pins could be a bit harder to last longer, but I think you'll be ok for the short run at least..

It is late at night here and I'm tired so I can't check out the technicalities, but engineering wise I would trust Chuck with my life.So he is giving good advice, but when you think of what the pins do they are nothing more than a pin punch.So what ever the engineering spec. is for pin punches should suffice.Bushes made from Grade 8 capscrews will last longer than the Titanic, but that was only a week despite assurances it was indestructable.

If you harden any mild steel with "Kasenit" it will only penetrate 5 to maybe on a good day 10 thousands of an inch, so the chance of them becoming brittle is slim. The outside may be hard and show stress cracks but the inside will still be mild steel.

The big question is, the bushings o.d. is .307 too big for 1/4 32, so maybe 5/16 32, threads are usually smaller than actual size of .3125.
It is just a bushing, soft mild steel is all they were made of, no need for them to have any temper to them.
The firing pins should, and I believe the Grade 8 bolts will be fine.