What's the Differance? Tool Post Styles, Piston or Wedge

[ddickey]

I have not allowed myself to spend real money on the Aloris and Dorian tool post stuff, and have a Phase II wedge set, that works great. I have bought several lots of extra tool holders from various vendors. The ones I got from CDCO are the best quality and were also the least expensive. YMMV, one of the biggest problems with Asian import tooling is poor quality control and quality assurance. Vendors also change their source of supply...

Phase II is a step or two above the other imports. I have a piston one and appears to be of good quality.

 

[4GSR]

I have a CDCO wedge (BOSTAR) quite good for the price. I took it apart cleaned it up, greased it up, and put it to work. Nice quality.

I recently bought one to replace my Aloris tool post on my 13" lathe I'm fixing to sell. No way, I'm going to let go of my Aloris tool post!!! I'll have to say, it's not too bad. The only two con's I've notice is the slop in the wedges when you lock and unlock the tool holders from the post, and I have a older Aloris holder that is too tight for the dovetails on the tool post. But that tool holder is not going with the lathe being sold anyways. Bot overall, it holds the tool holders tight and releases them okay, too.

Ken

 

[Sheldon0]

I bought a Phase II BXA last year and the piston and wedge were the same price. I did pick a wedge and very happy with it. Put it on my 13" SB.

 

[Doubleeboy]

Bought a CXA Phase II a couple years ago, wedge style, it is a total piece of ****. My no name wedge BXA on another lathe is worlds better. Same could be said for the 10" Phase II rotary table, it leaks like a sieve. No more Phase II anything for my shop. I like the CDCO toolholders, except for the expensive shipping to west coast.

 

[mikey]

Miiikke,



... look into my eyes, Miiikke ... you're getting sleeepy ... buy a Dorian tool post and never look back ... buying no-name tools will shrink your Nards ... SNAP ... wakey, wakey!

 

[whitmore]

Wedge, pressure on 2 Ddovetails, better than one

I agree with this (there are two surfaces next to the tool tip that have metal/metal contact force).
With the piston type, three surfaces are pressed into metal/metal contact, but #2 is the
(small) piston and #3 is an inch or two from the cutting edge.

There are lots of vibration possibilities (chatter being one) that can occur in a cut, and the
best acoustic coupling from the small tip to the large, soft steel (0r cast iron) parts will result
in the least oscillation, because sound energy will spread out into the acoustic dark spaces
instead of hitting an acoustic mirror and creating an echo chamber.

Similarly, a toolholder that engages the steel on one surface, with a holddown screw,
(bottle type) isn't as good as one with two surfaces and two holddown screws.

It'd be amusing to make toolholders that, instead of holddown screws, used a wedge
(like parallels) to fill the gap, so the tool had a complete over-and-under pair of
clamped surfaces. In theory, the tool tip would be more stable that way.
This is done, of course, for some cutoff tools.

The same theory (I'm a physics junkie) says that a collet-type boring bar holder
should be superior to screw-down toolbit holding. There ARE square collet possibilities.

 

[Catcam]

I've used both, have no preference from experience. Having said that, I note from the descriptions above, that while the piston type pushes the tool away from the post, putting pressure on the dovetails, the wedge type pulls the tool toward the tool post putting pressure on one of the dovetails (the wedge is not rigid, usually formed sheet metal) and the flat surfaces of the tool post, being somewhat more secure. This is from logic, I'd want to study both with indicators before making a positive judgement. In other words, which cutting tool would wobble more when clamped.

I have a wedge style version and the wedge is definitely not "sheet metal"

 

[Splat]

Multifix. Only way to go. I got mine from Create Tool in central China after reading good reviews of them. Absolutely love mine. Went with an "A" series for my G4003G. Highly recommended.

 

[Franko]

I've had both. I'm nowhere near an expert, but as far as holding the tool securely and repeatable indexing, I could perceive no difference.
I'm not sure I understand why I would need to switch tools so they needed to index precisely as they were.
What I didn't like about the wedge is it tended to jam and make it difficult remove and install a new tool.
The piston type doesn't have that inconvenience.
I much prefer the piston type. I've had no issues with piston AXA I have on my 12x28" lathe.

 

[darkzero]

I've always wanted a MultiFix type TP. At the time for me they didn't make sense for me. The holders, although made in China, were expensive & not readily available. I got a good deal on a brand new Dorian SQCTP so I went with it, no regrets though.

Wedge is superior to piston. I personally am not a fan of piston. My Dorian & my previous DTM wedge TPs have never jammed or bind up on me. The locked up feels great, much better than a piston. If a wedge TP does that, it might just need to be disassembled & given a good cleaning. I don'tbrecall having that problem with my China wedge that I had on my old mini lathe either but I only had it for 8 months.

The reason why wedge is superior to piston is rigidity. A piston pushes the tool holder outwards so it registers on the dovetail. A wedge pulls the tool holder in against the body of the tool post & is what makes it more rigid. There's a reason why Aloris don't make the piston style anymore as well as the other name brands. Dorian used to make a cam type TP, but it too pulled on the dovetail instead of pushing it out. Pretty much only China still makes the piston type from what I have seen. But one thing I've noticed is that the piston type is not very common in the big sizes. Maybe a reason for that IMO but maybe not.

When I took a machining course with my lil brother at the local CC, most all their lathes had piston type tool posts. With heavy cuts or vibration the pistons actually came loose sometimes. Had to keep your hand on the TP handle when that happened. The TPs could have just been worn but it tended to do that on multiple machines.

With smaller hobby lathes, the difference may never be noticed. Nothing wrong with a piston in that case. Wedge doesn't cost much more so if buying for the first time, might as well just get the wedge IMHO.

EDIT: Oops, sorry for repeating a bit of which most have already said, I didn't read the whole thread before I posted.