# Shop-made Ball Turner - with a Question



## tjb (Jun 11, 2021)

I made a ball/radius turner by copying the one made by Ade Swash in the attached youtube video.  I had a Criterion boring head that wasn't in the greatest condition, and had an opportunity to buy one that, after thorough examination, appears to have never been used (still in original case with sealed package of instructions and Allen wrenches).  I decided to convert the old boring head into a radius turner for my lathe.  The build turned out great (pictures below).  My first project was the black Delrin ball on the end of the handle.  I'm waiting on some round inserts similar to the ones Ade showed in his video, and I will need to make a holder after they arrive.  I'm very satisfied with the result.

But I do have a question.  At about 14 1/2 minutes into his video, Ade describes how he took the adjusting screw out of the boring head, drilled and tapped the end of it, made a spacer, and threaded a grub screw into it so that he could adjust the boring head from the opposite side.  I tried a Plan B that was almost guaranteed to not work (it didn't) by cutting the threaded section off a socket head screw and epoxying it to the end of the adjusting screw.  First time I used it, the epoxy gave.  I was hoping to avoid trying it, but it seems the only feasible approach is Ade's.  I soon discovered that the screw is very hard.  Any tips on how to drill and tap a hole into that screw?  (I posted a question on his video, but haven't heard anything back.)  As he explains, adjustments are much easier from the off side, but I think I need some guidance on how to accomplish that in a hardened screw.

Thanks for any advice.

Regards,
Terry


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## JimDawson (Jun 11, 2021)

Cobalt or carbide drill bit maybe?


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## tjb (Jun 11, 2021)

JimDawson said:


> Cobalt or carbide drill bit maybe?


I'd be willing to spring for one of those if that's what it takes.  What about threading?


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## JimDawson (Jun 11, 2021)

I would drill for 50% thread depth, and use a high quality spiral point tap.  Maybe 2 of them, standard spiral point to start, and bottoming to finish.









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## tjb (Jun 11, 2021)

JimDawson said:


> I would drill for 50% thread depth, and use a high quality spiral point tap.  Maybe 2 of them, standard spiral point to start, and bottoming to finish.
> 
> 
> 
> ...


Thanks, Jim.

Not sure what you mean by 50% thread depth?  I'm anticipating using a 10-32 socket head screw.

Regards


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## markba633csi (Jun 11, 2021)

Most tap drills specify for a 75% depth of thread, but you can cut less by using a tap drill a size or two larger than the recommended size
-M


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## JimDawson (Jun 11, 2021)

In that case a #18 drill (0.1695'') would give you 50% thread depth vs. a #21 drill (0.1590'') which would give a standard 75% thread depth.  That way you are removing less material with the tap and the threads will still be plenty strong for the application.


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## benmychree (Jun 11, 2021)

Can you file the screw?  If not it is not likely that you could tap it.


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## tjb (Jun 11, 2021)

benmychree said:


> Can you file the screw?  If not it is not likely that you could tap it.


No.  It's very hard.  But it's the same screw that Ade describes drilling and tapping in his video.


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## tjb (Jun 11, 2021)

Okay, Mark and Jim.  I thought that's what you meant, but I wasn't sure.  Earlier today, I mounted the screw on my lathe, made sure it was running true with a live center, attempted to drill with a #21, and it became very clear very quickly that wasn't going to happen.  I'm using Hertel bits that I think are cobalt, but I'm not positive.  Would carbide be better?


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## JimDawson (Jun 11, 2021)

If you can't drill it with a cobalt bit, then you are most likely not going to be able to tap it.

I built a similar turner and just adjust it from one side, a bit inconvenient but it works.


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## benmychree (Jun 11, 2021)

Carbide may drill it, but you still could not tap it; one possibility would be to partially anneal that section of the screw.


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## mksj (Jun 11, 2021)

Nice job Terry,
I put my knob adjustment on the other side, cut a hex key at the end of my knob and retained with a small screw. Will pull mine out and see about the other side. I went with a CCGT32.52  so I could get a sharp edge, others grind HSS or use small round inserts.


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## SLK001 (Jun 11, 2021)

Get a softer screw and drill and tap that one.


