Thread Chase Kit Recomendations

RalphG said:
Ok, I will show my ignorance here by asking why not use tap and die set to clean up the thread on used nuts and bolts on anything? I have a good (Hanson) tap and die set and have used it for years to clean threads on any rusty or damaged threads I've had to work with. No ill effects that I've ever noticed.
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Just my 2 cents, taps and dies are cutting tools and remove base material. Thread chasers are less aggressive and not very good at removing base material; in my experience they remove the crap but not the base material.


A chaser removes the crap which is what you want to do.


A tap/die also removes the crap but if you're unlucky/unskilled you'll inadvertently remove more than the crap and enlarge threads or remove more material than you wanted to.


I have a high quality tap and die set as well as a thread chaser set. I love the thread chaser set and use it a lot. I love the tap and die set too but rarely use it, only when making new threads.


A crude analogy is comparing sand paper to a saw.
 
RalphG said:
Ok, I will show my ignorance here by asking why not use tap and die set to clean up the thread on used nuts and bolts on anything? I have a good (Hanson) tap and die set and have used it for years to clean threads on any rusty or damaged threads I've had to work with. No ill effects that I've ever noticed.
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Taps & dies are hardened and designed to CUT threads (REMOVE metal), whereas a thread CHASER is the nominal size of a standard bolt, and will simply move DEFORMED metal around (boogered threads) to comply with the original shape that was normally displaced by a standard-sized bolt (or nut), as well as cleaning any dirt and grunge in the threads.

This is important, especially in certain parts on old Fords and others. As stated by Alan ABOVE, rear end BANJO bolt holes are a special UNDERSIZE, where along with their special OVERSIZED bolts, are designed to help seal against leakage of rear end lube. If you use a tap, it will remove metal in the threads to a looser, standard bolt size. The same thing applies with flathead HEAD BOLT threads in the deck surface of a block. NEVER use a tap on either one of these Ford items. DD

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I have asked this question many times in classes I have given and yet to get an answer that complies with the laws of physics.

"Concerning the use of thread chasers as opposed to the proper tap, if the thread in question was tapped at the factory with a standard tolerance tap what makes you think a standard tap is going to remove more metal from that hole than the original tap did other than damage?"

For a thread to hold properly, both male and female parts need to be BARE metal, not rusty, scaly debris as left by an undersize chaser. Thread chasers do have one good value, they enable the sellers to buy new yachts.
If after tapping an old hole and there are rust pits and debris left in the hole, it needs a repair insert.

Questionable holes are easily tested before assembly. The method has been posted several times on this forum previously.
 
Pete said:
I have asked this question many times in classes I have given and yet to get an answer that complies with the laws of physics.

"Concerning the use of thread chasers as opposed to the proper tap, if the thread in question was tapped at the factory with a standard tolerance tap what makes you think a standard tap is going to remove more metal from that hole than the original tap did other than damage?"

For a thread to hold properly, both male and female parts need to be BARE metal, not rusty, scaly debris as left by an undersize chaser. Thread chasers do have one good value, they enable the sellers to buy new yachts.
If after tapping an old hole and there are rust pits and debris left in the hole, it needs a repair insert.

Questionable holes are easily tested before assembly. The method has been posted several times on this forum previously.
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Pete, your question sounds a bit intimidating, but I'll give it a shot and believe I can give you the answer that does comply with the laws of physics.
The rust and debris that finds its way into a cut thread will never do so in a uniform manor, but rather, in a random manner, heavy here, lighter there, none somewhere else. The thread chaser will be bound by the steel thread on one side, and cut through the impurities on the other side, while a tap will bully its way through, cutting both steel and impurities. Moreover, the chaser will reshape and restore bunged up threads, while the tap will cut right through misaligned threads, removing steel rather than cleaning. In support of my analysis, you'll remember the advice given for cutting new as well as cleaning old threads by hand: 'Do not allow a buildup of displaced material to accumulate before the cutter, else the cutter may bind and gall the work'.
 
ford38v8 said:
Pete, your question sounds a bit intimidating, but I'll give it a shot and believe I can give you the answer that does comply with the laws of physics.
The rust and debris that finds its way into a cut thread will never do so in a uniform manor, but rather, in a random manner, heavy here, lighter there, none somewhere else. The thread chaser will be bound by the steel thread on one side, and cut through the impurities on the other side, while a tap will bully its way through, cutting both steel and impurities. Moreover, the chaser will reshape and restore bunged up threads, while the tap will cut right through misaligned threads, removing steel rather than cleaning. In support of my analysis, you'll remember the advice given for cutting new as well as cleaning old threads by hand: 'Do not allow a buildup of displaced material to accumulate before the cutter, else the cutter may bind and gall the work'.
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Allan, excellent explanation. I give a recent example of where chasers came in handy. I am not a machinist by any means, but I had to cut some threads on the end of a rod to use for an emergency brake pull.

Once done, tried to get the nut on and it wouldn't go. I could see at the end, the thread had an odd finish to it. I placed the chaser nut over it and I could feel the resistance, but then it went down the threads.

Took off the chaser and the nut went on nicely. In this case, the chaser smoothed out the fresh cut threads, but didn't remove any material.

Not a scientific example, but a recent one of mine.

I also agree with the cleaning bit. I use cutting oil with the chaser dies and then once done, I'll hit the hole, nut or bolt with a spirit of brake cleaner. It's surprising how much crap come out of the holes, even after the part has been cleaned.

Thinking about it more, after 80 or more years, is it possible that threads get deformed, even so slightly, from being taken apart and put back together with an over achiever at the other end of the wrench?

If that is the case, the die cuts the material vs. a chaser reshaping the material.
 
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Thanks guys for the thoughts, opinions and recommendations! I ended up adding the SUM-900199 chase kit to my Centerforce clutch order (free shipping), will see how that works out.
 
There is one important factor that has been missed here, That is the matter of thread classes. Thread fit is a measure of looseness or tightness of mating threads. For unified inch threads, there are 3 thread classes for external threads 1A, 2A, and 3A and three for internal threads 1B, 2B, and 3B. All of these are “clearance fits” which indicates that they assemble without interference.

It is my understanding that the threaded holes in a flathead block are of a different class than is generally used. A regular tap and die set is most likely specified to the most common thread class. By definition, it would always remove metal when used on threads of a "tighter" class. This is why Ford head studs didn't leak from the factory, but have a tendency to do so on some rebuilds. Chasers, if properly designed, will be looser than the tightest specified thread class and therefore would not remove any metal.
 
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