Ideas on knurling small diameter rod-Making a knurler

[mr coffee]

I'm new here, but I've been searching and reading everything I can find on the 'net on various tools and techniques for knurling trying to figure this out.

Here's what I am trying to do - put a medium diamond knurl on 303 stainless rod about 9 mm in diameter (or 11\32" - same difference).

I don't have a lathe. I do have a drill press. I can cut and notch fairly thick steel with an abrasive wheel fairly accurately on my old Shopsmith, although it does take a good while. I have more time than money these days - sound like a familiar song?

Since I only care to knurl one diameter, I'm not sure I really need a lot of adjustment for rod diameter, and the good quality 3-wheel hand knurlers seem like overkill, besides which they cost a pretty penny. I've also seen negative reports on the cheaper import versions (like the Enco).

Anyway, I figure I ought to be able to make a knurler with 3 wheels that I can clamp onto the 11/32" or 9mm rod in the drill press (or horizontally in the Shopsmith chuck) and knurl away. I want to knurl sections long enough to cut apart and make tiny knurled knobs (1/2" long) to go on fine threaded rod for adjustments (4-40). They will attach to the threaded rod with a set screw. I'm willing to spend some time making the thing (day or so).

Here's the ideas I've been playing with. Please share your experience with knurling and knurlers.

Would a knurler with ONE female diamond knurl wheel and two brass (or aluminum or even rubber-covered steel rollers) to keep it centered on the rod work? Would this be more or less likely to track than other designs?

What about one right and one left diagonal knurl and either a third diagonal knurl or maybe just a centering wheel (like above idea - i.e., one less knurl roller to have to track the other)?

On small diameter rod like this, how difficult is it to make the knurling track, i.e., not double? (Not trying to start anything, I've read all the old threads, but I'm guessing those discussions were more addressing knurling rod at least 1/2" to 1" in diameter, and I'm talking a tad less than 3/8". I can't figure out if smaller diameter rod makes tracking any harder - or easier, for that matter - hey, wouldn't THAT be nice!).

Would smaller or larger diameter knurl wheels be better for this application? The knurls seem to be mostly 3/4", but I have seen 5/8". Are the beveled knurls helpful? I don't have to knurl up to any flanges or make neat transitions to un-knurled sections of rod.

I am still trying to make sense of all this TPI and diametrical pitch stuff - I have read and am still re-reading all the stuff pointed out here from all the knurl companies, perhaps I'm just being a bit dense. Will any of the standard knurls track on 11/32" rod (or 9mm, if that's easier).

I'd like a medium knurl, but I'll take what works, preferably without buying a bunch of different wheels trial-and-error. Not asking for promises or easy answers, just what you think might be helpful to a novice at this other than the reading I've done and just diving in.

Thanks in advance for any help, thoughts, ideas.

And BTW, I LOVE this group. Hate I didn't find it sooner!

[radish1us]

If you don't want to fork out the dollars and want to make a knurling tool, then just take a stroll along to your closest engineering workshop and get them to do it.
You will still have to fork out with some dollars, but it will be a lot cheaper and easier this way.

[SGW]

Something like this?
http://www1.mscdirect.com/CGI/NNSRIT...MT4NO=36768068

[JCHannum]

This is a photo of a shop made hand knurl I aquired several years ago. I have never used it, but it has obviously seen quite a bit uf use. It uses three opposed knurls.



For a one off, having it done by a local shop if one exists might be most economical. Good knurling wheels are pricey, cheap knurls are a waste of money.

[mr coffee]

Thanks to all for replies, especially the picture by JC.

I was thinking I could make something like that. Or maybe I could find one used as you did. Any thoughts about where to acquire such a tool cheap?

SGW - Yeah, that's what I'm trying to avoid spending $300+ on ,<grin>

Has anyone tried using rollers and less knurl wheels on a hand knurler?

Any thoughts about tracking on small diameter rod?

Thanks

[deltaenterprizes]

That one from MSC looks like a pipe or tubing cutter could be modified to acomplish this task.

[Paul Alciatore]

To answer your question about tracking, knurls can mis track and produce a double pattern that is half the pitch of the wheel. However, they are also somewhat self compensating in that some slippage will occur as the wheels go around the work.

Each knurl has a particular pitch which should be specified when you buy it. The general held thought is that your circumference should be a multiple of that pitch (25X, 26X, etc.): at least approximately. If your circumference is half way between such a multiple (25.5X, 26.5X, etc.) then there is a good chance that mistracking and doubling up will occur.

