Quick change tool post question

[DFMiller]

What are the advantages and disadvantages of the Piston and wedge style of tool posts. Phase 2 etc sell both. Which one should I get?? Just upgrading my lathe from a old Shoptask 3in 1 to a new KMS 10x22 that looks really nice compared to all the other chinese stuff around.
Thanks

[Forrest Addy]

To piston or to wedge.

The wedge style is stiffer and stronger and inherently more accurate but the poston is very effective and considerably lower in cost.

Low usage in the home shop taking prediminantly light cuts and a limited tooling budget would indicate the piston style. Many owner of smaller lathe are very satisfied with theirs.

If yours is a rescued production lathe having plenty of power and precision then the wedge style would be a better choice.

[hoffman]

I have an import piston on my 10 x 24 and I love it. For home shop/tinkering I don't think you'd notice any difference.

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Hoffman in Warner Robins Ga

[precisionworks]

I have a wedge-type on my 10" South Bend. The advertising says the wedge type has greater accuracy than the piston but for what effect? The most important quality IMO is that every tool in every toolholder reindicates to its last setting (on centerline for OD turning, 0.010" above centerline for ID turning).

You'll be happy with either one since they are so much better than a lanten or a 12-position indexer. Whichever you get, buy extra toolholder blocks. I have a drawer full and still need just a few more........

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Barry Milton

[Rich Carlstedt]

precisionworks You said
"I have a wedge-type on my 10" South Bend. The advertising says the wedge type has greater accuracy than the piston but for what effect?

for the benefit of Newbes, and to answer your question, I am reposting some info I made earlier with reference to Aloris holders.

The tapered wedge design is far superior to all else. Even some wedge imposters are not true wedge operations (!). let me explain:
A button/piston post pushes out in one spot against two dovetail surfaces. This gives 3 points of contact in one axis.(say X)
The moving wedge (one direction only) uses a cam to push outward and engage both dovetails on 4 surfaces. This gives 4 points of contact and assumeing the wedge is locked, controls 2 axis of direction ( X & Y )
The Aloris has a tapered wedge which moves downward and out at the same time. This action solidly wedges the dovetail with 4 contact points and at the same time exerts heavy force downward, locking the tool holders height adjustment which is the fifth point of contact.This locks all 3 axis's (X,Y,Z)
Now remember that for repeatability, all 3 axis points must be controlled if tools are being rotated on a setup, or you will lose it. The added benefit is EXTREME rigidity.
Now, if you use Aloris, Or wellmade toolholders, the wedge cam handle will always stop 1/2 way between the tailstock and the operator. If you use "xxx" holders, there is no guarantee.

[viking]

I just bought a Phase II piston type set for my back up lathe and while I don't think the quality is as nice as my Dorian wedge type on the other lathe it is still a wonderful setup.

Anyone that is considering buying a quick change setup for hobby use can't go wrong with the set MSC has on sale until 3/31/05. With 4 holders and a knurling tool the costs are $99.95 for the 100 series, or $129 for the 200 series. Usually the tool post alone goes for more than this.

[lklb]

While on the subject,it might be worth mentioning John Stevenson's excellent, easy to make tool post.......

http://www.metalwebnews.com/howto/toolpost/toolpost.html

[hoffman]

In trade school one of our projects was a QCTP. It got away from me somewhere down the line.

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Hoffman in Warner Robins Ga