Knurling

I know that the advice to home-machinist types is to go for a scissor-type arrangement to avoid stressing spindle bearings and cross slide screw, and I have a couple of those. I don't like them very much though - the arms wobble too much. Question is - is a Chinese 6x36 capable of dealing with a 'bump' knurler without injury?

Rob

Edited By Robin Graham on 18/08/2016 00:37:23

The big thing about machining, and indeed making stuff in general is that it's 'the indian not the arrow' that counts....... So, to answer yoour question; ...yes you can knurl ok and safely on such a lathe, providing you do so intelligently and take into account all the variables including material type and diameter etc....and go to the 'trouble' of working things out in advance using a scrap workpiece as a test.

That said, there is no doubt that use of the old type of side action knurler is fraught with many pitfalls and some considerable dangers for the clumsy 'indian'....... At Epping Forest Horology Club we have actively discouraged the use of such devices and, as of recent weeks, their ban has been written into our H&S schedule. Certainly they have major potential penalties in both amateur and commercial workshops.

.....If your clamp type knurling tool is "wobbly" then you could do worse than to start there and work up good process and procedure so that you get good results with it..... analysing and defeating the wobble would be an excellent start!

I have a South Bend 10K lathe with bronze bearings in the head stock. About 40 years ago I had the opportunity to work in a shop that had similar machines that were used with side loaded knurling tools. One of the lathes was, at that time, set aside for that work as the head stock bearings were badly worn because of knurling. The other machines had been repaired recently to correct that issue. The shop foreman was adament that no knurling with side load tools would be done on any but the designated machine!!

I've purchased three scissor types in the last 20 years. None have been capable of doing the job without significant re-work. Of the three, only one will work truly properly. The other two are primarily for agricultural operations. These unitsare made to a price point that is way below the quality needed. They have way too much clearance in the parts and most all of the designs are wrong to start with.

Somewhere in the albums here are pictures of 'correct' designs that have big plates containing the arms on both sides. That concept, combined with big, tightly fitted pins and stout construction, is the way to go. Great care is needed when machining the parts to maintain true square and perpendicular parts and holes. The pin holes must be all parallel with each other or the wheels will walk all over during use. The arms must fit quite snugly between the plates which must be flat and parallel.

The junk tools are OK if you just want to make a rough spot so the hitch pin on the tractor is easier to grab. But to do quality work requires first class tools.

Off my box now,,,,

Pete

Here is one:

http://www.model-engineer.co.uk/albums/member_photo.asp?a=36958&p=635564

Edited By Peter Krogh on 18/08/2016 04:18:05

Edited By Peter Krogh on 18/08/2016 04:27:57

If you have a fixed steady, or even perhaps a travelling steady, it can be set up to take the load off the headstock. Place it between the chuck and the section to be knurled. Using a revolving tailstock centre also takes more of the strain away from the headstock end of things.

Beginners reading this should take careful note of this thread. Cheaper tools are not necessarily best and can stress your major investment.

Purchase decisions, for things such as the QCTP, where not paying the 'apparent better price' for a complete 'kit' and buying only what is needed, is a better option. I bought a complete set and have regretted paying more for something I will not use (hindsight, of course!). I daresay I will likely machine it into another basic tool holder eventually, but it is, nevertheless, annoying.

Surely you jest ?

Not April the 1st is it ?

Whatever next, ban all hammers over 12 oz.

Centre punches must have an angle between 118 and 120 degrees only.

You can't use center punches, they have pointy ends, someone might hurt them selves, scribers are out too.

Ian S C

Not a problem in the UK, we only use centre punches.

Andrew

I was taught to knurl in back gear - slow, but I recently watched a u-tube clip of a chap knurling at maybe 300rpm so I thought id give it a try. Blow me if I didn't get an excellent result in about 3 seconds!

John et al,

No, we're not at all draconian at EFHC!.....members can hit their fingers with whatever hammer they wish and the blunt centre punch contingent don't bother us........

...........But people (usually with no technical background) can't come into the workshop and smash stuff up any more!.......not without some shouting and rule book waving!....don't get me started on why this has had to happen!

I too bought a Knurling tool that turned out to be very wobbly when it arrived. My solution was to make my own.

An excellent article on Knurling by Jacques Maurel coming up in ME 4543 (16 September).

Diane

knurling schmurling, i don't see what all the hullabaloo is. I've sucessfully knurled long shafts of stainless no problem many times. But then i was shown how to do it few a year ago, wasn't like i just tripped over a lathe one day and decided i'd have a go.

(I then read a bit more about it with a sherline guide to machining) 

You wanna see that guy who made his own rope knurls, now THAT was something. 

Michael W

Edited By Michael Walters on 18/08/2016 15:41:55

Haha, reminds me of when I worked at Motorola Automotive in Herts. We were prohibited from buying a bench vise "because you might drop it on your toes". It was also pretty much impossible to buy any form of chemical "because they may be toxic" (adhesives and solder paste come to mind). The senior managers there were so far up themselves they forgot they were supposed to be running a business, instead spending their time sending thrusting management bullsh1t emails around the shop. It may be no coincidence that Motorola no longer exists in any significant form. When I was a "Motorolan" there were 150k employees....

I have a cheap clamp type knurler, can't remember where from. This was wobbly and a bit of a disapointment but worked after a fashion. Just making new side plates out of thicker plate, and a couple of decent pins made a great improvement.

.

Hope that old fall back of formulae = pi x square root of a cornish pasty doesn't surface yet again.

Thanks for your replies.

BobS - I was thinking more about injury to the lathe bearings / cross slide screw than to me. I'd be interested to hear more about the "many pitfalls and some considerable dangers for the clumsy 'indian' " which lurk in wait for me though! Also the " major potential penalties in both amateur and commercial workshops"? A bit enigmatic!

I'm aware that there are designs out there for improved clamp knurlers - I just don't want to spend the time to make one at the moment. I've just been through a phase of making things to make things to make what I want to make, and I can lose motivation when my eventual goal recedes too far.

What I really wanted to know was whether I'd knacker my lathe by side-knurling occasionally. It's not something I need to do every day.

My only formal training in lathe work is a ten hour course about 35 years ago in the postgrad physicists machine shop at Manchester Uni. In the knurling bit I was told to run the lathe slow and attack confidently with the (side) knurler, so it would dig deep enough on the first rev to register on the second and subsequent revs - pi didn't come into it! It worked. This would have been on perhaps a five and a half inch machine, maybe a Colchester, but I can't really remember.

The reasons I'm reluctant to use this experience at home are (a) maybe a proper British industrial lathe is better fitted to cope with the forces on the spindle and cross slide screw than my import is, and (b) the postgrad machine shop was mainly populated with machines pensioned off from the proper machine shop - good enough for the kiddies to play with, but no great tragedy when they're skipped....

Rob

Did my knurling 30 years ago during my apprenticeship at the in house training school. All on ex-industrial machines with loads of wear. Instructors taught us that if we could produce decent work to 0.0002" tolerance on these machines with all their wear then we could produce anything, has always stuck with me. Yet to try knurling on my newly acquired Super 7

I did this knurl, diameter about 2 1/2" in mild steel, on my mini-lathe, although it does have the taper roller modification I don't think that makes a real difference.

Neil

I'm not aware of any special safety issues with knurling. Can you give a bit more information on what the risks are and why you have banned them?

Neil