Tool My most hated tool

[6.5 Fan]

I actually don't mind my elcheapo knurling tool. I bought one of those triple knurl ones back in the stone age and have used it a few times with good success. Not something i use much due to the type of machine work i do, mostly repairing broke stuff.

 

[Susquatch]

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.

There are lots of differences. I'm only just beginning to understand them. My main issue was trying to understand the theory of how cut knurling worked. I "believe" I understand it now after literally days of painful research.

At one point, I thought perhaps there was a transition between forging the surface and cutting it sort of like you describe. I no longer believe that at all.

There are several primary differences.

Cut knurling does not "move metal around" and therefore does not increase the diameter at all. It literally cuts chips out of the metal with a sharp edge. It also results in deeper cleaner edges and patterns (eg diamonds). It also exerts essentially zero lateral pushing force. And lastly, there are zero inexpensive ones out there.

Push knurling, deforms or forges the metal by shoving it around. This work hardens the surface. It also increases the diameter. Very high pinching or pushing forces are required. Some chip removal might occur but they are minimal. Very low cost devices are available.

I don't believe there are any transitional devices or methods. One deforms the metal, and the other cuts it.

Studying the process and the differences drove me bonkers. NOBODY explains the theory. I did the best I can at this point in post #62 above. I think it's sad that the only available sources of info are hateful youtube videos.

 

[Susquatch]

I actually don't mind my elcheapo knurling tool. I bought one of those triple knurl ones back in the stone age and have used it a few times with good success. Not something i use much due to the type of machine work i do, mostly repairing broke stuff.

I don't mind it either. I think it has its place. It's especially useful to increase the diameter slightly when a fit is too loose. But it's also fine for many knobs and such.

I am a lot like you. I think it's a farming thing. We do a lot of fixing broken stuff. You can't mail a broken tractor away to get it fixed.....

 

[Former Member]

There are lots of differences. I'm only just beginning to understand them. My main issue was trying to understand the theory of how cut knurling worked. I "believe" I understand it now after literally days of painful research.

At one point, I thought perhaps there was a transition between forging the surface and cutting it sort of like you describe. I no longer believe that at all.

There are several primary differences.

Cut knurling does not "move metal around" and therefore does not increase the diameter at all. It literally cuts chips out of the metal with a sharp edge. It also results in deeper cleaner edges and patterns (eg diamonds). It also exerts essentially zero lateral pushing force. And lastly, there are zero inexpensive ones out there.

Push knurling, deforms or forges the metal by shoving it around. This work hardens the surface. It also increases the diameter. Very high pinching or pushing forces are required. Some chip removal might occur but they are minimal. Very low cost devices are available.

I don't believe there are any transitional devices or methods. One deforms the metal, and the other cuts it.

Studying the process and the differences drove me bonkers. NOBODY explains the theory. I did the best I can at this point in post #62 above. I think it's sad that the only available sources of info are hateful youtube videos.

I find this kinda strange that a cutting action does not apply lateral force as it is required to keep a tool engaged.

I went back to somethings I remembered being shown briefly by an old master years ago which was to slightly skew your knurling head no explanation just do it type thing, wish he was still around to ask. Having done it relatively recently (several years ago) I noticed skarf increases dramatically, with better "cuts" and a lot less pressure and load on the lathe. Same low cost push type device.

So think about this thread trying to understand the differences between cut and pressure knurling. What we see and call cut knurling is exactly that as it forces the a very localized and directions pressure point which removes material significantly more than straight pressure alone.

Thinking about it more, true "cut" knurling is more akin to checkering which truly requires a cutting action, or in the case of checker knurling a very course threading cutting action in both hands which it is not.

So some food for thought and discussion to determine what is actually happening. My feeling why there is little increase in diameter is that the skewed cutting wheels are clearing (scrapping) material in the rotational process besides displacing it and hardening it (though not as much of the latter).

Thoughts????

