Piston or Wedge

All discussion about lathes including but not limited to: South Bend, Hardinge, Logan, Monarch, Clausing and other HSM lathes, including imports

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BadDog
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Re: Piston or Wedge

Post by BadDog » Mon Jan 28, 2019 4:18 pm

I had a piston that came on my G4000. Worked well enough for that anemic noodle. And when I upgraded to my Rockwell 11x37, I originally added a Phase II AX piston (AXA is wedge) set from Enco. I liked it pretty well too. But that was on a 1 HP 11" lathe, and I noticed (as already mentioned) multiple occasions when making hard interrupted cuts, it would rattle loose. And likewise, I got into the habit of bumping the leaver closed, and then periodically during cuts with any vibration, though I never broke it. That's when I started pondering a wedge upgrade.

When I bought my next (and so far final) upgrade, a 17x60 7.5HP 4500 lb comparative monster, and knowing what I had planned for it, the piston wasn't even on the radar. I started with a PII CXA wedge kit from Enco. This lathe would more properly get a CX (a wedge one size larger than CXA, they change naming schemes), but the import CXA blocks are readily available cheap, and the CX blocks are absolutely not. Plus you have a better chance of cheap CXA name brand wedges.

So, that's my story. Given any choice in the matter, I can't imagine any reason I would ever run a piston again...
Russ
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pete
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Re: Piston or Wedge

Post by pete » Mon Jan 28, 2019 4:44 pm

Well to add this there's also the European made 3 position Tripan tool post that supposed to be very very good, and with a price to match that's typical of high end Swiss made machine tools and tooling. They allow much better clearance in some situations. Especially when using tail stock support. Stefan Gotteswinter on YouTube uses one and he's no fool. Then there's the Swiss or German made and recently the Chinese clones of the Multifix 40 position quick change. Very positive comments on the PM forums about those Chinese Multifix for whatever that's worth. Even Forrest Addy likes them and there's few with his combined experience and skills. Some members on the PM forums have mentioned about having a small set of the old school rocker tool post and tool holders for reaching in where an Aloris or Dorian can't. So far I've never really run across the problem, but it would depend on a fairly special part shape. I suspect one of those Tripan tool posts would do anything a rocker tool post could and do it far better. I've only used the rocker type back in high school and even then with the little I knew I still wasn't enthused about them. Dave Richards on YT uses them exclusively in his steam powered machine shop, but that's due to his requirement of historical accuracy and not because there any better.

I've always been impressed with George Thomas's writings and as skilled and competent as he was he had firm beliefs about using a 4 position tool turett like most lathes today have as OEM included equipment for the very good reasons that the tools are far better supported and aren't cantilevered out over the top slide. The standard cheap turett's have as expected really poor indexing repeatability, but he mentions one that was made by Herbert in the UK that was supposed to have been very good. Yeah those tool turret's are a bit slower to use while changing tools. But if the shims are made up and kept with each tool the time isn't that bad. There's some situations where I'm sure the chatter I was seeing wouldn't be there if I'd have been using the stock turett as poor as they are. I've read comments on various forums where some mention the piston type posts are more than good enough for anyone with a home shop and no one at the hobby level would ever see any benefit using a wedge type. Personally I don't agree with that. There's certainly enough clearances and moving parts between the tool tip and the lathe bed as it is. And I've yet to find anything that can cut metal as ever being too rigid. For the little extra in price I think I'd always chose the wedge type over the piston. In my opinion the better repeatability, tool holder locking and support more than makes up for the minor cost difference.

spro
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Re: Piston or Wedge

Post by spro » Mon Jan 28, 2019 4:49 pm

I had square turrets on everything but was constantly fiddling with shims. Heh, one of them is a South Bend and has individual rockers inside each station. I was on the fence about these newer tool posts and the piston type was new then. Glad I sat that one out.

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SteveM
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Re: Piston or Wedge

Post by SteveM » Tue Jan 29, 2019 8:45 pm

pete wrote:
Mon Jan 28, 2019 4:44 pm
I've always been impressed with George Thomas's writings and as skilled and competent as he was he had firm beliefs about using a 4 position tool turett like most lathes today have as OEM included equipment for the very good reasons that the tools are far better supported and aren't cantilevered out over the top slide.
I picked up a really nice, older Enco 4-way turret toolpost. It's very well made, made in the USA. It has very positive locking detents (12 positions, I think).

If I was going to do a job that required 4 tool bits in repeat succession, I would certainly use it, as I would only need to shim it once.

Steve

E189552
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Joined: Wed Feb 06, 2019 1:16 pm

Re: Piston or Wedge

Post by E189552 » Wed Feb 06, 2019 4:39 pm

I second the wedge design over the piston, much more rigid & secure.

I do believe that the original mfgr for KDK is out of business but a company called Ajax Tool Supply still sells a KDK clone line of toolposts & toolholders.

737mechanic
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Location: Dallas

Re: Piston or Wedge

Post by 737mechanic » Fri Mar 22, 2019 10:06 pm

I started out with a piston style and it worked great but when I got my new lathe I went with the wedge style and am glad I did. Seems to work more smoothly and solidly.

spro
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Re: Piston or Wedge

Post by spro » Sun Mar 24, 2019 6:08 pm

I became so engrossed in your other videos that I didn't see the toolpost. Really fascinating.

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