Simple Ball Turner Attachment for the Lathe

[Paul LousickParticipant @paullousick59116]

I have to turn some ball shapes and contemplated making one of the designs already published but decided on a simple attachment utilizing the existing features of my 9" Southbend lathe.

The compound rest and top slide on the lathe are mounted on a pivot (as are most other lathes) which has all of the features required for a ball turner. It just needs a diferent tool holder. It rotates about a centre point which can be positioned in any position in the X and Y direction and has a fine feed slide for advancing the cutter. After a few hours work using scrap materials I made this simple tool holder.

Spherical shapes and curved grooves can both be machined.

[Paul LousickParticipant @paullousick59116]

[I.M. OUTAHEREParticipant @i-m-outahere]

How many machinists have made or purchased a dedicated ball turner when there was already one on the damned lathe !

Food for thought right there !

😄

[Clive FosterParticipant @clivefoster55965]

Works well if the pivot behaves when used for dynamic rotation. However they aren't really designed and made for such duty so may not work on all machines. Tried it on my first SouthBend 9", a well used machine, with iffy results. Got the job done OK after copious use of emery to give a proper finish. Looked spherical but I suspect it wouldn't have measured that well. But visual appeal was sufficient.

Hardly surprising really as the pivot is simply a dovetailed ring with two rods with matching angles on the end pushed into engagement by screws to hold it in place. Fine to lock it down but not exactly a shining example of bearing guide and gib system design. The pivot ring is usually a good stiff fit in the cross-slide which must help. both mine needed care, accurate pulling and talking to to get them out for maintenance.

Thanks for the reminder tho'. My Pratt & Whiney B has a decent diameter post over 1/2" long on the base of the top slide nicely fitted into the cross slide with a T slotted ring carrying the locking bolts and Tee nuts. That appears to be much more appropriate engineering for the job so I'll give it a try next time. Whether such field expedient solutions are appropriate on a hefty 12" (American extended definition so true swing nearly 14&quot swing industrial machine is perhaps another matter.

Clive.

[JasonBModerator @jasonb]

I seem to remember doing the curve of the smokebox door on my Minnie that way many years ago. That wa son the Emco that had a small spigot under the topslide, can't do it on the current WM280.

[Anonymous]

Posted by XD 351 on 24/08/2018 07:37:17:

How many machinists have made or purchased a dedicated ball turner when there was already one on the damned lathe !

Oooopsie:

Talk about OTT.

Andrew

[Paul LousickParticipant @paullousick59116]

I don't intend to machine many balls and a proper ball turner would be a waste. The balls do not have to be perfect, they are for the body of the drain cocks on my traction engine and just for apperance.

Paul.

[John HaineParticipant @johnhaine32865]

Ah, the joy of CNC…

[Russell EberhardtParticipant @russelleberhardt48058]

Thanks for that Paul. It should work perfectly on my Atlas lathe. Why hadn't I thought of it?

Russell

[jimmy bParticipant @jimmyb]

Nice idea.

I had thought of trying that on my Crusader, but .015" size difference put paid to that one….

Jim

[Clive HartlandParticipant @clivehartland94829]

If you can mount a rotary table on your cross slide and then mount a tool on it to work height then you have a precision ball turning device! Centering the cutting tool to the center of the rotary table and just back off the cross slide to the half diameter.

[JonParticipant @jon]

File it

Looked at buying one last year, none are very user friendly for setup and actual use. ie taking the jig off and or mounting normal tool post etc with many tool changes. OK for a one off.

Then thought about making one and came to same result even mounted on rear tool post, would always be in the way for other ops.

Did have to profile a few things when i had an ML7 using the top slide, worked quite well.

[VicParticipant @vic]

Posted by XD 351 on 24/08/2018 07:37:17:

How many machinists have made or purchased a dedicated ball turner when there was already one on the damned lathe !

Food for thought right there !

😄

Nice idea but my lathe cross slide doesn’t go back far enough.

[Clive FosterParticipant @clivefoster55965]

If your cross slide arrangement and / or topside mounting system don't suit the simple version it ought to be possible to come up with some sort of intermediate "plate" device to carry a suitable pivot onto which the topside could be bolted. Tool height may well be an issue. On smaller machines you'd probably need some sort of drop mount carrying a small toolbit in front of the slide. Tangential type might well be better / easier than conventional.

That sort of arrangement can be thought of as a more sophisticated version of the device described by Edgar Westbury writing as "Ned" in Model Engineer volume 100, p 582 et. seq. A 1949 issue but I don't have the exact date. Geo. H Thomas writes approvingly of its simplicity but, like me, doesn't care for it swivelling directly on the cross slide with the inevitable turning debris interfering with smooth motion. Also on older, well used machinery the flatness of the cross slide top may well be less than would ideally be desired.

George added a baseplate to take the rubbing and also provided a simple slot in which the toolholder slides for easier tool position adjustment when setting the radius of the sphere. Ned simply advised adjusting the projection of the tool from its fixed holder. Using the topslide for tool carrying and adjustment is clearly even better. Arguably less work too.

