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16 tpi straight form knurl 303ss

Jdrake333

Plastic
Joined
Nov 22, 2023
Haven't done a ton of knurling in the past so I'm looking for some tips or advice. Forming a 16tpi straight knurl in 303 ss. Finish diameter is 2.984 after knurl. Traversing 1.000 in Z @. 005/rev after plunge feed in @.003/rev, 54 Rpm.
Using Dorian double wheel cnc modular head. Using Dorian calculator for speeds, feeds, diameter pre/post knurl.

Do I need to form straight knurl or is cut knurling a practical option? We wanted to do a single wheel bump knurl but our tool rep insisted that we needed to form for straight knurl with double wheels so that's what we're using. I've had some success and also some problems. I understand it's a trial and error thing and theres not an exact science to knurling. Am I feeding way too slow, possibly work hardening my material? We're replacing wheels about every 100-150 pcs due to consistent double tracking or triple tracking, if that's even a thing, or cosmetically bad (galled material/burrs). Should I be getting more tool life? Can I increase feed rate? I've tried cobalt wheels with minimal success. HSS seems to be the way to go.
 
I use these types of knurl holders. Screw Machines, straight from the turret. I have put diamond knurls on about 3000-3500 parts on 1/4" 303, before the knurls started to get tapered and needed to be flipped around.

HSS knurls for me, maybe Cobalt but I think the cobalt ones can crack easier so I think I went with HSS.

I think I went with Reaming Speeds and Feeds. I forget the actual #'s because I usually go by "feel", then its trial and error. I was skimming .008" off the O.D. and then knurling with no work hardening.

I cant imagine putting a straight knurl on it would be too hard. You will find the sweet spot and it will run great.

Good Luck,

Dan
 
I run straight cut knurl in various materials on my CNC. Only issue I have is adjusting the tool angle to make sure that they are dead straight. Brand is Quick. Agent in Australia is as useful as tits on a bull, spent 2k on the tool and when I asked for directions on use received no help at all so I just wing it.

OT we will slip in a joke about salesman and hope E Kretz doesn't delete it. :D

Two guests at a dinner party one says to the other. What do you do, replies I am a surgeon. Guest 1 asks what is the easiest patient to operate on. Surgeon replies t's a mechanic, comes with a manual. No wait it's a electrician comes with a manual and everything is colour coded. No wait it's an engineer, manuals, colour coding, SOP's, drawings, BOM and 3D files. No wait it's a salesman they have a mouth and an arsehole and they are interchangeable.
 
Are you using a pivoting scissors type double or are the wheels rigid? Make certain the Y height is dead nuts so both wheels start spinning/contacting material at the same time if using rigid. You’re right - it seems to be touchy-feely BUT I believe your in feed should be very fast…you need to make sure there is a sufficient track for the knurl to fall back in to upon beginning its second trip around the stock. The term, “ram” is often used…”ram the knurl into the stock.” Lastly, make sure you’re not getting a 100% fully-formed knurl…that would imply over stressing the tool…It should look like the peak of a form-tapped thread. I have had incredible success with Accutrack and their service is great. They have a scissors type that you open up so it makes contact at 12 o’clock and 6 o’clock on your stock so there is virtually no load on your x-axis. In the meantime maybe start with .010” ipr in-feed? Oh…I should have mentioned I work almost exclusively in carbon/alloy steels and have virtually no experience in stainless. Good luck!
 
I’ve been using a Quick brand cut knurling tool for straight knurling with kurls I got from Accu Trak. Pretty nice setup. Not as big a diameter parts as yours though. Whatever you do you need to experiment with slightly varying diameter and depth. Accu Trac is a great resource for knurling info and tools.
 
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