Table designs (wood, steel, other)

[jerry]

Hi everybody,

I am soon to be a new putting owner and have been following the forum for a couple of months now. I am at that stage now of designing and building my wood table. I have downloaded the plans from Shopbot for the wood table, but was wondering what other neat and clever ideas other Shopbot owners have done. I created this subject so that these designs can be shared and maybe post some pictures of different table designs. If putting pictures on the forum will take up to much space they could be e-mail to me. I plan to build a wood table so any help/ideas would be greatly welcome. Thanks.

[RgEngrave@aol.com]

Well my tip would be if you do make a wood table make sure you space the legs so you can slide plywood in and out, say 8'5".

This will let you have room to store plywood under your machine, you can even make different levels to store different sizes, this will give the machine weight and keep it steady, make sure to use cross braces on the ends.

I would use 4x4 as legs, just notch out for a 2x8 and use blots with washers and 2 set screws, this way the weight on the 2x8 will be on solid wood and not sag or drop in time.

If you are going to use 2x8s or 2x6s for the side boards, this is where the X rails will mount,I would use 2x4 brackets to hold the 2x4 cross studs, just lay in the studs and use 3 inch wood screws and go thru the 2x6 or 2x8 , best to pre-drill the holes first, doing this will help if you ever need to replace the stud.

Now wait till you have your machine installed before you add any plywood top to the table, you will want to use the machine to plain the 2x4 studs so it will be level with the machine, you will only need to plain a 1/8 inch off the tops, makes sure that you are cutting wood and not air, if you see that it did not cut the top? move home and start over, move the bit down another 1/6 and resume cutting all the studs, this will give you a level table.

I use 2 sheets of mdf for my tops, 1 use 1/4 lag blots with 3/8 head, and counter sink them into the first sheet,I use 3 bolts per cross member, then I lay the second sheet on top and use 6 bolts, 2 on ends and 2 in the middle to hold in place, counter sink them,I them z the router bit down on a piece if 1/4 inch material then stop, remove the material and move the machine around the table and the see if the material will slid in under the bit the same way it did when you removed it, this is to see if you have the same height in different places on your table.

Hope this help you a little.

Ron

[Dave Nadeau, ShopBot]

Jerry,
Just a few suggestions that worked for other users... We know of several ShopBotters using the lower portion of their table to store materials such as plywood and sign foam. Entire sheets can be stored there prior to cutting, or the space can be used to contain and organize the collection of usable strips and odd-shaped scraps of material that accumulates in every shop. I have also used the floor under the ShopBot table to store material temporarily on long pallets and to temporarily store materials which are "works in progress" to protect them from damage or loss in a busy shop until completion.
If your ShopBot will be equipped with vacuum, remember to plan your table around the vacuum manifold (PVC pipe) which will occupy some of the space under the table. If you will be using clamps instead of vacuum to hold material on your table, you could consider putting a full-length clamp along one edge of the surface of the table to hold material. The clamp could be made from a variety of materials [I have used two hardwood strips held together by 3/8" threaded studs (with knobs) screwed into tee nuts], and it is most useful if the materials you cut most often are the same (or nearly the same) thickness.
A few other ideas... If your ShopBot control box will be located in the same room as your ShopBot and if space is limiting, you can place the control box under the table in a "dustproof" enclosure. The outside of the table near your workstation is a handy place to attach hangers to keep often-used items such a bench brush, remote control, cordless screwdriver, and calipers handy. If you will have a variety of router bits on hand at any time, a series of shelves with holes in them or a small, thin vertical cabinet could be added to the outside of the table to keep bits organized or to separate new bits from bits needing resharpening.

[bill.young]

Jerry,

My current table is WAY overbuilt, but I really wanted to make sure that it didn't move with humidity and temperature changes. I laminated the rails out of three layers of 1x12 pine shelving board, glued together with carpenters glue and LOTS of drywall screws. The legs are 2x10s that are through-bolted to the inside of the long rails, and the cross rails that support the top are lag bolted into the legs. The legs in the corners are made of two pieces of 2x10 fastened together at 90 degs so that they're attached to both the sides and the ends. It's pretty beefy but REALLY stable.

I also drilled holes in the bottom of each leg and used threaded inserts with carriage bolts screwed into them as height adjusters.

Bill

[jerry]

Thanks everybody,

There are a lot of great ideas there. I will probably use a little bit from everyone. It is nice to know that so many people are willing to take time out of there busy lives to help out the beginners.

