# QCTP with both holders installed, possible?



## dml66 (Oct 27, 2022)

There may be much better ways to accomplish this but, I wondering if it can be done with the QCTP and holders I already have.

I'm turning both the inside and outside of a cylinder. For the inside I install a boring bar on the QCTP, for the outside I install an indexable cutter on the QCTP. This requires swapping cutters and making two passes, one for the inside, one for the outside. If both cutters were installed at the same time that would lead to one pass and done.

The QCTP and it's holders don't allow for two holders to be installed at the same time. I wondered to myself, what if I cut off the end of a holder so they can both fit on the QCTP? I don't mind ruining a holder to see if this will actually work but, they are made of hardened steel, I have no way to cut that. I haven't tried grinding on it, that may be a possibility.

Maybe "skinny" holders are available, I just can't find one.

Ideas welcomed, thanks.


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## benmychree (Oct 27, 2022)

That would be a quite impractical proposition; for one thing it would not be easy to arrive at either size accurately and your machine may not have the power or rigidity to allow combined cuts.


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## rabler (Oct 27, 2022)

Even with a reasonably rigid machine, I suspect the backlash and tool deflection under load would defeat you.


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## dml66 (Oct 27, 2022)

The material is brass with about 0.001" being taken off the inside and about 0.0005" taken off the outside. 

Positioning the tools is not an issue, they will be positioned independently, then combined.


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## rabler (Oct 27, 2022)

Shars does have skinny holders for BXA at least, not sure what size you're dealing with.


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## twhite (Oct 27, 2022)

Sounds like you need some turret tooling. 


Cutting oil is my blood.


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## pontiac428 (Oct 27, 2022)

Unless both dovetails and tool holders involved have the same fit precision, one holder (the tighter one) will stop the wedges when locked down, the other will not be equally locked because the mechanism for each wedge is bound to each others movement.  FIMS has a balancing mechanism that allows three tool holders to be mounted at once for convenience, but I don't think it would work with your typical Aloris/Dorian/Chinesium wedge post.   Maybe you can fab up a double-barrel boring tool holder, but then what everybody said above applies.  You want to cut simultaneously .001 and .0005, but boring bars are susceptible spring action like any other long tool, so to me this naturally appears as two cutting processes.  If I had a part or ten to make, I'd bore then skin the part in two steps.  If I had two tons of part blanks to finish and one set of hands, I'd do it on a turret setup.  Your dual-tool sounds to me like a big, flexible form tool by description, with two components that deflect and resonate differently, and only a few tenths of wiggle room.  I don't even think this presents an interesting challenge because there is little to gain for the effort, at least from my understanding of what you're trying to accomplish.


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## Mitch Alsup (Oct 27, 2022)

If you are looking for precision:: not these cannot be done together.
If ±10-thou is good enough then you can give it a try.

When an inside boring bar has deflection it cuts deeper.
When an outside turning tool has deflection it cuts less.

As the tips become worn, the OD increases and the ID decreases.

So everything is working against you.


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## benmychree (Oct 27, 2022)

Something not said so far is the length of the cut and the diameters being dealt with, also I wonder at the accuracy of chucking to allow such a fine cut as 1/2 thou.


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## dml66 (Oct 27, 2022)

OK, some more specifics:

Depth of bore and turn is about 0.25".

Workpiece diameter is about 0.25".

Boring bar is solid carbide with 0.5" shank length.

Turning cutter is 5/16" indexable with carbide bit.

Tool post is OXA size, Aloris knock-off.

Workpiece is chucked in a straight shank ER collet which in turn is chucked in a 4-jaw independent, and yes, it's butt-ugly. Once the workpiece is secured in the ER, the 4-jaw is used to dial workpiece midpoint OD runout to <=0.0005", it's a bit tedious but it seems to be working fine. Either OD or ID may take off a bit more than 0.0005" or 0.0010" respectively depending on the specimen, I only care about what's left. After running 50+ pieces, wall thickness consistency is more than adequate for the application.

Once the tooling position is set, the cross-slide is LOCKED, it does not need to be moved. The compound is locked as well. Power feed is used.


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## dml66 (Oct 27, 2022)

pontiac428 said:


> Unless both dovetails and tool holders involved have the same fit precision, one holder (the tighter one) will stop the wedges when locked down, the other will not be equally locked because the mechanism for each wedge is bound to each others movement.  FIMS has a balancing mechanism that allows three tool holders to be mounted at once for convenience, but I don't think it would work with your typical Aloris/Dorian/Chinesium wedge post.



This is my concern as well. Even when used individually, I can clearly feel a difference in how a tool holder locks in one tool post position versus the same holder locked in the other position. I thought maybe a shim of sorts could even things out but, since I can't actually try it, it's conjecture.


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## mmcmdl (Oct 27, 2022)

2 tools in the same holder possible ?


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## dml66 (Oct 27, 2022)

mmcmdl said:


> 2 tools in the same holder possible ?


I thought about that.

I can't see a way to do it with off-the-shelf tools. Maybe two similar boring bars, one RH, one LH, side-by-side with a shim to dial in the wall thickness, my head hurts thinking about that, lol.


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## mmcmdl (Oct 27, 2022)

dml66 said:


> I can't see a way to do it with off-the-shelf tools.


This is why we have tools to make tools .


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## mmcmdl (Oct 27, 2022)

Lets see a pic of what you're doing !  Casings maybe ?


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## mattthemuppet2 (Oct 27, 2022)

if those dimensions are off of the diameter, then you're into lapping/ burnishing territory. Taking 0.00025" depth of cut and getting the OD bang on size is something I would suggest would be beyond almost all of us.


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## Eyerelief (Oct 27, 2022)

Sounds almost like your processing rifle brass. If so, there is a machine designed to do that


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## mmcmdl (Oct 27, 2022)

mattthemuppet2 said:


> burnishing territory.


Yep , this is where I was heading .


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## Liljoebrshooter (Oct 27, 2022)

Do a search for IDOD neck turning tool.  It does exactly what you are describing. 
Joe


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## Eyerelief (Oct 27, 2022)

IDOD
					

Advanced Case Neck Turning



					www.fclassproducts.com


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## JRaut (Oct 27, 2022)

Aloris, Dorian, and maybe others make quick-change-tool posts that can lock in tools on all four sides.

Not sure if offshore equivalents have made it to market yet.

I suppose that’s one option.



			https://cdn.mscdirect.com/global/images/ProductImages/9432703-11.jpg
		


What you’re really searching for, as others have mentioned, Is a turret lathe (or some sort of turret attachment — they make MTx turret holders to fit in your tail stock if you want to get your feet wet).


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