Form taps - how long do they last ?

C

compact8

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I started using HSS form taps of sizes M2 to M4 a while ago and like them a lot. They offer many advantages compared with conventional taps - less force is required, no need for reversing regularly to break the chips ( there is none ), they have larger cross section areas hence harder to break ( a BIG issue for small taps ) and the threads are believed to be more durable although this is yet to be experienced.

At first I used them only on soft metals like alumium and brass but later I found them to be good for 1018 mild steel and 303 stainless steel as well. As there is no cutting action, they do not get blunt so I wonder when they need be replaced.
 
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There have been a number of discussions on this subject on one of the professional boards. Those that keep close track of their performance are averaging around 1,000 cycles before changing them out. Keep in mind they are being run under almost ideal conditions as far as rigidity, accuracy of placement, speed, and lubrication are concerned. They may go somewhat longer but are changed out an abundance of caution against breakage and potentially ruining expensive parts.

I personally have a couple dozen different sizes in stock. They are only used on aluminum and more malleable steel alloys. Most are at least 2-3 years old and have not been used extensively. They seem to do a good job, but do require more torque, need more lubrication, and perfect alignment to avoid breakage. I only use them in the mill, and only at somewhat lower speeds than standard thread cutting taps.
 
I make these kind of taps for tapping wood. The steel I use is a unknown type (not stainless) work hardening steel. I don't do a lot of tapping in wood but I haven't broken or wear down these form taps.
Use your taps until you break one, that will give an idea of when to replace.
 
compact8 said:
I started using HSS form taps of sizes M2 to M4 a while ago and like them a lot. They offer many advantages compared with conventional taps - less force is required, no need for reversing regularly to break the chips ( there is none ), they have larger cross section areas hence harder to break ( a BIG issue for small taps ) and the threads are believed to be more durable although this is yet to be experienced.

At first I used them only on soft metals like alumium and brass but later I found them to be good for 1018 mild steel and 303 stainless steel as well. As there is no cutting action, they do not get blunt so I wonder when they need be replaced.
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Since the first 2 or 3 threads take almost all the force you can make like new
by grinding down the first 2 or 3 threads.
 
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