Knurling speed

There is a lot of miss-information about knurling. Many references state that it’s rather like cutting gear teeth and that the circumference of the item to be knurled must be an integral number of knurls, otherwise they won’t line up and you get cross knurling. This is total nonsense; it’s nothing like cutting gear teeth; each dimple is formed by deforming or moulding the metal, not by cutting it. Yes, you do get some powdery swarf, but nowhere near enough to fill the dimples.

Once the pattern has been established, as the workpiece revolves, each “hill” of the knurling wheel slips into the next “valley” of the workpiece, provided that the valley is deep enough to exert sufficient force to change the speed of the knurling wheel. If the next valley isn’t deep enough, then the next hill tries to make its own valley and you get a cross knurl. The secret is to make the first set of valleys as deep as you can by exerting as much initial force as possible. You can then deepen the pattern until you get a really nice, deep, knurl.

No, it's caused by knurling a material which can not cold flow as far as would be required for a full knurl.

John Stevenson once proved, by knurling a taper, that calculation for formed knurling is not required for adequate engineers

I have to strongly disagree here. It is absolutely critical to producing a precision knurl that properly matches the standard fingerprint profile to ensure optimum grip of the knob being knurled that the diameters and knurl pitch are properly calculated to a minimum of four decimal places. Furthermore no knurl so should ever leave the shop without full inspection on a shadow graph and final verification of the major and minor diameters with a tenths micrometer.

Actually though I think there are far too many people with far too much time on their hands to even be considering this aspect of knurling. Sadly I suppose that includes me for even bothering to post on this subject!

Paul.

The calculation exists, it works, so why have a go about it nudge wink etc.

Makes me wonder why bother posting when such negative attitudes shine out.

Some will wax lyrical about minutiae without a thought for hobby level folk like me then jump on a genuine attempt to pass on information from a text book that does actually work if you take the time to try it.

Sarcasm is the lowest firm of wit and it seems to flourish here from time to time.

Thank you for your time gentlemen, I'm sorry for wasting it by encouraging your need to shoot people down.

Thanks for all the replies gents; It was really the speed at which the chap did it that surprised me; not how he found the correct diameter. I never calculate the size, but I can only recall two failures and they were ok on the second try. Next time I am a loose end, I will try making a knurl without back gear, just out of curiosity. Thanks again

Maurice

If you are working on an hourly rate in a shop, by all means do the full calculations for knurling, make at least 8 anti-springback passes at slowest lathe speed, do several experimental no-contact runs to verify oil flow rate, then knurl, check and re-check depth of knurl, do a validation piece, and have the QC lab look at the form on the shadowgraph. Always wise to inspect against stock from previous runs too. Take several anti-stress breaks with frequent anti-backache stretches. (10 points extra for yoga poses if HR staff are walking by)

If working on models or tools at home, just wing it and see. Most of the time this works fine, in my experience.

Yet more sarcasm. Another good reason not to bother posting replies here, at least at a club you can avoid the annoying know alls who like to look smart but actually are not.

Thanks for your incisive and well thought out input Daniel, very grown up.

At risk of provoking a man with a moderators hat on and a big key in hand I would like to respond on behalf of the nay sayers and pessimists.

My contribution to this thread was solely based on a reason you quote - the thought for the hobby level folk and more particularly the new hobby level folk. There have been a few people join up here in the last few years and three of which have from very little knowledge or facilities turned out some very decent work and more importantly displayed independent thought and I have complimented all three gentlemen on what they have achieved. Sadly it seems all too common that a beginner asks a basic question and very quickly becomes overloaded with safety advice, theory and standards of accuracy way in excess of what is required for the job in hand. I tried to inject some humour into this thread rather than rubbish the concept outright but the truth is the OP question was about speed and that had been answered and it was heading again into theory and accuracy territory. There is nothing wrong with working to fine tolerance or expounding theory where it is necessary but there seems to be a culture on this forum that rather than encourage beginners and answer simple questions simply, information and standards have to be introduced way over the top of the simple answer required. As skills develop so will the questions and that is the time to bring in the deeper thought.

i could counter to the sarcasm accusation that expounding wisdom beyond the need is also a means of "showing off". Let us not discourage those just starting out or those asking simple questions by bombarding them with information that to the task in hand is largely irrelevant is my simple point.

If it was my post that offended you then I apologise unreservedly with the exception of asking you consider the above.

Paul.

When I saw that episode it seemed to me that he had managed to achieve a cross-knurl, but I can't be certain

I sincerely apologise, if a little light hearted humour offends you so.

I was, in fact, replying to Paul's post, just before yours. We must have hit the send button about the same time. 

Edited By Daniel on 03/04/2019 22:53:38

Edited By Daniel on 03/04/2019 22:56:03

This would seem to provide the definitive answer.

Even posthumously, Mr Stevenson does it again.

At one time, I used to think that the work diameter ought to be an integer of the knurl pitch, like gears meshing together. Being absolutely bone idle, never really tried it out, and have been just clamping the knurls onto the work. Mostly, without problems.

Without wishing to be sarcastic, I rear that Paul Kemp's calendar is running three days slow; "matching the finger print pattern"!

Howard

Lets all relax a bit

There's more than enough to stress about in the world outside our workshops at the moment!

I think Tim hit it on the head - using a tool with two parallel knurls demonstrates how the knurls fall into step easily.

Neil

I have knurled Nylon and it seems as if there were a material that would be hard for the wheels to be forced into alignment, something soft would show the problem. Had no problems.

I use low back gear with the knurl I use the most, it is made from a ciggy lighter flint wheel, and produces a nice fine straight knurl.

Ian S C

Hope this isnt condescending certainly not intended to be in 27 years i have never ever measured the diameter or circumference of any part to be properley knurled. Say proper because i have never ever seen a decent knurl short of a cut knurl and normal knurler with human knowledge.

A good knurl to me is not leaving flats but are pointed, look for that next time more apparent o course.

Bit more proof you dont need to measure before knurling, done 22 course this week like this and well over 1900 in total over the years. Typical speed is 85rpm with coolant, any faster job rings often misses a beat and scraps the job.
**LINK**

That's a fine looking six barrel ion exchange transmogrifying thingamabob Jon. Great looking knurling on the face.

Wassitfer? bicycle part maybe?

That's interesting! Never thought of knurling the face of a job, only ever the circumference. Food for though there, if only for decoration.

Howard