 

[gerritv]

Studying the process and the differences drove me bonkers. NOBODY explains the theory. I did the best I can at this point in post #62 above. I think it's sad that the only available sources of info are hateful youtube videos.

You missed out then on the other pleasurable activity: reading patents. ". A knurling tool comprising a tool head which carries at least one knurling wheel and which is mounted adjustably on a shaft, wherein the tool head is mounted on the shaft linearly displaceably transversely with respect to the axis of the shaft, wherein there is provided a fixing device for Securing the relative position of the tool head and the Shaft, the fixing device being arranged between the tool head and the shaft."

Google Patents

Search and read the full text of patents from around the world with Google Patents, and find prior art in our index of non-patent literature.

patents.google.com

This pulls up most knurling related patents

 

[gerritv]

And having suffered through 151 of them, here is an early embodiment of the cut knurler (there is a fascinating arrray of styles of knurling tools, including multiple variations of the scissors style): https://worldwide.espacenet.com/patent/search/family/003671430/publication/GB724693A?q=pn=GB724693A British patent version of the orignal German one, 1945 era

You will have to follow the various headings to get all the scoop.

Gerrit

 

[Susquatch]

I find this kinda strange that a cutting action does not apply lateral force as it is required to keep a tool engaged.

I went back to somethings I remembered being shown briefly by an old master years ago which was to slightly skew your knurling head no explanation just do it type thing, wish he was still around to ask. Having done it relatively recently (several years ago) I noticed skarf increases dramatically, with better "cuts" and a lot less pressure and load on the lathe. Same low cost push type device.

So think about this thread trying to understand the differences between cut and pressure knurling. What we see and call cut knurling is exactly that as it forces the a very localized and directions pressure point which removes material significantly more than straight pressure alone.

Thinking about it more, true "cut" knurling is more akin to checkering which truly requires a cutting action, or in the case of checker knurling a very course threading cutting action in both hands which it is not.

So some food for thought and discussion to determine what is actually happening. My feeling why there is little increase in diameter is that the skewed cutting wheels are clearing (scrapping) material in the rotational process besides displacing it and hardening it (though not as much of the latter).

Thoughts????

Sort of, but try to stop thinking about simething in between that is part pressure and part cutting. It isn't a little of each. One deforms the metal with a few chips breaking off as the get pushed around, and the other is pure cutting with zero deformation.

Yes, cut knurling is exactly like checkering. If you think of it as a hand held metal graver, but with the part and tool both rotating you have the action taking place. The rotating wheel on an angle provides the tap tap tap function of the graver hammer.

You can also think about it like a sharp lathe cutting tool traversing right to left except the lathe tool rotates with the part instead of standing still. Perhaps, in your mind, replace the fixed lathe tool with 30 lathe cutting tips mounted on a wheel. Although that in itself will work, it will require significant longitudinal force because there is no tap tap tapping. But if the wheel is tipped, it starts tapping. Each tooth of the knurler moves the cut a little further down the part because of the angle of the knurling wheel, and the carriage moves the whole graving process along with each cut tip on the knurling wheel tap tap tapping along as they follow along. Better yet, think of it like a shaper with an extremely short stroke that rotates around the part as it progresses down the length.

As @gerritv said earlier, the difference between the two shows up as forging and moving metal which expands the diameter vs cutting tiny little chips out with no metal forging at all.

Push Knurlers forge the part squeezing metal along the entire width of the tool. Cut knurlers cut on the leading corner and the rest of the groove merely keeps everything going in the right direction and provides some leverage to keep the cutter and groove aligned almost like a gear would.

Very very similar to a checkering tool.

Another visual would be annular gravers mounted on a swash plate that is slowly moved down the part as it swashes along.

It's actually a very elegant process once you see it in your mind.

 

[Susquatch]

And having suffered through 151 of them, here is an early embodiment of the cut knurler (there is a fascinating arrray of styles of knurling tools, including multiple variations of the scissors style): https://worldwide.espacenet.com/patent/search/family/003671430/publication/GB724693A?q=pn=GB724693A British patent version of the orignal German one, 1945 era

You will have to follow the various headings to get all the scoop.

