Vacuum hold downs

[bcondon]

Well I would not have believed it!

Bill Polumbo has been recommending in each of the camps
that I have attended to use a little vacuum pump and make
pucks out of extruded decking material instead of clamps and screws.

I purchased from Harbor Freight a 3CFM, 2 stage, 1/4 HP pump,

machined up a bunch of pucks, a little reinforced 1/4" tubing,
tapped the decking with the 1/4" NPT tap and that little system
worked better than I can imagine. I am setting up a quick disconnect
and maybe a manifold to attach the pucks for quick changeout or
some will be permanently attached to the bed.

Used AllAdhesive gasketing. I think I will be smiling for a week!

Now to start thinkin about that lathe...

Thanks Bill!

You showed us the pump but I would never have

[billp]

Bob,
Glad you finally got a chance to try them! ;)
Now that you have your pucks in a row, try them for holding down parts for sanding, edge work, and assembly as well...

[sc.crab]

Do you have any pictures of your setup?

[WMNH]

I went online and bought a pump from Joes Woodworker as soon as I got home from the Maine camp this summer. It really is awesome. I can't believe I got along without one!

[bcondon]

A picture is on snapfish

http://www5.snapfish.com/snapfish/fe/l=en_US/p/Organizer/AlbumID=9442972028/s_c=0/s_mvm=NAP/s_se=FDR/s_pt=REP,PMB#state={%22pl%22%3A{%22uc%22%3A2%2C%22 aid%22%3A9442972028%2C%22vp%22%3A%22g%22%2C%22sb%2 2%3A5}%2C%22ovm%22%3A{%22v%22%3A%22s%22}}

(cut and paste it into a browser)

The four pucks in the front are different sizes. Each Puck has a tapped hole for the brass barbed connector with a 1/4" hole running horizontally about 3" into the material. The grooves on the surface pierce that horizontal channel to allow the vacuum to pull down.

I then put the gasketing on (as seen in the puck behind the vacuum pump)

Thanks

Bob

[JimDav]

snapfish requires an account. : ( Can a pic be posted here perhaps?

[bcondon]

I search because I know I have read it many time but can not find it.

If someone can let me know, I would be glad to post picture!

Thanks

Bob

[billp]

Bob,
When you hit the "Post reply button"you'll see the reply box, and underneath that box is the place to "attach files/manage attachments" as shown here. You'll see a box come up which lets you know the size limitations the forum can handle. If you're not sure, attach the pix,"upload"them, and then hit "preview", and it will let you know if they are too large or not....

[gerryv]

I've often wondered if these would work well for lumber, assuming it's been planed. I'm thinking of 8" wide x 6' and 8' long planks using an 8' PowerStick with no spoil board - just pucks.

[billp]

Gerry,
I can't think of any reason why it wouldn't, unless you had some VERY porous wood. And even then a coat of shellac,or even shelf paper on the bottom should solve that.
You could even buy a long piece of "Trex" or any other similar "recycled plastic bottle wood"product and make FULL length pucks/pods...

[WMNH]

I've used my pucks for lots of pine lumber but nothing that long. The only issue I see would be if there is a lot of twist in the board. On smaller pieces I've done (2 ft or so) a slight twist can be pushed down onto the puck to to get the vacum to hold. Once it gets sucked down it's not moving!

[gerryv]

Thanks much everyone, The new workshop/studio should be complete by the end of November so I'll give it a try and post how things work.

Any suggestions on gasketing for the pucks as I'm sure I'll be cutting through it now and then :-)

[Ernie Balch]

I worked in the semiconductor wafer business for many years and almost every piece of equipment used for handling wafers uses vacuum chucks in one form or another. It is really great to see this method being used for woodworking.

I started out with a old fashioned welch oil type vacuum pump and pucks made of corian. This allowed me to engrave Rowmark materials for small signs and name tags. With this material no gaskets were required. I just machined a bunch of grooves as vacuum channels.

Going to wood required a better seal so I tried thick adhesive foam gaskets from the hardware store. Of course this did not work very well because the foam did not compress flat enough or uniformly enough. It also allowed the part to wiggle causing chatter during cutting. I started using sandblast masking material for gaskets. I cut it on a vinyl cutter then put down an entire layer on the vacuum chuck and weed out the vacuum areas. This works for my applications. Bill P mentioned a better gasket material at a recent shopbot camp and I am anxious to give it a try.

Once you start using vacuum chucks you will think of all kinds of new uses as Bill indicated. The small pumps can achieve a better vacuum than a shop vac can but have a much lower flow. The low flow means that a small leak can cause an instant failure in holding power, so keep that in mind. You can't cut through anywhere in the puck hold down area.

