The broken tap is out! Tips for tapping threads?

Mike CA · Nov 3, 2009

A tractor restorer from my club came over today, looked at the tap and said "that should be easy". Took a thin chisel he brought, and proceeded to pound the heck out of it. Broke it apart in less than 5 minutes.

Now the hole is clear and clean. I need to get a new tap, and this time do it slower. Then put in the stud, then I'll be back in business.

Ok, so... tips I've learned:

Go slow with the tap. Quarter turn, back it out, clean it. Back in, cut a quarter turn, back it out, clean it.

Right? Anything else I need to know?

Vito · Nov 3, 2009

Cutting oil helps.

Vito

Midnightrider01 · Nov 3, 2009

Use a good quality tap. However i broke a Matco tap in my continental engine used a small chisel to bust it up also.Sometimes you just have to use a big hammer.

Larry B 1486 · Nov 3, 2009

1st. A good tap and not one made in china. 2nd use a starter tap and then go back with a bottom tap. They make special cutting oil but light weight oil such as 10w will work as well. WD40 does not work very well, does not stick where needed. Have a air hose and keep turning untill the tap stops. If the tap stops before you reach bottom, back it out, blow it out because the shavings lot of time is what locks up a tap and keeps it from going any further, reoil and go again. Use a tap handle that has handles on both sides to keep even pressure and not a crecent wrinch.

Art Massing · Nov 3, 2009

Mike,
I highly recommend that you use cutting oil and a bar of solid tap lube, when ever you are cutting new threads.
Regular motor oil or even WD-40 is ok when you"re simply cleaning out rust/crud from existing threads but new threads will cut cleaner and easier when you use cutting oil and lube designed for the purpose.

Good luck,

Art

scott mcintosh · Nov 3, 2009

The cost of education on these old machines are something else at times.Things come to he who waits.Good Luck Scott

ScottyHOMeY · Nov 3, 2009

I think somebody mentioned last night or the night before, if you're just cleaning up otherwise good threads, get a chase instead of a tap. Chases are sharb nut not as hard and brittle as a tap.

Light oil is always good. As far as action, yes, only a quarter turn or so at a time, but back off each time more than the last cut. More true with a tap than a chase, but the idea is to use the backstroke to cut off what's curling up in front of the cutting edge. Those chips will go into the flute. If you're doing any serious cutting at hand speeds, you may need to back it out and clean up the tap and blow out the hole (to clean up the chips at the front end of the tap that the back stoke didn't pick up) both when it starts to feel more than a little gritty.

Glad ya got the ugly one squared away.

SDE · Nov 3, 2009

Most of the taps that I have broken, broke because I accidently applied some sideways pressure. You will learn to feel the resistance and to back off and start going forward again. Always try to get as much dirt out as you can before starting the tap. Oil and dirt, still makes MUD.
SDE

Wardner · Nov 4, 2009

Unless all the foreign metal from the old stud has
been removed, you run the risk of breaking another
tap. The thread chaser or tap should only be used
to clean up the damaged cast iron threads from the
chisels, punches, and picks used to remove the
fragments of the old stud.

Please don't try to cut out old stud threads. You
have done that once already and it didn't work. I
call that method "cheating". You will probably get
another failing grade. How many "Acks" are you
willing to endure? Use heat, picks, and small
chisels to remove the old stud fragments. Don't
worry about buggering up a few threads. You have
plenty to secure a lousy water jacket cover. And
there is always epoxy thread repair material.

Mike CA · Nov 4, 2009

As far as I can see, all of the old stud is out. I can get a bolt about 3 threads deep before it stops, and that is where it looks like the threads are buggered up in the hole.

John M · Nov 4, 2009

Maybe you should let someone else do it, perhaps the same guy who got the old tap out.

rustyfarmall · Nov 4, 2009

I will assume that you are turning the tap with a wrench? If so, you will get into trouble nearly every time. You need to use the "T" handle that is designed specifically to hold a threading tap. Makes it much easier to start the tap straight into the hole, and much easier to "feel" how much force you are applying. The "T" handle can be purchased seperately, and it will hold several different sizes.

Kevin Meier · Nov 4, 2009

Use tapping oil. I use tap magic. Also make sure you get the correct type of tap for the type of metal to be cut. There are better taps to use for cast compared to steel.

GordoSD · Nov 4, 2009

Go slow, don't use brute force. Just firm pressure. Use lt oil and your blowpipe from compressor to constantly clean the tap and the hole.

Gordo

The broken tap is out! Tips for tapping threads?

Mike CA

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Vito

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Midnightrider01

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Larry B 1486

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Art Massing

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scott mcintosh

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ScottyHOMeY

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SDE

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Wardner

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Mike CA

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John M

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rustyfarmall

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Kevin Meier

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GordoSD

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