Holdfast vacuum heads leaving marks

[Michael Ginsberg]

I have all three sizes of the plastic vacuum drums from Holdfast. I am finding that when using all three sizes on softer woods, when the rubber gaskets get compressed from the vacuum pressure, the plastic edge between the two gaskets leaves an indentation on the wood. Anybody have this problem and what have you done to fix it? I was thinking of speading a layer of rubber cement on the plastic between the gaskets...
by the way.. the vacuum pressure is 22-23

Thanks.

[John Keeton]

Michael, you have accurately described the problem I am having, as well. Usually, it is something I can easily sand out. I have not done it yet, but my intent is to take out the gaskets, and round over the edges slightly. I think this will work. I am afraid trying to layer the plastic would leave an uneven surface and you might have difficulty with a good seal.

Let me know what you end up with.

[Michael Ginsberg]

John,
I like your idea about the rounding. I am waiting tio hear back from tech. support from Craft Supply. Hopefully they can get me in touch with the manufacturer for some input as to a sollution.

[James Combs]

I have all three sizes of the plastic vacuum drums from Holdfast. I am finding that when using all three sizes on softer woods, when the rubber gaskets get compressed from the vacuum pressure, the plastic edge between the two gaskets leaves an indentation on the wood. Anybody have this problem and what have you done to fix it? I was thinking of speading a layer of rubber cement on the plastic between the gaskets...
by the way.. the vacuum pressure is 22-23

Thanks.


Michael, you have accurately described the problem I am having, as well. Usually, it is something I can easily sand out. I have not done it yet, but my intent is to take out the gaskets, and round over the edges slightly. I think this will work. I am afraid trying to layer the plastic would leave an uneven surface and you might have difficulty with a good seal.

Let me know what you end up with.

Michael/John, My vacuum chucks are homemade but when I was making them I did make sure the edge that holds the rubber seal was rounded over. I have not noted any problems with indentation and I am typically drawing 26-27 inches of vacuum. I think rounding over your rubber supports edges would definitely be a plus if it doesn't effect the rubber seal attachment.

[Bruce Pratt]

If the fibers are not broken, will water or steam raise the dents back up? I seem to remember some previous threads (here or elsewhere) where this was part of a deliberate design technique.
-----------------
Bruce

[Roger Chandler]

perhaps this new seal for the Holdfast chuck heads would provide a solution:

http://www.rubberchucky.com/index.php?option=com_content&view=article&id=80&Itemid=112

I am thinking about ordering a couple of these seals............I have not had the problem you have described, but these look as if they would give you more vacuum than the ones that came with the heads.

[Steve Vaughan]

Good ideas here. I get that little indentation every now and again and have been able to sand it out with no problem, and usually only with the last fine grit of sandpaper I'd used. But I like John's idea and might give it a try. But Roger's find looks even more promising cause my little rubber gaskets keep coming off.

[Larry Marley]

I had the same problem, I just glue up and turn my own chucks with a soft radius and use white hobby foam for the gasket. I use for Beal spindle tap to thread it. No marking.

[Russell Eaton]

Michael the parent company of Holdfast is TMI products. I have a friend with the same problems and he bought the Oneway replacement gaskets and applied those to the chuck to solve the problem.

[John Keeton]

Russell, when you say OneWay, are you talking about the link Roger posted?

[Michael Ginsberg]

John and Russell, I just checked with Oneway. Their gaskets are 3 1/2, 5 1/2, 8 and 12 inches. My Holdfast heads are 3, 6 and 8 inches. So some may fit.. I do not have the heads with me so I do not have the exact dimensions. I am not sure if my sizes are inside or outside dimensions. I am waiting to get a call back from Oneway as to the exact dimensions of there gaskets to see if they will fit before ordering. I will let you folks know soon.

[John Keeton]

I just tried to buy a set of the rubber gaskets in Roger's post, but they are out of stock.

[Cathy Schaewe]

I use the white hobby foam on my vac chucks too. No marks. Just cut a circle, peel off the adhesive and stick it on, and then wrap some electrical tape around the outside. Ends up being a very soft surface. I would think it's very similar to those gaskets.

[Russell Eaton]

John, I was talking about the Oneway gaskets that Highland Hardware sells for a replacement. It is about 1/2" wide and covers pretty well. I live close enough that I go by there some days on the way home from work. That can get habit forming...and leave a hole in the wallet.

[Michael Ginsberg]

OK.. I jusdt spoke to peter at Oneway. Good news! it seems that they will fit! Here are the dimensions for their gaskets:
The 3 1/2 inch is 4 inches and 1 inch wide, the 5 1/2 is 6 1/2 inches and 1 3/4 wide and the 8 inch is 9 inches and 1 3/4 wide. $5.00 each with flat rate shipping of $7.50

[Michael Ginsberg]

I just spoke with John at TMI. He said that their design is to have the flat piece in between the gaskets as a holding aid. He said the flat was supposed to make contact with the wood. I asked why when they make the heads, why do they not put a radius on that piece? He said good question. He was going to check with the engineers and get back to me. I am not sure if I want to round over the edge if it will affect holding power. By using the Oneway gaskets, I will be eliminating the flat making contach with the bowl and am not sure I will have the same holding power when using a gouge.

[John Keeton]

Russell, just measured and the smaller Holdfast is 3.43" and the larger is 5.77" to the outside of the hard rim.

I think I will get the Oneway gaskets - for the money it is worth a try.

[Roger Chandler]

I just left them my email at rubber chucky.........they will notify me when they receive their new shipment.

[John Keeton]

Roger, I did that, too, but in the meantime, seems the Oneway are cheaper (a little) and at least worth a shot.

[Joe Bradshaw]

Michael, like Cathy, I use the white Foamies from Wally World. I use the non adhesive instead. Also, my vacuum chucks have rounded edges. I just cut a square piece of foam and punch a hole in the middle. Once I pull a vacuum, everything stays in place.

[Michael Ginsberg]

Roger and John,
Before you order the gaskets ...
I have more info.
I just spoke to John again. He spoke with the engineers. Apparently the mold has a radius on the lip that we are questioning. They get rid of that lip and make it flat to true it up. John said, that the engineers said that it is absolutely just as strong and holding power will not be compromised if you sand the corners with a bit of a radius. As a matter of fact, he said that they plan on doing that to all their new heads that will be in production...

[Roger Chandler]

Sounds reasonable to me Micheal........I don't see how it could hurt anything......Just a little off the square edge and sanded back at a reasonable angle should do the trick.

[Russell Eaton]

If you do order the Oneway gaskets they come 5 to a pack so it will last for a while. Just FYI.

[Michael Ginsberg]

Russell,
Oneway said that one can be purchassed for the $5.00 if you don't want all five.

[Steve Vaughan]

Gonna round my Holdfast chucks over on that flat you're talking about. Glad for this conversation and all the info.

[Jeff Nicol]

You can take some rubber or soft plasctic hose and slice it so that it will go around the edge and then use CA to glue the end joint. With the correct size tube to fit whatever chuck you have quick and simple.

Jeff