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Tool My most hated tool

Tool
I just want to add a comment here that all this recent discussion is good. I think it helps everyone understand the issue better.

But please try to keep the debate from becoming personal.
 
gerritv said:
The wheels for cut knurling have a sharp edge, unlike pressure knurls where this edge doesn't matter.The various angles involved result in the edge cutting, the angles providing relief to the cutting edge. The fact that cut knurling doesn't really increase the diamenter of the object provides a hint that it is cutting, not deforming or swaging.
And yes, there are some totally clueless twits on YT who describe this, incorrectly. Dave M is the expert in doing a truly pathetic job on this (and most other topics). I had interaction with him on some d-bit grinder stuff, I gave up.
I found the best, reliable info on manufacturers sites, e.g. https://accu-trak.com/knurl-holders/cut-type-knurling.html/

The 'We Can Do That Better' video(that was linked to earlier in this thread ) at the end shows the cutting action, with chips streaming off the leading edge of the wheel.
Click to expand...

Your comment about the fact that cut knurling does not result in an increase in diameter was compelling to me. Cutting it is. Forming or swaging it is not.

I still have not seen a video that describes the theory adequately. But I have seen some that provided me with a few clues.

It was absolute torture for me to do all this you tubing. I hope others appreciate the following description of what I now believe is the process theory for cut knurling. I welcome corrections or criticism.

If I first imagine that nothing is turning and the cutter is instead simply pushed longitudinally down the side length of the part, it will act like a broach cutting grooves down the part. However, all the force is longitudinal - no sideways pressure. Now if I imagine the parts turning, I end up with lengthwise grooves all around the part.

The process is significantly improved by putting the cutting wheel on an angle such that each tooth on the cutter digs a little deeper and a little further down the axis of the part as they individually rotate across the face of the part. This horizontal movement of the rotating cutter teeth provides significant cutting force as each tooth slides forward along the part. If the carriage is also advanced at the same time, this forward cutting can be seen to exert a tap tap tap cutting action much like a graver tool hit by a small graver hammer.

For this to work, the teeth on the side (leading corner) of the wheel must be very sharp. In fact the side of each tooth essentially acts like the tip of a graver tool tap tap tapping their way down the part.

Once I could visualize this process in my head, I went out to the shop and put some parts together to see how it worked physically.

The process is not a lot different than a normal lathe tool traversing the part from right to left. It's just that in this case, the cutter does not stand still while the part rotates - instead it rotates with the part and thereby staying in the groove that it is cutting by following along with it. In this way, each tooth just cuts the groove a little deeper as it rotates downward toward circumferential tangency and also a little further down the part as it follows the tilted angle of the rotating tool.
 
It was absolute torture for me to do all this you tubing. I hope others appreciate the following description of what I now believe is the process theory for cut knurling. I welcome corrections or criticism.
Click to expand...
I treat YT channels much the same as individuals on forums, some I watch for info, some I watch for entertainment and some I just ignore/block/skip over :)

I think your description covers the gist of how it operates. Probably not correct in some details but in the end those likely don't matter much to get to the result.

I haven't yet made McGyver's version, I got stuck on trying to buy 'real' cut knurl wheels at a price I am willing to pay. I found a source in US but getting them here tripled the price.
My interim one is from design by Guy Lautard (published in Machinist Bedside Reader Vol 1, HSM), single wheel, that works well enough for straight cut knurling (my preferred for knobs etc as the grip is better). I bought some FormRoll sharp edge used rolls from eBay, good enough for now.

Depth of cut is (according to Dorian and others) Circular pitch * 0.35 (some say 0.5) . Plunge in to that depth while part is turning, then feed slowly. Donot reverse the feed, if you realy must go over it again go back to start, the wheel will track on the existing grooves. If in a hurry you will leave slight burrs at the end of the pass. Lots of cutting fluid helps keep things clean of swarf.

IMGW2178 (Medium).jpg



the photo is of an early knurl did using a normal wheel sharpened at the leading edge, I since switched to a straight knurl wheel as it is easier to align.

Gerrit
 
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gerritv said:
I treat YT channels much the same as individuals on forums, some I watch for info, some I watch for entertainment and some I just ignore/block/skip over :)

I think your description covers the gist of how it operates. Probably not correct in some details but in the end those likely don't matter much to get to the result.

I haven't yet made McGyver's version, I got stuck on trying to buy 'real' cut knurl wheels at a price I am willing to pay. I found a source in US but getting them here tripled the price.
My interim one is from design by Guy Lautard (published in Machinist Bedside Reader Vol 1, HSM), single wheel, that works well enough for straight cut knurling (my preferred for knobs etc as the grip is better). I bought some FormRoll sharp edge used rolls from eBay, good enough for now.

