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Knurling?

Stuart Samuel

Stuart Samuel

Ultra Member
Premium Member
Turned down a side job for a bit of knurling today. Don't have the time, and I'm not convinced I could get a satisfactory result on my Super 7, at least not in the next two weeks.

Steel, 2.25" diameter, 3" long. 1/4" through hole, threaded one end 1/8-27 NPS, to a depth of 1". Chamfer 2mm both ends (yes, mixed units, not the end of the world), and remaining surface knurled. Fineness/coarseness not specified, but had to be extremely clean (that is, well formed diamonds end to end). Two pieces required, for a different lighting company. (as in, not my day job)

Anyone have any tips for knurling success?
I think the only time I've had a chance to do any was more than 10 years ago, brass parts for a tripod and telescope-sized kaleidoscope for a glass artist.
 
IMG_2672.webp
 
Thats a lot of pressure for bump knurling on a small lathe like a Super 7. Doable with a scissor tool though. Leave room on the blank for a startup area for multiple passes, something like 1/8" to 3/16" extra . Use cutting oil.
 
Yep, I'd need to pick up or make the scissor tool.

The lathe came with a fair bit of tooling, but ~1/2 of it was far too big. I bought it down near London Ontario, from the son of the owner. I didn't get to meet the owner, as he was in hospital, but I got the impression, going through the stuff, that there was some sort of surplus shop in the area that he couldn't resist. So there's a knurling tool, but the shank's 3/4". It's not marked, so I don't know that I'd bother milling it down to fit in a tool holder.

Now if only I knew where to get a nice, heavy, Japanese manual lathe...

(If anyone's wondering why I can't do this at work, the request came from a semi-direct competitor, so not really kosher)
 
I tried a bit of knurling today and quickly said why bother. I don't have a baby lathe, and it won't shy away from pressure, but the tools I have are from much more delicate lathes and also make a very fine knurl and I want course.
So I feel your pain and maybe someday my cheap gene will get cancer and I'll go get a better one.;)
 
Darren said:
thats 2 tpi, 2 start, lh and rh. Obviously 4 start would be finer, might try it next.
Click to expand...

What a great idea Darren. I have some garbage bar I got from a bent drive shaft repair I did. I'd like to play with that idea a bit too.

What was your thinking to start with 2tpi? Why not 10 or 12 or 16 with 4 start? Maybe shallow angles don't look good?

Maybe I should just try it and learn why the hard way......

Thinking it will be obvious when I do...... LOL!

Edit - Actually, just thinking about it made it obvious. So how about 2tpi 8 start (or something like that).

Might be difficult to index unless its all done with a plunge cut and a compound set at 90 and then index just like picking up an existing thread. Should be fun trying it! Sort of a poor man's cut knurling!
 
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Watch out for the max capacity of a scissor knurl. For example, Doug Gray's 'Heavy Duty' design maxes out at 2-1/16 inches:

COVER_2048x2048.jpg

d-gray-drafting-and-design.myshopify.com

Heavy Duty Knurling Tool Complete Kit

Heavy Duty Knurling Tool Complete Kit NOW SHIPPING!! Fantastic project for the lathe and mill (95% lathe work). Complete materials, hardware and drawings to create a valuable tool for your shop. Even the smallest of equipment can be used to produce this kit. This kit will provide several...
d-gray-drafting-and-design.myshopify.com

Craig
 
Susquatch said:
What a great idea Darren. I have some garbage bar I got from a bent drive shaft repair I did. I'd like to play with that idea a bit too.

What was your thinking to start with 2tpi? Why not 10 or 12 or 16 with 4 start? Maybe shallow angles don't look good?

Maybe I should just try it and learn why the hard way......

Thinking it will be obvious when I do...... LOL!

Edit - Actually, just thinking about it made it obvious. So how about 2tpi 8 start (or something like that).

Might be difficult to index unless its all done with a plunge cut and a compound set at 90 and then index just like picking up an existing thread. Should be fun trying it! Sort of a poor man's cut knurling!
Click to expand...

2 TPI is as course as my lathe will cut, as far as i can tell. It would work better if it could cut 0.5tpi or something.

For a 2 start , 2tpi thread on a lathe with a 4tpi leadscrew, you just open the half nuts and move the carriage over 1/4" and close the half nuts, with the leadscrew stopped, of course. So it was very simple and that first experiment only took a couple minutes.

One observation is that knurling over the course threads like that took very little pressure. The material was more easily displaced I guess.
 
Years ago I acquired a straight knurling tool designed for use in a lantern tool post.
I decided to make a tool with the two knurls that I could use in an AXA tool post.
When I ground the two shafts off and tapped them out with a pin punch one of the
wheels split in half. I have had that one lonely wheel in my tool box for years.
Last night I made a cut knurling tool with it.

4.JPG


3.JPG


The first attempt with the tool on a piece of 3/4" mystery metal. Having to take the tool out of the holder and rotate it 90 degrees then get the same depth of cut is tricky. I'm going to put a stopper in the tool holder under the last set screw then the tool butts up against it then the depth of cut should be the same going by the cross-feed dial. It did a pretty nice clean cut with not a lot of pressure.


The knurling wheel has a pitch of around .030".
IMG_3300.JPG
 
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terry_g said:
Last night I made a cut knurling tool with it.
Click to expand...

I would NEVER have guessed you could do that! NEVER!

That is a total eye opener Terry!

Forgive me for doubting you. But are you sure it Is really cutting and not swagging? Did you measure the before and after diameter?

If that is really cutting I am VERY VERY impressed!

Can you take a closeup of that as well as of the tool?

I have put a cut knurler on my wanted list but the cost has deferred the purchase vs other priorities. It's possible that you have just changed everything for me!
 
The shaft is .750" and where I knurled it it measures .758" So there is some swagging happening.
The tool started life as a piece of 5/8" key stock.

IMG_3310.JPG

IMG_3306.JPG

I lighty touched the right half of the knurl with a file taking .002" off .
IMG_3313.JPG
 
terry_g said:
The shaft is .750" and where I knurled it it measures .758" So there is some swagging happening.
Click to expand...

Yes, it's easy to see the swagging in your photo on the far left as well as the dimples in all the squares. But it still looks GREAT! Kudos to you for even thinking of it let alone doing it!

I'm very impressed. Nice interim way to knurl about halfway between cutting and pressure knurling.

Which brings up another question, how much pressure do you think that required? Not expecting a numerical answer. A little, more than just a little, medium, a liitle less than a lot, and a lot, etc will do just fine.
 
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