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QCTP

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Old Mud

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#1
Hi, i would like to go to a qctp on my Smithy 12 20. Where i only have 1.017 over my cross slide would i need an AXA ? Machine in a T slot ?
Thanks for any help or suggestions.

Don
 

Dave Paine

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#2
I am not sure what you mean by only having 1.017 over the cross slide.

I have a 12in swing lathe and a Phase II AXA QCTP.

My tool post block is about 2 1/4in from the top of the compound, but the end of the handle is about 4 5/16in from the top of the compound.

I have about 3/4in between top of my compound and centre height of the lathe so I am able to get the tools on centre height with the AXA tool post.
 
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Bob Korves

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#3
The only measurement that matters is height from the top of the compound rest to the center line of the spindle. The different manufacturers usually list that information on their sites. From that you can determine the range of tool heights available on your machine using the different tool holder blocks. Also consider the range of tool bit sizes you plan to use as well. The size the machine swings, by itself, has no bearing at all on what tool post size you should use. That is especially true regarding three in one type machines.
 

Chipper5783

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#4
"Machine in a T-slot"? Wow.

You probably do not need to do that. Whatever arrangement holds the existing tool post should be able to adapt to a QCTP. I have 2 lathes, they just use a center post (no T-slot). Securing a QCTP was no problem - just made up a custom mounting stud.
 

magu

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Don,

I would imagine that you can adapt a qctp to your smithy without any major re-work to your cross-slide. Most of us with old iron use some sort of "T-nut" arrangement to hold our tool post because that's what our lathes started with, but that's the only reason and really doesn't provide any benefit.

If my memory serves me right, the smithy has a 4-way tool post bolted to the cross slide, correct? If so, you should be able to remove the bolt and tool post, and mount your new one. The only thing you may have to do is adapt either the bolt (get a new one and mess with it, then you can always switch back if you want to) or making sleeves/spacers etc if the existing bolt diameter is smaller than the hole in your qctp. What diameter/threads currently hold down your tool post? We can better help you from there.

To answer your question though, I would go with AXA. You may also wish to look at the KDK style holders. I have one and prefer it to the aloris design, but it is only personal preference.
 

RJSakowski

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#6
An AXA QCTP need a miimum of just under an inch from the top of the compound (base of the QCTP) to the spindle axis.
 

Nogoingback

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#7

magu

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#8
Looks like nogoingback has you covered Don
 

Old Mud

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#9
Thanks for all the help guys. Yes i have a 4 way tool post mounted to my compound rest. I made a mistake it is 1" from top of my compound rest to center of my spindle as shown in the pic. My Turret bolt is 10 MM or 25/64" . I'm not a big fan of how sloppy it is in that oversize hole
but it has never given me trouble. I'm guessing i should turn a slug to insert when i change over, with the proper size hole and for more bearing surface with the QC . All good info !! Thanks

Don
 

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magu

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#10
Thanks for all the help guys. Yes i have a 4 way tool post mounted to my compound rest. I made a mistake it is 1" from top of my compound rest to center of my spindle as shown in the pic. My Turret bolt is 10 MM or 25/64" . I'm not a big fan of how sloppy it is in that oversize hole
but it has never given me trouble. I'm guessing i should turn a slug to insert when i change over, with the proper size hole and for more bearing surface with the QC . All good info !! Thanks

Don

You can turn a bushing for it if you like, but it won't matter much. The point of the bolt is to provided a compressive force between the mating surfaces of the cross slide and tool post, the bolt should not be withstanding any bearing loads.
 

Nogoingback

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#11
Just for reference, the stud that comes with a Phase II AXA tool holder is 14mm in diameter. The hole it passes through measures around .610.
Could you drill and tap the compound for a larger thread and then make a new stud? It would be much more rigid that way and really not much
more work than making a bushing. 9/16-18 would work if you didn't want to do metric.
 
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Old Mud

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#12
Thanks guys, Yes i can do that i will check the thikness of that rest to see if it's beefy enough. Think i should get the QC first. I was thinking of Shars, any good ?
 

magu

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#13
Don't tap the cross slide.

It is a captive bolt; while I don't personally think the gains would be worthwhile, just replace it with another, larger, captive bolt if you want to do anything. The only thing helping you is the amount of preload you apply with the bolt, so unless you're torquing the bolt passed where it should be, you aren't gaining anything. Also, if you tap the cross slide, your new week point just became the cut threads in your cross slide, not the rolled threads in a high strength bolt. The former is almost certainly weaker and more expensive to replace than the latter.
 

Old Mud

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#14
Well now i just took the slide off and see i would only have a thread depth of 3/8". So maybe i will just change the Turret bolt, I can always re configure what i need on that. I weld so not much of a problem.

Thanks

Don
 
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