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## extropic (Jun 11, 2021)

Rotate the cutter to be below the workpiece and reverse the spindle rotation.
Be careful if you're using a screw on chuck.


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## tjb (Jun 11, 2021)

JimDawson said:


> If you can't drill it with a cobalt bit, then you are most likely not going to be able to tap it.
> 
> I built a similar turner and just adjust it from one side, a bit inconvenient but it works.


Unfortunately, I think you're right.

Wonder how Ade did it?


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## tjb (Jun 11, 2021)

extropic said:


> Rotate the cutter to be below the workpiece and reverse the spindle rotation.
> Be careful if you're using a screw on chuck.


Now, that's a thought.  Thanks.


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## tjb (Jun 11, 2021)

mksj said:


> Nice job Terry,
> I put my knob adjustment on the other side, cut a hex key at the end of my knob and retained with a small screw. Will pull mine out and see about the other side. I went with a CCGT32.52  so I could get a sharp edge, others grind HSS or use small round inserts.
> View attachment 368933


Characteristically beautiful work, Mark.  Do have pix from other angles?

I used an El Cheapo boring bar insert just to try out the tool.  It performed very nicely.  I have round inserts on the way and will try those out.  I suspect I'll be okay with those, but if not, I may end up doing what you did.

Regards,
Terry


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## John O (Jun 11, 2021)

tjb said:


> Unfortunately, I think you're right.
> 
> Wonder how Ade did it?


Ade didn't have a Criterion boring head


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## tjb (Jun 11, 2021)

John O said:


> Ade didn't have a Criterion boring head


Oh!  Well that solves the mystery!  His looks nearly identical to mine, and I jumped to the conclusion that it was a Criterion.  I went back and listened a little more carefully, and I don't think he ever identifies the brand of his boring head.

Good catch, and thanks for clearing that up.

Plan C, here we come.

Regards


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## Grinderman (Jun 11, 2021)

I bought one of those cheap china boring heads for my ball turner and that screw drilled and tapped easily. I use that end of the screw for feeding all the time.


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## mksj (Jun 12, 2021)

If I recall I drilled and tapped the other end through the center of the hex machined into the end of the knob to hold it on. The OD is such that it fits into the boring head, I had to shorten it so it would not hit the tool post slide. Doing it from the other side is possible but nothing to prevent it from unscrewing/loosening, Probably do the set screw with Loctite.. Black dot is just for rough indexing. I used a Shar's boring head, and a Dorian 5C holder which presented a bit more of a challenge vs a straight boring bar holder. The head has a locking set screw to prevent it from loosening, the shaft has a thrust washer which you can set the tension, and stops that can be used to set the swing. It works well, but need a sharp insert with the largest nose radius for the size insert.  I may play around with other types of inserts in the future, not sure how you can cut a complete ball like on my QCTP with the round type.


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## tjb (Jun 12, 2021)

I got an answer from Ade.  He did, in fact, use a Chinese boring head in his build and indicated he had no issues with drilling into the screw.  I think we're dealing with a case of apples-and-oranges here.  I don't see any likelihood that I'll be able to replicate his approach with the Criterion.  I'll study this some more and see if I can come up with a solution.

Thanks to all who responded.  We'll see what happens.

Regards,
Terry


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## tjb (Jun 12, 2021)

mksj said:


> If I recall I drilled and tapped the other end through the center of the hex machined into the end of the knob to hold it on. The OD is such that it fits into the boring head, I had to shorten it so it would not hit the tool post slide. Doing it from the other side is possible but nothing to prevent it from unscrewing/loosening, Probably do the set screw with Loctite.. Black dot is just for rough indexing. I used a Shar's boring head, and a Dorian 5C holder which presented a bit more of a challenge vs a straight boring bar holder. The head has a locking set screw to prevent it from loosening, the shaft has a thrust washer which you can set the tension, and stops that can be used to set the swing. It works well, but need a sharp insert with the largest nose radius for the size insert.  I may play around with other types of inserts in the future, not sure how you can cut a complete ball like on my QCTP with the round type.
> View attachment 368949
> 
> View attachment 368950
> ...


Thanks, Mark.

Typically spectacular work.