Gerrit

You are right. Reviewing patents is more painful than YouTube in many ways.

I did try looking at patents and found that none I looked at provided any really good theory.

As is often the case, I actually got the most insight from things the members said. Putting the pieces together was only difficult until I let go of my predudices about what was happening. Then suddenly, the fog cleared and there it was.

I think a magic moment happened when @Dabbler mentioned a graver to me, you pointed out that there was no diameter change, and I stopped the wheel and part from rotating in mind - or perhaps better said, stopped letting the rotating fool me into not seeing the longitudinal component of the movement of the cutting teeth on their own.

 

[Former Member]

Sort of, but try to stop thinking about simething in between that is part pressure and part cutting. It isn't a little of each. One deforms the metal with a few chips breaking off as the get pushed around, and the other is pure cutting with zero deformation.

Yes, cut knurling is exactly like checkering. If you think of it as a hand held metal graver, but with the part and tool both rotating you have the action taking place. The rotating wheel on an angle provides the tap tap tap function of the graver hammer.

You can also think about it like a sharp lathe cutting tool traversing right to left except the lathe tool rotates with the part instead of standing still. Perhaps, in your mind, replace the fixed lathe tool with 30 lathe cutting tips mounted on a wheel. Although that in itself will work, it will require significant longitudinal force because there is no tap tap tapping. But if the wheel is tipped, it starts tapping. Each tooth of the knurler moves the cut a little further down the part because of the angle of the knurling wheel, and the carriage moves the whole graving process along with each cut tip on the knurling wheel tap tap tapping along as they follow along. Better yet, think of it like a shaper with an extremely short stroke that rotates around the part as it progresses down the length.

As @gerritv said earlier, the difference between the two shows up as forging and moving metal which expands the diameter vs cutting tiny little chips out with no metal forging at all.

Push Knurlers forge the part squeezing metal along the entire width of the tool. Cut knurlers cut on the leading corner and the rest of the groove merely keeps everything going in the right direction and provides some leverage to keep the cutter and groove aligned almost like a gear would.

Very very similar to a checkering tool.

Another visual would be annular gravers mounted on a swash plate that is slowly moved down the part as it swashes along.

It's actually a very elegant process once you see it in your mind.

Not so sure I agree with this (yet) have to do some nore digging on the subject time permitting.

 

[Susquatch]

Not so sure I agree with this (yet) have to do some nore digging on the subject time permitting.

Digging helped me very very little. I got my best tips from @Mcgyver, @gerritv & @Dabbler. After that it was all about seeing the parts and the process in my mind and then confirming in the shop with a mock up.

Again, I recommend reading my theory description in post 62.

 

[Former Member]

Digging helped me very very little. I got my best tips from @Mcgyver, @gerritv & @Dabbler. After that it was all about seeing the parts and the process in my mind and then confirming in the shop with a mock up.

Again, I recommend reading my theory description in post 62.

I did and don't see it that way based on all the information and my experience (though limited) along with engineering and machining.

As I mentioned before I am not sure it is a cutting action as we normally define it but more of a hybrid that mimics a cutting action and achieves similar result.

I'm sure there is an answer on the web, question become how do the search engines hide it to maximize profits?

 

[Former Member]

Found this to start.

Cut Type Knurling - Knurl Holders

Accu Trak makes and sells knurls, knurling tools and knurl holders that are manufactured to extremely high standards from premium alloy tool steels and made to fit any machine.

accu-trak.com

 

[Former Member]

And this which I think somewhat confirms my suspicions, as it matches what the old school trick did.

I also suspect that new style tooling improves on the action, though it is still a hybrid function.

https://www.practicalmachinist.com/tips-and-tricks/the-basics-of-knurling/amp/

 

[PeterT]

just noticed on your link, wrench flats on the tightening wheel

 

[Susquatch]

Found this to start.

