Vacumn hold down which is best.

[hrshie3]

We recently acquired a used PRT96 and are impressed with its capabilities. We would like to upgrade to a vacumn hold down system and would like to know what experience other people have had. Our work is usually a 48"x96" 3/4" oak or pine veneer with cut outs rangine from a 3" circle to a 21" x 62" dresser top.

At times we will cut rocker blades that at 2 1/2" wide. What would you recommend for hold down requirements.

[gerald_d]

Try the Keyword Search (http://www.talkshopbot.com/forum/cgi-bin/discus/board-search.cgi) feature of this forum, you are going to find a lot of stuff that has already been discussed to death. When you start a new thread, and get very little response, it could well be that some of us think the topic has been covered enough times already.

[toys]

After lots of trial and error I've found that the most important feature to a good vacuum system is versatility. Then the pump. The vacuum plenum should allow you to quickly change from a gasketing setup to a spoil board system. This way you have the best of both worlds. Most of the high price machines have something like this. Komo for example has a series of channels milled in there aluminum table top that allow a round "o-ring type" gasket to be tucked in to seal against a jig. Holes on the top are sealed with a disc or removed to expose a vacuum port. You can quickly open up any size area and tuck in the gasket. What seals on top could be a spoil board or some other ficture jig. I've also found the size of the hole allowing proper air flow is important. I had been using a 1/16 hole under each part that led to chamber under the part. I found out from a pump manufacture that my holes were much too small. I increased the size to 1/4 inch and suddenly my undersized 3/4hp vaccuum pump does everything I need it to. This tidbit saved several thousand dollars. Big pumps are expensive. I went from barely holding one puzzle to holding down 12 at the same time and and not loosing a single piece. Another good find, mentioned in other places, is a gasketing material made by AllStar plastics. It makes making jigs painless and quick. Hope this helps.


5390

[toys]

Howard, my puzzle pieces are much smaller than a 3 inch circle. The smallest is a about 1.5 square inches. I'm using a used Gast rotary vain pump. It pulls 25 inches of mercury but after pulling through all twelve puzzles it only pulls between 8-10 inches. I should note that I'm using an air turbine that spins at 65,000 rpm's and a bit that is only 3/64ths of an inch so there is a lot less cutting force compared to electric routers. When I cut the backing boards I use my porter cable and can easily hold down 9 -12"x12" boards. If I were you I would call some pump manufactures and talk with there technical folks. They could give you a better idea of whats needed for your specific applications.

[toys]

A very effective way to seal a board for making jigs is to use 100% silicone and thin it down using white gas (for obvious reasons do this outside). I've sealed MDF this way and it works as well as using acylic for sealing out airflow.

[papadaveinwy]

to save time etc to blank out (seal airflow on what you don't use of the table) just buy some 1/8 inch masonite the kind with white on one side, or buy for a little more money the shower surround made from plastic 4x8 smooth and you can cut it with a good pair of sissors. very light weight. David in Wyoming

[rgbrown@itexas.net]

Or gule a layer of 2 to 10 mill polyethelyne on the back or in a layer of the base... Or, seal with epoxy. Several coats of thinned down white glue will slow the leaks.