Vacuum chuck

Glue the fabric face to the chuck (MDF in your case). You'll also get more of a friction fit with the foam facing the wood this way. Of course, if you have slipping between the foam and wood, you'll get some of the foam color transfered to the wood. I found that the mousepads held up poorly and were too open-cell (let too much air flow through) though.

If you have enough suction, the chuck should work with the fabric side against the wood. Just not as well as otherwise.

I've made 3 different vacuum chucks for use with a Shop-Vac attachment. It's not great but it works well enough (for now) for large surface area items.

- Andrew

You'll get a lot of air leakage though the open pores of mouse pad material, I read of a tip sometime ago that sounded good, this guy ran a goodly bead of hot-melt glue around the rim of his chuck, and when it set up he turned it to true it up.

Hi Phil, Home Depot sells a spongy type shelf liner (about 1/4" thick) that works excellent for what your doing. Your bowl will compress it with vacuum applied and it will return to shape when your finished. It won't slip or loose vacuum and won't transfer anything to your turning. I've used the same piece for a couple years. Works great. I drew concentric circles on it with a marker for centering.

Bob, Naugatuck Ct.

Hi Phil, Bob made a suggestion for a thinner material for your sealing means. I suggest you go that route as 1/4" and thicker material lets the piece move even when being held by vacuum. Thinner material is more desirable in my opinion with 1/8" being about right.

Jim

Phil Lackey wrote:

I use mouse pads and experience no noticable loss of vacuum. I use contact cement to glue it on (fabric side to the MDF), but a single coat never seems to look like it's enough, so the pad side gets about 3 coats. No failures yet and no noticable leaks. I have not had good luck with the hot melt glue method, but I'd like to understand why it won't work for me.

Art

Phil Lackey wrote:

===================================== Art, Could be it's not working because it's not hot enough. The recommendations I've heard for this is to use a skillet with a hot plate or an electric skillet to heat the glue. The guns aren't hot enough to heat the glue over the area required., but if you heat it in a pan or skillet, then dip the face plate into it and IMMEDIATELY attach to the work piece, then the results are better. Also, there are 2 types of hot glue, low temp and high temp; use the high temp.

Ken Moon Webberville, TX

Sorry Ken. I wasn't very specific in my "hot melt glue" comment (or I have misinterpreted your response). James Barley made mention of an idea to use the hot melt as the seal between the vacuum chuck and the work piece by laying a bead of glue on the MDF (or whatever) and, once solidified, turn it true as the sealing surface. I've tried this, as well as laying the bead on the end of a short piece of schedule 40 PVC pipe set into a wood faceplate, but have not had any luck with either method. I tried that right after setting up my vacuum system. I have learned a lot since then, so maybe I should go back and try it again. Maybe I'm misinterpreting you response, but it looked like it was directed at attaching a waste block to a workpiece to allow attaching to a face plate. Actually I haven't tried MDF yet. Since I wanted a more contoured surface that could also be used to fit inside natural edge bowls, I mounted a piece of 3" thick maple and turned the contour before gluing on the mouse pad. It took me a few minutes of leakage to realize that using a wood base, I had to seal the maple because so much vacuum was lost through the wood's porocity (that "wood is just a bundle of straws" thing). A couple of coats of sanding sealer worked for me. I have one more method to try that I'm not sure I've heard mentioned yet and that is using a large and fat O-ring set into a wood plate as the sealing surface. My second hobby is beer making and I've graduated from bottling the brew to kegging it in 5 gallon SS soda containers. The top of the keg is sealed by an O-ring that's about 4" in diameter and 1/4" thick. I have an extra and it would seem to me I could cut a groove in an MDF faceplate,then set the O-ring into it (probably sealed somehow into the groove). If anyone has tried this, I'd like to hear how it worked out. In any case, I'll let the group know if it works.

Art Learmonth

Ken Moon wrote:

Art, Sorry about the misunderstanding on the hot glue. I thought you were trying to use it to attach the MDF to a faceplate. Now I understand how you were trying to use it as a sealing surface. An idea along that way, would be to try RTV silicone as you would the hot glue. I don't know how long it would have to cure in thick quantities, but it should be fairly durable. Since I don't have vacuum chuck, I can't experiment on it myself, but you might give it a try.

recommendations

Hello Art,

I saw Soren Berger of New Zealand make up cups for holding small projects. Soren used hot meld glue, applied with a glue gun. He ran a bead around the top edge of the cup. He then turned this to smooth it out and to even up the glue. He then sanded it smooth. He noted that you could sand it lightly just before applying the object to be held. This warms the glue a bit and makes it conform to the shape of the object better. I've never used this on a vacuum chuck, but it worked very well for Soren. I'm not sure how well it will work on larger chucks.

Fred Holder

A couple of things to try. Wet suit material may work. Use a piece of Saran wrap or similar plastic wrap to cover gasket and ensure that you do not transfer black mark to your work. Be sure to poke a hole in the center before use.