# Lathe toolpost size



## KC2IXE (Nov 13, 2013)

Hey Gang,
OK, it is "robot season" again, and I may get a nice gift for the team, a toolpost for their lathe

They have a Sheldon EM-46-P (aka a 13.5" 8 speed)

The center height of the spindle to compound appears to be 1-3/4" (leatherman, and a quick measurement trather than 'doing it right', but...)

That puts me in an interesting dilemma - a C sized SHOULD just fit, and a B size will fit, but be "up" a bit

Anyone have any experience with lathes this size?

Charlie


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## brickbat (Nov 13, 2013)

I don't subscribe to the bigger-is-better philosophy. My lathe swings 12.5" and the BXA is usually great. But, when I first set it up, I used an AXA, and it was fine, too. I'm not taking massive interrupted cuts, ever. And the bigger the toolpost, the more it hinders your view of the workpiece. I'd go with a BXA. Cheaper, too.


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## KC2IXE (Nov 14, 2013)

Problem is I THINK the center height might be high enough (circa 1 3/4") that the can't be adjusted that high


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## gadget_lover (Nov 14, 2013)

KC2IXE said:


> Problem is I THINK the center height might be high enough (circa 1 3/4") that the can't be adjusted that high



I'd match the available tooling to the height over the compound.

According to page 4 of this guide from the aloris web site, ( http://www.aloris.com/catalog/aloris_catalog.pdf ) ... 

A BXA toolpost with a BXA-1 holder using 5/8 inch tooling will have the cutting edge 1 1/8 above the bottom of the holder. The holder will only need to move up around 1/2 inch. The BXA toolholder is 2 3/4 inch high and the tool holder is 1 3/4, so there is one inch that you can move the tool. 

A CXA toolpost with the CXA-1 holder using 3/4 inch tooling will have the cutting edge 1 7/16 above the bottom of the holder. The holder will need to move up less than 3/8. The CXA toolpost is 3 inches high and the tool holder is 2 1/8, so there is is only 7/8 inch that you can adjust the tool.



Obviously in your particular case you can use either one if you have 1/2 inch or 5/8 tooling. If you have 3/4 inch tooling you need to go with the CXA. Buying the bigger holders if you are using smaller tooling will not buy you much, and will use up more real-estate on the compound.

Dan


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## precisionworks (Nov 14, 2013)

If your cuts are light & you work mostly in aluminum/brass/plastics the BXA is a good choice. In titanium, stainless, prehard alloy steel, etc. the larger post & larger shank of CXA holders give a more rigid setup. Inserts are generally larger in CXA & that may or may not be a benefit for you.


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## KC2IXE (Nov 15, 2013)

OK, this is a HIGH school shop. The ONLY carbide tools they have are a couple of old 3/8" shank TPG 22x holders, which sit in the teacher's drawer. Everything that is done right now is done with 3/8 and 1/4" HSS blanks. I might grab some of my larger stuff to donate. I'm probably the MAIN user of the lathe. Mostly AL, some steel, some acytal. Titanium? Stainless? You feel like donating some to the team? (they wouldn't use it anyway)


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## precisionworks (Nov 16, 2013)

KC2IXE said:


> ... this is a HIGH school shop ...


In that case the most indestructible toolholder is the best one. Whatever is most likely to survive a high speed come apart, powered crash into spinning chuck, BFH, etc.


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## gadget_lover (Nov 16, 2013)

KC2IXE said:


> OK, this is a HIGH school shop. The ONLY carbide tools they have are a couple of old 3/8" shank TPG 22x holders, which sit in the teacher's drawer. Everything that is done right now is done with 3/8 and 1/4" HSS blanks. I might grab some of my larger stuff to donate. I'm probably the MAIN user of the lathe. Mostly AL, some steel, some acytal. Titanium? Stainless? You feel like donating some to the team? (they wouldn't use it anyway)



The BXA will be a better fit if you are using bits that small. Small bits tend to be shorter too. If the tool holder does not go up far enough some shimming may be necessary to make it work. I wanted to use a specific 1/4 inch blank in my BXA (normally use 1/2 inch) and just put a 1/4 inch thick steel shim under it. 

