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bob ward
05-13-2008, 08:30 AM
I thought I would dip a toe into heating and quenching, starting with a learning project by making a marking punch from a 10mm grade 8.8 bolt.

I'd had a look through the archives, and this thread http://bbs.homeshopmachinist.net/showthread.php?t=23798&highlight=grade+8+carbon confirmed my thoughts that the steel in a grade 8 bolt should be be heat treatable.

I heated the point to red heat, or maybe a bit higher with the oxy and plunged it into a tin of water, but the point has ended up being no harder than the rest of the bolt, judging by a file test.

What's likely going on here? Maybe this particular 8.8 bolt does not have as much carbon as one would normally expect?

rkepler
05-13-2008, 09:03 AM
What's likely going on here? Maybe this particular 8.8 bolt does not have as much carbon as one would normally expect?

A metric grade 8.8 is usually made from a low carbon steel - you might have been thinking of a US Grade 8 with would be a high grade, in metric that would be something like a 10.9 or 12.9 - but you have to be careful there as bolt grades can often be from mechanical processing of low carbon steel as from heat treatment of medium to high carbon steel.

Evan
05-13-2008, 11:12 AM
Regular SAE grade 3, 5 and 8 bolts are graded only by strength, not by alloy so the carbon content will vary depending on what they are made from.

oldtiffie
05-13-2008, 08:08 PM
Any help?

http://www.raskcycle.com/techtip/webdoc14.html

The raskcycle home page might bo of interest to "bilers" and "others" at:
http://www.raskcycle.com/techtip/webdoc10.html

And this?
http://www.engineersedge.com/torque_table_sae_ftlbs.htm

This too?
http://www.engineersedge.com/hex_bolt_identification.htm

jacampb2
05-13-2008, 08:39 PM
Go to your local industrial fastner supply house and buy a grade "b7" bolt in the size you desire. B7's are made from 4140 or 4142 alloy.

Paul Alciatore
05-15-2008, 01:23 AM
If you are trying to learn, why not just buy some oil or water hardening drill rod? That is what it is made for. With bolts, you are working with mystery metal and you will never know why it does or does not work.