# QCTP question



## psychodelicdan (Jul 8, 2014)

Gentlemen 
  How do I correctly choose a QC tool holder for a lathe. I've  seen them sized according to chuck diameter but it doesn't seen to be a constant with all the suppliers. What things do I need to consider to make the smart choice? I believe that I should get a wedge type. Is there more than one style of wedge. It will have to be a lower price unit. 
	

		
			
		

		
	



It's a
Webb 16x40 like this one. I don't yet know the the chuck center height. I won't be picking the lathe up until Saturday. Just doing a little advanced recon. 
Thanks Dan



Master of unfinished projects


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## hvontres (Jul 8, 2014)

Judging from the picture, it looks like either a BXA or a CXA size holder. The governing dimension will be the distance from the top of the compound the the centerline of the spindle. IIRC, there is a bit of overlap between sizes. A BXA is reccomended for 10-15" swings and CXA for 13"to 18". I would go with a wedge. I have a PHASE II BXA and it seems to perform fairly well. Look for ENCO to have them on sale, you can pick them up for about the same price as a No-name import from Ebay.

Have fun, and may the swarf be with you


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## samthedog (Jul 8, 2014)

For many manufacturers, the HP rating is also used as a measurement. This has more to do with rigidity however even a little QCTP will handle pretty heavy work. This is more a consideration for those using their machines in manufacturing where the tool post will be seeing hard work day in and day out.

I have yet to see a tool post itself break under use but have seen a few rammed into spinning chucks :angry:

Paul.


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## zmotorsports (Jul 8, 2014)

My personal opinion, and this is just MY opinion on QCTP sizes, 12" and under swing I prefer an AXA or 100 series, 13-16 BXA or series 200 and over 16" CXA or series 300.

That said, the 12" could also use a BXA and the 16" could also use the CXA as they are borderline for either up or down on toolpost sizes.

Again, this is what I have used and comfortable with, you mileage may vary.

Mike.


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## old_dave (Jul 8, 2014)

As Henry said, it's the distance from the top of the compound to the centerline of the spindle that determines what size of wedge type (i.e. Aloris pattern) QCTP will work. If you go to: http://www.doriantool.com/catalogs and download the Lathe Accessories catalogue and then look at page 34 of the PDF you'll find a table at the bottom that helps a lot. For each size, AXA, BXA, CXA, CA, DA and EA, Dorian gives an optimum height of centerline above compound top (well actually above whatever surface the TP is being mounted on) and also a maximum and minimum distance. As Henry also said there's often an overlap in what sizes will be usable with a given machine.

This table can be used as a guide for any brand of this pattern of QCTP, you may have to do some translating of the given brand's size nomenclature to the AXA/BXA/ etc standard.

David


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## psychodelicdan (Dec 8, 2018)

I can't believe I've had this thing for over 4 years and still haven't set up a power supply for it. I tried to make a rpc but it was way loud and wouldn't run it. The lathe was a opportunity purchase so I'm not surprised.
I would like to put the Bridgeport to work and start making a QCTP.
I have in the past spent many hours looking for plans to build one with no satisfactory results. I would like to be handed a proven set of prints to fabricate/ machine a wedge style tool post. 
I need clear prints that I can refer to after weeks / months off the project, and get back on track. An aloris knock off would be nice so I could buy stock parts to fit it when needed.
Can anybody provide these for me or guide me to them.
Thanks

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## Dabbler (Dec 8, 2018)

-How many HP is the spindle motor?.  An offshore VFD would get you going.  Why not start with an offshore QCTP, and work from there?

I usually prefer to go brand name but this might be a way to get it up and running??


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## psychodelicdan (Dec 8, 2018)

I believe it to be a 7.5 HP motor. I think that's too much for my home shop to feed.

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## Dabbler (Dec 9, 2018)

At 220V, your breaker size would be about 30A.  If you have a welder outlet, you could share it with the lathe.  A 10Hp VFD is not super expensive if you go offshore.  a Domestic will be a little over 500$.  To properly start a 7.5 HP motor you should have at least a 10HP rotary phase converter, which needs a 40A breaker (50 would be better)...


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## psychodelicdan (Dec 11, 2018)

Anyone have prints for the QCTP?

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## DAT510 (Dec 11, 2018)

QCTP are sized based on the distance from the Compound Mounting Surface to the Centerline of the Lathe.  

Here's Shar's info on Sizing QCTP's.


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## psychodelicdan (Dec 23, 2018)

Thank you Dat510 that will help with chosing a size.
Marry Christmas to you,

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