Knurling on a small lathe?

[Nick Hacking]

Dear All,

I have decided to give knurling a try and I bought a six wheel knurling tool on eBay.

Now that it has arrived, I see that it is designed for a Myford (small hobby lathes, very popular in the UK) and the shank of the tool is nearly 9/10". Now, the standard tool holder on a Myford is no more than 1/2" so, am I correct in assuming that it is designed to go in the rear tool holder?

I don't have a rear tool holder, but I can make one. However, is it worth the effort? Is a rear tool holder more rigid? If it doesn't matter, should I simply try to mill the shank down to fit my front tool holder? (I have some carbide end mills and cutters which should do the job, if I go slowly).

My gut feeling is that it would be more fun and less destructive to make a rear tool holder, which I could also use for parting off. But, it would still mount on the cross-slide, so would it be any better than using the existing front tool post?

Or should I try to make a really rigid tool holder which would mount directly on the ways?

All advice and experience gratefully received.

Kind wishes,

Nick

 

[rgray]

A rear tool post would be a nice accessory. Press type knurlers are a little hard on things and don't always give the best results.
A bump center http://www.clickspringprojects.com/bump-lathe-centering-tool.html could be used in the compound to put opposing
pressure on the piece being knurled, and the bump center of course has it's own use and is a fun project also.

 

[Nick Hacking]

Essentially, a bearing mounted on a shank?

That does look like a nice little project. Now I've got two things to make!

Many thanks,

Nick

 

[BaronJ]

Hi Nick,

Bump knurling on a small lathe is not a good idea ! It places a very high side load on the headstock bearings, particularly Myford type lathes with white metal or bronze bearings. You really need a pinch type of knurler where the load is shared equally by both knurls.

Making one is a useful way of developing machining skills ! There are a lot of designs out on the web, have a good look at some of them. Compare them and decide what attributes you want yours to have. I'll give you a start: very often you will need to knurl something quite close to the chuck jaws !

I'm actually about to set to to make another one, simply because with the one that I made I couldn't get within 3/8" of an inch. The new ones I make will have to get within 1/8".

 

[rgray]

The bump center idea would be to take the side load away. It would be a little fussy to get right and then a bearing running on the top of you new knurl is not the best thing....could be fine depending on the look your going for.
I might rather move one of the knurl wheels onto a bump center. That way having one from each side.
That may not work on the knurler you have if it requires two wheels in contact or it rotates.

For an idea here is a little vid of the opposing knurl holders I made for my cnc. No side load was a plus.

The knurlers are first up.

 

[Nick Hacking]

Jings.

Don't you worry that your machine is about to become self-aware, climb up the stairs at night and murder you and your family while you sleep?

I'm working on an old Myford and an equally ancient Sheldon both made in the early 1940s. They may be primitive, but the nearest they get to autonomous movement is a powered cross-feed!

So: I need to make a RTP; a bump centre; and an opposing knurl holder. This will keep me happy for hours: thank you.

I'm actually on a high at the moment. To date, all of my projects have been either stuff made on the lathe for the mill, or made on the mill for the lathe. Except that, today, I made a plate to hold two captive bolts, with a hole for a clutch master cylinder in between, to make changing the master cylinder on my old Land Rover less of an ache in the parts department. I know it's not really relevant to this thread, but I think it's the first time that I've used my machines to make something practical for every-day life (as opposed to machining) and it is a really good feeling.

Thanks for the advice: opposing it is.

Kind wishes,

Nick

 

[mikey]

Nick, I would highly recommend the rear tool post. The cutting forces lift whatever tool is in play and the bolt/bolts that lock the rear tool post down act as a fulcrum, resulting in the rear of the tool post pushing down on the cross slide. This improves rigidity.

I use a rear parting tool post on my Sherline cross slide and it parts anything I throw at it without any chatter. It is probably 15 years old and has NEVER chattered. It also allows me to part at very high speeds with a P1-N blade. There are controversies pertaining to how these tool posts work but I ignore most of them because for whatever reason it works, it works well. Consequently, I would highly recommend that you make a parting tool holder to fit the rear tool post.

I would not use a bump knurler if I were you. I would use a scissors knurler instead, and I would either mount it to your rear tool post or make one that bolts to the cross slide itself. This eliminates the stress on your spindle bearings and will produce really good knurls. The rigidity improvement that results from mounting it in the rear really helps the knurling tool work better in my opinion.

Chris Heapy of the UK used to have a wonderful site that included pics of his rear tool post along with the parting tool holder and scissors knurler that sat on it. I cannot find his site now - too bad.

Here are some pics:

 

[savarin]

I'm knurling a bunch of stainless thumb screws at the moment.
I use one of these
https://www.hobby-machinist.com/threads/camjack-knurler.3533/
I cannot praise it enough, The amount of pressure I have to use would be impossible with a bump knurler and very difficult with a standard scissor knurler.
I have found if it double tracks then I just ramp up the pressure till it cuts correctly.