View Full Version : Fabrication and Shop Techniques Question about 3-knurl knurler

Juan Hovey
03-22-2016, 9:27 PM
Hey, folks:

I'm making myself a three-knurl hand knurler as follows:


I plan to machine the middle and lower steel cross pieces to accept the knurl wheels and pass pins through both cross pieces to act as axles for the three knurl wheels.

But it occurs to me that the two upper wheels might need to be separated by a specific distance in order to generate proper diamond patterns. Am I right about this? If so, how far apart must they be?

The two upper wheels are 3/4 inch in diameter. The lower wheel is smaller, at 5/8 inch. All three are 14 tpi wheels.

I don't think the smaller size of the lower wheel is a problem, but it I'm wrong, please let me know. On the other hand, I do wonder whether the third wheel is a problem for a different reason -- namely that the pattern of the metal it deforms will not be congruent with the pattern generated by the two upper wheels. Am I right about this? If so, is there a solution?

If not, I may have wasted some time with this knurler. Still...

Thanks in advance for any help you can give me.

Marion Smith
03-24-2016, 11:26 PM
This looks interesting, but in my machining experience, knurling is a " get on-get off" kind of world. Dwell is not your friend. I'm curious, are you trying to knurl up ridges to increase the OD for gripping characteristics? If so, perhaps a "staking" jig might be in order. I saw one a guy made years ago, he rigged up a vee block, a homemade lil frame, and a letter "I" punch with spring retract. It was pretty neat. Simple, functional. I like the looks of your gizmo there tho!

Juan Hovey
03-25-2016, 8:12 AM
Marion - I'm making this knurler in hopes that it will produce better knurls than I've been getting with scissors- and bump-type knurlers for the lever cap screws of my infill hand planes - "better knurls" meaning sharp and consistently shaped, with no run-on patterns.

My theory is that at the very least a three-wheeler should prove more stable than other types of knurlers, given the forces generated inward by two wheels above and one below. Also, as I will operate the knurler by hand using a shop-made crank to turn the spindle, I expect that this will give me better control over the pattern being created. Last but not least, I'm hoping all this will happen without stressing the spindle on my Seig C3 mini-lathe.

I don't have the third knurling wheel in the device yet; it's on the way from my e-Bay supplier, won't get here till Monday. But I rigged a workaround by wrapping a soft rubber grommet around a hard-plastic spacer, then ran a 3/4 inch brass rod through the device and got these knurls":


As you can see, they're crude, but I'm confident that, given time to practice, I can produce better results.

Here's a photo of one of my infill smoothers - a NO. 3 in ebony and another in English walnut.

Brian W Smith
03-26-2016, 8:06 AM
That's pretty slick,first off.We're all going to approach things a little different,this is good.So this isn't a criticism but what popped into my pea brain at first glance.If that knob/handle was longer(leverage),and more robust..to the point of being integrated with the forces generated whilst turning..whew,

I'd lock the part in a vise/fixture of some sort and use your tool in a pipe cutter fashion.

We do our knurls on one of the bigger lathes,but power off,manually turning the spindle...advancing the carriage by feel.Your turner would work nicely in our shop,albeit with a longer handle(mentioned).

Juan Hovey
03-26-2016, 9:59 AM
Brian - I like your ideas. Tell me more about the handle and how to integrate it with the forces generated while turning.

Also, I do plan to use it pipe-cutter fashion and to turn the spindle manually. But I can't quite see how 1) I might mount a vise on the lathe or 2) mount the tool in a vise. Tell me more - and many thanks.

Brian W Smith
03-26-2016, 6:34 PM
Juan,should have been said,vise/fixture OR lathe chuck.We do ours second op after turning in a lathe.But it takes time....which is something we take very serious because of $$.So,your knurler would save us a precious few minutes,but that does add up.

As for the handle,just saying it needs to be designed in a way that "supports" the overall design vs trying to either tear the assembly apart or otherwise compromise the tool.There,clear as mud,haha.One idea(one of several),would be like large tap handles work..in that your tool is a sub assembly that fits into a window of sorts within the handles design.Another tool you may gain insights from are used in gunsmithing,google "action wrench".Made for separating barrels from the receivers.Along those lines again is a revolver frame wrench.I believe it's Md. Gunworks.

Marion Smith
03-30-2016, 6:48 PM
Juan, I see what you are doing there now. There are formulas for knurling that determine the pitch required for your knurl rolls. You can't knurl just any diameter with any pitch knurl roll. It has to do with circumference. If your pitch or diameter is off, you get poor results. If you contact Reed with your project specs, I'm sure they can get you the proper pitch rolls. Then, I would bet you can go back to your two roll knurling tool.

george wilson
04-15-2016, 7:33 PM
I knurl any diameter I want with good results,and I never worry about diameters. Knurling is more of a skill than a mathematical process.

Knurling changes the diameter of the metal anyway,and there are different pitch knurls. Knowing that Juan has a Seig lathe,I certainly do recommend a 3 wheel knurling tool. I don't think the Seig could handle a 2 wheel model. I recommend forgetting about a 4 wheel knurling tool.

I recommended use of FINE pitch knurls for brass. Brass starts coming apart if you try using coarse pitch knurls. I have trouble on brass even with the more coarse knurls I made,called micrometer knurls on brass.

Another thing I recommend is annealing the brass before knurling. Using half hard brass,you are already half way to the brass getting over worked. Heat the brass red hot and LET IT AIR COOL. Quenching brass when it is too hot can cause splitting,cracking,distortion,etc. Best to just let it air cool. It will be just as soft if air cooled. Don't worry about the brass being too soft to make your cap screws from. They used cast brass on most things in the 19th. C.,and on everything in the 18th. C..