My own ball turner is a boring head based up'n over type. Effective enough and looks the professional part but objectively I'm unconvinced that the game was worth the candle when balancing the work needed to make it against the use it gets.

Clive.

[Paul LousickParticipant @paullousick59116]

Clive,

I was interested to read Ned's article but the ME digital library does not go back to vol 100.

Originally I intended to make the boring head type ball turner and may still do when I get one of those round-tu-its. I only have to turn 2 jobs in brass and this attachment is all I need.

Paul.

[Clive FosterParticipant @clivefoster55965]

Paul

I thought the basic layout drawings for Ned's tool were around on t'net and fairly readily findable. Usually as a source for other folks improved version or different tool. Apparently not so. Not even in Edgar Westbury's review of Spherical Turning series here :- **LINK** although that does include information on the sort of complex versions disliked by Geo. H Thomas. There is a sketch, but no significant dimensions of the Thomas version in the book Model Engineers Workshop Manual which I could scan for you.

Internet search did turn up some other interesting things tho'. This tailstock mount type from Popular mechanics looks to be fairly fast build :- **LINK** as such things go.

Also found that what was effectively Steve Bedair design was the subject of a Batchelor of Mechanical Engineering degree project by four lads from the University of Mumbai in 2015-176 :- **LINK** . A quick skim through the "nearly English" was interesting. Unusual to see formal engineering analysis was applied to the typical Home Shop Guy, Model Engineer design by eye to "looks right proportions" that experience shows will work. This old fart thought it a bit light for a degree level project but I'm way out of touch with what's appropriate in the teaching environment.

Mention of Steve's design makes me wonder if a vertically mounted inexpensive boring head could be fitted in that configuration to give screw adjustment of tool position and ball radius.

In practice the greatest difficulty with single point ball turners is fining room on the machine for the tool to swing without requiring excessive projection of the work. Especially so for small spheres.

Clive.

[Paul LousickParticipant @paullousick59116]

Hi Clive,

I have seen the tailstock mounted type and the one from Mumbai, like that below.

Both are fairly simple but what is missing from the design is a quick, accurate way of advancing the cutter. The only way in these is to loosen the clamp screws on the cutter and manually re-position it.

The cutter holder in the above sketch was what gave me the idea for mine but I mounted it on the existing top slide on my lathe instead of the rotating base shown. The lathe top slide already has a micrometer adjustable slide.

Paul

[JasonBModerator @jasonb]

You only need to advance the cutter to set the initial radius on the Bedair (mumbai) type then just use the cross slide to put on a cut. It will do the two outer edges first and then slowly form more of the curve. If the work is the OD of your ball you just need to touch off to set which takes a few seconds, at least it does for me.

If you want a way to fine adjust the radius then it only needs a stop end on the groove and a push/pull screw into the cutter block.

[Clive HartlandParticipant @clivehartland94829]

I did at one time have the task of making a lot of 5 mm dia. ball ends in Alu. these to be used as targets at fixed points on bridge building.They were fitted to magnetic bases and were then set in place on center popped places on the bridge to measure deviation during building.

The method I used was as earlier posted but on a milling machine. Turned the vertical head horizontal and mounted the work in an ER collet and set the rotary table on the machine table and used a small lathe tool to turn the ball ends . The milling mach had 2000 rpm so was quite adequate for the purpose.

Edited By Clive Hartland on 25/08/2018 08:19:05

[Paul LousickParticipant @paullousick59116]

Thanks Jason

[Nick HughesParticipant @nickhughes97026]

Not ball turning, but for larger rads this publication gives some interesting methods:-

**LINK**

Nick.

[VicParticipant @vic]

Posted by Clive Foster on 24/08/2018 23:19:14:

If your cross slide arrangement and / or topside mounting system don't suit the simple version it ought to be possible to come up with some sort of intermediate "plate" device to carry a suitable pivot onto which the topside could be bolted.

Clive.

To be honest Clive it was easier to make the Bedair type as I had the materials in stock. I modified the design to include a nice large bearing I also had in the cupboard. The top slide pivot on my lathe is a bit rough and ready anyway and would not have rotated anywhere near as nicely as my ball turner. I only have a 8 1/2” Lathe so tool height was also a consideration. The only thing missing on my ball turner is a scale for setting the ball diameter, I had intended to include one but never got round to it!

[JasonBModerator @jasonb]

For small balls such as the 5mm mentioned a form tool is often quicker. Also works for drain cocks, these had a 9/16" dia ball.

[Paul LousickParticipant @paullousick59116]

Jason,

Mine are 3/4" dia.

Out of interest, what angle are the tapers on your drain cocks ? I have seen all different angles on drawings from 5 degrees to 10 degrees included angle. (or 2.5 – 5 degrees lathe top slide angle setting).

Paul.

[JasonBModerator @jasonb]

8 Degrees included angel so 4deg on the topslide.

Reamed with a tool made at the same time as the spindles

Then lapped with 600g silicon carbide. Do the lapping while the spindle is still on the bar so you have more to hold.

[Author]

Posts