Stock Diameter For Knurling Tools

Franko

Franko

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I haven't knurled anything before and I'm thinking of making some knobs to replace the bar levers on some of my C-clamps.

Does the diameter of the stock matter when knurling?

It seems like the diameter would have to match the interval of the number and spacing of the grooves on the tool, or on the second rotation, the tool would miss the grooves of the first turn and make ragged cuts.

Is that so, or does it take care of itself somehow?

If it is so, how do you compute the ideal diameter of a part to be knurled?
 
Perfect, Will. Thanks.
That's exactly what I need.
 
Franko, you will find there are two schools of thought on this subject. Some like to use formulas or math and some just knurl the piece as is. I used to be in the former and now I am in the latter. The precise diameter of the work can be off a bit and still knurl fine if you use enough pressure, and I have no problem with tracking.

My suggestion is that you try both ways and see. When I did this I had better results just increasing pressure and haven't looked back. I should qualify that I use a scissors knurler, not a bump knurler, so keep that in mind.
 
Thanks, Mikey. I will experiment.
Bill, the calculator on LMS doesn't work, but the spreadsheet I downloaded does.
The other mentioned in the link that Will posted won't work for me because I'm on a Mac, and not inclined to install Windows parallel.

The pitch of my knurling tools is not on them anywhere. I had to get out my microscope and flood light to measure the marks.
 
mikey said:
Franko, you will find there are two schools of thought on this subject. Some like to use formulas or math and some just knurl the piece as is. I used to be in the former and now I am in the latter. The precise diameter of the work can be off a bit and still knurl fine if you use enough pressure, and I have no problem with tracking.

My suggestion is that you try both ways and see. When I did this I had better results just increasing pressure and haven't looked back. I should qualify that I use a scissors knurler, not a bump knurler, so keep that in mind.
Click to expand...

I wouldn't really call it two methods of thought. It really depends on the material hardness one is working with & the type of knurl they are after.

For softer materials & fully formed knurls you can get away with just feeding in until the knurl is formed properly. For harder materials & partial form knurls calculating is almost always needed to avoid double tracking. For partial form knurls you could get away with just feeding in until a proper knurl is formed & then skim the peaks off to get a partial form knurl. That is if final diamter is not important. And if you are working with a cut knurler you will more than likely need to calculate rather than getting lucky.
 
I'm going to have to try those accu-trak knurls. Thanks for the tip.

My knurling results are often inconsistent, but I've been getting better (LOTS of cutting oil, power feed, and clean tools seem to help). It doesn't seem to matter whether I do the pitch/diameter calculations or not (though it makes sense that it's more important for harder materials).

One thing I've always been curious about is the diameter calculations: Since the resulting knurl has appreciable depth (what, about 0.010" per side or 0.020" on the diameter?) why do the formulas ignore this fact and only use the outer dimensions of the stock for calculating?

I suppose that with forming tools the process moves material from the indentations outward, but it always seemed kind of arbitrary to just use the precise stock diameter. I know that knurling usually makes the stock diameter larger as a result — press fits in a too-large hole depend on the fact. So why do the calculations at the original diameter?

Just curious.
--
Rex
 
Franko said:
Thanks, Mikey. I will experiment.
Bill, the calculator on LMS doesn't work, but the spreadsheet I downloaded does.
The other mentioned in the link that Will posted won't work for me because I'm on a Mac, and not inclined to install Windows parallel.

The pitch of my knurling tools is not on them anywhere. I had to get out my microscope and flood light to measure the marks.
Click to expand...

It only works with Internet explorer. I downloaded the whole page and use it offline. Firefox is using the latest specs so many javascripts will no longer work with Firefox. Just a head up if you want to use it.
 
The spreadsheet I downloaded works fine, Roy.

I downloaded Numbers (Apple spreadsheet app) for my iPhone and iPad, so I use that spreadsheet to compute my knurl diameters on them.
It couldn't be more convenient.
 
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