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

Cadillac STS said:
This topic shows up once in a while with very similar responses.

Is it too off topic to throw in here whether it is better to spend more for a Phase II, Dorian or genuine-authentic Aloris brand QCTP? Or it the lowest price model just as good?
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I couldn't find the thread, but someone was doing a very comprehensive study on the various tool posts and tool holders: high-end vs. low-end. I recall the run out numbers being very close on them all, Aloris or Dorian did not blow away Shars or CDCO. For a hobbyist, low-end is fine, production shop with customers coming in looking at your equipment, might be worth getting the high-end.

Bruce
 
12bolts said:
I have a wedge type and think that the wedge is betterHowever without knowing who wrote the literature its hard to determine whos right.
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Do you mean the individual who wrote the copy for the catalog??

http://www.doriantool.com/tool-post-toolholders/

http://www.aloris.com/aloris_cat/31e970.pdf

Regardless, the point is that this isn't just a matter of tribal knowledge passed around users of internet machining fora. There's a reason Dorian doesn't make a piston-type quick change tool post (hint: their QCTPs are designed for CNC use as well as manual use). Aloris stopped offering theirs. The piston design predates the wedge type. Why would anyone bother to make a new type if the piston was sufficiently good?

I've never seen anyone claim that the piston is superior, countless real-world users report that the wedge is superior, and manufacturer literature and pricing schemes (among manufacturers who offer piston and wedge types) both indicate that the wedge should be superior. How much more do you need?
 
BGHansen said:
I couldn't find the thread, but someone was doing a very comprehensive study on the various tool posts and tool holders: high-end vs. low-end. I recall the run out numbers being very close on them all, Aloris or Dorian did not blow away Shars or CDCO. For a hobbyist, low-end is fine, production shop with customers coming in looking at your equipment, might be worth getting the high-end.

Bruce
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https://www.hobby-machinist.com/threads/qctp-holder-review-part-1.52672/
 
intjonmiller said:
I recall seeing literature from Dorian or Aloris that confirmed that the wedge type is more accurate and repeatable, and I am at least 95% sure they also said it's more rigid.
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I've seen something to that effect, too, Jon. I only have wedge-style posts for my Emco lathe but I have both a wedge and piston post for my little Sherline and I have also found the wedge to be better in terms of how solidly the post holds. The way I tested this was to take a 0.050" deep cut (0.100" stock reduction) in mild steel and checked the tool height with my tool setting gage right after that cut; I repeated this 3 times for each type. The wedge style held the height every time, while the piston allowed a very small shift upward once. Not very conclusive, I will admit, but it was good enough for me to have more confidence in a wedge-style post.
 
I think rigidity only starts to become a factor when you get to the lager end of the typical hobby size lathe which seems to be a 14" swing and up to 3 HP. Even then unless you are taking very deep cuts all the time I don't think there is a significant enough difference performance wise between the wedge or piston type. I think it would be more of an issue when you get into heavier machines of 5HP or more.

I do like the way the wedge type feels when locking vs the piston. It just feels better but the testing I did comparing the two types didn't show a significant difference.

I have taken up to .35" DOC in aluminum and .25" in steel which is what I feel is the safe maximum for my machine. I don't do finish cuts at those depths so what is important to me is how the system work at finishing cut depths.

The lathe I setup for the high school has a no-name import AXA wedge style QCTP. I find it is too loosely built and personally really awful to use but it works fine for the students. I had a no-name import BXA wedge on my old lathe and the quality was very close to the Aloris I now have on my new lathe so it can be luck of the draw on unbranded imports quality wise.
 
T Bredehoft said:
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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My chineese made AXA wedge is not sheet metal, it's a ground piece of metal. If it were sheet metal, how would it hold at all.
 
woochucker said:
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.
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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...
 
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