Lathe Dimensions And Compatible QCTP's

[Mr Mike]

It's been said before but it bears reiterating. The critical dimension when deciding on a QCTP is not the swing of the lathe but the distance from the top of the compound to the spindle centerline. This is the minimum height that a tool mounted in a tool holder can be and still hit the centerline. I measure this height by mounting a pin of known diameter in the chuck and either measure the separation between the pin and the compound and adding half the diameter of the pin. For my Grizzly G0602, that distance is .924". Unfortunately, this information is not provided in machine specs so when buying a new lathe, one must either go on other's experience or wait until you have access to the lathe for an actual measurement before purchasing a QCTP.

One can always use smaller tools than the tool holder will accept. I prefer to use 3/8" brazed carbide or HSS tooling in my AXA tool holders so I don't have a problem with the minimum height restriction. How3ever, if your choice is insert tooling, you have to be able to accommodate the tool shank. 1/2" insert tools won't work with my lathe and most AXA tool holders, the exception being the AXA-XL holders. However, 12mm insert tooling will.

On a final note, the B dimension in post #2 above varies even in tool holders from the same manufacturer. The clue is that the specified dimensions are given in fractional inches rather than decimal inches. There has also been some indication that the spindle centerline to compound distance can vary for lathes of the same brand and model depending upon year of manufacture.

The Dorian catalog has a section on sizing and includes a worksheet for determining the best tool post size for your needs. Dorian is easy to translate to Aloris sizes too.

Too big to upload today at 8 megs? I thought the limit was 30.

Here's a link.

https://www.doriantool.com/wp-content/uploads/2022/06/TOOL-POST-CATALOG-2022.-6-6.pdf

All good info, thanks gentlemen.
while reading a bunch of post I noticed on Davidpbests chart there is a large variation between the Aloris and Dorian TP height...

Just would be nice to have a chart of tool posts that work well on a particular model lathe where you can see that a Dorian AXA fits better than Aloris or visa versa.

 

[mksj]

There are many variables to which tool post, holders and tooling will work, so any specific chart/recommendation is going to be problematic. It is one reason that sizing is generalized for QCTP's. Also the QCTP holders can vary quite a bit as to the height of the tool in the holder, and if you plan to use undersized or oversized tooling you plan to use. With the QCTP holders you can usually shim smaller holders to the correct height, but for boring bars, cutoff blades, etc. you do not have this option. The lathe manufactures usually give you a recommendation as to the recommended size. You also have input from other that have the same lathe as to what works for them, but each person's setup tooling will be different.

Dorian QCTP holders have a very wide variation as to tool height, while others like Dorian and many of the generic ones are more similar. Below one can see that using a BXA on a 1340GT that in most cases the tool holder is at the maximum height.

 

[tailstock4]

I thought I’d post some pictures of my tool posts. I thought some might find it interesting as I have several machines that share tooling and alternate between Multifix, Aloris, and Dorian tool posts.

The first pictures ares of the 10EE with a E-size Multifix and BXA Aloris and a couple of their tool holders.



This next pictures are of a Rivett 1020S with a E-size Multifix and a BXA Aloris. Note the spacers underneath so that the 10EE and Rivett can share tooling.



Next are of a Toolmex TUM-35 D2 with a B-size Multifix and a Dorian CXA. The Multifix has a spacer and t-nut all made into one and split into two halves – upper and lower. These are drawn together by four cap screws and also the tool post stud. This makes for a very ridged setup.



The Toolmex shares tooling with Pratt & Whitney 12C which has a Dorian tool post. On top of this tool post you can see two small allen cap screws that set the tooling height to be the same as the Dorian on the Toolmex.



These final pictures are of the CA Phase 2 on a 1654 American Pacemaker (actual swing 18.5”). And the little Southbend Heavy 10 with AXA Aloris.



The Multifix has the advantage of being able to have multiple positions and still have a fixed zero point. They have a little more capacity of the size of tooling. The height adjustment and clamping are superior to the Aloris style. Although they are a little more sensitive as to their sizing for a particular machine in part because of less vertical movement of the tool holders. The Aloris style is easy to find tooling for, has a more versatile array of tooling and is more common.

 

[Mr Mike]

There are many variables to which tool post, holders and tooling will work, so any specific chart/recommendation is going to be problematic. It is one reason that sizing is generalized for QCTP's. Also the QCTP holders can vary quite a bit as to the height of the tool in the holder, and if you plan to use undersized or oversized tooling you plan to use. With the QCTP holders you can usually shim smaller holders to the correct height, but for boring bars, cutoff blades, etc. you do not have this option. The lathe manufactures usually give you a recommendation as to the recommended size. You also have input from other that have the same lathe as to what works for them, but each person's setup tooling will be different.

Dorian QCTP holders have a very wide variation as to tool height, while others like Dorian and many of the generic ones are more similar. Below one can see that using a BXA on a 1340GT that in most cases the tool holder is at the maximum height.
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This is how I'm seeing your photos, I'm a lost cause so bare with me... In the the 1st photo set, 3rd photo I can plainly see your fully topped out and the boring tool just makes it. In the 2nd photo set the tool holders are playing a huge roll where your tooling lands...

Correct me if I'm wrong, what I'm seeing here is the BXA Dorian tool post height is adequate for this lathe, but that's fully dependent on the tool holders design that's placed on it.

In this case Its how big and where the Dado is placed on the tool holder that makes all the difference, if one manufacturer cuts their Dado in their regular tool holder 0.25 higher or lower than another manufacturer, that would make a world of difference. add that to all the different heights of cross slides and compound rests, and you have quite the puzzle.

I just ordered 2 new AXA tool posts and holders, Accusize and Colton the other AXA I have is off my old lathe that just says china, Ill also be trying out the Generic PM BXA stuff that was recommended, If I like the fit over the AXA tooling I will trade it out for a name brand one and sell off the rest.

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Edit: I went on Dorians site to find out the difference between the SD25AXA, SDN25AXA, SD30BXA & SDN30BXA Such as CH height to no avail. While searching the Net you see both Red and Gray tool post, On Dorians site they just only show the Red SDN25AXA & SDN30BXA so I assume its just the new model... of interest is Dorian also claims their AXA is up to 12" lathes and BXA is for 13" to 15"

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I've read tons of posts, I may be wrong but there doesn't seem to be that many PM-1236T lathes on here, I've never seen a thread that states they have X Brand QCTP with X Brand holders that fits like a glove. I have seen some people say they use AXA with their PM-1236T cause that's what they have and it works great, while others swear by BXA stuff, being new to this hobby I have no way to differentiate that...

So I too though it would be nice If there was a thread with a common denominator "much like a manufacturer recommendation" but for different QCTP and sizes I can use with my lathe, when I bought my lathe the only option I was given was the generic chinese PM-BXA stuff, I asked about other brands and sizes and was told they can only recommend what's listed on the lathe page which is their generic BXA stuff...

Also the PM-1236T & Recommended BXA instruction doesn't list info such as tool post height, CH, center line distance over compound that would help make easy comparisons to other brands of QCTP. The PM-BXA doesn't have an online pdf instructions page, info just says will generally fit 12" to 14" lathes.

Figuring this all out isn't hard it just makes getting gratification take longer... unfortunately I have to learn everything the hard way.