QCTP with both holders installed, possible?

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dml66

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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.
 
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.
 
Even with a reasonably rigid machine, I suspect the backlash and tool deflection under load would defeat you.
 
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.
 
Shars does have skinny holders for BXA at least, not sure what size you're dealing with.
 
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.
 
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.
 
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.
 
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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