extra-fine knurling

Hello, I'm new to the forum so hope this is the correct place for my query.

I'm currently trying to reproduce some pieces in brass based on 18th and 19th century original parts. Most of machining is basic and straightforward but some components require very fine knurling (bit like scientific instruments).Problem is that I cant find any knurls fine enough commercially, and was hoping I wouldnt have to make/bodge something myself (not sure my skills are up to that!) Someone did suggest jewellers 'milgrain wheels' but they appear to produce 'cups' rather than lines. Would have thought perhaps clockmakers might need something similar.

Any thoughts/info would be much appreciated.

Thanks, Richard

A few times when I have wanted fine straight knurls I have done them on the mill by indexing the part and then using some form of engroving cutter. This can just be an old ctr drill ground into a Vee and neld stationary while the work is moved below it and it scrapes the V groove, other times a similar cutter spinning in the spindle.

You can make a fine knurling tool using the flint wheel from an old disposable lighter. You do need to put a bush in the hole, I used a bit of bronze. It took about twenty minutes to make, a bit of rusty old scrap steel, a 3/32" x 3/8" needle roller for the spindle. Ian S C

Finest threading set up and run down it with a suitable cutter?

When I first started making the Graham Meek designed Graduated handwheel for the Myford lathe, I needed a reliable, repeatable method to produce a fine knurl on the periphery of the dial body.

I ended up utilising the slotting head that had lain redundant at the rear of my Bridgeport mill since I acquired it. The general idea is that the slotting head behaves in the normal manner but a rod connects the movement of the ram and indexes a rotary table via a ratchet borrowed from an old steam engine lubricator.

The original ratchet wheel was replaced with a wheel that had only seven teeth and this allowed an amount of overstroke, which in turn allows the cutting tool to clear the work before the indexing for the next cut takes place. The tool is ground to give a 90 degree tooth form and the job takes 8 minutes to complete one revolution. In this time I can prepare the blanks for this op and the finishing op when the “knurling” is complete. There are 504 “teeth” which gives a pitch of just over 0.016”. I hope the photos show the idea of the setup adequately.

Best regards,

Steve.

Why this text appears in the middle of the photos, I don't know!

I must admit, I cut a slot in the end of a 3/8" bar, poked a 3/16" drill through a suitable knurl, applied some insulation tape to stop the drill slipping and whacked it in the toolpost. Since then I have made a nice PB bar to replace the drill as its shank started to get worn!

I wish my numbers were as nice as yours, Steamer.

Edited By Neil Wyatt on 28/09/2016 14:03:31

If you have a rotary table that has a centre height that matches/nearly matches the centre of the lathe when sitting on the bed, use the saddle with a lathe tool as a shaper tool, then rotate the table a pre-determined amount every time. Slow I know...

Regards,

Richard

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O.K. ... I'll bite

How does that produce anything approximating a fine straight knurl ?

Please enlighten me.

MichaelG.

There was no mention by the OP of wanting a straight knurl. However I would have thought the coarsest pitch was needed and a way to get multiple starts if trying to get diamond pattern by threading

Edited By JasonB on 28/09/2016 15:37:42

Steamer, that is a clever set up. beginning to regret selling my Bridgeport slotting head. I sold it to finance the purchase of a "Cherry Head" but that was sold when I arrived to pick it up. The dealer just gave my deposit back and walked off.

.

Silly me ... I was misled by his reference to 18th & 19th Century scientific instruments.

[and, of course by your post immediately following]

MichaelG.

Would the old stuff have had rope knurls on a rounded surface?

There are some (incomplete) explanations of making rope knurls on t'web.

They would make a nice article if someone volunteers to write them up.

Neil

Steve

I have one of your hand wheel dials on my S7 and very nice it is too! Good job - thanks.

Norman

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Yes, some of it ... Others had straight knurling

Diagonal [cross] knurling is relatively modern, I believe.

MichaelG.

Richard, is there any chance of uploading a photo of the type of knurl you are hoping to recreate and also some idea of pitch as one mans fine pitch is anothers coarse.

J

O.K. ... I'll bite

I won't bother to bite back, but I hope you have enough to chew on. I didn't see any reference to ''straight'' either. So I have nothing to apologise to you (hint).

NDIY, could you explain how a fine thread pitch would work, as I mentioned above I would have thought a coarse multi start thread was needed?

.

I'm bewildered by your response ... < I'll bite > was an analogy to a fish taking the bait.

I wasn't expecting an apology; I just asked nicely for enlightenment.

MichaelG.

Edited By Michael Gilligan on 28/09/2016 20:40:57

Many Thanks for all the suggestions, plenty of food for thought there!

Just to clarify, I should have specified 'straight knurls'.( However 'rope knurls ' may well be required at some stage, so its all of interest)

I'm away for a few days now but will indeed post an image as soon as I have the originals to hand, to give a bit clearer idea. Also try and get an approximate measure of the actual pitch, (-they are very fine)

Thanks again, Richard