Oops. Lathe workholding issues.

M

Mauser lover

Registered
Registered
Joined
Dec 30, 2017
Messages
117
Got the whole project figured out, then upon starting, can't figure out how to hold it.

Trying to make a socket head cap screw. Because I despise flathead screws. Figured the easiest way to get a 1/4-22 Whitworth screw with a socket head was to order some bigger screws (5/16-24) and machine down the shank and thread to my needed diameter/pitch/form. Obviously a beginner here, as a real machinist's first thought would be "how am I going to hold it", and I didn't even think of that part of the project until basically right now. Not sure how I can hold it securely without chopping off the head (which was the part I particularly wanted!) without some sort of gymnastics.

I've got six inch three jaw and four jaw chucks, and drill chucks in case I just want something smaller. Ideas? Not looking to spend several hundred dollars on some sort of specialty chuck just for a screw.

Thanks for the help!
 
I've had to do something similar except it was a countersink screw & LH thread. Here's how I would do it.

Center drill the end of the screw. Skim the OD of the head so you can hold it securely in the chuck or chuck up a hex bit & use that to drive the screw. Support with live center, then single point the threads you need. If you rather not have a center drill in the end, start with a longer bolt, do the machining, then cut off the center drilled section.
 
Found the pics (don't mind the live center ext thing, I didn't have an extended point live center at the time & I needed to get the screw done).

Img_8980.jpgImg_8981.jpg


M5 LH screw I made in the middle. On the right is what I started out with (M6).
Img_8988.jpg
 
chuck up a hex bit & use that to drive the screw.
Click to expand...

Thank you! Blessings upon your head! If I had ever needed to turn something between centers with a dog I might have though of it, but I never have needed to. So... Thanks!
 
MSD0 said:
The hex bit in the chuck is genius.
Click to expand...

Yes, pure genius.

And I even have one that is set in a socket for a quarter drive. Being round, I might be able to manipulate that to fix any concentricity issues. Of course, that might not work, but it's a possibility. I'm a little concerned about slop between the bit and the socket in the screw, but I'm guessing it will work out fine.
 
That there is a simple, elegant solution, Will. Makes perfect sense, too. Funny that in all the years I've been doing this stuff I never saw anyone come up with that. I agree with MSD0 - that is genius!
 
1/4" BSW is the same pitch as 1/4" UNC - 20 tpi. Only the thread form is different and for the most part due to normal tolerance are interchangeable at that size. Either way knocking the tops off the UNC threads and/or running through the appropriate die cures all.
It may be a Whitworth form thread but at 22 tpi is not BSW or BSF.
 
You must log in or register to reply here.
Back
Top