Ping: Machinists (Knurling question).

[T i m]

Hi,

I am about to turn up some steel bearing insertion drift / tools for a friend (cycle shop) and fancied putting a knurl on the 'handle' area.

I've not done any form of knurling before and with only a Myford ML10, don't have a lot of machine power so believe I would (from checking out Youtube etc) need a 'scissor' type that applies the knurling load itself, rather than the cross slide versus the job etc.

But the sort of questions I have (and please only reply if you have actual experience of such yourself ...) are:

Would an 'in-line' tool, that may require the tool post to be quite a long way back from the job be better than the type that has it's mount down the side of the tool? I'm thinking the extra leverage of the in-line tool versus the twisting effect of a side mounted tool?

How 'fussy' is the diameter of the job to be knurled (IRTW)? eg, I want (ideally) to knurl whatever diameters I have, rather than turning the final diameters just to satisfy the needs of the knurling tool (although I understand the maths).

If I want to cover the range of 20-40 mm OD, would it be reasonable to do that in one tool or should I get two? I'm thinking of how much stability I might get / lose from a lighter tool (for a smaller lathe) when going to the bigger diameters?

Plus anything else I've forgotten / don't know about. ;-)

I'm not looking at a professional / commercial solution here, just something that might help an oily hand hang onto such a tool easier and be a bit 'fancier' than just turning some radial grooves. ;-)

Cheers, T i m

[Harry Bloomfield]

T i m submitted this idea :

I have an even smaller lath and use a scissor type tool. The material needs to be soft and the knurl applied gently in stages, a little at a time.

[T i m]

I have seen those also. It seems to go ...

Straight bar, single wheel. Straight bar, swiveling two wheel holder. Straight bar, swiveling six wheel rotating holder. Scissor type, two wheels. Clamp type, two wheels.

I understand the one to exert the least load on the latch / job is the latter.

Unfortunately in this case the material needs to be fairly hard (free turning mild steel) as it's to form a drift / punch for fitting a bearing into a frame / hub (in a shop).

The idea is to turn the OD of the tool down to a touch less than the OD of the bearing and turn a spigot on the end that will allow it to locate the tool in the centre of the bearing (I may put an o-ring grove on that to hold the bearing on the tool slightly). I may undercut the centre of the front face of the tool to ensure it only contacts the outer race of the bearing.

I may also bore it though to take some studding so they can draw the bearing in if they prefer / can.

On that then ... have you found any issues with the wheel cutting multi knurls doing it that way and how much attention do you pay to the diameter of what you are knurling versus the spacing of the knurls on the knurling wheel(s)?

Do you use any lube? ;-)

Cheers, T i m

[nothanks]

I've knurled a few things with the scissor type of tool, but don't profess to be an expert. Once started keep the knurls engaged and gradually increase the pressure on the scissors, use oil, and do not let the knurls run off the job. I haven't worried about knurl or job diameters and it has always worked fairly well to date.

[Harry Bloomfield]

T i m explained :

It sort of digs itself in and self synchronises. I have had them not synchronise and make a mess, but I just turn the mess off and try again.

[Tim Lamb]

In message , T i m writes

I expect your Granny blew her eggs but.... if you make the tool multifit, aren't you likely to hit the situation where the bearing inner race is wider than your original model (design reasons etc.) and risk loading the balls?

I have a low opinion of the average grease monkey's knowledge of the causes of brinelling in ball races:-)

[T i m]

;-)

I did have the idea of making some of the tools 'multifit' but that only really works on a couple so not possibly not worth it (a double joggle on the nose where the OD of the outermost shoulder was smaller than the ID of the innermost one). The 'range' I mentioned was simply the range of bearing diameters I had to make tools for, not the range of one tool. ;-)

The biggest issue therefore so far is getting the steel stock at the right price.