Cut Type Knurling - Knurl Holders

Accu Trak makes and sells knurls, knurling tools and knurl holders that are manufactured to extremely high standards from premium alloy tool steels and made to fit any machine.

accu-trak.com

The accutrack is good stuff but provides no theory.

And this which I think somewhat confirms my suspicions, as it matches what the old school trick did.

I also suspect that new style tooling improves on the action, though it is still a hybrid function.

https://www.practicalmachinist.com/tips-and-tricks/the-basics-of-knurling/amp/

There are errors in this writeup. Can't believe everything you read on the internet.

I no longer have any doubt at all. Cut knurling cuts. No ifs ands or buts about it. No halfway, no grey. It cuts just like a lathe tool cuts. It's just that the cutting is in motion.

My advice is to stop fighting it or doubting it. Open your mind to it and ask how not if. If you don't, you will prolly never see it.

Have a real close look at this photo. It might help.



The carriage is not being moved in this photo. It is strictly cut by the cutting edge of the knurler as both the shaft and the knurler rotates around. The cuts are made be the leading edge of the knurler as the rotate around on an angle. This particular one cuts a horizontal knurl. You can also see how the cutter starts shallow then progressively deeper as it rotates through closest approach.

 

[Former Member]

I saw the photo and it shows more than just a cut, if you notice the band where the "cuts" are that would indicate displacement. So....open mind...I still think that there is more involve than a simple cut, I'll keep digging.

 

[Susquatch]

I saw the photo and it shows more than just a cut, if you notice the band where the "cuts" are that would indicate displacement. So....open mind...I still think that there is more involve than a simple cut, I'll keep digging.

I clipped this particular photo from a video back when I was trying to understand how it worked. The slight band is the result of starting in the middle of the bar for calibration. As a result it will rub a bit before it gets going - a bit like a plunge cut. You are not supposed to do that. It should be started at the end with a starting chamfer. You don't get that mark when it is started properly.

 

[Former Member]

I clipped this particular photo from a video back when I was trying to understand how it worked. The slight band is the result of starting in the middle of the bar for calibration. As a result it will rub a bit before it gets going - a bit like a plunge cut. You are not supposed to do that. It should be started at the end with a starting chamfer. You don't get that mark when it is started properly.

Yes I would agree, but look again it on both left and right side. Based on how the cutter works a band on the left only I would agree but where/how does the contact on the right occur when there is no cutter present to make contact with? Again, open mind.....there is more going on and its not as cut and dry. More research is needed.

 

[gerritv]

The same way a lathe cutting tools works, it cuts at the point of contact. You will have seen that this photo is part of aligning the tool, this particular photo is of getting the angle correct. The wheel never cuts along its full width, only the left tip. The wheel must be at an angle (usally 30dg) for this to work.

The operation always starts at the end of the work piece (or a step if knurling in mid of some length). 1mm or so wide, crank in 0.5 of pitch and then feeed slowly axially. With the wheel (and thus tips) at an angle, it cuts as you move along.

I suggest you either model this in Fusion360 or make one. Even better, do both . Like the Euraka relieving tool, this is easier to understand when you see it in operation than it is to explain in words. If you make one, get the proper wheels, Quick/Zeus/Accu-Trak/Dorian etc. all make cut wheels. You will notice that these are narrow, since they cut only at the leading tips.

I will start a thread when mine arrive and I have the tool built. Single wheel only for RAA pattern

Gerrit

 

[Susquatch]

Yes I would agree, but look again it on both left and right side. Based on how the cutter works a band on the left only I would agree but where/how does the contact on the right occur when there is no cutter present to make contact with? Again, open mind.....there is more going on and its not as cut and dry. More research is needed.

Stop fighting it, and stop letting doubt cloud your mind Degen. I have been where you are. I don't think you will ever see it till you let go of your prejudices. Once you see it, you will wonder how you missed it.

I agree with @gerritv, some people just have to see it for themselves. Model it or make one. Even if you never see the way it works, cutting knurlers belong in your toolbox.