Bump knurling!

pjf134

pjf134

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Since most of us have a bump knurling tool that come in a set of QCTP setup and do not use because of spindle stress, would a follow rest or steady rest be the ticket to fix the problem with spindle stress? Does anyone use this method or does it not work that good? Everybody just seams to make or buy the adjustable spring type. Maybe this has been discussed before, but I have not seen it that's why I brought it up. Any input would help the people who are new to this also. I have used a knurl a long time ago, but don't remember what type it was and did not have any problems back then. The first time I used one it worked fine and did not bother to give it any thought.
Paul
 
I have an old '37 Atlas/Craftsman 12" Lathe. I have used both types of knurlers but only on brass and aluminum. I would never do steel in a lathe this size using either types. But even on brass & aluminum I just put the minumum pressure on the part and keep going back and forth over and over. I put very little stress on the spindle this way. Since I only do knurling once in a great while and I have lots of time this works for me.
 
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Any material that work hardens won't like knurling with either pressure type knurler. A cut knurl is the only way to go on stainless.
 
Paddy, all austenitic stainless grades will work harden to a degree, and 303 is not recommended for heavy cold work because it will work harden. Granted, knurling isn't heavy cold work, but I was just making the general statement that for all intents and purposes, stainless doesn't knurl well.
 
Frankly, T303 is my favorite ss to machine. I just wish it were stronger, more corrosion resistant, less magnetic, weldable, heat treatable.....etc. I've machined my share of it as well. I didn't mean to say you couldn't knurl it, but in a production environment, the knurling tool of choice would be a cut knurl.

I designed a poly bag sealer that used T304 rolls to press the seam together. They were knurled using the scissor type tool, and we went through a few rolls. Most knurling is for cosmetic purposes, but in that case, a specific PD was required to control surface speed. It was a bit tricky.
 
I am with Paddy. I have knurled all sorts of materials. Work hardening has never presented itself as being a particular problem on any. Of course some materials are easier to knurl than others. I have been using the same rollers for @ 10 years now.

Randy
 
Don't get me wrong, I'm not saying you can't/shouldn't knurl 303. I've done plenty myself, it's just not my stainless of choice for it. :)
 
I sprung for a set of those new diametral pitch, convex knurls. I bought them direct from Accu-Trak. They work extremely well and always track on material with a diameter a multiple of 1/64". They're a bit pricy, but it's worth it if you do a lot of knurling. I don't, as is true for most HSMs. In that case, the TiN coated HSS knurls will last a good many years...

The convex knurl appears to put much less stress on the spindle and compound and the knurl can be fed axially. Since I have a Atlas "flexible flyer" lathe, stress is a killer.

John
 
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