QCTP Sizing - AXA or BXA

[Yarz]

I'm looking to get a wedge style QCTP for my lathe, and I'm struggling to choose between AXA size or BXA size. I've got a spreadsheet setup to calculate the maximum and minimum heights of each tool, using the maximum size tool each can fit (I assume that will be the worst case scenario).

The one that is giving me trouble with the decision is the parting tool (holder #7). Based on my calculations, with the tool holder sitting on the compound, and since the tool holder holds the tool at a 4° angle, I can get the tool to stick out a maximum of 0.432" with the AXA and 0.270" with the BXA before the tool would be above the centerline.

Neither of those seems like enough - I wouldn't even be able to completely part a 1" diameter piece.

Can the tool holders sit below the level of the compound, if I put the post at the edge? Or is there something I'm completely missing in my calculations?

Thanks.

Possibly pertinent lathe info: 1 5/16" to center, above compound; 14" swing over the ways

 

[Mgdoug3]

Go with the BXA. The bigger QCTP will be much more rigid.

 

[DocsMachine]

Mild disagree. While the BXA is indeed a little larger, and all things equal being stronger, that particular machine won't tax either one. The belt will slip long before the rigidity of either post comes into play.

I'd say you'll likely be just fine with an AXA. It will probably fit a BXA just fine as well, so it's kind of a 'flip the coin' thing. The AXA ill be a little cheaper, and additional blocks will be somewhat less as well. But I doubt you'd be disappointed with either one.

Doc.

 

[dutchgray]

I think I would choose the BXA, having looked up the specs for both, but I have never even seen an Aloris type tool post over here, though I know plenty of hobbyist use Chinese copies.

You can always get the holder for carbide insert parting blades, as those are held level and only the insert is held at the cutting angle.

 

[Yarz]

The bigger QCTP will be much more rigid.

That is the main reason I was thinking I'd want that one - if it'll fit.

that particular machine won't tax either one. The belt will slip long before the rigidity of either post comes into play.

That's probably true, especially with how I have the tension set right now. I've got it tight enough to work, but loose enough to slip if I screw something up. One time I had the lantern loosen/move and jam and the belt slipped rather than breaking something.

You can always get the holder for carbide insert parting blades, as those are held level and only the insert is held at the cutting angle.

I hadn't seen those yet - I'll have to look at them!


Thanks for your answers. I've got some more reading/thinking to do!