VN Acme size

Glad it worked for you! Did you take any pics along the way?
 
Ok, so really green yet, but is the new thread acme or square? I don't see any angle looking down the threads to a square bottom on the side by side pic of new and old. Just wondering? I'm not sure I have Ever seen new acme thread so I may have to climb back on the turnip truck just for asking this.


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May I also ask how you decided to bore the "dial end" and how you secured it to machine?


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The original lead screws were machined as one single piece. They could have been square since many threads created at the beginning of the 20th century are no longer available.

The new lead screws are acme due to availability.

Determining the diameter of the bore was based upon an adequate wall thickness. I used a 3/16”x0.75” pin so I wanted roughly the same diameter of pin as wall thickness.

I am not sure what you mean by securing it to the machine. There is a locking but that keeps the lead screw in place and acts as thrust washer.
 
Sorry, poor writing on my question. I'm asking how you held the cut off dial in the mill or lathe to machine the bore. Did you use the mill or the lathe?What did you "clamp" on to hold the part securely? I have a feeling I may be doing this same procedure in the not to distant future

Thanks for the info so far.


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I first cut the old lead screw off and removed the handles. I chucked the dial end in a lathe and used a test dial indicator to minimize the amount of runout.

I then drilled a pilot hole and stepped up to 7/16” drill. I did not bore the hole smooth. I also faced the end flat.

I then cut the new lead screw to length plus 1-1.5” of one end to be turned down to bore size on dial end. Made the fit as close as possible without having it become a press fit.

Once the two parts were assembled, I chucked in mill and centered a drill spot on the dial end where lead screw slipped in. The hole is roughly 0.5-0.75” from faced end on dial shaft. Drilled a 3/16” hole as assembled then drove a 3/16” spring pin into the assembly. Filed the ends of the pins to be round with dial shaft.

The pins allow for future service if the lead screw needs to be replaced.
 
thanks again. As mentioned, may have to do this myself someday. I'm still getting the feel of the #12. I need to start measuring play soon.


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