In search of the ultimate non-vacuum table surface

[srwtlc]

It's time for a new top for my table and I've been trying come up with what would be the ultimate non-vacuum table (at least for my purposes). My old table was just two layers of ply that I'd screw into wherever I needed. Needless to say after three years my wife could now use it for a colander. 8-) I do so many different jobs throughout the year that it needs to be very adaptable to the varied tasks. I use vacuum when needed with specialized jigs for production runs of many small parts. I'm not totally sold on a T-track setup as I would need to have a smaller grid. And what do you do about a waster surface then. I've thought about an array of holes that you could drop some custom clamp blocks into and tighten down, but they would need to be able to be released without having to get under the table to do so. With that setup you could use various types of benchdogs for stops to corner a part.

I'd like to hear some of your opinions to further fuel the creative juices.

Scott

[beacon14]

So what was wrong with "just two layers of ply that I'd screw into wherever I needed".
If it served your purpose, was adaptable, flexible, and affordable, what's the big deal about having to replace it after 2 years?
Sometimes simplest is best.

[srwtlc]

It's the plywood that is more of the problem than the screw holes. Seasonal changes in humidity require that it be resurfaced often and some sheetgoods are so warped/curled/twisted that it's difficult to pull them flat. I'm considering two layers of 3/4" mdf, but every time after you run a screw into that you would have to shave off the swells made by the screws.

[kerrazy]

Scott,
I am in a similar situation to you. Although I use one sheet of ply and one sheet of MDF, on top.

I am still searching for the best answer currently myself.
As for the screw holes swelling, I use a piece of 80 grit sand paper to knock those off rather than resufacing the table each time. I do get the flexibility I need but I too would like something simpler???
Dale

[rgbrown@itexas.net]

My "next" table will be of Baltic birch. I plan on sealing the bottom and edges of the sheets. It will attach, by glue, to wooden stringers I have machine leveled. I will then flatten the first layer and bond a second and maybe a third one on.

On my old MDF table when an area would need to be replaced, I would cut out the "offending section" and glue another piece of **** board - MDF, in and cut the excess off with the ShopBot.

One of the things I used on the "hybred" table of MDF with ply overlay was Nylon 1/4 X 20 bolts. I kept the proper drill bit and tap handy and when it came time to fix a piece "hard" to the table, I drilled a hole, tapped it and ran in the Nylon screw. I also used Nylon washers. I have Quick couplers on all my battery powered drills and adapted a tap to fit the proper shank.

I will use these methods and more on my "next" table. I like vacuum holding a lot. And, it can be inexpensive too.

Ron

[shuttle]

I thought GP (1/16") plastic laminate backer board might be good as a final skin, it could be stuck on with tile cement and then run the Bot over it with a weight or roller on a grid pattern to get it good and level.
If it were attached face down you would have a suface that provides a lot of drag resistance.

[billp]

Scott,
I have a table which is similar to Ron's next one.. Two layers of Baltic birch glued together. The top one has vacuum channels for holding full sheets of plywood, etc. After planing it flat I immediately sealed it with two coats of a water based polyurethane, including the channels walls, and sides of the ply. I am 10 miles from the ocean, so I go through major changes in humidity as the seasons revolve. I also screw a lot of pieces right to the table and when it gets lumpy I surform the table back to flat, and fill in the holes with a latex filler.
I like this setup because it is versatile, practical, and requires little maintenance. I have resurfaced it a few times in the last few years, and I still have a lot of "meat"to go.And I'm not afraid to USE the table the way that some guys using more "exotic" surfaces ( Komatex/Sintra/PVC, etc) seem to be.
If I need smaller vacuum areas, I make smaller vacuum jigs. My table has remained flat ,and stable enough for me to cut many delicate 3D items, and lithophanes without having to worry about it's state of being "true".
In short it's a pragmatic tool, it works, so it's good....

[Steve Minuskin]

A ply or MDF table with threaded holes drilled in a grid pattern may be the solution for you.
To get threaded holes in wood, through drill the table surface with the desired hole pattern and embed pronged T nuts in the bottom of the table at each hole location. You will have plenty of meat above the T nut for use as a sacrificial top.

[srwtlc]

I've thought about the T-nut approach. My one concern with that is with the holes getting plugged with sawdust, etc. That would depend somewhat on the size of T-nuts used though.

Does anyone know of somekind of... say a toggle bolt that you could drop into a hole, set it, then be able to release it when needed, all from the top?

Baltic birch is a good choice also. I've used that and a product by the name of ApplePly in a birch veneer that is pretty good too.

Scott

[tlbusch@tuohyfurniture.com]

Here's an expanding Cam bolt that works like Scott suggested.
http://www.carrlane.com/catalog/index.cfm/27625071F0B221118070C1C513E111D081B0006280B1713050 245221E0107070F1A3C3B28535444

[gerald_d]

Why be complicated?