So, as I see it, the trick is to adjust the diameter (circumference actually) so that you are closer to a whole multiple than to a half. Or pick a knurl size that works with your diameter. This may be possible if you look around as they are available in several pitches in either inch or mm units.

On the diameter of the knurls, I don't think that will make any difference in the tracking. But for small diameter work, smaller wheels are better perhaps as the work has to fit between them.

I would stay away from things like pipe cutters. One thing necessary in the tool is rigidity and no play. Pipe/tubing cutters are made with very loose tolerances that will cause trouble when knurling. I made a tool with a pair of slip joint pliers but it is difficult to use. You are actually better off with the cheap imported tools. If you are making a tool, do not allow too much slop in the pivots.

On a drill press, three wheels are an absolute necessity. You would never be able to keep it on the work otherwise. For a diamond pattern, you need one left and one right hand diagonal wheel. Someone may make a single diamond pattern wheel, but I would bet it is expensive. You may be able to use a plain roller for the third, but I would not even try. Rubber would be too soft for the forces involved. Heavy pressure is needed for knurling. Aluminum may work initially but will deform and distort under the pressures and eventually turn into a knurl shape itself. But it will continue distorting and will likely need to be replaced in short order. Harder metals will tend to flatten the pattern you are trying to make so they wil be counterproductive. Knurl wheels are relatively cheap so I would just buy two lefts and a right or vice-versa.

Another thing to keep in mind is control of the tool. Large forces are needed to knurl metal. With stainless, this is to be emphasized. It will be hard to keep the tool on the section of the work where you want it. This may be OK as you say you are not working to a particular shoulder or end point, but will be cutting to length after knurling. But it may be difficult to move the tool along the stock. You will need to either have a good, long handle for a good hand grip or the tool will need to be locked down (perhaps with some room to wiggle) to the drill press table and use the quill down feed. I think I would try the lock down idea myself, but I have no experience here.

You might want to consider an easier metal to work with like aluminum or brass.

[JCHannum]

There have been many pro and con threads on the pitch of knurls, and I won't go there except to say that I am a convert to the "pitch has no effect" side of the argument.

Diamond knurls are available either in male or female patterns that are about 50% more than straight or diagonal knurls. Perhaps a single diamond knurl opposed to two solid knurls that were offset from the knurl pattern would work. This would only produce a wheel wide knurl and might not be the desired outcome.

The hand knurlers can be applied and operated by hand with the work held stationary, not turned under power.

[Hal]

Mr Coffee

You might try on the practical machinist forum, and scroll down to the antique section. There do a search on rope knurling. If nothing else there is some of the finest examples of knurling. Be sure to click on the link, something to do with Ford.

Hal

[Paul Alciatore]

At the risk of starting one of those sessions that never get resolved to anyone's satisfaction, I just had another thought on the pitch and diamond pattern thing that was brought about due to the mention of rope knurls.

Straight knurls are a lot like gear teeth in that there is not a lot of wiggle room for the pitch to vary from the tool's pitch. It can and does vary a little and with a large diameter this is sufficient to allow the process to work. But the slippage is strictly along the length of the pattern.

Diagonal wheels have an additional factor as they can effectively slip sideways. That is to say, if the pitch of the workpiece needs to be different one way or the other the pattern wheel can turn at a slightly faster or slower speed and allow the pattern to match. This effectively allows a sideways slippage and is perhaps an easier thing.

With rope knurls, the pattern is very coarse; perhaps 1/4" or even 1/2" long. In this case, the length of the circumference would have to closely match a whole number of patterns as the slippage would not allow for very large adjustments. There is no room for what I called sideways slippage up above as the pattern is not a simple Vee or other linear shape so the additional leeway that diagonal wheels have is not present. A close match between pattern and work size is really essential.

A diamond pattern wheel would act much like a rope knurl. It would not allow the sideways slippage as the diamond pattern would not allow this. The pitch is not as large as most rope patterns so the problem is not as severe, but I would still recommend doing a calculation and matching the work size.

In view of the above, I would think it would be easier to produce a diamond pattern on a wider variety of sizes with diagonal wheels as opposed to using diamond pattern wheels. However, the diamond pattern wheel may produce a cleaner pattern on some materials as both sides of the diamonds are formed at the same time.