For what’s it’s worth, a cleaning tap, also called a “restoring tap”, is all that should be used when restoring threaded holes.

a regular cutting tap will remove too much metal, and thereby weaken the holding power of the threads.

Craftsman sells a nice moderately priced set of cleaning taps, which I’ve been using for years with no apparent wear.

Lang sell’s a similar set, sold by Summit Racing.






Z

 

my taps are all base size. I could not find a long, 6 inch, tap to chase threads in block so I had to have extension put on my tap. Very little removed on any hole.
Those would not work for the deep head bolt threads.

 

While we are here talking thread restoration what is this tool intended for ?