Tool post input needed?

[blaser.306]

Ok, Second part of the first question. How does one go about measuring a lathe to determine what exact size tool post is needed? Acording to one of the vendors over at a popular auction site a measurement from the top of the compound to the center line of the live / dead center point. Is that correct? If so I likely have the only lathe in existance that will not accept a qctp! I only have 3/4" and from what I have seen I need a minimum measurement of 1". Please help me see the error in my( ways )! Pardon the lathe humour

 

[darkzero]

Ok, Second part of the first question. How does one go about measuring a lathe to determine what exact size tool post is needed? Acording to one of the vendors over at a popular auction site a measurement from the top of the compound to the center line of the live / dead center point. Is that correct? If so I likely have the only lathe in existance that will not accept a qctp! I only have 3/4" and from what I have seen I need a minimum measurement of 1". Please help me see the error in my( ways )! Pardon the lathe humour

You would measure the distance between the top surface of the compound slide where the tool post would sit to the centerline of the spindle. Then get the measurements for AXA & BXA tool holders. Generally on most tools cutter height would be inline with the top of the shank. Take the measurement for the thickness on the bottom of the tool holder plus the slot for the tool. If the measurement is larger than the measurement from the compound slide to centerline then that tool post is too big. This measurement is to allow the max tool size for the particular size TP.

For a BXA size TP you need at least 1.125" distance between the coumpound slide & centerline of the spindle. For a10x lathe it should be an AXA size. BXA is usually for 12x & larger, some 11x lathes might have enough room.

 

[Ray C]

I gather it's a 10 swing lathe so, an AXA style is needed. AXA is typically used from 9 to 12" lathes. Lathes smaller than 9" there is a 0XA but, I'm not familiar with them -but know they exist. BTW: 12" lathes also accommodate a BXA just fine too. I happen to have both for my 12" lathe and like them both a lot.

Ray

FYI: Jeff at tools4cheap.net has the best prices and good quality QCTPs....

 

[Ray C]

I've been meaning to show pics of AXA and BXA because this comes-up all the time. I happen to have both as I grew-up from one to the next. Not only that, it just got too dark for me to continue on the backyard deck boards (thank heavens).

Here's an AXA holding a 3/8" tool. My finger is pointing to the amount of clearance between the compound and bottom of tool holder. Plenty of room. If I put a 1/2 tool in that holder -and I often do, it would have to be adjusted downward just a tad with plenty of clearance.



Here's a BXA with a 1/2" tool. It's almost bottoming-out on the compound. I think 5/8" tooling would still clear it but don't know about 3/4. Actually, I don't even know if a unmodified BXA holder can accommodate a 3/4" insert holder.


FWIW: The lathe is a PM 1236 and is representative of a lot of lathes in that size-range. Sometimes I wish there was (A+B)XA/2 size which would be perfect for this particular lathe. Another thing I think is "fishy", is that the wedge size from AXA to BXA is almost trivial. They are very, very close -so close in size that I doubt highly there's any strength advantage from BXA tool holders over AXA. The insert holders (3/8 vs 1/2") are significantly more rigid of course.

Ray

 

[darkzero]

a BXA with a 1/2" tool. It's almost bottoming-out on the compound. I think 5/8" tooling would still clear it but don't know about 3/4. Actually, I don't even know if a unmodified BXA holder can accommodate a 3/4" insert holder.

Ray

AXA/100 = 1/2" max tool size
BXA/200 = 5/8" max tool size
CXA/300 = 3/4" max tool size

Only Aloris & Dorian make oversized tool holders which will jump up one tool size, eg. BXA-1S will hold a 3/4" shank but just because the oversized tool holders are available that doesn't mean you will have enough clearance to use a 3/4" turning tool on a lathe that is on the small end of the tool post size.

Dorian actually makes even larger oversized tool holders. I have an oversized Dorian BXA tool holder that accomodates a 1" shank but there is no way I can use a 1" shank on my lathe. I use a 3/4" shank in that holder but it's a knurling tool.

To add, for those who use indexables, there is a much wider selection of tools available in BXA than there are for AXA.