Knurling tool modification

[mklotz]

I like the modification. I do most of my knurling in stainless steel rods using three passes with increasing knurling tool pressure per pass. I usually start with one pass toward the headstock, stop the rotation and reverse the carriage to go back towards the tailstock, and then a final pass towards the headstock with slightly more knurling pressure without disengaging to carriage feed. I use lubricating oil and not cutting oil. If I discover on the final pass the knurl depth is not deep as required it is easy to reengage the knurl pattern by slowly tightening the scissor-type knurling tool on the knurl pattern and running another pass. It is easier to take a little longer when during the knurling than trying to do it in one pass.

There are different opinions on using the correct diameter of the bar stock before starting the knurling operation but I prefer reducing the bar stock for an optimum knurl pattern. I used to use a formula for the optimum diameter but as they say there is an app on your phone for this. I use the free phone app "Knurling Calculator". It only works for Imperial dimensions but very easy to use. The drop-down menu is for 12 to 80 TPI knurls. Next the blank diameter is specified in inches and calculator provides the starting diameter. I usually add 0.002" to the final calculated diameter. I achieve perfect and sharp knurls every time.

For the folks like me who won't own one of those smart phone timesuckers*, there's a program to compute perfect knurling diameter on my page as well as one from Little Machine Shop on the interweb...

https://littlemachineshop.com/reference/knurler.php

The basic mathematics is simple...

Compute the circular pitch of the knurl wheel... p = wheel diameter / number of teeth

Compute the integer number of p's in the stock of diameter D... N = int[ pi*D/p ] where the "int" operator denotes truncation to an integer

Then the desired knurling diameter is given by N*p / pi.

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* Yeah, that's right, I'm retired and gloat on the fact that I can get along just fine without one.