Vacuum Advice

[David Delo]

Wanted to see if any Hold Fast users had ever switched over to a real vacuum pump (instead of the vac generator) but still continued using the HF adapter and chucks with a "real" vacuum pump. I have the Hold Fast and really like it and their chucks seem to work well for me also but I came into possession of a Oneway system with gauge, adapter & Gast pump along with the drum chucks. Only things I need to make a complete Oneway system are the adapter for my lathe (3520B) and their drum chuck adapter for 1 1/4" which would be 75 bucks + shipping.

I think just hooking up the pump to the Hold Fast components I have now would work just fine but have 1 concern. Is the curtain-rod that goes thru the headstock in any danger of collapsing from the lesser ID of the rod versus using the entire ID of the headstock itself that the Oneway uses.

[Mike Goetzke]

Check out the classifieds I have a Oneway vacuum adapter that fits the 3520b - yours for $45 shipped. I think this sells for about $90 new. I bought a used system with everything and all three drums have the 1-1/4" chuck adapters so you may want to purchase one for each chuck - these aluminum chucks are stout!

Mike

[David Delo]

Check out the classifieds I have a Oneway vacuum adapter that fits the 3520b - yours for $45 shipped. I think this sells for about $90 new. I bought a used system with everything and all three drums have the 1-1/4" chuck adapters so you may want to purchase one for each chuck - these aluminum chucks are stout!

Mike

Mike,
I don't need the rotary adapter, already have one. To make the Oneway work on the PM, I need the adapter that fits on the no thread PM outboard spindle into the female side of the Oneway rotary adapter. I'm proposing taking off the hose from the Oneway rotary adapter (see picture) and connecting it directly onto the barb of the rotary Hold Fast adapter.

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[John K Jordan]

I think just hooking up the pump to the Hold Fast components I have now would work just fine but have 1 concern. Is the curtain-rod that goes thru the headstock in any danger of collapsing from the lesser ID of the rod versus using the entire ID of the headstock itself that the Oneway uses.

David,

I don't have the Hold Fast (for the 3520b I use a machined aluminum rotary adapter with o-ring seals that plugs into the handwheel). However, I can't imagine you could collapse the tube (actually, a piece of lamp rod) with the most powerful vacuum pump on the planet. I'll say zero danger!

My reasoning: The forces from vacuum are not very strong compared to the forces possible with compressed air. The strongest pressure possible with even a "perfect" vacuum on the surface of earth is about 15 psi. In addition, a hollow cylinder is the strongest tube shape you can make, and in fact the smaller the diameter the stronger it is against the forces of pressure. It would have to be an extremely weak tube to collapse under vacuum. (You could test it to put your mind at ease: plug the ends of the tube, put into a pressure chamber, and pressurize to 15 psi with air or water and see if the tube collapsed!) If a rubber hose won't collapse, the metal tube certainly won't.

Lots of people use a system like the Hold Fast with vacuum pumps, some home made. Look at this pdf: www.azwoodturners.org/pages/tips/vacuum3.pdf

You may want to add a bleeder valve to your pump, not to protect the tube but to protect the piece - a strong vacuum with a large diameter chuck can break a thin turning. This was mentioned recently in another thread and I added some notes: http://www.sawmillcreek.org/showthread.php?259201-Vacuum-pump-need-help&p=2742635#post2742635

BTW, if you (or anyone) could use a Oneway rotary vacuum adapter for the 3520b I have one I don't need. This is the one that requires removing the handwheel which I disliked since I do a lot of spindle turning and had to repeatedly remove the adapter to use the knockout bar. If you want I could send it and you could try it - I actually have some free time this week and next so I could actually get it to the post office! (The first in months!!)

JKJ

[David Delo]

Thanks for the advice John, think I'll try it out and see how it works. I do have a bleeder on this rig, it's just hidden behind the handwheel in the picture. Besides the cost of getting the adapters for the rotary and the drums, the taking on/off of the handwheel was another reason I was looking to just use the existing HF components.

[John K Jordan]

Thanks for the advice John, think I'll try it out and see how it works. I do have a bleeder on this rig, it's just hidden behind the handwheel in the picture.

I think I see it. I didn't see the message with the picture until after I posted. It looks like you have a stack of nice wood there to play with!

