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

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Rd2nowr

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Ok, so what's the difference between a piston QCTP and the wedge type? Pro's and cons of both? Shar's has the AXA piston type in a set for $114. and the wedge type for $183.
Thanks, Tim
 
It's the way the tool post locks the tool holder in place. Correct me if I am wrong but I believe the wedge type holds the tool holder not only tighter but more accurately as well.


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I have both types.

The piston type pushes the tool holder out from the tool post to force it against the dovetail. The wedge type drives down a wedge for the same purpose.

I have them on two SB 9s. I haven't had any trouble with either one.
 
I have the wedge type on a lathe I purchased from a friend. No issues with my toolholder. The friend got a new lathe and a piston type. He has commented he prefers the wedge type. I did not try to get details on the difference.
 
The difference has been stated above but I will add that the piston type pushes the holder away from the base while the wedge type brings the holder closer to the base. So my take is that the wedge type is the better holder. I have used both.

"Billy G"
 
Charles Spencer said:
I have both types.

The piston type pushes the tool holder out from the tool post to force it against the dovetail. The wedge type drives down a wedge for the same purpose.

I have them on two SB 9s. I haven't had any trouble with either one.
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So the AXA is the correct size?
 
Size of the tool post depends on the size of your lathe. What lathe do you have?
 
Both tool post types work just fine. Get the wedge type if it is about the same price. It if is a lot more expensive, then go with the piston type. The only thing that is really at issue here is repeatability, that is taking off the tool holder and then putting it back on again, and expecting the tool to be in the same place again, exactly. How often is that really an issue with a lathe, and if it was .001" vs. .0005", would that cause huge problems?
 
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.
 
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