If each tool ends up being ~120mm long (10mm spigot, 10mm shoulder to allow for the bearing to go 'into' a tube, 100m for the width of a mans hand to hold the tool) and I have 16 tools to make I'm gonna need

2+m of bar. The biggest diameter I'm going to need is 42mm and the smallest 22 so I'd ideally need a few sizes of stock to save on the turning (don't really want to turn 45mm bar down to 22 or have a 45mm OD handle on a bearing that small).

A 250mm length of 45mm OD steel bar on eBay is about 16 quid and whilst that's not a dealbreaker, I imaging quite a lot of that will be the postage?

I've made a couple of calls to local engineering Co's but none so far has say 45mm OD or any off cuts to sell.

Quite, hence the tools etc.

To be fair, the guys know what they are doing and have been 'getting by' with a mixtures of sockets and bits of tube etc.

On that, I could use tube for the body but would still need to turn a solid nose to provide the centring spigot and another for the cap for them to tap the bearing in with.

I also thought of using a larger diameter nose and a piece of std round stock to for the handle / drift part and brazing / metal epoxy the two together but I think that sort of tool often gives you quite a shock though the handle when the bearing isn't hit square?

Cheers, T i m

[T i m]

Cool.

No probs. It was just the practical feedback I was looking for. ;-)

Understood. I'm also aware there are different tool-face-shapes that determine if you can say extend the knurl down a piece or if you want a nice transition between knurled and un-knurled. Square, bevel, convex etc.

I think I'd like to ensure some decent EP oil on the pivots for the knurling wheels themselves and a lighter cutting oil on the workface?

Understood.

That's the strange bit. Given that the teeth on the tool would be at a fixed interval, in theory that number would have to divide cleanly into the circumference of the job (+/- the min / max depth of knurl),

*unless*, you are happy with a finer knurl as is splits the tpi of the knurling wheel?

Eg, say you had a knurl that had a 1mm step tooth (at the circumference of the knurl) and a 20mm circumference of the job you would expect to see the knurl create a well defined number of evenly spaced knurls around the job (20?). If the job was 20.5 mm circumference, the knurl would do the first revolution at the 1mm increments but would effectively half step at the transition and then back into sync again at the 2nd transition, giving 20 'knurls' in total. This would be the same effect as if you had used a knurl with twice the number of teeth?

At least, that's how I would imagine it should work? ;-)

So, you may well be right in that you should end up with 'a knurl' of some sort but not necessarily the 'pitch' you wanted (assuming you were looking for something specific).

The only real impact all that might be is how 'bold' the knurl might end up?

Cheers, T i m

[T i m]

And by doing that you may happen to end up with a circumference that is more devisable by the 'tpi' of the knurl. ;-)

Cheers, T i m

[Tim Lamb]

In message , T i m writes

I have used lorry half shafts from the breakers for tractor loader fork tines. Prolly 45mm+

[T i m]

Ahhh, interesting, thanks. ;-)

I wonder what grade steel they are though (thinking of the turnability here) ... if they are strong enough in that role they could be more difficult to turn than basic mild steel?

I do have access to a truck repair Co so they may have a broken half shaft I could have and try it on.

Cheers, T i m

[Tim Lamb]

In message , T i m writes

Anything found here is going to be 50+ years old. So pass on turnability of younger stuff. I managed to turn spigots on mine but can't remember if they required annealing first. The inner end is splined if that gives any indication.

[Nightjar]

I'm not sure how the ML10 compares to the CL7 (ML7 with a capstan instead of a headstock), but a cross slide mounted knurling tool with two wheels (for a diamond knurl) always worked fine on the CL7.

[T i m]

I think the chances are the ML10 is going to be smaller (only 3.25" over bed height I believe) but that shouldn't be an issue as long as the lathe doesn't have to do too much of the work (eg the clamping / knurling effort is mainly in the knurling tool not the lathe).

I have seen the clamp type that say (on eBay) that it will cope with a

50mm bar and the same (looking) ones on tool supplier sites that suggest they go up to 40mm.

The ones with the tool in a straight line means that the toolpost will have to be a long way back and maybe putting more load on it all than the one that has the mount down the side and so would all be closer to the job (but with some side loads)?

Cheers, T i m