Holdfast Vacum Chucking System

[Paul Kane]

Ive just acquired the Holdfast Vacum Chucking System,this is my first time trying Vacum Chucking,I've only the 3inch chuck at the moment,to be honest ,I was expecting the hold on the blanks to be more rigid,so,at the minute I am not very confident using the system,I'm sure I've got the right settings on my compressor,Would the bigger 6 inch chuck ,give me more grip on the bigger 16-20 inch platter blanks?Is there any material ,I could use on the chuck or the blank,that would enhance gripping power?All help and advise would be appreciated.

Kindly Paul

 

[Dwight R Rutherford]

Here is a handy chart that will give you an idea as to holding power of various sized chucks at different vacuum bevels.

 

[hockenbery]

A material for a really good hold is double sided tape. This is an alternative to vacuum that I use occasionally.

Dwight’s chart shows you will get a stronger hold with a larger chuck.

A tight seal wood to chuck eliminates air loss.
I prefer a dense foam that has little give for round pieces.
This gives the most stable hold for turning the bottom.

If I have pieces that are slightly out of round that won’t seal to the dense foam, I will use a thick foam and non rigid chuck made from cardboard tube for concrete - Sonatube. The tube will deform slightly conform to an out of round piecemand the thick foam will take up the rest. The trade off here is that the turning gets a spongy feel as the hold is flexible and moves with cutting pressure. Light cuts and light bevel pressure will let me turn on with this chuck.

 

[Dwight R Rutherford]

The best foam I have found is the closed seal foam used to make diving wet suits. It’s about 1/4” thick and has some give as hockenberry suggests.

 

[Bill Boehme]

When using the chart that Dwight showed, the diameter is the inside diameter of the chuck. Also, the thickness of your seal material will reduce that diameter further. If I remember correctly, the vacuum gauge on Holdfast is at the Venturi. In order to get an accurate measure of vacuum the gauge needs to be as physically close to the headstock as it can reasonably be located. There are several leaks that will reduce the actual vacuum.

• The seal between the chuck and the wood will have some amount of leak because the seal material isn't perfect and the wood isn't perfectly flat.
• Air leaks through the wood itself like a sieve ... far more than you might imagine. You can reduce leakage through the wood by covering it with painters masking tape.
• The rotary coupler leaks. How much varies greatly depending on the quality of the design and fabrication.
• I assume that your system also has a bleed valve to control the vacuum.
• The amount of vacuum that any system can pull depends on the volumetric flow rate (cubic feet per minute here or cubic meters per minute over there). The greater the flow rate the better.

If you are turning large diameter pieces then you should be using larger vacuum chucks. A six inch diameter chuck would be a good size to have.

 

[john lucas]

As has been said earlier the larger the chuck the more holding power you have. I have also found sometimes when reverse turning bowls that the wood warps just a little and won't seal as well. I use a square piece of closed cell foam that I buy at Hobby Lobby. It has a hole cut in the center. I put that over the vacuum chuck and use the square corners to help position it. Then put the bowl on. It has just enough compression to seal the warped bowls. You haven't mentioned if you have a gauge on your set up. It is by far the best way to check for leaks. 3" isn't bad for bowls in the 8 inch range but for large platter blanks bigger is better. I made my self an 8" shallow vacuum chuck and it holds so good you can't pull it off.

 

[Theodore Perry]

Don't forget if the wood is spalted or wormy it may leak vacuum and not hold well no matter what size or seal the chuck is.

 

[Damon McLaughlin]

Paul, I had the Hold Fast with three inch chuck and used it a lot in the past year and a half. I have never had any problems with it and no complaints either. I always have the tailstock up against the piece until the very last little bit just to help keep the wood in place. For porous woods I sometimes put a coat or two of sanding sealer and let it dry and other times I have used a single layer of painters tape. Both help with the holding power. Because you're using the air compressor you should check to see that its rated at the minimum required cfm, lower air volume may affect your holding power as well. Everyone else has made some great suggestions as well. The next time I'm in town I plan on getting some foam squares.

 

[Tom Hitch]

I recently acquired a V811 holdfast vacuum system.
My question for those of you who use the holdfast systems is if you leave the vacuum attachment in place all of the time or only attach it when you need to use it.
My thought is that the sealed bearings could wear out prematurely if they are engaged all of the time
Thoughts?
Thanks in advance for sharing your experiences.

 

[Gary Beasley]

Mine get pulled as soon as I get done with it. Ive noticed the bearings getting warm during long use.

 

[Brad Winesett]

+1 on what Gary says.