Precisely cutting screws and bolts

[ieezitin]

Ladies & Gentlemen

I seem to remember a little project on here where someone made a fixture for the lathe where he could insert a bolt/screw and part it off very precisely every time. The head of the bolt/screw was inserted into the chuck first leaving the threaded end sticking out, also the head of the bolt hit a stop that was incorporated into the fixture.

I have a requirement to make about 25 screws and I need them cut to pretty tight tolerances, but lately I have found I have had this necessity for such a tool anyways so I am prepared to invest some time and make the fixture. If anyone could help either remember the past project or could explain their way of doing this I would appreciate the advice.

Many thanks     Anthony

[awemawson]

Start with a piece of hex stock:

First it is through drilled and tapped for the screw you want to shorten, then counter drilled and tapped with a thread larger than the head of the screw you are shortening.

Thread the target screw into it with the head lost in the counter bore.

Screw a grub screw of the larger diameter up against the head

Mount in chuck and machine to length

[black85vette]

Start with a piece of hex stock:

First it is through drilled and tapped for the screw you want to shorten, then counter drilled and tapped with a thread larger than the head of the screw you are shortening.

Thread the target screw into it with the head lost in the counter bore.

Screw a grub screw of the larger diameter up against the head

Mount in chuck and machine to length

Very nice tip!

I don't need that much accuracy and tend to just tap a piece of 1/8th inch scrap metal and hold it in a vise.   Insert the screw and measure with a digital caliper.   Then just cut it off flush with a Dremel using a cut off wheel.   The scrap acts to hold the screw and as a heat sink.  Once cut you just back the screw out which cleans up the threads.   I order almost all my screws in the longest length I can get and then just cut down to size.   Only have to stock one screw.

[joegib]

Suggestions already made will certainly get the job done. The posh device for this job. developed by the watch/clockmakers I believe, is the Lantern Chuck. Here's a nice example of one:

http://www.model-engineer.co.uk/forums/postings.asp?th=66771

Joe

[ieezitin]

Joe

Thank you for the link. that looks like a great set up and very well made. strangely enough i am halfway through making a similar fixture out of some old pipe fittings when its finished i will post it.


Anthony