[gerald_d]

Keep it simple . . . . . .


8419


.

[srwtlc]

Those are interesting Trent, thanks for the link.

Ok Gerald, nice picture, but how about a little info to go.

[gerald_d]

Scott, here we call them "Fischer plugs" and every homeowner recognises them immediately. I don't know what they would be called in America, or whether you guys with your timber houses use them at all. We normally drill a 1/4" or 3/8" hole in masonary, drop the correct plug in, and turn a normal woodscrew into it. If the screw is only in about 2 turns, then they can be pulled out by pulling on the screw.

The British call them Rawlplugs. Herr Fischer designed the one in the pic in Germany - there they are also known as Fischer Plugs. The only thing I seem to find with Google in America is "plastic dowel". Surely you guys have something better than just a plastic dowel? Those little wings are very efficient at keeping the plug in place while starting the screw.

Editted to add:
Then I found this discussion (http://www.leo.org/dict/archiv/20020129102654e_en.html). "Plastic screw anchor" maybe??

[kerrazy]

Gerald,
Once again way too much time on your hands.

Dale

[alano]

My solution.....

Buy one sheet of 1" MDF. Seal the back side and edges with your choice of sealant. Bore 1" counter-bored holes (1/2" deep) with 3/8" through holes and bolt (with washers) the sheet of 1" MDF to the tables metal web frames. Surface the top flat. Seal the top of the freshly surfaced 1" MDF.

Seal the back side and edges of a sheet of 3/4" melamine. Place a half a dozen or so strips of double sided carpet tape on the top of the 1" MDF and carefully place the melamine over it.

Advantages:
This yields an easily replaceable spoilboard (quickly) that doesnt need to be surfaced as the sublayer (i.e.; 1" MDF is already flattened).
The melamine has a hard and durable surface to work on.
There are no screws or other mounting hardware to deal with (or worry about if your bit hits it).
Surface can be drilled or screwed into or T-Track added at this point.

My 2-cents worth....

Alan

[smoores@rogers.com]

I am also makeing a now table. I am using 2x3's glue together to make a solid slab. As for clamp, I made a program and cutter to cut 1/2 - 13 threads into the table. I also made threaded plugs that can be glued into unwanted holes.

[K Simmerer (Unregistered Guest)]

Here's my observations on MDF vs Ply. MDf is basically fairly stable material formed under heat and pressure. The end result is a material though that has a much denser skin than the core area. Once you machine off that first layer you unleash a tremendous internal stress that results in a huge curling force that I have seen strong enough to pull screws out of my tables wood stringers. Take a 2'x2' piece and machine a 1/16th off one side and look at it the next day. Plywood doesn't do this, much more stable as a spoil board or vac. board.

Keith

[TELRAE1961@YAHOO.COM]

I just finished building my steel table for the PRT96 ShopBot that is on order. My problem is where to get 1 IN MDF 60 IN wide By 120 IN Long Top for my machine.
Any Help

[stickman]

T Earle,

You might look to a cabinet maker or talk with your lumber yards. We get White Melamines and timblend in those widths and lengths, now MDF could be another question. But that would be my first steps, get with a material provider. I used melamine for my table surface.

[tberkner]

I use 1" Ultra-lite MDF (same density all the way throught). Use one side, next year flip it over and use the other. Next year replace it. I use screws to hold down wedges to keep all my work pieces in place when I'm cutting, so I have lots of screw holes, but it doesn't matter. I also routed a 1" wide by 1/8" deep channel along the edges of the X and Y axis, and screwed in a 1" x 3/4" plywood strip. This gives me a replaceable fence, permanent zero position, and something to jam the work piece against.

[prosigns]

I made my table with 2''x2'' square tube cross braces rather than angle iron. 5 crossbraces 16" on center. I bolted a 4'x8'x3/4" sheet of oak vaneer plywood to the table using a grid of 16" on center 1/4" carriage bolts countersunk so the sacrifice board (3/4" MDF) would clear the heads. I then drilled a grid of 16'' holes through the oak plywood (spaced between the carriage bolts) one size bigger than the screws I used to screw down the sacrifice board. That way the screws would draw the sacrifice board down to the plywood table without binding. I used small aluminum screws so if I accidently hit a screw it would cut it off instead of breaking the bit. And yup I have hit the aluminum screws since I have resurfaced the sacrifice board fairly thin by now. I cut aluminum and steel on the table from time to time so flat is a nessesity if you don't want to bury the bit on the first pass. Aslo, since I drilled the holes for the aliuminum screws oversized, when I replace the sacrifice board, if a couple twist off they will just fall out of the plywood table top. This set-up not too different than what Shopbot recomends, works great. It's simple, So I figure if it's not broke don't fix it. My 2¢. I hold my workpiece down with screws. If the table Really needs to be flat I use an orbital sander to knock down the screw holes before doing the next job.