[How do I?] How to make a serrated roller?

[7milesup]

Thanks for liking the idea. The only problem that one can encounter is that the diameter
of the roller may not match the knurl requiring one to machine off several thousandths off
the roller until the knurl pattern matches the knurl. A lot of the time it works fine on the first
try. This phenomenon occurs with all knurling of course.

Yeah, there is a formula for that!
You take your knurling wheel and roll it along some paper so that it will make marks on the paper. Count off five marks at a time out to at least 80 marks. Measure the distance between the 80. The number that you measure isn't really important, but the larger the number, the more accurate your measurement will be.
Take your distance and divide by the number of wheel marks. In my case, it was 90 marks and a distance of 5.662." 5.662/90=0.0629 This is your circular pitch. Divide CP by Pi. 0.0629/3.14159=0.02002. Now, take this number and divide it into the diameter of your workpiece. You want it to be a whole number. I had a workpiece diameter of 1.375". 1.375/0.02002=68.68, which, of course, is not a whole number. Now, to know what diameter my workpiece should be, I take 68 (a whole number that is smaller than my calculated number) and multiply it by 0.02002. 68*0.0220=1.361. So, my workpiece should be 1.361" in diameter to get the knurler to make perfect knurls. The other option is to find a knurling wheel of a different diameter or number of cutting teeth to make it work.

I did not come up with that, so here is a link to the website that will walk you through it.

 

[piper184]

Joe Pie shows that the diameter is not as important as the math would suggest. He went through the whole thing on his youtube channel. The math, and then a practical demonstration on the lathe. He was just using aluminum but I think the lesson was solid.
Basically the knurls work their way down to a diameter that matches the pitch. It might not work so well in really hard material but for softer stuffyou don't have to be precise on diameter.
I only have a cheap bump knurl tool and sometimes it won't track no matter what I do. A scissor type is on my short list of need to make items. Quality wheels and lots of pressure seems to be the secret.

 

[cathead]

One can spend a lot of time cogitating over diameter and knurl size but the easiest thing to
do is to try the knurl and machine off a hair of diameter if needed. That's what one would have to do anyway
if it doesn't match up. I tend to look at things from the practical side rather than get cobbled up on an empirical
road block. Pi is good but then so is cake.

 

[7milesup]

@piper184 @cathead
For sure, the try-and-see method is my favorite, but I thought it was interesting that there is science behind the knurling process.

It is probably going to be a few days before I get back to this project since I have a wood and metalworking project for my niece's wedding that I need to get done.

 

[brino]

You would need closer spacing of the serrations

Fully agree with that.

I made splines here:
https://www.hobby-machinist.com/threads/my-first-and-second-attempt-at-cutting-splines.83187/

but notice they have a flat top. I would think you'd need sharp tops by doing less spacing or deeper cuts......

Please let us know what way you go and how it works out.
Very interesting thread!

Brian

 

[7milesup]

@cathead Where did you get your knurling wheels from?

 

[Radials]

Wester Roller Corp. in Bend Oregon will recondition that roller in polyurethane.

 

[7milesup]

Wester Roller Corp. in Bend Oregon will recondition that roller in polyurethane.

True. I can also buy a new one for a couple of hundred dollars from Woodmaster, but what fun is that?!

 

[Parlo]

Cut a series of grooves and fit o rings along the length.

 

[cathead]

@cathead Where did you get your knurling wheels from?

Neil,

There are a lot of listings on E-Bay for straight knurls. I would pick a coarse one for your application.
That's where I got my straight knurls. It looks like prices have gone up since I bought mine. You might
also check out Shars for a reasonably priced straight knurl. You need only one knurl.