Dan


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## KC2IXE (Nov 17, 2013)

when I say "Not high enough", what I'm saying is that if you have the adjuster all the way DOWN (aka the bit is as high as possible) on the BX, it is lower than it would be on the CX


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## precisionworks (Nov 17, 2013)

On many lathes in that size range either B or C will work. If B will not raise up high enough to get the toolpoint on center than C is the only choice.


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## KC2IXE (Nov 17, 2013)

It is borderline, which is why I asked if anyone had any experience with a M series Sheldon


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## gadget_lover (Nov 17, 2013)

KC2IXE said:


> It is borderline, which is why I asked if anyone had any experience with a M series Sheldon



Sorry, I have not used a 13.5 inch M series lathe. I thought you asked about lathes of that size.

I'll throw in another 2 cents anyway. 

If you get the CXA ( it may be what you want) it's rated for tooling 1/2 inch and bigger, so be prepared to substitute longer screws. 

If buying the Aloris BXA, the bottom shelf is 1/2 inch, and the total adjustment is 1 inch so it will work without problems for 3/8 and above, assuming you actually have 1.75 inch center height.


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## precisionworks (Nov 17, 2013)

Match centerline height to chart. Each size is 0.5" higher.

http://cdn-2-service.phanfare.com/i...00-2-Web_0_a6283b7ac915ecad058ad46500b25c6f_1


*Image tags removed see Rule #3 Do not Hot Link images. Please host on an image site, Imageshack or similar and repost – Thanks Norm*


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## gadget_lover (Nov 17, 2013)

precisionworks said:


> Match centerline height to chart. Each size is 0.5" higher.
> 
> http://cdn-2-service.phanfare.com/i...00-2-Web_0_a6283b7ac915ecad058ad46500b25c6f_1
> 
> *Image tags removed see Rule #3 Do not Hot Link images. Please host on an image site, Imageshack or similar and repost – Thanks Norm*






I'm pretty sure that the numbers in that chart relate to the drawing ABOVE the dimensions, not the one you posted. Using that drawing leads you to believe that the AXA tool post uses a T-slot bolt 2-1/4 inches wide. That's not possible. The drawing above the chart also has the H and R dimensions. 

They don't make it real clear, but you need to use the HOLDER dimensions. The variable A is height from plinth to top of tool pocket. B is height of tool pocket, and determines the max tool size. D is the height of the holder. CC is height of tool post dovetails.

(A-B) + tool shank size = minimum tool height (MTH).

CC - D is the amount you can raise the tool holder, AKA the travel (T)

The center height it will work for is anything between MTH and (MTH+T)

It is probably worth while to spend an extra couple of bucks and buy a bunch of new tool bits to work with the new tool post. 3/8 or 1/2 inch HSS bits are dirt cheap. 

Daniel (yeah, I'm up to 8 cents worth of advice now. Worth every cent you paid for it.)


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## precisionworks (Nov 18, 2013)

precisionworks said:


> *Image tags removed see Rule #3 Do not Hot Link images. Please host on an image site, Imageshack or similar and repost – Thanks Norm*



Norm,

Phanfare is the paid image hosting site that I use. Similar to free hosting sites, better IMO & well worth the $29 annual fee. This isn't a hotlink according to the definition in Rule #3.

http://www.phanfare.com/corp/pricing.aspx



> pretty sure that the numbers in that chart relate to the drawing ABOVE the dimensions, not the one you posted.


You are correct Daniel, my mistake on that.

When I purchased my current lathe I looked at the Aloris & Dorian sites, found the info confusing & telephoned both companies for advise. Both suggested CXA for my machine & that's the size I bought.


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## KC2IXE (Nov 20, 2013)

So, I was up at the shop today. It is 1 11/16 center height. Could go either way, but the C size probably works better. That said, the other lathes are all southbend 10 inch lathes, so I'll probably get the B, so just in case, it could be moved.


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