MEW 255

[KWILParticipant @kwil]

The front cover of MEW 255 has a tool "cutting" a brass ball and there was I thinking that tool bits should be sharp and well ground at the correct angles..

[KWILParticipant @kwil]

Ball turning device

[Gray62Participant @gray62]

Must say, I thought much the same, it actually makes my ball turning tool bit look good!, that one looks like it was shaped with an axe. Not a particularly good example of how a tool bit should look, and the 'turned' ball looks as rough as a badgers ….

[HopperParticipant @hopper]

As I think it was GHT said, when it comes to tools, it's the little bit on the end that matters.

Looks like any number of well used toolbits in my HSS box. They get repurposed and reground and there is no point in grinding them all the way back to a fresh blank and wasting all that good HSS for the sake of appearance. And I think its obvious the ball in the pic is in the roughing stages — no wonder it looks rough. Give the guy a chance.

[KWILParticipant @kwil]

But he does admit to needing to file it later, Good HSS tool should leave it bright and clean,

[JasonBModerator @jasonb]

The tool looks to have a good sharp point to it, only problem with that is it has left a finish more like a" thread" than a more suitably shaped one would have done.

Kwil was that the tool bit or the ball that needed filing

[egaParticipant @ega]

GHT also confessed that at one stage his boring tool looked like Harry Lauder's walking stick!

One feature of the JAR/GHT/Hemingway ball turning tool is that the tool bit is very easy to shape and is capable of giving a good finish from the tool.

[MWParticipant @mw27036]

Point was too sharp and no nose radius producing a torn and sharp finish.

But we have to remember that he is using this sharp point to rough as much material as possible and therefore needs as much cutting action as he can as close to the tip as possible, a nose radius would be undesirable, for that particular purpose.

If he was using a form tool then we could expect a much cleaner appearance. The point is that having a nose radius would produce a fillet where he might intend a hard corner.

The radial movement combined with a wide round nose would produce undue stress and chatter on a small machine. Like Kwil said, was cleaned up with a file, in industrial practice they might have finished or just used with a form profile tool.

As machinists I'm sure we can sympathise with this struggle. 

Michael W

Edited By Michael-w on 14/05/2017 14:25:15

[egaParticipant @ega]

I am reading the article concerned and was initially puzzled by the reference to "(fig. 3)" in the second column on page 50 where, I think, (ref. 3) was intended.

I have turned numerous ball handles but never in brass. The author suggests that the negative rake tool as recommended for this material may not be practicable with the method used. I wonder, however, whether the large overhang may also be a factor (photo 6).

[D.A.GodleyParticipant @d-a-godley]

The contributor has made a decent fist of explaining how he produces these products , which , I presume are for himself , and not some commercial enterprise , so instead of finding fault in what does it for him , and for which he offers merely a suggestion as to how others might produce similar items , perhaps a somewhat more appreciative view of his offerings should be commented on , or no view ! .

I don't count , but how many of the detractors have themselves committed an article to these pages ? , I am sure it is a difficult task , and one made more so by unwarranted criticism such as contained in earlier posts , no wonder Neil appears to have problems finding contributors .

[egaParticipant @ega]

I followed up my comment about the author's negative rake for brass point by turning a nominal 1" ball in brass with my JAR/GHT/Hemingway spherical turning tool. The 1/4" dia toolbit on this tool has approximately 4 degrees of front clearance and works well on steel.
All went well with this to begin with until a nasty dig occurred. I then reduced the effective front clearance by honing a land on the toolbit in the way recommended for drill bits used on brass with the result that I was able to complete the ball without further digs but with the tool rubbing and a poor finish.
I plan to experiment further with different tool geometry and or size.
Whilst I have no present use myself for turned balls in brass I realise that others do and invite them to say how they go about making them; I have in mind that clocks often incorporate decorative balls.

[JasonBModerator @jasonb]

I've made a few balls and spherical parts in brass, for small ones I have used a form tool made from Gauge plate and shaped to a template.

For larger balls where a form tool can start to chatter I revert to my Bedair type tool, this is a 28mm ball done with that. Sorry no pick of it during cutting but I do use an insert with a 0.4mm tip radius to give a smoother finish.

This pic shows the finish straight off the tool on steel

As for the comment about don't post unless you have had something in the mag, the originator of the thread has had items published, given talks at MEX etc, I've also had a couple of things in teh mag but mostly prefer to put my designs onto the forums.

[Anonymous]

An alternative, if you have a suitable lathe, is a hydraulic copy unit. Then you're not limited to balls. You can have any shape you want. Like these:

Andrew

[Neil WyattModerator @neilwyatt]

Bon Scott would have been proud of you lot

Neil

[egaParticipant @ega]

Jason B:

That high finish on the large ball leaves the photographer nowhere to hide! As to the Bedair, would it benefit from an alternative lever location to avoid the apparent need to reach under the work? I gather you are increasing the insert radius for brass as opposed to steel.

Andrew Johnston:

Presumably, there has to be a second op to part the work and clean up the end(s)? And is there a practical lower limit to the size of the radius of the "neck" between the tapers and the balls?

Neil Wyatt:

New heights of obscurity for those who, like myself, know even less about heavy metal than than they do about brass!

Edited By ega on 19/05/2017 11:30:15

[JasonBModerator @jasonb]

Ega, if you look at the photo of my ball turner, just to the left of the slot the tool holder goes in is a threaded hole. This is for the handle but it does mean I have to take the topslide right off the cross slide to use it, 90% of the time the toolpost spanner works well when poked into the middle counterbore of the clamping screws and the unit bolts to the back of the cross slide. I probably should make a shorter screw in lever for it but doubt I will as I'm not really into making tools.

As I said in my first post the tool shown on the mag cover looked to be sharpened into a pointed Vee so will tend to leave a rougher finish than one with a rounded edge as several have mentioned above. I use the same 0.4r tip on all materials when using the ball turner as it is my only tool that takes these triangular tips so avoids having to keep several types.

I have not found a need to file the machined surfaces but the large brass oiler did get polished.

[Anonymous]

Posted by ega on 19/05/2017 11:29:06:

Andrew Johnston:

Presumably, there has to be a second op to part the work and clean up the end(s)? And is there a practical lower limit to the size of the radius of the "neck" between the tapers and the balls?

Correct, the first op machines everything apart from the hemisphere on one end, via a CNC milled template (bottom right):

Second op forms the remaining hemisphere with the work in a split collet and using an old school template marked out and filed by hand (too idle to program the CNC mill):

I used a profiling tool with a radius of 1.5mm, but you can go smaller. Depending upon the geometry one may be able to use an acute V-form tool to get even sharper internal corners.

Andrew

[Neil WyattModerator @neilwyatt]

Posted by ega on 19/05/2017 11:29:06:

Neil Wyatt:

New heights of obscurity for those who, like myself, know even less about heavy metal than than they do about brass!

AC/DC are rock and roll, not heavy metal

Neil

[Mike PooleParticipant @mikepoole82104]

According to Lemmy "we are Motörhead, we play rock and roll"

Mike

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