What type of Knurl?

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asallwey
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Joined: Sun Dec 31, 2006 6:49 am
Location: N. Virginia

What type of Knurl?

Post by asallwey »

I have several pairs of knurl wheels from Cabin Fever and other places. I recently decided to brush up on knurling and one of the first things I started to wonder about is what do I have. Some have mfg markings, a couple just a name, one pair is blank. How can I tell the difference between a circular pitch pair or diametral pitch pair? Or doesn't it matter? I have the formulas so that is not an issue.
Lew Hartswick
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Re: What type of Knurl?

Post by Lew Hartswick »

Forget the "formula" just use a scissor type holder and crank the pressure till they track.
...lew...
asallwey
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Location: N. Virginia

Re: What type of Knurl?

Post by asallwey »

That's what I've been doing, generally successfully. My question came up because I was watching a video and at one point the presenter gave descriptions of knurl types. Made me wonder what I have and if there is any way to differentiate between them if no markings. Just one of those "mystery of the universe" type question.
pete
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Re: What type of Knurl?

Post by pete »

There's a good enough explanation of the difference between circular and diametral pitch knurls here Asailway. https://accu-trak.com/general-knurling-information For a commercial large run of parts then I'd probably use the calculated formula for the knurls pitch spacing verses material size. I do it the same as Lew and it seems to work just fine for at least diamond shaped knurls.
asallwey
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Re: What type of Knurl?

Post by asallwey »

Thanks Pete, I've been to their site, but must have missed this one.

I don't knurl very often, although I do like the result on some tools or handles. I'll just use mine as I've been doing and the way both of you seem to do and let life go on. And run a test piece before committing to a final part.

Alex
pete
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Re: What type of Knurl?

Post by pete »

Since this thread is about knurling maybe this will help someone in the future since I spent a lot of time digging up and figuring out the little I know about it. While knurling is done for good reason to increase grip, there's also a certain amount of aesthetics to it as well. And getting good well formed knurling isn't nearly as easy as it seems with less than good quality knurls and the tool to run them in. Maybe they are made, but so far I haven't seen any, the cheap off shore knurls don't seem to be all that sharp, well formed or there incorrectly heat treated to produce decent knurling. Mine chipped the edges off some teeth way too easy in my opinion. The much better European or American knurls are fairly expensive for a reason. Second, everyone of the off shore knurling tools and all of the designs I've seen so far for a shop made pinch knurling tool are way under built. The cheap one I had would produce knurling on a part, but they were never all that well formed and I almost always got a spiral effect on the part instead of inline diamonds along the length of the shaft. I finally figured out that's from the light weight arms holding each knurl slightly twisting due to the sideways pressure as the knurls are traversed along the part. Unless the tool arms holding each knurl are very rigid you'll always get that spiral effect. Once I started using a lot higher quality knurls and a rigid tool to hold them in the whole process produced much better results.

Comparing something like an Eagle Rock pinch knurler to any of the off shore one's shows what I mean as far as how heavily built the tool needs to be. Pinch type knurling or any other tool that isn't using the cut knurling method is an extrusion process with bit's of material flaking or spalling off the closer you get to a sharp tipped diamond shape on the knurl points. If you try to go too deep or past what the knurl can generate the material has to start breaking those points off. But flakes of material are still being produced even in the early stages, it's those chips being run back through between the knurls and your part that degrades the knurling quality. Most recommendations I've read for commercial knurling highly recommend high volume food coolant to help wash off those metal particles as there being generated. Since I don't have flood coolant on my lathe I just use LOT'S of the cheapest oil I have. It also helps to use a stiff metal brush to clean out the knurls and knurling on the part before making the last pass. And once I get the knurls tracking properly I never run them off the part until the jobs finished. I'm unsure about larger lathes, but with mine it seems to ease the tool pressure to tilt the leading edge of the knurls out and away from the part by a degree or two. That way the leading edge of the knurls aren't doing all the work and the knurling gets progressively deepened across the whole face of the knurl.
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BadDog
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Re: What type of Knurl?

Post by BadDog »

I got a Enco scissor knurling tool years ago. I've successfully used it a few times with varying success, and still use it on big stuff (like a replacement 5C draw tube). However, for more run-of-the-mill stuff, I've found that old school knurling tools from turret lathes are among the best options, and sometimes quite reasonable on ebay. VERY sturdy and rigid; far more pleasant and consistent to use than the scissor type, at least for me. I've bought several in different sizes, and in each case they came with slightly used (apparently) high quality wheels.
Russ
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rmac
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Re: What type of Knurl?

Post by rmac »

A lot of my knurling problems went away when I stumbled onto one of Harold's old posts where he explains his technique. Here's a link:

viewtopic.php?p=192071#p192071

-- Russell Mac
pete
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Re: What type of Knurl?

Post by pete »

Thanks Russ, I don't recall reading that one before.
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rmac
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Re: What type of Knurl?

Post by rmac »

pete wrote: Thu Apr 15, 2021 2:29 pm Thanks Russ, I don't recall reading that one before.
Well, it was ten years ago! I'm lucky if I can remember what I had for breakfast.

-- Russell Mac
pete
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Re: What type of Knurl?

Post by pete »

Lol, exactly the same here or the location of any tool I was just using not 5 minutes ago unless it's bolted down. So I may well have read that before, but sure can't remember doing so.
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