Merits of one QCTP design over another?

[websterz]

When I first got my 7x12 I built a piston/dovetail style post and after fighting my parting tool for a week I gave up. I ended up shelving the toolpost, along with the compound from the lathe. In it's place I installed a solid plinth on the crossfeed and mounted my tools on that for a while. Still having rigidity issues with parting I built a rear toolpost just for parting off and replaced the plinth with a dedicated tangential toolholder, built to use 5/16" HSS tool bits. Now that the parting tool is no longer a problem I find myself wanting more flexibility (no pun intended) in my toolpost. I miss being able to change out a tool in seconds and having it right on height every time. So, I am back to the QCTP. I have been studying the different homebrew designs online and the choices basically cook down to a dovetail style toolblock with a piston or wedge arrangement, and a round solid post with toolholders that use a clamp screw to "pinch" them tight on the post, like this one:

http://homemetalshopclub.org/projects/toolpost/toolpost.html

I used to think the former was the only way to go, but having gotten really familiar with my equipment (read "torn it apart and rebuilt several times") I now see the possibilities of such a round post arrangement. I am definitely leaning towards that style but wanted to find out what everyone here uses and why. Tell me about your toolpost. 

[Mike K]

The style that clamps to a post. 
Plus, they're easier to make than the dovetail style.

http://www.toolsandmods.com/library/ralph_patterson_qctp.pdf
http://www.aardvark.co.nz/pjet/qctp.shtml

Mike

[Andy]

My Chester Conquest 7x came with the black cheapo QCTP with a few spare holders in place of the standard 4 tool post. This is ok some of the time but some of the dovetails on the holders are machined better than others. Not a precision device.

I saw the round post type in Model Engineers Workshop magazine a few years ago and it looks like a very good idea, also easier to make for someone of my limited skills and machinery.

Thanks for the drawings, that will be a big help.

Websterz, I would be interested to know more about your rear toolpost for the 7x. I had one on my Taig but that was easy, because there were T-slots on the cross slide. 'Upside down' parting was almost a pleasure on the Taig and I'd like to have that facility on the bigger lathe.

By the way, I have tried parting with the tool upside down and the lathe running in reverse (ok because the chucks are bolted on) but the cheap QCTP isn't up to it, so no advantage. Hence the desire to have a more solid, dedicated rear tool post.

[kvom]

I have a AXA piston type QCTP.  That said, I recheck the centering almost every time I remount a new tool.  It takes only a few seconds.

[websterz]

My Chester Conquest 7x came with the black cheapo QCTP with a few spare holders in place of the standard 4 tool post. This is ok some of the time but some of the dovetails on the holders are machined better than others. Not a precision device.

I saw the round post type in Model Engineers Workshop magazine a few years ago and it looks like a very good idea, also easier to make for someone of my limited skills and machinery.

Thanks for the drawings, that will be a big help.

Websterz, I would be interested to know more about your rear toolpost for the 7x. I had one on my Taig but that was easy, because there were T-slots on the cross slide. 'Upside down' parting was almost a pleasure on the Taig and I'd like to have that facility on the bigger lathe.

By the way, I have tried parting with the tool upside down and the lathe running in reverse (ok because the chucks are bolted on) but the cheap QCTP isn't up to it, so no advantage. Hence the desire to have a more solid, dedicated rear tool post.

The rear post I built is very simple. I'm no artist but here's a rough sketch:



To get the tool height correct I chucked up a scrap of drill rod and turned it to a sharp point, then I mounted the rear post and fed it across the drill rod to scribe a line. Simple matter of milling out the tool slot and drilling/tapping for the set screws. I plan to modify the design in the near future to make it a two piece arrangement. The base will be semi-permanently mounted, and sit only a half inch or so high. The top section will be held in with one bolt for easier removal. That will allow me to turn larger stock by slipping the rear post off its' mount and out of the way.

[Andy]

Thanks for the description and drawing. That makes it very clear. I wondered about doing it with a separate permanent base as well, you've confirmed that for me.   

[websterz]

Well, I whipped up a 1" round post out of a bit of stainless I had laying around the shop and made one toolholder for it out of 6061 just to see how I liked the design. Now I have to make MORE toolholders!!

I am as impressed with that design as can be. Solid as a rock, simple, easy to adjust. It's a winner in my book. Pics to follow...