Knurling tool build

[rogee07]

I would like to build a copy of the Marlco knurling tool or the copy of Marlco by Hemingway. Looks easy except for one thing I can't figure out how the fine feed lever on the back of the knurling tool works. Any advise would be appreciated.

Photo of the Marlco tool, note feed lever on rear of the unit.

http://www.hemingwaykits.com/acatalog/info_HK_1115.html

[brian Rupnow]

I'm pretty sure the lever is a cam-lock. The threaded adjustment brings the rolls in contact with the part, then the cam-lock adds the additional degree of force to actually force the knurls into the material.

[rogee07]

I'm sure that you are correct, however because of it's position I can't visualize how it can apply pressure on both arms at the same time.

[brian Rupnow]

Is it possible that each arm has gear teeth that mesh, so that cam action on the top jaw lever is automatically transferred to the bottom lever?

[BCRider]

It only needs to apply pressure on one and the floating arms divide it to both.

I've got one of the floating "X" style or scissors tools. The tension screw it came with is fairly light. In my thinking about it and from watching some videos of both the scissors types and Marlco type tools but without that rear cam I got the idea that it's not the best option to directly crush into the work with the screw but instead to set the spacing and the push onto the work.

Of course this means it's not a purely no side force job. But the strong wedging nature of working near the top and bottom of the work means that the side force applied to the lathe is light while at the same time the force between the knurls is high. And in fact from using the tool I found working it this way was far easier and put the knurls onto the work for a shorter time this way. So that quickly became the standard way for me to use the tool.

I see the cam as not so much an adjustment but a way to set and move onto the work in this same manner and then at the end of the pass(es) to release the pressure and clear the knurls off the work. I may well be wrong on that mind you. Depends on what the instructions say.

[rogee07]

OK, it is taking a while for the ideas to sink in, I'm getting a bit slow in my old age. The way this is starting to form in my brain, is that the top arm pivots on a cam/pin. Then by rotating the cam pin with the feed arm, pressure is applied to the top arm, thus causing pressure to be applied to the bottom arm. However, I don't understand how it causes upward pressure to be applied of the bottom arm.

[Bented]

Clamp tools can exert a large amount of force on the knurls.
I have broken them in the past, it is not pretty.

Of course I was making parts where the customer specified a diameter after knurling, + .010 - .000", do not try this at home.
Near full depth of teeth, this was a test in an effort to determine a starting diameter which the customer rudely omitted (-:



From the looks of the cam driven tool I would assume that the loads could be very high indeed.

[rogee07]

OK, the light bulb just came on and I can see how the pressure is applied to the bottom arm.
Thank you B.C.Rider your input was very helpful.

[BCRider]

You were thinking that the mid arm yoke didn't float up and down? I know that the first appearance when I first saw the Marl'co design a few years ago had me wondering until I thought about it and looked more at the pictures found out on the web.

[Bented]

Quite elegant really, the course adjustment sets the rough diameter, the lever operated cam sets the final diameter in use.
Side plates not shown for clarity.

[rogee07]

Bented, thank you that takes all of the mystery out of my thought process. Who ever it was who said a picture is worth a thousand words was sure wright in this case.

[Bented]

You are welcome, I could develop the full cad drawings for such a device but that would be a good deal of work, an hour knocking out an illustration is not.

[dian]

thinking about these knurlers i wonder about the mounting of the rollers. the rollers are hardened, right? and they run on a hardened pin? pins never seem to be bronze. are they pressed in in this case? that never seemed a good idea to me.

[ammcoman2]

This is the Hemingway knurler I made. A pleasure to use.

Geoff

[rogee07]

Bented,
I'm really pleased with your illustration, taking an hour of your time to answer my inquire is quite impressive to say the least. If your illustration is to scale, the tool turns out to be larger than most knurling tools. That size I'm sure would take all of the drama out of any work I would require it to do. What would the maximum diameter this tool be able finish. Could you give me a measurement from the center of the arm pivot to the center of the knurl support shaft, to properly put the true size of your illustration into prospective.
Thank you again.