# Simple raduis/ball turner using QCTP and boring head



## r3292c (Mar 26, 2019)

As many of other hobby machinists I bought a QCTP kit including different types of tool holders.
The one of the most rarely used holders is a Heavy Duty Boring one for 3/4" bar shank. I typically don't use large boring bars like that, so this holder just stays on a shelf. But recently I realized I can build a raduis turner tool with it.










I think it looks pretty clear. I've got 3/4" OD, 5/8" ID bronze bushings perfectly fitting into 3/4" boring bar holder. The straight shank boring head arbor with 5/8" shank fits inside the bushings. I use thrust roller bearings and 3/8-16 bolt and nuts to pre-load the arbor/spindle. The only part I've made from scratch was an aluminum washer in between of thrust bearings and nuts. CCMT-0602 insert holder was made for one of the previous projects.


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## r3292c (Mar 26, 2019)

This is how the radius cutter looks assembled



The height of the tool can be adjusted



The tool works as expected


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## RJSakowski (Mar 26, 2019)

A couple of years ago there was a ridiculously cheap offering of boring heads on e-bay and a number of forum members took advantage to build ball turners simialar to your design.  A few of them were documented on the forum.


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## r3292c (Mar 26, 2019)

Yes, I know that using a boring head is pretty common. I think the main idea here is to use the QC boring bar holder together with a boring head. You see, all components are standard and available. In my case the boring bar holder was just sitting on a shelf and waiting 
And it also takes just a minute to disconnect the parts and use them separately.


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## pontiac428 (Mar 26, 2019)

I did mine with cartridge bearings instead of bushings and a thrust bearing. Works well, but slow she goes. Easy set up and use.
	

	
	
		
		

		
			





(from mobile)


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## benmychree (Mar 26, 2019)

I may have posted pics of this ball and radius turning attachment before, but here it is!  It id made much more compactly than using a boring head, avoiding problems with interfering with the machine's maximum movements, it does not use bearings in the QCTP holder, just a snug fit, and it has bronze thrust washers. As can be seen on the handle end, it has adjustable limit collars for maximum rotation.  It was designed to use standard flat boring tools, cutting on the end rather than the top flat surface.  This unit was designed to use bronze sleeve bearings, but it was sized for an BXA holder, and is now used with an AXA holder; no room for bushings.  With as little use as it gets, I'm sure it will outlast me without any significant wear.
The lathe it is used on is a Monarch 9" swing from likely the 1920s; so far as wear is concerned, it is in near new condition.  I posted more pics of it some time ago.


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## darkzero (Mar 26, 2019)

RJSakowski said:


> A couple of years ago there was a ridiculously cheap offering of boring heads on e-bay and a number of forum members took advantage to build ball turners simialar to your design.  A few of them were documented on the forum.



Yep. I got one of those with the intent on making one of these also. I totally forgot I got one until I saw it in my ebay purchase history. $24 from Industry Recycles. Luckily the gremlins didn't find it & I was able to find it stashed in one of my drawers.


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## Nogoingback (Mar 27, 2019)

benmychree said:


> I may have posted pics of this ball and radius turning attachment before, but here it is!  It id made much more compactly than using a boring head, avoiding problems with interfering with the machine's maximum movements, it does not use bearings in the QCTP holder, just a snug fit, and it has bronze thrust washers. As can be seen on the handle end, it has adjustable limit collars for maximum rotation.  It was designed to use standard flat boring tools, cutting on the end rather than the top flat surface.  This unit was designed to use bronze sleeve bearings, but it was sized for an BXA holder, and is now used with an AXA holder; no room for bushings.  With as little use as it gets, I'm sure it will outlast me without any significant wear.
> The lathe it is used on is a Monarch 9" swing from likely the 1920s; so far as wear is concerned, it is in near new condition.  I posted more pics of it some time ago.




What type of head is that?  The shorter length looks good.


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