Turning screw threads down

mariner3302

mariner3302

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I have an 11'' South Bend built in 1937. The spindle thread is 1 5/8 x 8 tpi. Im having no luck finding chuck plates but there are tons of 1 1/2 x 8 tpi. Would turning the 1 1/2 to 1 5/8 work?
 
You could rethread the 1 1/2" 8 tpi thread but you would have to be careful to follow the existing thread. You could also just buy an unthreaded back plate.
 
I've spent the last 3 weeks cleaning, cleaning, disassembling, cleaning, stripping, cleaning, cleaning, cleaning (see the trend?? lol) and now I'm ready to paint. Then it's just putting in the new wicks and reassembly!! I could have saved a week of work if I had just disassembled first and then cleaned but I wasn't sure where I needed to go at first.
 
mariner3302 said:
I have an 11'' South Bend built in 1937. The spindle thread is 1 5/8 x 8 tpi. Im having no luck finding chuck plates but there are tons of 1 1/2 x 8 tpi. Would turning the 1 1/2 to 1 5/8 work?
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I personally would never consider doing this. As suggested, you can make/thread your own plates. I would only work on my spindles if they were damaged and needed repair.

Ted
 
That didn't come out right. I meant turning a 1 1/2" threaded chuck plate down to 1 5/8". Not touching the spindle. Basically I want to make a thread protector for the spindle nose to practice and work up to a chuck plate for my 4 jaw.
 
I am hoping to find something at an auction. So I can turn a 1 1/2" witch seem to be easily found. Much more so than 1 5/8.
 
You might be able to get away with "boring out" and re-threading a 1-1/2" backing plate with the same pitch as your spindle as long as there will be enough wall thickness left in the hub when you're done. Two things to consider:

1- You should align your new threads with whatever is left of the old thread.
2- You will need to indicate the backing plate in very well so your chuck will run true after you get it threaded. The inside of the hub also typically has a register area that should fit the spot on your spindle closest to the bearing where it isn't threaded with a close tolerance. Any misalignment will make your chuck run out when mounted to it.
3- For both my lathes I made a male gauge of the spindle. That way, when making new mounting plates I had a way of verifying that the threads I was cutting were deep enough. When making the gauge you can use pitch mikes or I used thread wires to measure the threads. Thread wires are inexpensive and a good tool to have.

When I make a new mounting plate I thread it first, then screw it onto the spindle to finish all other operations and that way I know everything will be perfectly aligned.

Ted
 
It would probably be better to make one from scratch than modifying one. I read somewhere that cast iron is better than steel for things like backing plates and the like because cast iron absorbs vibration better. Is that true and if so, should I forgo steel in place of cast iron for spindle caps, backing plates, etc? I thought things were cast because of cost mostly.
 
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