Sheer Pin for Standard Modern 9” Model A

[Emery]

Hey guy, I mixed up my direction of travel on my auto feed yesterday and started my lathe with the carriage against the tail stock and it broke the sheer pin on the leed screw. Rather easily... it was a small “pop”.

The question now is where do I get a new sheer pin? It’s 1/8 OD by 1 1/4.

Unfortunately the website won’t let me post pictures right now but my sheer pen looks identical to a 1/8 brass rod. I even went out and bought a brass rod to compare... Is this what the lathe came with?

What are you guys running in your Standard Modern 9” model A?

I have called around and “sheer pins” don’t seem to come under a 1/4 in diameter.

Side note: I inspected all the gears in the apron, quick change gear box and headstock assembly no damage but I wanted to make 100% sure. =)

 

[Emery]

@YotaBota @YYCHobbyMachinist
Hey Gentlemen, What do your 9 inch model A’s have for sheer pins on the lead screws?

 

[YYCHM]

@YotaBota @YYCHobbyMachinist
Hey Gentlemen, What do your 9 inch model A’s have for sheer pins on the lead screws?

Per the Operator's Handbook, the Lead Screw Shear pin is brass, the Gear Train Shear Pin is aluminium.

I have a piece of 0.125" brass wire/rod that I use. Got it from a Hobby Shop. A brass brazing rod would work as well.

When I bought my machine some one had stuck a nail in there LOL.

BTB - What did you end up doing pulley wise?

 

[cuslog]

Yes, been there, done that (or similar). I just turned down a piece of brass I had - don't remember the exact dia. but it was a different lathe anyway. Seemed to work fine (but I never ran the carriage into the chuck again either).

 

[Emery]

Per the Operator's Handbook, the Lead Screw Shear pin is brass, the Gear Train Shear Pin is aluminium.

I have a piece of 0.125" brass wire/rod that I use. Got it from a Hobby Shop. A brass brazing rod would work as well.

When I bought my machine some one had stuck a nail in there LOL.

BTB - What did you end up doing pulley wise?

I looked in the manual and I couldn’t find that. Thanks for pointing it out!

I think I bought the correct stuff then. I wouldn’t imagine there would be a wide variety in tensile strength through the different grades of brass out there...

Unfortunately still using the same set up. I actually had it on my calendar today to call the guy in Calgary. I’m driving through tomorrow so I think I’ll try picking up a new one.

Works been busy hahah

 

[YotaBota]

IIRC it's a tapered pin, if you measure the hole on each side of the coupler you'll find on side is bigger than the other. You can turn your own pin, set your compound for about 1.25 degrees and use the compound to turn the brass rod into a taper pin. If you use a 1/8 rod you'll have to go slow and gentle otherwise the pin will jump onto the bit, ask me how I know. When you go to reinstall the pin make sure the taper in the lead screw lines up with the tape in the collar.

 

[Emery]

Yes, been there, done that (or similar). I just turned down a piece of brass I had - don't remember the exact dia. but it was a different lathe anyway. Seemed to work fine (but I never ran the carriage into the chuck again either).

IIRC it's a tapered pin, if you measure the hole on each side of the coupler you'll find on side is bigger than the other. You can turn your own pin, set your compound for about 1.25 degrees and use the compound to turn the brass rod into a taper pin. If you use a 1/8 rod you'll have to go slow and gentle otherwise the pin will jump onto the bit, ask me how I know. When you go to reinstall the pin make sure the taper in the lead screw lines up with the tape in the collar.

That is a very good observation! I noticed that the previous pin I broke didn’t seem to go through all the way. This is probably because they did not taper the pin.
Thanks!

 

[Johnwa]

There’s some shear pin technical discussion in this thread
https://canadianhobbymetalworkers.c...g-it-up-and-running-picture-heavy.1278/page-2

 

[Emery]

There’s some shear pin technical discussion in this thread
https://canadianhobbymetalworkers.c...g-it-up-and-running-picture-heavy.1278/page-2

Hey Johnwa, that’s a great link thanks. Seems that regular brass rod would work just fine.

Are you familiar with the annealing process? I might try this to confirm it will “sheer”

 

[Johnwa]

The quick way to anneal brass is to heat it until it starts to glow red and then quench it it water. I don’t think the water quench is necessary but it’s faster than letting it cool in air.

 

[YYCHM]

IIRC it's a tapered pin, if you measure the hole on each side of the coupler you'll find on side is bigger than the other. When you go to reinstall the pin make sure the taper in the lead screw lines up with the tape in the collar.

That explains my 50% failure rate with seating a replacement LOL. It either slips in or you bend it.