Qctp mounting choices

I am about to mount an Aloris qctp (Thanks Jon!) on a lathe that has no t slot on the compound. The original 4 way post has a press fit stud with a boss on it that stabs in from under the compound. I can make a hollow bolt to attach to the original stud or I could tap the compound to thread the included 9/16 Aloris stud directly into the compound. Thj e other option would be to bore the compound hole to accept the 9/16 stud and make a nut that presses in the bottom of the compound.

The reason I ask is I am) 9naturally inclined to go the easy route and tap the compound to accept the included stud. But I think there is a reason lathes that do not have a t slot in the compound always use a stud with a boss or shoulder vs threads. Could threads distort the compound and bind things up? Or could the compound end up with a lump where the threads have been pulling on it?

I know the hollow bolt solution will work but a 2 piece solution seems less rigid.

This is mounting on an Emco Maximat super 11. Thought I should mention that before someone cries Chinese hobby machine

Or you could make a one-piece stud similar to the original and just open the hole in the compound to whatever diameter is needed for the through-hole of the QCTP.

Correct. That crossed my mind as well. I am in no hurry and want to make the setup as rigid as possible. It's such a small compound to begin with, the less material I have to remove, the better.

I made a new stud to fit my compound also, but with 1 lathe it's quite tedious to do.
First disassemble the compound, press out the stud. Measure, assemble again to make the stud.
And disassemble again to press in the new stud and hope it fits at the first try.
Assemble with the new compound, in that way you dont damage the compound or the toolpost. And u have some practice to make a press fit and a thread.

I have a Super 11 and decided to do solid toolpost mount directly on the cross slide. For rigidity, and tool repeatability, this can't be beat.

I know this doesn't address your questions regarding the compound but thought I would throw it out there.

BugRobotics, I like that riser. Looks like some engineer's wet dream

What size is the original stud in the OP's compound?

HuFlungDung said:

BugRobotics, I like that riser. Looks like some engineer's wet dream

What size is the original stud in the OP's compound?

Click to expand...

Hahaha thanks, this engineer's wet dream at least .

The stud comes through the compound at 12mm OD and then transitions down to 9mm OD.

I think if I was gonna have the toolpost mounted to the compound at all times, I'd probably add a dowel pin into the compound and a bracket to push against the toolpost with set screws to provide some rigidity. With that type of setup you wouldn't necessarily have to worry about the rigidity of the two piece stud like you mentioned because you would only be relying on that stud to pull the toolpost down. The set screws and dowel pin would be taking on the moment loads. Of course this preloading of the toolpost would result in some deformation of the compound. The amount of deformation, it's influence on the compounds movement/smoothness, current accuracy of the lathe and how much the compound is used would drive the decision on whether to address this or not.

A rough idea of what I'm describing...


and an exploded view...

Wow thanks Bug! I do like the idea of a backup support to the tool post as in your renderings. Mostly what I was concerned about is what you describe. Torquing the tool post down and then end up binding the compound in the dovetails. I may come up with a solution to mount directly to the cross slide also. I do want.to have a functional compound as an option though. Nice that the super 11 has a t slotted cross slide you have mounting options easily exploitable. Was there a significant improvement in rigidity once your compound was eliminated?

The dimensions bug mentions for the post are correct. Will take a closer look at this when I get to my laptop.

Thanks for everyone's time and replies

No problem Andy. Mounting the toolpost solid to the compound made an enormous difference in rigidity, improved cut quality, made parting a breeze and allowed me to store my tool datums reliably in my DRO. Highly recommend.

Just for the heck of it I called Aloris. Luckily I work for an Aloris distributor so they will answer technical qurstions. Aloris said drill and tap and mount their stud right into the compound.

Update: I went ahead and tapped the compound to fit the Aloris stud. I am going to try it out. If I need to later I can make a stud. So far seems to be ok with no binding of the compound.