# standard bolt turning query



## timtheauthor (Nov 13, 2011)

Hi, bit of a dumb question but are the machine bolts that you buy in a hardware store made of hardened steel or are they soft enough to turn on my lathe. I want to cut the head off of one and then turn down the diameter on the non threaded end but l dont want to waste a cutting tool finding out!

Any help appreciated.
Tim


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## Brian Rupnow (Nov 13, 2011)

They are soft. Any time you are in doubt, try and cut it with a hand held hacksaw. If a hacksaw cuts it, then you won't be ruining any tooling when you machine it.


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## Ken I (Nov 13, 2011)

Watch out for high tensile bolts and cap screws.

They can be machined but the material tends to work harden.

That means you can't fool around taking "light" cuts or allow the tool to rub - particularly drilling.

You must feed aggresively and disengage or back out rapidly so as never to "rub".

Drilling cap screws is particularly troublesome - it can machine quite easilly and then harden on you (because you let it rub).

It really is a case of "he who hesitates is lost".

Ken


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## timtheauthor (Nov 13, 2011)

Thanks guys, will proceed and will avoid high tensile ones.

Tim


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## Rocket Man (Nov 17, 2011)

Bolts come in different grades. The low cost bolts are usually grade 2. One step up slightly more expensive is grade 5. Then grade 8. Most hardware stores have 2, 5 and 8. Socket Head Cap Screws are grade 12.5 to 12.75 according to the manufacture but some sellers call them grade 12 other sellers call them grade 13. I don't know much about aircraft bolts but I was told they are grade 15. They all turn ok in the lathe. Shoulder bolts are different I think they are case hardened they will distroy a lathe tool. Test the bolt with a file, if you can file it then it will cut in the lathe.


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## rake60 (Nov 18, 2011)

In the US market bolt grades are marked by raised lines on the bolt heads.







Grade 2 is almost too soft to get a good finish.
Grade 5 is cuts like a 1018 steel.
The Grade 8 is a very much like cutting 4140 steel.

I have cut Grade 8 bolts on my lathe without a lot of trouble, but as already stated,
they are pretty tough to drill or tap.

Rick


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