Whats The Best Way To Shorten Harden Bolts ?

E

ebgb68

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Hello need advice My neighbor wanted me to cut off some bolts for his project. He is particular so I need to get the cuts square and a good taper on the thread tips.
The bolts are eight grade allen head cap screws 3/8x11/2 needing cut down to 3/4" . He needs a longer shoulder that is the reason for shortening rather than buying 3/4 " bolts. If they were longer I would just put it in a collet . Thought about double nutting them to use a three jaw chuck but wasn't sure if that would hold while cutting ?
The bolts are eight grade would a parting tool cut or should I die grinder cut then straighten with the lathe ?
Sorry for the newbie questions I only have four no extras so they have to be done right first try.
Thanks Ed
 
I would just angle grind them and tell him not to look a gift horse in the mouth. But, if he insisted- put it in a 3 jaw and use one nut and the head of the bolt and part off.


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no question is stupid, unless you don't ask it.
there are many ways to skin the same cat, but i'd be inclined to cut it off with an angle grinder and face it on the lathe to the desired length.
don't be afraid to use softer grade 5 nuts to capture the bolt threads during the cutoff sequence and the machining sequence too.
when you back the nuts off it will have a cleaning effect on the work you just performed. chamfer as you see fit after that.
good luck
 
mzayd3 said:
I would just angle grind them and tell him not to look a gift horse in the mouth. But, if he insisted- put it in a 3 jaw and use one nut and the head of the bolt and part off.
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The bolts are allen head smaller than the nut size so that's why I suggested double nuts .I didn't know if they would hold ? He is mocking up a motor plate on a drag car they will be taken in and out a bunch so I wanted the tips tapered some.
 
i cut them all the time on my band saw them clean up on belt sander
 
they seem to cut easy for me and I have even run a thread die down them with no issues
 
I usually just cut them with a hacksaw and face to length in the lathe if I want them nice and square. They're only grade eight, not terrible to work with. I also have a bunch of various size nuts that I've sawn through on one side (again, hacksaw) . Thread them on to the bolt and when it's chucked the nut can squeeze closed a bit and grip the bolt. I do have collets, but sometimes the nut-thing is just faster especially with a 3-jaw mounted.

-frank
 
I do this all the time. Cut on band saw or a cutoff wheel. Chuck the head in the 3 jaw, with the lathe running use a soft mallet and tap it to get it running true by eye. face and chamfer, done Grade 8 machines fine.
 
As Ulma said, lots of ways to get it done. Grade 8 is not hard to cut (HSS will do fine). I get it that the threaded portion is pretty short (which is why you are cutting off the longer bolts). Usually a double nut (or a long "coupling" nut) is a handy way to hold a bolt. How about making up a sleeve (piece of 3/4" round bar with a 3/8" hole drilled in it), and slit it length wise. When gripped in the chuck (try with the 3 jaw, if it doesn't hold good, switch to a 4 jaw - they have higher clamping pressure), it will grip down on the smooth shank. You could even bury the bolt head in a countersunk hole in back of the sleeve.

Once that little bolt is held securely, you can part off, face, chamfer - whatever you want.
 
Thanks guys I like that split nut idea in the lathe . If it was for one of my projects I would just chop and grind them but my neighbor wants thing perfect . He's done alot for me so I want to help out.
 
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