QCTP opinions needed

JR49

JR49

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Both AXA and BXA toolpost specs claim they fit a 12" lathe ( logan model 2557VH to be specific). I thought the bigger one (BXA) would be better for the rigidity, but now I've read where some guys say that the bigger one on a 12" Logan is "too big" and gets in the way and, unless I'm turning large stock, the BXA is overkill. I'm not concerned about the small price difference, but I would like the right fit for my lathe. All opinions much appreciated, Thanks, JR49
 
JR49 said:
Both AXA and BXA toolpost specs claim they fit a 12" lathe ( logan model 2557VH to be specific). I thought the bigger one (BXA) would be better for the rigidity, but now I've read where some guys say that the bigger one on a 12" Logan is "too big" and gets in the way and, unless I'm turning large stock, the BXA is overkill. I'm not concerned about the small price difference, but I would like the right fit for my lathe. All opinions much appreciated, Thanks, JR49
Click to expand...

The strength and stability of an AXA (and certainly a BXA too) can probably "out-perform" any 12" lathe -there's little doubt in my mind about that. I happen to have AXA and BXA units and, I use the AXA on a modern 12" lathe all the time. If it was the only one I had, it would suit all my needs and personally, I think the AXA "looks better" and is more appropriately proportioned on a machine that size. Take that last statement for what it's worth because it's based on pure visual appearance.

Lot's of folks start with smaller lathes and work their way up to a 14" unit. In that case, it makes sense to start-out with a BXA since, an AXA is too small for a 14" lathe.

The only time, I've felt a BXA has helped me is to use 5/8 tooling in a few rare cases where I had to extend the bit a longer distance to reach the cut. Other than that, I use 3/8 and 1/2 tooling almost exclusively and find that, for general purpose work, the 5/8 is cumbersome and gets in the way.

Ray
 
I had the AXA on my 12" lathe for over 15 years and I never felt like it was not rigid. It fit the machine well as far as size goes and performed flawlessly. It was an inexpensive import but it held up well.

For my new 13" lathe I purchased a Dorian BXA because a friend had a bunch of Aloris tool holders that his dad left him that were brand new and never used which I bought. I let the AXA go with my 12" when I sold it.

If you are thinking at all that you may step up to a larger lathe down the road I would suggest going with the BXA due to the investment amount, otherwise the AXA will work fantastic on your 12" lathe.

Mike.
 
... Here's a pic of an AXA and BXA sitting on a newer 12" lathe compound. The BXA is actually sitting lower because it's installed inside the compound slot. The BXA is a good 25% larger than the AXA. As for rigidity... the strength of the AXA could twist the compound right off the machine if something bad happened.


QCTP Sizes.JPG

Ray

QCTP Sizes.JPG
 
Here's another size comparison of AXA & BXA.

Img_5447.jpg



I also have the same modern import lathe as Ray. The BXA on the right is what I am using now (12x36). The AXA on the left is what I had on my mini lathe (8x14). Having used AXA on my mini lathe I guess I have grown accustomed to the AXA looking so small. I also prefer the BXA size. I know a few people with the same lathe, we all use BXA. I would say this lathe is borderline in between though. 5/8" tools sit low on the tool post & 1/2" tools sit high on the tool post. I would rather have the tool sit lower on the tool post than high though. My main knurling tool is 3/4" shank in an oversized Dorian holder & it still reaches center line of the spindle. I love my Dorian BXA & I will never sell it!

With the knurling that I do, I would spin an AXA tool post every time. I spin the BXA sometimes but the Dorian has the ability to be pinned so that takes care of that. Rigidity is not the main reason why I prefer BXA over AXA although it is a factor. There is just so much more tooling that is available for BXA (5/8" shank) than there is for AXA (1/2" shank). I remember that is one of the things I hated the most when I had the AXA. Like MCLNR/L holders (CNMG/CNGG), I use those often & they aren't available in 1/2" shanks. Sure I could always mill down shanks & modify tools to fit & I have but I'll avoid that whenever possible. After all there is a reason why certain tools aren't made that small & I'm sure rigidity is one of them.

However I don't grind my own tools, I mostly use indexables, so that can be another deciding factor. I mostly use 5/8" shanks & few 1/2" shanks. I work on a lot of small stuff as well but not often do I run into interference issues with my tooling, I have but I have other tool holders to get around those situations. Perhaps I may be pushing the size limit of my lathe with the tooling I use but I haven't felt like I've pushed my lathe to the max yet.