Depth of cut is (according to Dorian and others) Circular pitch*.35 (some say 0.5) . Plunge in to that depth while part is turning, then feed slowly. Donot reverse the feed, if you realy must go over it again go back to start, the wheel will track on the existing grooves. If in a hurry you will leave slight burrs at the end of the pass. Lots of cutting fluid helps keep things clean of swarf.

View attachment 25552


the photo is of an early knurl did using a normal wheel sharpened at the leading edge, I since switched to a straight knurl wheel as it is easier to align.

Gerrit
Click to expand...

Thank you for taking the time to read my description and for endorsing it for the most part.

In the interest of making the description accurate, and giving me the opportunity to further improve my understanding, what minor details would you quibble with?

And yes, obtaining wheels will be a challenge.

I agree with you sentiments on the best knurl for adjustment knobs.
gerritv said:
I got stuck on trying to buy 'real' cut knurl wheels at a price I am willing to pay. I found a source in US but getting them here tripled the price.
My interim one is from design by Guy Lautard (published in Machinist Bedside Reader Vol 1, HSM), single wheel, that works well enough for straight cut knurling (my preferred for knobs etc as the grip is better)
Click to expand...

Who/where is the US supplier with expensive shipping? I may have other options.
 
In the interest of making the description accurate, and giving me the opportunity to further improve my understanding, what minor details would you quibble with?
Click to expand...
Nothing specific, I am just hedging my bets that someone with more expertise comes forward.
My only input would be that due to the angle of the leading cutting edges on each tooth, that this is where they actually cut. The angles provide both side and back relief, leading to tiny chips flying off to the left and up a bit in 'We Can Do This Better' video. Having sharp edges then becomes vital, otherwise burrs start forming and lateral feed pressures increase. (going by my empirical observations of my own attempts).

The supplier I was looking at is https://accu-trak.com/knurls/cut-type-knurls-metric/cp-series.html , they do not ship to Canada at all. Their local distributor here wants >CA$45 for a US$18 knurl, and the frugal in me just can't go there :-). I haven't got to the point where I want to do the 20 min drive across the border to CBI yet. Euro Tech in Oakville distributes Zeus and Quick, haven't tried them yet. I think I just need to decide to spend some $$ and get on with it, just have to juggle some competing projects.


This video btw is a good example of using a single wheel style cut knurler. Functionally the same as what I made per Guy Lautard.
Note that he sets the tool holder at angle.

Gerrit
 
I contacted Euro Tech about 8 years ago, and let me say - be seated when you get the prices. I was dumbfounded. At the time I could actually fly to Germany, buy a Zeus knurler and 2 sets of knurls retail and return for cheaper than they were asking. sheesh.
 
@Dabbler, @gerritv, @PeterT, @Mcgyver -

At prices like that, it looks like my dreams of clean cut knurling are fast disappearing......

Wondering if it's possible to sharpen a regular knurling tool - one with straight grooves .... Would not be ideal, but if it works.......
 
Accu Trak knurls are affordable (US$18-25). The holders are pricey but as McGuver and others have shown, very doable to make your own..

Most non-cutting knurls are not sharp enough, even if you grind the edges. Most inexpensive knurl wheels donot have sharp peaks either.

Even the Quick ones are affordable, at least in UK in the size you would want to use. I'll see what Euro Tech wants for the same knurl wheel.

You would want 0.5" or so for diameter, bigger is more $ and not really what we need.

Gerrit
 
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Euro Tech pricing for the wheels is very reasonable so will be ordering a BR 14.5 and a BR 21.5 wheel from them (29 and 35 resp.). A big plus: Simon Li responds quickly which is becoming something of a rarety with suppliers. I'm still (not) waiting on a reply from Jan 2022 to local one about Accu -Trak wheels.
I'm presently only interested in single wheel coining knurls so just need to decide which design to implement. One is doodled up in F360 already for the 14.5 wheel, have to doodle up another and decide which to make. I'll start another thread when that happens.
 
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I'm glad their wheels are reasonable. My experience is from 8 or so years ago, and the world has changed since then :rolleyes:

I, like you are only interested in coining (straight) knurls...
 
VicHobbyGuy said:
Actually, the initial post in the thread -establishing the topic- was about :
Click to expand...

Yup you are right. I thought all that was in another thread but you are right, it's in this one too. I stand correctly corrected!

Gotta stick with the OP on this.

My own interest in this is the cut knurler and I have my own thread on a pressure knurler I am working on.

Too many knurling threads all at once. Too much for an old man like me to keep straight.

Thank you!
 
It's normal for discussions to wander. @Degen was just getting things back on track for a bit.
I couldn't resist a chance to point out a glaring price disparity.
Carry on.. :)
 
I have primarily used a pressure type push tool but am beginning to suspect that depending on how you set up with it it goes from being a forming tool to a cutting tool.

Aside from ease of knurling in a hard material and crisper lines of cut knurling, the advantage of a good pressure knurling is the work hardening of the surface of the material (forging of the knurling) for a longer life.
 
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