Vacuum pucks use the atmospheric pressure to hold your part down, so at best you have 15 pounds per square inch at sea level. Thus a puck with 4 square inches of surface can provide as much as 60 pounds of weight to hold your part in place. You will have remember that small leaks and higher elevations will reduce the max weight you can achieve.

ernie

[gerryv]

Thanks Ernie, We all benefit from "crossover" experience :)

[WMNH]

A couple pictures of the puck I used last week for a small production job. I just use white PVC trim material from the big box stores, regular 3/8" air hose with quick connect couplers tapped into the side and All Star gasketing. This paticular puck was used for something else originally and I needed it smaller so I added some more gasketing to make it smaller, then I just screwed in some scrap to make a 90* corner for registration everytime. Worked great and made quick work of this job. Less than 30 seconds to remove the finished part and add a new blank.

[bcondon]

I have a 3 CFM 2 stage vacuum pump. Purchased at Harbor Freight for $159.

The pucks are made of Trex deck flooring.

The holes is 1/4" ID or 1/2" OD which has a weave or braid for strength (will not collapse under vacuum)

I tapped the Trex with a 1/4" NPT.

I use barbed connectors / Thread to connect 1/4" hose to trex (which is tapped)

I plan on putting small quick disconnects in line and a manifold on the vacuum pump to reduce the re-configuring of tubes.

One of my fixtures is 54" long for window Shutter side rails (54")

[donek]

I've been playing with going to this type of vacuum hold down for some of the aluminum parts I make. I recently purchased some of the vacuum tape. It seems to be almost identical to the foamies available from walmart and Michaels.
http://www.walmart.com/ip/Darice-Foamies-Sticky-Back-Foam-Sheets-Assorted-Colors-40-pkg/24672073
This material can be cut to very specific shapes with the drag knife. I've ordered some vac attachments so I can attempt a use specific fixture. I need fixtures that are about 10 to 12in wide. Can you get the trex in something that wide? I was considering using MDF as the fixture base and coating it with epoxy. I have several 1 gallon samples of epoxy resins just going to waste. Any thoughts on wider materials similar to the Trex?


I have a 3 CFM 2 stage vacuum pump. Purchased at Harbor Freight for $159.

The pucks are made of Trex deck flooring.

The holes is 1/4" ID or 1/2" OD which has a weave or braid for strength (will not collapse under vacuum)

I tapped the Trex with a 1/4" NPT.

I use barbed connectors / Thread to connect 1/4" hose to trex (which is tapped)

I plan on putting small quick disconnects in line and a manifold on the vacuum pump to reduce the re-configuring of tubes.

One of my fixtures is 54" long for window Shutter side rails (54")

[WMNH]

I use regular PVC trim which I believe you can get 12" wide. The widest I have in the shop is 10" but I thought I saw 12" pieces at the big box stores.

I use the 1/16" thick Allstar gasket material, I tried regular foam door seal gasket material and it worked but had some side to side movement probably due to it's thickness. I bought the Allstar through Joes woodworker, Allstar didn't have online ordering available when I bought mine.

[Howley]

Can I assume that you have to leave the vacuum pump running while you were doing your cuts?

Does anybody have cut files for the pucks, or just design your own?

[WMNH]

Yes pump must be left running, at least with mine anyway. I have a switch conviently mounted that turns the pump on and off. I don't machine anything for my pucks. I just drill a 1" or so in the middle and then a 1/4" hole from the side that intersects the bigger hole. I then drill and tap the 1/4" hole to accept a 1/4" NPT fitting and I use regular air line quickconnects. Then the gasket material is carefully attached to the PVC "puck" for the size I need. Make sure the gasket leaves no gaps or you won't get a good seal. If it's a larger area I put some extra gasket material in the middle to keep the vacuum from bending my material to the puck.

[curtiss]

If you don't mind a few small holes on the backside of your work "pulldown" from below with a few lag screws works well.

You can cut about anywhere as long as you miss the screws, so far so good...:confused:

[bcondon]

The Trex comes as a 1x6. You need not worry because a 5 1/2 x 11 will hold your 10x12 object in place. I did run the Trex through my surface planer to get a good surface and then put the grooves in and the plug in the side.

I used the AllAdhesive product on the resource list. It is design for the application, has many widths and thickness (thinner is better) and different densities. I used Medium density, 1/2" thick and it works just GREAT!

My 5x5 puck holds a 12x12 piece of marble in place.

If the trex did not work, I would use HDPE instead. You can get that in many thickness and sheet side (High Tech Plastics, Anaheim California is where I bought it and had it shipped) The customer backed out of the project after I bought it because the shopbot was technically too challenging for his abilities. He was unwilling to get training so Ted, being the good guy he is, bought the system back.

Oh well, now I have product to play with on a quiet day!

Today I needed to cut some letters out of Azec so just dropped it on the vacuum puck, turned on the switch and cut away!

Thanks

Bob