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Curved Knurling

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WayneP

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#1
I posted this question on another thread, may not have been the right place so ... does anyone know how to do curved knurling like this? photo (1).JPG
 

British Steel

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#2
Never done it, nor seen it done...

A straight knurl somehow attached to a ball/radius turner? If you started on the parallel/cylindrical section, it would probably track the initial knurl if you slowly advanced around the curve - would be quite a force on the ball turner though, knurling's hard work!

What springs to mind is where a ball/radius turner uses e.g. an inserted tool carried in a holder, a new holder with a slot in the end and a knurl wheel carried on a hardened pin through the "fork" so the middle of the knurl teeth is square to a line through the turner's pivot and the pivot is aligned with the centre of the radius you want to knurl - a tricky setup... But probably how I'd do it if I really had to!

Dave H. (the other one)
 

Wreck™Wreck

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#3

WayneP

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#6
Hi Chipper..wow..the guy made his own knurl for the job. I'm tempted to use Wreck tm Wreck's advise and buy a knurl...although somehow I get the feeling it'll cost a bunch. Thanks for the information.
 

Silverbullet

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#7
Just think the knurling looks great , I bet it locks up and loosens well. Total cost $300. Try getting that back on a few parts.
No I'm not knocking his great job I'm just saying Joe public ain't gonna pay. That's why plastic has taken over on jobs like that.
 

Silverbullet

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#9
For a pair of knurls?!
The time it took for him to make the tools to make the knurling tool. It's all time I'm saying not just the knurling . I don't know what the company charges per knurling tool , but I do know the time it takes to make them. Time is money you work to make money don't you. How many hours do you think it took to design , do the cutting , hardening , recutting with time setting up , then more heat treating . All time and I only took $50. Per hr as the start . Most shops need $200. Per hr. Do the math .
 

crazypj

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#10
You find them on depth adjusters of Stanley planes.
You lot may be aware there are a lot of people who collect old woodworking tools and planes in particular (and pay thousands of dollars for some rare stuff)
I think there is a Chinese version of the knurling wheel available reasonably priced. (I like making stuff to make stuff sometimes)
 

ezduzit

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#11
Sb--ah! OK. I thought that was the price for the commercially available ones in the other link.
 

benmychree

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#12
I have a couple of small concave knurls (for producing convex parts); you only need one knurl to do this work, at least in the sizes that I have; you also need to make a form tool to pre shape the work to the proper radius before knurling.
 

crazypj

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#13
Thinking about it, couldn't a small tap be used to hob a 'knurl' from drill rod?
You wouldn't have straight knurl due to helix angle but I'm pretty sure it would look OK and be way easier to make?
 

benmychree

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#14
Thinking about it, couldn't a small tap be used to hob a 'knurl' from drill rod?
You wouldn't have straight knurl due to helix angle but I'm pretty sure it would look OK and be way easier to make?
Unfortunately, machine screw taps have no relief on the body of the tap, the only relief is on the chamfer. Pipe and acme taps are the only ones that occour to me that have relief on the body.
 

george wilson

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#16
i have described how to make concave knurls before. I just run the blank wheel against a tap that is rotating in the lathe. The concave surface of your knurl blank must pretty well match the size of the knurl at its diameter at the tips of the teeth,or you ill get a messed up knurl. I make them from 01 or W1 drill rod,and harden after completion. Draw the color to a dark brown or purple.

By tilting the blank knurl blank,you can make the rope knurl type of knurl. I use a round ended knurl holder that I make,so it can be tilted in the tool post holder. I can get away with about 20º tilt towards the right. Too much tilting,and the knurl will start getting "serrated" by the back side of the tap's teeth. Tilt the knurl wheel a LITTLE bit back towards the left,and you can make the knurl grooves perfectly vertical. Otherwise,the knurl grooves will have a bit of tilt to them,as if they were threads,since taps do cut threads,of course,and the threads do have a bit of tilt so they'll screw into a hole ! I hope you can make sense of my rather poor description.
 

crazypj

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#17
Hi George, I guess if anyone's trigonometry is up to snuff it would be simple to work out correct helix angle?
As you've done this and described it, is it possible to use next size down tap on a larger concave radius so it will cut 'straight' grooves? (because blank is tilted the 'curve' will be 'smaller' than 'correct' core diameter)
 

george wilson

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#18
Tilted backwards a few degrees works perfectly. No need to get more complicated. It is still close enough to the groove in the knurl blank to work just fine.

I forgot to mention,MSC co. sells convex knurls that you can use as the "mother knurl". They only come in one size of convexity,but different pitches are offered from coarse to fine. They aren't real cheap(abt. $35.00 IIRC). I bought one and it worked just fine,but I prefer to make different knurl concavities by using the taps. I expect the convex knurls are really for making long knurled surfaces by feeding them along a straight rod or cylinder.
 
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