# Hydraulic DIY QCTP



## cascao (Jul 27, 2017)

Not mine, but deserves a look


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## Bamban (Jul 27, 2017)

Nice project, now if you can find a DIY hydraulic or pneumatic follow rest, I will be interested in copying it.

Thanks for posting it.


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## Silverbullet (Jul 27, 2017)

Bamban said:


> Nice project, now if you can find a DIY hydraulic or pneumatic follow rest, I will be interested in copying it.
> 
> Thanks for posting it.


How about using bimba pneumatic cylinders with bearings in the yoke , with a valve to lock position. A tire valve would do . Of course I don't see the need for a powered steady or follow rest.


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## Bamban (Jul 27, 2017)

Silverbullet said:


> How about using bimba pneumatic cylinders with bearings in the yoke , with a valve to lock position. A tire valve would do . Of course I don't see the need for a powered steady or follow rest.



To play wth, I bought a 2 inch Bimba, that should give enough pressure on the work piece with around 3X the incoming air. I was thinking about machining a Delrin saddle that will straddle the barrel when turning. Using a regulator for the incoming air from a reserve tank might do it. Thoughts?


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## kd4gij (Jul 27, 2017)

You would need a way to monitor your tool pressure to maintain even pressure through the entire cut.


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## cascao (Jul 28, 2017)

for a rest, Maybe a symple coil (or a bolt) will be better than a complicated Hydraulic system.....


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## gonzo (Jul 28, 2017)

If the hole through the body from the piston chamber to the inner chamber were drilled at the top of the piston chamber instead of the center then it would preclude getting air trapped behind the piston.


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## hman (Jul 28, 2017)

Hmmm ... Good thought!  While watching the video, I kept wondering about trapped air, which would result in "lost motion" for the small piston - requiring several turns to release the springiness of the compressed air when releasing the tool holder, then requiring several turns to build up pressure when trying to hold it.

Perhaps the originator will see this, or maybe somebody can add a comment to the Youtube posting.  If nothing else, he can drill a second hole at the top of the piston chamber.  Two holes will not affect operation of the hydraulics.  Might even aid in the removal of air!


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## mhooper (Jul 28, 2017)

What about boring the hole for the slave piston (large one) through to the T bolt hole and moving (or adding a second hole) near the top O ring on the T bolt to vent the air during filling.   Just a thought.


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## whitmore (Jul 29, 2017)

In this incarnation, the idea takes four O-ring seals (the most accessible one being doubled),
and complicates the central post of the toolholder.   The multiple O-ring
seals is a bother, any one of 'em that leaks during a cut
would ... drop the tool.

 A variant could use gas-over-liquid
pressurization (like, from a CO2 cartridge) with a single O-ring seal, and wouldn't require a post (so a holder could be bolted to a mill table or somesuch, and still hold the tool).

I've seen wedge quickchange designs with tension on a rod to actuate the clamp, http://hobby-machinist.com/threads/a-quick-change-toolpost-by-john-stevenson.268/ 
and a cylinder-and-linkage could provide tension hydraulically.  Then the 'master piston' could
be a sealed bellows under a toggle-clamp.   Two-dovetail holders could be accomodated
with multiple master pistons, just swivel the toggle clamp to a second push-position.

All told, the Stevenson design has more appeal (though the
central block with dovetail innies instead of outies is... unsettling).


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## cascao (Jul 29, 2017)

If it was mine, I will just add a bleed bolt at the top of qctp


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## whitmore (Jul 29, 2017)

Silverbullet said:


> How about using bimba pneumatic cylinders.... A tire valve would do


Aha!  There's the solution to the bleed issue, just put a Schraeder valve in the piston, hold it open
during insertion.  There's plenty of length to play with, the piston can have a step to larger
diameter (so the tightening knob bears on the piston rim while the Schraeder stem is accessible
through a central hole in the knob).

I'm unsure, though, how I'd make a seat for a Schraeder stem.   Maybe just solder in an
old brass stem from an innertube?   What's the cost of a Schraeder reamer?

As for initial oil filling, I'd go with vacuum backfill; bubbles are a BAD THING.


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