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How to align knurler?

DPittman

DPittman

Ultra Member
What is the proper way to align my scissors/pinch knurler o the vertical axis of the material I want to knurl? How important is it to get that perfect? I've always eyeballed it and sometimes my knurling is ok and sometimes not so great,View attachment 29827 but I've been doing a few other things less than optimal also when it comes to knurling.
 
Hmnn that picture showed up as a link?

Try another... a quick knurling turned out not too bad?
20230122_131034.jpg
 
DPittman said:
What is the proper way to align my scissors/pinch knurler o the vertical axis of the material I want to knurl? How important is it to get that perfect? I've always eyeballed it and sometimes my knurling is ok and sometimes not so great,View attachment 29827 but I've been doing a few other things less than optimal also when it comes to knurling.
Click to expand...
This is from Accu-Trak's tech information:

1674418561991.webp


The only thing I did different, was when I determined where my top dead center would be, I stayed back about 0.020" from that point. I wanted the forces directed slightly rearward into the cross-slide lead screw. My thinking is that if the knurls were exactly centered, the play in the lead screw could shift the whole cross-slide forward and back by the amount of the play. I honestly don't know if that would make a difference or not.
 
I demo'd a LOT of knurling when I was teaching guys and gals to use a lathe!

I had one hard and fast rule. The was, go hard, and go fast!

Trying to find the perfect diameter or the perfect place to start, has proven to be a failure, to me. Dig the bugger in, make it work like it owes you money, and you hate it for that, and it almost always turns out to produce clean and sharp diamonds!

A little coolant or cutting oil helps, but mostly, it's about how hard you dig in!

Cut knurling may be a whole 'nuther thing. Dunno. never used it. Formed knurling, has always worked as described!
 
trevj said:
I demo'd a LOT of knurling when I was teaching guys and gals to use a lathe!

I had one hard and fast rule. The was, go hard, and go fast!

Trying to find the perfect diameter or the perfect place to start, has proven to be a failure, to me. Dig the bugger in, make it work like it owes you money, and you hate it for that, and it almost always turns out to produce clean and sharp diamonds!

A little coolant or cutting oil helps, but mostly, it's about how hard you dig in!

Cut knurling may be a whole 'nuther thing. Dunno. never used it. Formed knurling, has always worked as described!
Click to expand...
Wow very interesting and completely contrary to other info. Thanks for sharing your experience, I'm going to try tour method next time.
 
DPittman said:
Wow very interesting and completely contrary to other info. Thanks for sharing your experience, I'm going to try tour method next time.
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Strong part, or well supported from both ends!

It is a forming/displacing operation, and really does require that you not try to sneak up on it.

I have seen a great number of guys that were convinced that they had all the math worked out, so that their knurls came out perfect, which is fine, until they stop working right...

One of the confidence exercises I had apprentices do, was to cut a raised shoulder on some stock, knurl it, then shave it off, and repeat, to get a feel for the forces involved. A little cutting oil or coolant, goes a long ways too, to keep the chips flowing clear, rather than being pressed back in to the surfaces formed.
If I had a length of knurl to do, I wold start at maybe half or a bit less of the face width of the knurl, hanging over the edge of the raised area, and then use the power feed to move it along.

What worked for me, anyways.
 
DPittman said:
Wow very interesting and completely contrary to other info. Thanks for sharing your experience, I'm going to try tour method next time.
Click to expand...
I'll say that I just noticed that you were looking for pinch knurling info! All the stuff I did was old school, two roller knurling.

From the picture of your results earlier in the thread, I would suggest that you try a little tighter setting on the jaws, towards helping form up the diamonds and covering the double-cut pattern.
 
The math approach never made a lot of sense to me with knurling as the circumference the ends of the teeth start with, isn;t where they end up.....so how does having the circumference some multiple of the pitch accomplish anything?

Like trevj says, apply the pressure. I do not like the old style two roller knurls. Too tough on the machine and I can see that amount of pressure doing bad things.....like embedding any crap present in the flank of the bronze nut thread. The scissor knurls otoh, have at it, with mine I knurl in one pass. The scissors I have are forged ones, not sure the brand, but old quality stuff. They are somewhat loosely constructed; I assume that if floating a bit they can find their own alignment? Seems to work. crank them down until you get a good knurl then feed.

