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Knurling with a single knurl

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Stub Mandrel24/03/2013 20:06:35
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I've done some serious knurling today. I needed to put a 'fine straight knurl' on a 66mm piece of EN1aPB, too big for my 'scissors knurl' so I made up a simple sinmgle knurl tool. It was stressful knurling a 1" diameter test piece, but this worked surprisingly well.

To do the big job, I had to swap to my t-slotted cross slide to get enough room, and the amount of pressure was very scary. I used the approach of letting about 1/16" of the knurl overlap the work and winding in 5 thou, then traversing slowly back and forth with lots of neat cutting oil.

Initially I got a double knurl, but it sorted itself out.

It took more passes than the apparent depth (I didn't count though) suggesting there was a lot of flexing going on!

I found it happiest at about 145rpm, twice that seemed OK on the small work.

I was surprised how much extra pressure was needed for the larger diameter, I'd assumed it would be only a little more.

In the end I was pleased with the result, but it's not something I'd like to repeat in a hurry.

Has anyone got any advice for knurling like this that might make it easier in future?

Neil

Stub Mandrel24/03/2013 21:24:01
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Hi Gray,

I'll give you one guess what i was knurling...

That's exactly the sort of advice I should have sought first!

I'm afraid the graduating hasn't come out 100% perfect, but otherwise everything is on target.

Neil

Gone Away25/03/2013 00:14:37
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Does that advice just apply to the single knurl, Gray, or does it work with a standard two-wheel or scissor knurler?

Michael Gilligan25/03/2013 09:18:15
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I only use an over-under Knurling tool there is a photo in my album of my design.

That's a very useful-looking tool, Gray

MichaelG.

Steamer191525/03/2013 10:22:02
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Fine straight knurl on 66mm dia EN1APb. Sounds familiar - I've just done that, times 25. As Gray says, it's not a two second job, although by number 25 I was starting to get the hang of it!wink

Ian S C25/03/2013 11:08:27
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For fine straight knurls, my tool is based on the flint wheel from a Bic disposable lighter, it has a bronze bush, and a hardened steel pin, it's mounted in the forked end of a bit of 3/8" sq x 3" long bit of steel bar. It takes less than an hour to make ( the ciggy lighter, a bit of road kill ), It could be made in the clamp type form, but why bother, maybe for one of the very small lathes. Ian S C

Gone Away26/03/2013 00:52:14
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Thanks, Gray ..... helpful advice.

Gone Away27/03/2013 21:52:55
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Gray, that knurling tool of yours ..... have you written it up somewhere? (I thought I'd seen it but I can't track it down).

Gone Away28/03/2013 13:18:51
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Hi Gray,

Understood ..... thanks a bunch!

Steamer191530/03/2013 09:24:09
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Gray's apprentice tales about knurling remind me of my time spent in a Toolroom in South Africa in the '80's. The inspector and one of the milling machinists joined forces to design and build a small rotary table to fit to their hobby lathes. Progress was made and two very nice tables soon emerged. Great debate then ensued about how to graduate the table with 360 divisions. I added my penny's worth and stated that the only way to do it was to set it up in the dividing head and have a pointed tool in the milling machine's spindle and move the table back and forth etc. They had different ideas and the Miller decided that he could do it alot quicker by merely applying a straight knurl to outside of the rim. He had calculated that using a knurl of a given pitch on a particular diameter would give him 360 divisions. I told them that this was ridiculous and couldn't possibly work, but was ignored. I came in on the Monday morning and asked how the "engraving" had gone, only to be told by the miller that it was spot on. I was duly presented with a table that had 360 divisions! After consuming a large portion of humble pie, the miller told me that the inspector's table was slightly different but would say no more. It eventually transpired that the inspector had paid little attention to the depth of the knurl in his calculations and from that point forward the inspector had to concede that there are only 355, slightly larger, degrees in a circle.

Steve.

Edited By Steamer1915 on 30/03/2013 09:24:48

Edited By Steamer1915 on 30/03/2013 09:54:04

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