extra-fine knurling

Well as Not Done It Yet has not got back to us yet I'll enlighten you as to how the screwcutting method may work in theory.

Any fine pitch thread won't be any good as you will get a very long groove pattern that runs around the rod not across it so only good for pulling not turning.

If you up the pitch then you start to get something more like an oil groove, pitch is 1D

As I mentioned earlier and Steve also mentioned to get something like a knurl then a multi start thread is needed, this is the same pattern as above but with a 24 start

Still the diamonds are a bit long so playing about with teh figures to get the optimum diamond pattern the pitch of the "screw" needs to be Pi x D and the number of starts sufficient to make sure one Vee runs into the next and does not leave any flat tops to the diamonds (had to shorten the sample as it was taking the CAD a long time to do the cutting)

If you want to look at this finished knurl in more detail there is a 3D pdf here that allows the part to be moved about, zoomed into etc

The only problem with this is that unless you are trying to cut knurl a 1mm dia rod most lathes can't easily cut PiD pitches, the example above was 50mm dia so needed a 157mm pitch or about 0.17tpi. So the only real options for a screwcut method would be an electronic leadscrew, 4-axis CNC or as Michael hinted at above it could be done on an ornamental lathe.

J

Edited By JasonB on 30/09/2016 08:11:26

I'm not likely too, eiter. I made a suggestion. Im not an engineer. Others have added that it should work, but with a small pitch(?) multi-start thread setting. Go figure for yourselves. Snarky comments from (a) poster(s), who think he/they are above the rest, can sort it out between himself/themselves.

.

Excellent logic, Duncan

The cap on my toothpaste tube is slightly tapered; a suitable diameter; and quite strongly 'knurled' ... Ergonomically designed for its purpose.

One ergonomic subtlety is to use different styles and 'strengths' of knurl for different controls on an instrument: This allows them to be interpreted by touch, and, done well, that can be helpful.

Picking-up on yor closing remark: I think the diamond knurl might involve less 'shifting of metal' to produce a given visual and tactile effect [still pondering that one]; and may therefore be more efficient, production-wise.

MichaelG.

I read it as a question as it had ? at the end. But if it was a statement other members asked how that would work and I provided an answer to both as you did not come back with anything.

Also can't see anyone else suggesting a fine pitch, as I said above steve also mentioned multistart and I had mentioned it previously. Pitch is related to diameter but how fine the knurl is will be a combination of depth of cut and number of starts, as depth gets less number of starts has to increase.

Jason, not an engineer either.

Edited By JasonB on 30/09/2016 08:39:56

Two reasons I can think of - firstly, as Duncan suggests, it may be for production reasons / more forgiving of slight misalignment. The second is that if it is the head of something that needs to be pulled, diamond gives grip when applying axial force.

...." Jason, not an engineer either."

Oh yes you are:-

ENGINEER : A person who designs, builds, or maintains engines, machines, or structures.

Norman

( and, although I have engineering qualifications and worked as an engineer ( not mechanical I grant you)  you are a better engineer than me!)

Edited By NJH on 30/09/2016 12:12:49

Oh no I'm not.

What I meant was that apart from school metal work I have no engineering training or background and have never worked in the engineering profession.

Now if there was a definition of Model or Hobby Engineer as a person who designs models, builds models and maintains models all with no training or relevent qualificationsthen that cap may fit

Well Jason by the dictionary definition I posted what you do makes you ( and I guess the rest of us ) an engineer.

That you do this as a hobby with no formal training or experience makes you a very fine engineer in my book. That you are also prepared to give others on this forum the benefit of your experience is splendid. Don't be modest man - accept the praise!

Model engineers are often trained in the university of life, supervised by them selves, gaining instruction from books that are maybe 80 years old, and more. That was the time when industry closer matched a good bit of what we do. My first book on arc welding is dated 1942.

Ian S C

The Clickspring chap has a good video on making the tools to make rope knurls, if that is what is being requested.

**LINK**

Ed.