Myford ML7 Spindle Thread

[oldengineguy]

Hello Myford owners. I want to make a "dummy" spindle to use my small 4 jaw chuck on my larger lathe. I measure the spindle thread at 1.125 in. 12TPI. Is this 55 degree Whitworth ? or 60 degree SAE? I can't measure close enough to be sure and would like to make only 1 part. Lathe is a 1953 model serial K28744. Thanks Colin

 

[fcheslop]

55 degrees ,Whitworth

 

[oldengineguy]

Thank you. Darn , will have to grind a new cutting tool. Colin

 

[fcheslop]

Yep , such is life . Had to make an internal one myself recently for a variation on a Keats chuck
keep well

 

[goldstar31]

But if you have threaded 60 degrees, you should have aenough 'meat' left to do 55 Whitworth!


From what I have learned about screwcutting, Kenneth C Hart witing as Martin Scleeve and his Screwcutting in the Lathe and earlier tomes, he often 'truncated' the threads for special threads 'without complaint' and following the Gospel Acording to Professor dennis Chadock, he truncated the thread on the micrometer on number one bedbar on the Quorn and it comtinues right through now to the Mark3.
I mmade mine, for a Mark1 and have the kit and plans for the Mark3.
As you will appreciate we have moved from Whitworrth coare to acme threading


Regards

Norman

 

[oldengineguy]

Being an external thread it was easy enough to grind a 55 degree tool. My lathe only goes down to 60 RPM and with a 1/2 in. long 12tpi thread to a shoulder, I set up to cut the thread in reverse as per Joe Pie's video. As he says, once you try this method you'll wonder why you ever went the other way. It worked fine but it's hard to unlearn years of right to left threading. Colin

 

[a41capt]

Being an external thread it was easy enough to grind a 55 degree tool. My lathe only goes down to 60 RPM and with a 1/2 in. long 12tpi thread to a shoulder, I set up to cut the thread in reverse as per Joe Pie's video. As he says, once you try this method you'll wonder why you ever went the other way. It worked fine but it's hard to unlearn years of right to left threading. Colin

All of the Mauser actions that I choose to rebarrel have Whitworth 55 degree threads. I have a couple single point threading tools ground, and you can bet they’re WELL marked! Now, if I could only remember to set my compound over to 27 degrees each time before I start cutting…