.....


To answer the OP's question. Every manufacture has different specs when it comes to machine size which is why the sizes tool post manufacturers list for tool posts will be a range. To be sure you have to measure your lathe.

Measure the distance from the top surface of the compound slide (where the tool post sits) to center line of the spindle. If you have at least 1.125" or considerable more distance than you should be fine with BXA. If you have right around 1.125" or less then you will need AXA size. I'm sure you have the distance but just for reference, for AXA you will need at least .9375" clearance.
 
Once again I am amazed with the great guys on this forum. Thanks, I learned something from every answer you guys posted. After reading darkzero's last paragraph, I measured the compound top to centerline distance, and got exactly 1.000 ". So, although darkzero seemed to be favoring the BXA, following his measuring advise, leads me to the AXA. OK, please follow me, and correct this newbe, if needed ( this newbe will be proud if I did indeed get this correct ). Based on the comments you guys made, I just went out and took another measurement. I have nothing mounted on the spindle, so here is what I did. The ID of the outermost part of the spindle is 1.583". Half of that is 0.7915". So, 0.7915" below the "top ID of spindle" is CENTERLINE. Top of compound to "top ID of Spindle" measures 1.809". THEREFORE, 1.809" minus .7915" gives me a "top of compound to centerline of spindle" distance of 1.0175". So, according to darkzero's advise I should get the AXA. WHAT SAY YOU GUYS? PS. I actually enjoyed doing this. Does that mean I've been bitten by the hobby-machinist bug ?? Thanks for this GREAT forum, JR49
 
JR49 said:
Once again I am amazed with the great guys on this forum. Thanks, I learned something from every answer you guys posted. After reading darkzero's last paragraph, I measured the compound top to centerline distance, and got exactly 1.000 ". So, although darkzero seemed to be favoring the BXA, following his measuring advise, leads me to the AXA. OK, please follow me, and correct this newbe, if needed ( this newbe will be proud if I did indeed get this correct ). Based on the comments you guys made, I just went out and took another measurement. I have nothing mounted on the spindle, so here is what I did. The ID of the outermost part of the spindle is 1.583". Half of that is 0.7915". So, 0.7915" below the "top ID of spindle" is CENTERLINE. Top of compound to "top ID of Spindle" measures 1.809". THEREFORE, 1.809" minus .7915" gives me a "top of compound to centerline of spindle" distance of 1.0175". So, according to darkzero's advise I should get the AXA. WHAT SAY YOU GUYS? PS. I actually enjoyed doing this. Does that mean I've been bitten by the hobby-machinist bug ?? Thanks for this GREAT forum, JR49
Click to expand...

Yes, that sounds about right. Also take into consideration the size of the tooling you plan to use. With (for example) 5/8 tooling, the holder will need to be seated very far down on the QCTP and not so far down with 3/8". On my machine, using a BXA with 5/8 tooling pushes the holders down almost as far as they'll go on the QCTP with only about 1/16" to spare. Furthermore, this could depend on who manufactured the holders as the only "standard" is the angle and size of the dovetail. The location and depth of the slot that holds the tool could vary from one manufacturer to another. You won't have any of these (potential) problems if you're using a QCTP and tooling that's commensurate with your machine size.

FWIW, I think older lathes do better with AXA and newer lathes (which tend to have a lower riding compound) do OK with BXA.

About a year ago, one of the users here bought a BXA and a bunch of 5/8 tooling and he couldn't seat the holders down far enough to cut at centerline. He sent all of them to me and I shaved 50 thou off the bottom of each holder and another 25 thou off the area where the tool sits. -Bigger is not always better. He ended-up a happy camper in the end. Another thing that mildly bugs me about using 5/8 in a BXA setup is that the tooling over-hangs the side of the holder by a good 1/8" or more. 1/2" tools fit perfectly flush and 3/8 are a tiny bit recessed (which is just fine).

The only problem I can foresee is that some of the nicer knurl tools have 5/8" shanks which won't fit in an AXA. Solution: Take one of your AXA holders and widen the slot 1/8" on the mill.

Anyhow, if you're not planning to upgrade your lathe anytime soon, an AXA with a mix of 1/2" and 3/8" tooling is just peachy.

Ray
 
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