I've also made a cut knurling tool which is the best approach, no strain on anything and sharp crisp knurls, even in brass. A calculation probably makes some sense with cut knurling, but I've not bothered and it seems to work out. If it doesn't, advance in 15 thou and take another pass lol
 
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Its a good point, I don't know the exact answer. Other than to note the big name companies all have similar formulas as was mentioned. They don't make money selling formulas, they make money selling tools that do what they are supposed to do. The math isn't hard & you have to turn the OD to something anyway. So if it puts you into a, lets call it 'preferable range of increased success', than its worth the minor effort. My own gut feel is because its a deformation process, there probably is some latitude. Its not as stringent as 2 gears meshing on their pitch diameters with matching tooth pitch. But I also think that there are combinations of stock diameter & knurl pitch that don't play as well together, like small diameter + large pitch means you are potentially deviating from a sweet spot. Now we typically choose finer knurls for smaller knobs so it could be this kind of self-compensation going on. This was my personal experience. Part A looks nice, different diameter/knurl pitch combination part B, not so much. The other thing is, hopefully not offending anyone on the forum, its more of a general internet thing - sometimes knurls look like sh*t and the person just doesn't know it or doesn't particularly care about it. If its grippy & you're happy, that's really the end of discussion. No different than sanding or buffing or chamfering machined surfaces vs leaving it as is. But commercial output may have to live or die by other aesthetic standards, which is kind of what knurls are for the most part. Having said that I have commercial tools that look like knurl tire tracks, they don't even meet the 'grip' criteria.

In terms of push in style vs scissor style, not even a question in my mind. For typical hobby style lathes that stress has to go somewhere. The worst is probably increase wear & tear on your cross slide feed screw & ABL nut, all focused on a tiny surface area of few engaged threads. Those lathe components can be a pain to source or replicate unto themselves, why aggravate the timeline & expense.

Now what's interesting is the same discussion applied to cut knurling. Some cut knurl toolmakers have a similar but slightly different formula (which maybe infers there is some basis to the calculation). But with cut knurling, virtually no deformation, its predominantly a cutting action. I've also seen a another manufacturer not even mention the issue, but still chasing down what that infers. Do they mean refer to machineries handbook or CAM guidance (ie. not our responsibility to educate you). Or do we infer diameter doesn't matter? @Mcgyver did you come across any literature when you developed your cut knurler?
 
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Hi Peter, I don't recall ever reading any requirement, but that doesn't mean it wasn't there. The whole diameter matters/doesn't debate is as old as the overhead drive. In my experience, via plastic deformation or cut, diameter has not mattered. Not mattering for deformation has logic to it, not mattering for cut kind of doesn't, but is my experience. Maybe with the cut, I've been like the broken clock that is still right twice a day..... and there are lots of guys in the other camp as well even with deformation. Whatever works for you.
 
Mcgyver said:
I've also made a cut knurling tool which is the best approach, no strain on anything and sharp crisp knurls, even in brass.
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Straying a bit from deformation knurling technique and I will start a new post about cut knurling soon, But while on this topic, have you ever come across data like conventional knurling requires 100 units of feed force and cut knurling only requires 20 for a comparable pitch form? Or maybe 20 is actually 60 or...? Maybe there is something in CNC guidelines but I couldn't find a quick answer. I'm not taking your words as 100% literal but no strain to me means 'very little' and what I'm seeing is 'something' just experimenting & traversing by hand. 0.6mm pitch isn't very much, but even a dedicated cutting tool taking 0.6mm (0.024") DOC infeed requires some lateral carriage force at low RPM & a rotating knurl wheel must surely be less efficient mass removal mechanism.
 
PeterT said:
Straying a bit from deformation knurling technique and I will start a new post about cut knurling soon,
Click to expand...

Can't wait.

I am totally fascinated by cut knurling and can't wait to make my own tool for it!
 
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