# QCTP boring bar holder question



## hman (Aug 29, 2014)

I have QCTPs on both of my lathes - an AXA on the 9x20 and a BXA on the 12x24.  I have a question about the boring bar holders.  On the AXA set, the thru hole diameter is 3/4" and the included sleeve has a 5/8" diameter hole.  On the BXA, the holder has a 1" hole and the sleeve a 3/4" hole.

I'd like to be able to use smaller boring bars in both, and was wondering what's the best way to design additional sleeves.  The ones that came with the holders are both C-shaped, with a small gap in the circle to allow clamping.  But in the case of the 1"-to-3/4" sleeve, that's some pretty stout steel, and I really need to reef down on the clamping screws to get a reliable hold on a 3/4" boring bar.

I can see making 1/16" wall sleeves using the C-shape design.  But what if I want to go smaller?  Should I split the sleeve completely in two or three places, or else cut all the way through in one place and nearly through (ie, weaker "hinge" section at 180* or 120*) in one or more additional places?

What do YOU do?

Thanks!


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## 12bolts (Aug 29, 2014)

Make a 5/8 bar that will clamp in your AXA holder, about the length of your tool holder,(length not critical) and drill/bore/ream a hole in it to take your small boring bar. Drill and tap your 5/8 bar crosswise to take grub screws that will be of a length less than the depth of the threaded hole, (so they dont protrude from the 5/8 bar) Now you can clamp your smaller bar in the 5/8 rod and clamp that in your holder

Cheers Phil


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## kd4gij (Aug 29, 2014)

For smaller bars I use the boring/turnning holder. It looks like the turning holder but has a V grove in the bottom for a round bar to sit in.


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## mikey (Aug 29, 2014)

hman said:


> I can see making 1/16" wall sleeves using the C-shape design.  But what if I want to go smaller?  Should I split the sleeve completely in two or three places, or else cut all the way through in one place and nearly through (ie, weaker "hinge" section at 180* or 120*) in one or more additional places?



I cut through completely on one side with a thin slitting saw and part way through the back side, directly opposite the open slot. I machined a flat on top of the sleeve so any scarring of the mild steel sleeve from the clamping screws wouldn't cause the sleeve to jam in the holder. I've used my sleeves for only about 8 years but they haven't cracked yet. I drilled and reamed the sleeves for a very close fit and they work great!


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## hman (Sep 7, 2014)

Thanks, guys!


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## Malave16 (Sep 8, 2014)

When i got my qctp from cdco i got 10 extra boring/turing tool holders(the ones with the v notched at the bottom) works like a champ for small boring bars and i can leave the common ones on the holder. At 9$ a pop for bxa cant beat it.


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## epanzella (Sep 8, 2014)

I just make a simple sleeve with set screws.


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