--- jerry

[srwtlc]

Jerry,

I first considered building mine out of laminated joists to keep it stable with changes in humidity, but when I checked on buying the steel from a local steel and manufacturing company the price was much better so I built a steel one from Shopbots new steel table plans. With the steel,bolts,and paint it cost me $150. I couldn't beat that with laminated lumber. And it's blue to match ;)

Scott

[jimt]

Jerry,

I agree with Scott. I have had a wooden table ever since day one (about 5 years) and I've finally tired of it flexing with the seasons. I also priced out the steel materials and came up with about $200 using a place that sells "surplus" steel. It's never been used, but it has some rust and you mat not get the exact sizes, but I'm certainly going to build it. The new plans are very simple and I'm sure the table will be very strong and stable.

Jim

[sheldon@dingwallguitars.com]

I'm thinking of installing a couple of MDF underlayers on my table, topped with 1/4" steel. I have the Z room, that's not a problem. However if the MDF moves with humidity, that will be a real problem.

Has anyone tried sealing there wood tables with epoxy? How stable have you found that to be?

[jorgy.tucson@worldnet.att.net]

My table is fabricated from steel channel and angle iron cross braces. Bolted together to allow for tweaking, much the way red iron of multi-story builings is done. 1 3/16" particle board main top sits upon 6" square MDF pads that have been leveled with the SB. This allows for a lot of air movement around the table surface to maintain a "balanced" panel. Remember to take into account the MOE of the table top material. Also, the "flatness" of the cutting surface is relative to the deflection of the x and y rails.

[Gerald D]

Hi John,

Your last sentence should really be the departure point for a lot of these discussions on "flatness". I get the impression that the wood guys have an overated impression of how flat steel is.

The SB rails are very flexible and their flatness depends on how well the end-user sets them up (my rails were curved 5/16" before bolting them down.

A sheet of 1/4" steel plate will "droop" more than 1" under its own weight.

Mention is often made on this forum that the straightness (flatness) be checked with a line. How much does the line "droop" under own weight, and can one really see where it touches a surface?

Lasers are also mentioned, but construction type lasers or only okay down to about 1/8". (other lasers are better, but I suspect we are talking of the simpler types here)

Given all these flexible variables, we must stand back and decide if we want a flat table or if we want the tool to move parallel to the table surface. If the latter is the case, then get the SB to cut it's own table surface. The SB will not cut steel, so the choices become simple.

Your method of facing the support pads is nice and simple and it sounds like you have a really sound table!

Sheldon, what would be the purpose of the steel over the MDF? The only thing that I can think of is as a "wear-protector", but a sacrificial sheet of MDF would serve the same purpose? The thin steel sheet will add nothing to the structural strength of your underlying wood construction.

Can you guys get the equivalent of "masonite hardboard" over an inch thick? Here we have "Supawood" which is very stable, but then again, our weather is also rather stable. ;-)

[garbob]

"Water Resistent" mdf is available. The manufacturers won't call it "Water Proof" as it will expand if soaked in water.

I haven't tried it yet, but it sounds like a good idea. It's very humid here. Has anyone ever worked with this stuff?

[sheldon@dingwallguitars.com]

Gerald,

I can't think of a short way to answer your question of why steel over mdf so here's the long one.

My table is a custom laser cut plate/welded tube design. Our RH cycles from 15% to 80% throughout the year so I'm trying to avoid wood wherever possible.

Problem one: The 1/4" laser cut steel top seemed like a good idea at the time but it's pretty resonant. 3/8" doesn't laser cut as cleanly and would be harder to shim flat. I wanted steel so that I could have permanent index holes and threaded mounting holes for fixtures that maintained their absolute possition throughout the year.

Problem two: I'm running 2 Z axis' so for clearance reasons I have to mount the Zs in the upper holes which means the Zs will be working close to their fully extended position. I think this creates a leverage problem that will lead to more vibration and resonance. I would like to shim up the table by 3" or so.

I was thinking that laying down 4 sheets of MDF and running bolts from the steel top to the tube braces would raise the surface to where I need it and also damp resonance of the top. But since I can't surface the top if the mdf moves, I have to make sure it's stable.

[gdorrington@iafrica.com]

Sheldon, good clear reasoning, and maybe I can make some suggestions - but some more questions first unfortunately:

1. What are your cross members (tube members?) made of, and how far apart are they spaced?

2. How was the top attached to the cross members when you discovered the resonance?

3. Is the resonance higher frequ. (noise problem), or lower frequ. (machine stability, loss of accuracy, chattter marks problem)

Our time zone is same as West Europe, and I have just been called to supper (6.50pm) - so please excuse me if I go to bed before I get your reply!