Regards


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## Grinderman (Jun 12, 2021)

this is the setup I use for adjusting the head from the other end. The SHCS is held in place with a little Loctite and the Allen key tool is magnetized so it stays in place when swinging the head back and forth. I tried the round cutter shown but it didn't work at all for me. I ended up making a tool holder for a nice small DCMT insert. I can get almost a full ball with that setup.


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## tjb (Jun 12, 2021)

Grinderman said:


> this is the setup I use for adjusting the head from the other end. The SHCS is held in place with a little Loctite and the Allen key tool is magnetized so it stays in place when swinging the head back and forth. I tried the round cutter shown but it didn't work at all for me. I ended up making a tool holder for a nice small DCMT insert. I can get almost a full ball with that setup.


Very nice.  What did you not like about the round inserts?  Mark (mksj) seems to agree with you - he, too, was dissatisfied with round inserts and prefers a CCGT setup (see his post #'s 13 and 22 above).  I've never used a ball turner, so I'm curious about the pro's and con's of various assemblies.

Thanks for responding.  That's a big help.

Regards,
Terry


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## Grinderman (Jun 12, 2021)

For me the round inserts (RCMT) cut very poorly and left a horrible finish. The DCMT leaves just a small collar on the ball which I really don't mind. Turning a ball for your new ball turner handle is the mandatory first project by the way!


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## xr650rRider (Jun 12, 2021)

tjb said:


> I got an answer from Ade.  He did, in fact, use a Chinese boring head in his build and indicated he had no issues with drilling into the screw.  I think we're dealing with a case of apples-and-oranges here.  I don't see any likelihood that I'll be able to replicate his approach with the Criterion.  I'll study this some more and see if I can come up with a solution.
> 
> Thanks to all who responded.  We'll see what happens.
> 
> ...



You could anneal that screw and then be able to drill and tap.  Heat to cherry red and let it air cool, it will soften.


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## tjb (Jun 12, 2021)

Grinderman said:


> Turning a ball for your new ball turner handle is the mandatory first project by the way!


Been there, done that!  (Kinda.)  I turned the black Delrin knob that's on the pictures in my original post.  I used an el-cheapo Chinese boring bar from a set that I had laying around - mainly because it's the only thing I had with a 1/2" round shaft.  Basically, did that for practice (turned out fine, but not great).  After playing with it for awhile, I plan on making a nice aluminum or brass knob.

The knob you made looks great, by the way.

Regards,
Terry


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## hman (Jun 12, 2021)

Getting a hexagonal pocket in the end of a hardened screw ... sounds like an ideal task for an EDM (if you have one)


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## tjb (Jun 12, 2021)

hman said:


> Getting a hexagonal pocket in the end of a hardened screw ... sounds like an ideal task for an EDM (if you have one)


Nope.  I don't have one of those.  As a matter of fact, I don't even know what one is.  Never seen one.  Never heard of one.  Never used one.  Never even watched a youtube video on one.  The closest thing I can find by googling 'EDM' is 'Electronic Dance Music'.  Even the name sounds oxymoronic to me.  And, for the life of me, I can't begin to imagine why learning how to Moonwalk is going to help me drill a hole into the end of a case hardened screw.  I obviously have a lot to learn about machining.

But thanks for the tip.

Regards,
Terry


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## hman (Jun 12, 2021)

Good one!  Moonwalking is definitely not applicable to what we do.

The "EDM" I meant was Electrical Discharge Machining, also known as spark erosion.  Just for fun, here are a couple of links:




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I've purchased Ben Fleming's book and the printed circuit board he's designed (second link).  Right now I'm thinking about whether I can justify the time/space/cost of building one, versus how often I'd need it.


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## tjb (Jun 13, 2021)

hman said:


> Good one!  Moonwalking is definitely not applicable to what we do.
> 
> The "EDM" I meant was Electrical Discharge Machining, also known as spark erosion.  Just for fun, here are a couple of links:
> 
> ...


Now, that makes a lot more sense than Moonwalking!  I suspect that's a good bit more involved than my immediate need, but it sounds interesting.  If you choose to pursue it, I suspect many of us would like to follow a thread on the build.

Thanks for the lead.

Regards,
Terry


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