What Is The Proper Way To Shorten A Bolt?

[Epictetus]

You can just pop a nut on the threads and then hacksaw off excess from the bolt then unscrew the nut to clean up the threads. It will usually do the job but doesn't look nice. I'm thinking there must be a better way, especially now I have a 7x12 lathe.
Problem is - I don't think the chuck can adequately grip, say. a machine screw and, add to that, the fact that parting off would put it a lot of pressure - ie it would probably come flying out of the chuck?
Maybe the chuck could grip an allen head screw?

Cheers!

 

[Franko]

I use a belt grinder to chamfer the sawn end back about the depth of one or two threads. It cleans off the burr left by sawing and the bolt will feed into a nut or threaded hole very well.

One way of chucking a bolt in a 3-jaw lathe chuck is thread a nut on it to give more purchase for the chuck jaws to grip. The nut doesn't have to be turned all the way to the bolt head, just close enough that the lathe chuck jaws can clamp down on both it, and the bolt head.

Once chucked, you can spin the bolt and smooth and bevel the end with a file.

 

[Mark_f]

Cutting a bolt in a lathe is , I consider, kind of like over engineering and borderline dangerous. You already know in your mind what probably will happen. You already have most of it figured out. The quickest way, is hacksaw it off then dress the end flat on the belt sander or grinder, then hold at a 45 degree angle to the belt and lightly dress the end thread. It will look just like before you cut it.i have a piece of angle iron with all sizes of tapped holes in one side. I clamp it in my band saw , screw the bolt through to where I want to cut and saw it off. Then clean the end up on the belt sander.

Anything under a 1/4" I cut with a screw cutting tool ( a wire stripper cutter) that has the holes you screw the screw in , squeeze and cut the screw to length . The threads straighten when you screw it out of the tool.

 

[chips&more]

In a lathe the standard lathe chuck has a hard time holding fasteners because of the head of the fastener. It gets in the way. If you want to use the lathe you can safely hold fasteners in a collet, like a 5c collet. You can also make a split bushing to hold fasteners in a standard lathe chuck with excellent success. A lathe can be used without any problems…Dave.

 

[Ulma Doctor]

i'll keep small sections of nylon, copper and aluminum tubing and split the tubing longitudinally to make split bushings. i'll use the split bushing to protect the bolt

 

[Billh50]

I put a nut on the bolt or screw up toward the head and then cut the bolt with my angle grinder while holding the bolt in a vise. I then take the bolt and using either a bench grinder or belt sander chamfer the end slightly. Then remove the nut to push off any remaining burrs. I will also hit the end on a wire wheel to make sure all burrs are gone and nut starts easily.

 

[Epictetus]

OK, many thanks to all who replied! Best of all, it all makes sense.
Mark, you are talking about a horizontal band saw, right?

 

[Tony Wells]

Bolt cutters anyone? So named for a reason. Just kidding!

 

[karim]

I do almost exactly the same thing. In my piece of angle (aluminum because I typically work with very small screws), I have tapped holes down one side of the angle and clearance holes down the other (opposite the matching tap). I use the tapped holes to hold the screw while cutting, then I put the screw into the clearance hole and press against the angle bar with the appropriate driver for the screw. This lets me hold the screw against the belt sander/grinder by holding the angle, while rotatating it to get a smooth, even bevel all around the cut face.

 

[Mark_f]

OK, many thanks to all who replied! Best of all, it all makes sense.
Mark, you are talking about a horizontal band saw, right?

Yes. and for larger bolts such as 1/2" or larger, I saw in the band saw and then put in the lathe and face the end.