[gdorrington@iafrica.com]

Hi Sheldon, it was a good supper(bobotie):-)
(hope this is not a cross-post. . . . )

I think that the wood will only help for higher frequency noise, and then it must be bonded to the steel with a mastic or RTV silicon (non-hardening). A wood thickness of about an inch should be more than enough for noise deadening, and it will still be thin enough not to deflect the steel if it wants to swell and shrink.

Low frequency flexing can only come from a support structure that is too flexible. Adding wood between steel will not add strength unless the wood is hard-bonded (epoxied) in place to prevent shearing between the layers. If the flexing is in the vertical direction, then it is simple enough to double up on the cross members (halve the spacing), or stiffen the existing members as in the sketch below.

But you may find that the table is moving horizontally, in which case you need more cross-bracing down to floor level. (The latest table design looks a bit flexible in the y-direction?)

Some sketches for ideas: (notice the height adjustment possibility for each fixing point.

3209

3210

[sheldon@dingwallguitars.com]

Gerald,

Thanks for your response. I really like the long bolt, height adjustment idea. I've got 16 mounting points on a 4' x 4' table, what size of bolt would you recommend? 1/2"?

1. The cross members are 2" square tube 3/16" wall on 17.5" centers.

2. 1/4" flat head bolts with aluminum and left over shopbot shims

3. I haven't done any heavy cuts on it yet to know for sure if I am getting chatter marks and it would be difficult to tell if the chatter came from the table or the carriage, but the table area between the cross members flexes quite easily and wrenches left on the table while testing moves rattle.

If I build my fixtures heavy enough, there may not be a problem, however, since I would like to raise the whole table anyway, I thought it might be nice to damp some vibration while I'm at it.

[Gerald D]

Sheldon, by the time you read this I am probably at the airport waiting for a flight to Frankfurt - back on Friday.

1/2" bolts connected to 1/4" plate would be an overkill. My choice would be 5/16" (actually 8mm because we metricated 30 years ago).

Suggest adding 3 more cross members and halving the bolt spacing. That means 49 bolts! in which case I would use 1/4" bolts. Very rigid and a lot of scope for adjustment.

Wood will not help to reduce the flexing between the members. If it did, then it means that the wood would also have been strong enough to flex the table with moisture absorbtion. So, consider the wood only for HF noise dampening.

To cure rattling wrenches, the best solution is to have them plastic dipped :-)

[ducsy]

Anybody have plans for a wood table...I need to build a table for a PRT96 with twin 24" Z-axis.

I looked over shopbottools.com and could only find plans for a metal table.

Thanks in advance.
Sylvain

[rgengrave@aol.com]

Use the plans for the metal table but just use wood.

Use 4x4s for the legs or 2x6s and use 2x8s for the x axis and 2x4s for the cross members.

Then cross stud the ends to make it sturdy.

Then after you mount your machine just plain the 2x4s with the shopbot to make it level.

Check with shopbot to see if the plans have not changed.

Ron V

[Mayo]

I have made a wood table largely following the plans for the metal table with one exception.
After seeing how much the table moved while cutting, I added diagonal braces on both the x and y axis legs (4 additional diagonal braces).
This helped a lot.

[wood_fun@hotmail.com]

Hi
I’m planning on building a steel table for a PRT 48. I have been reading up on assembling a steel table.( A 4 by 8 table is shown ) The parts lists for the steel parts seem different depending where you look. Should my angle iron be .250 or .50 ? The length of the parts seem to differ also .
If I use the plans for PRT 48 Will I have a good table?
Why .625 holes for a .50 bolt?
Is there any thing you would change to make it better?
Thank you
Dan

[wayneo@alaska.com]

Here is a question to the forum regarding Table Design: Has anyone built a table out of Aluminum rather than steel? If so, please comment. I was just thinking that aluminum is a lot lighter and the 6061-T6 is nearly as strong as steel, plus you can cut it and machine it with woodworking tools for the most part....

[aring@ee.net]

Dan

I've built both a 4x4 and a 4x8 out of steel, your
angle iron should be .25".
The steel makes a good sturdy table.
The 5/8" hole for the 1/2" bolt allows you to adjust or square the table.
I do not understand your question about different length parts? If you download the plans all sizes are correct. Just make sure you grind or file ALL edges before assembly and take your time so you get if level and square.

