Broken tap solutions

[JIMinPHX]

The post heat treat dimension change is due to the various forms of compounds formed by the alloying elements in the steel. Quenching, normalizing, annealing, and tempering all have differing effects on which compounds are formed and when. Find a good explanation of steel heat treat - I don't recall for sure but Machinery's Handbook may cover this.

BeeMan

I don't think it is due to a change in compound. I think that it is due to a change in the geometric structure of the molecules in the metal. There are different terms for the same material with different internal geometric molecular structures. Austentite & Martensite are two of the common ones in steels.

[David2011]

+1 on the Tap Magic. That is some really good thread cutting fluid. In gunsmithing class tonight I found a newbie trying to thread a block of aluminum deep (1/4 x 20 threads over 1" deep) and dry. He was amazed at the immediate difference with the addition of thread cutting fluid.

David

[Jim_Fleming]

add me to the Tap Magic list...

Only thing I despise about that dang stuff is that it stinks to high heaven...

UGH!

[JIMinPHX]

add me to the Tap Magic list...

Only thing I despise about that dang stuff is that it stinks to high heaven...

UGH!

If I try to blow the chips out of a blind hole with compressed air after having used that stuff, it goes aerosol & makes me choke. The stuff works, but it's not my preferred substance for all applications.

[j23]

I broke a tap off in a rifle tang once, tapping for a tang sight.. I took a steel punch and hammer and smacked the punch which was resting on the broken tap. The tap, being made of extremely hard, yet brittle steel 'shattered' out. The threads I had been cutting were finished with a second tap, no harm no foul, the screw went in smooth as butter.

YMMV of course.

[Russel Nash]

Another trick I have heard was to use a carbide tipped drill bit in a hammer drill, yeah, like what you would normally use to drill concrete. Chuck that into a hammer drill where you can turn it to just plain hammer mode (some of the better hammer drills have a switch that allows them to be regular drills drills, hammer drills or hammer only).

Then gingerly set the the carbide tipped bit on the end of the tap and hit the trigger on the hammer drill.

That supposedly will cause the tap to shatter.

I haven't tried it myself...just heard about it.

[BeeMan]

I don't think it is due to a change in compound. I think that it is due to a change in the geometric structure of the molecules in the metal. There are different terms for the same material with different internal geometric molecular structures. Austentite & Martensite are two of the common ones in steels.

Jim,
My point was that the change in dimension from pre- to post-heat treat is caused by volume changes due to phase transformations within the alloy. The dimensional change is a not a function of thermal expansion, as was inferred by someone earlier in this thread.

My memory of the particular terms involved in steel phase transformations was / is fuzzy so I suggested a good reference. For a brief summary see the short paragraph Volume Changes here:

http://books.google.com/books?id=_a9...nsions&f=false

I think we are trying to say the same thing re: the volume change. Have a good day!

BeeMan