JKJ

[David Delo]

It looks like you have a stack of nice wood there to play with!

JKJ

The Bubinga from the inquiry the other day on the bottom, zebrawood, 3 blocks of macassar ebony, purpleheart, bubinga & wenge on top row.

[John K Jordan]

The Bubinga from the inquiry the other day on the bottom, zebrawood, 3 blocks of macassar ebony, purpleheart, bubinga & wenge on top row.

Yikes, I hope you don't have the same wood acquisition disease I have but from that picture it doesn't look promising. I came back from the last symposium with several hundred pounds of exotics and figured maple I didn't need. :) I don't much like wenge but I love working with bubinga. In fact, I named my first llama Bubinga, got him when he was one month old.

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BWT, I grew up a little south of Pittsburgh (near Elizabeth) with the Monongahela river in our back yard. Some of the stuff that floated past our house in the spring floods probably went past yours a little later!

JKJ

[David Delo]

Yikes, I hope you don't have the same wood acquisition disease I have but from that picture it doesn't look promising.

No need to worry about that. I was just collecting all my stash to take to our next meeting to swap or sell. I'm pretty much a plain vanilla kind of guy so anymore my idea of exoctic is cherry burl or maybe some spalted maple.

[Bill Boehme]

The vacuum doesn't even come close to collapsing the plastic or rubber hose from the pump ... It certainly is no threat to a lamp rod. However, I would forget about that approach and instead get this rotary coupler (https://www.jtturningtools.com/PM3520-adapter) from JT Turning Tools.

[David Delo]

The vacuum doesn't even come close to collapsing the plastic or rubber hose from the pump ... It certainly is no threat to a lamp rod. However, I would forget about that approach and instead get this rotary coupler (https://www.jtturningtools.com/PM3520-adapter) from JT Turning Tools.

Thanks for the reminder Bill. I knew of JT and this product but completely forgot about it as a solution.

[Jeffrey J Smith]

David - I used the Holdfast adapter for a while on my old 1642 - it worked fine, but wound up opting for the oneway adapter for a more permanent soltion. When I upgraded lathes a while back, the JT Turning Tools adapter came as an accessory to the new lathe - it is great - simple attachment gets the vac chuck setup quickly - it works great.
I still use a couple of holdfast chucks - mainly on a bench vacuum carving stand. They continue to work great after about a decade of use.

[David Delo]

Finally had a chance to fiddle around with setting up the Gast pump directly to the Holdfast system today. As advised, everything worked out just fine. Grabbed an old crappy bowl to test it out and walla 26" on the gauge. Once I figure out a little better place to stick everything on a more permanent basis, I think I'll like this setup better.
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[Dwight Rutherford]

Here’s a graph I find useful in determining holding power and estimate how much vacuum is too little or too much.

[Bill Boehme]

Finally had a chance to fiddle around with setting up the Gast pump directly to the Holdfast system today. As advised, everything worked out just fine. Grabbed an old crappy bowl to test it out and walla 26" on the gauge. Once I figure out a little better place to stick everything on a more permanent basis, I think I'll like this setup better.

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I like using a street elbow rather than a straight connection to the rotary coupler. The right angle keeps the tubing from flapping around.

[David Delo]

I like using a street elbow rather than a straight connection to the rotary coupler. The right angle keeps the tubing from flapping around.
Bill,
It does vibrate some but wouldn't say it's flapping around. I'll eventually get one of the JT adapters but this should satisfied until then. Just trying to get away from a full tank of compressed air. Made a video clip but can't seem to get the link t appear.

https://www.youtube.com/watch?v=yYsgN3P44nU

[David Delo]

Here’s a graph I find useful in determining holding power and estimate how much vacuum is too little or too much.
Thanks for the useful info Dwight.

[John K Jordan]

Here’s a graph I find useful in determining holding power and estimate how much vacuum is too little or too much.

That's a nice chart. Saves calculating the area and remembering the conversion from inches of mercury to psi (.491)

The harder problem to answer is how much pressure is needed to keep from dislodging a given piece with typical turning forces, including catches. And how much pressure will cause a given piece to implode! So many variables, some not non-destructively measurable...

JKJ