Andy

[bjwat@comcast.net]

Wayne,
I wouldn't consider AL for making a SB table. It costs twice as much, is tricky to weld and you want the table to be heavy. Steel angle is a heck of a lot stiffer than AL angle of the same size.

The steel table plans are the way to go or just buy the table already powdercoated and ready to go from ShopBot.

-Brady

[wiese]

I have considered making the table out of plywood so that the base would be more like a cabinet. This would make use of the space under the ShopBot for storage. The cross members that form the support for the table could be made from a few layers of plywood glued up to form a more substatial "joist". My thinking is that the plywood is more stable than dimension lumber and is more easily workable that the steel for those of us who don't weld. Any thoughts on the subject?

[bjwat@comcast.net]

I'm sure that there are guys running a wood table that would say it's just as good as steel...I beg to differ on that. A wood table can be somewhat stable IF you seal the wood completely with epoxy. This would reduce water/humidity swelling and movement.

If it were up to me I would wait a little longer and buy the table from ShopBot. The reason I say that is many people don't have welders and grinders to make the steel table and it's nice to just uncrate it and assemble it knowing that you didn't forget anything.

I don't know of any commercially available CNCs out there that use a wooden table frame...The whole idea is to build a solid, dimensionally stable table. Wood and repeatable accuracy just don't go hand in hand.

Again, wood may be right for you and it sure is nice that ShopBot offers plans for those on a tight budget. As with anything else, you get what you pay for.

-Brady

[gittel]

My friend Dave and I built my table out of plywood using boat-building techniques. We were concerned about the tendency for dimensional lumber to warp. The plywood table is very stable. The X-rails are built up of three layers of .75 inch plywood laminated together. The control box fits in a cabinet under the table. As I remember, it cost about $300 in materials and about 30 hours to build. Email gittel@twocats.com (mailto:gittel@twocats.com) if you want to see the construction photos.

[rgbrown@itexas.net]

" Wood and repeatable accuracy just don't go hand in hand."

Sorry Brady, can't let you talk like that even though I built a steel table. From Western Wood Products Association I found this little goodie: "The coefficient of thermal expansion varies slightly with temperature, but for all ordinary uses may be considered constant. In the longitudinal direction, thermal expansion of wood is from 1/10 to 1/3 as great as the expansion of metals, concrete, and glass."

As for your first statement, "A wood table can be somewhat stable IF you seal the wood completely with epoxy. This would reduce water/humidity swelling and movement." There are better, and cheaper, easier to apply products than epoxy that do a better job of sealing.

Personally, I think building a steel table, putting MDF on as spoil-board and complaining about accuracy of the table isn't smart. MDF moves about for too many reasons. I think a well-built table with proper thought given to the construction and a plywood or other multi-laminated wooden bed is about as good as is needed for the work a ShopBot has the accuracy and speed to do properly.

Ron

[beacon14]

Just my 2 cents, but first let me say that I totally agree with Ron that a wood table, especially a plywood table can be as accurate as 99% of ShopBotters would need it to be. My (recently sold) machine had a home-made plywood table, and it worked great for almost 4 years. As Ron said, it was the spoilboard that gave us the most trouble.

Now to "correct" the correction: "In the longitudinal direction, thermal expansion of wood is from 1/10 to 1/3 as great as the expansion of metals, concrete, and glass."
It's not the thermal expansion of wood which gives us woodworkers sleepness nights, but the expansion due to changes in humidity. Steel and glass may have more thermal expansion than wood, but virtually no moisture-related expansion. Also, the term "longitudinal direction", if I am thinking right, refers to the length of the board, parallel to the grain direction. The coefficient of expansion will be much greater in the radial and the tangential directions, that is, across the grain. In fact, it isn't the amount of expansion that causes most wood-movement related problems, but the very fact that wood moves more across the grain than along it, and even more tangentially than radially that causes warpage. Steel and glass (not that I see anyone proposing a glass table for the ShopBot), may have more thermal expansion than wood, but their expansion is uniform in all directions. Your steel table may very well be a couple of thousandths wider in the summer than the winter, but as long as all the parts grow at nearly the same rate, all is well in ShopBot land.

(Not that you could tell, because your steel tape measure is also a few thousandths longer in the summer)

That said, my next table will be steel, for ease of assembly, sturdiness, weight and strength, and besides, you just can't beat that blue powder-coated finish.

[noah@noahsart.co.nz]

Hello Everyone.
I recently took delivery of a PRT96, having had a beautiful welded steel table made locally.
For the surface I first put down 2 sheets of 25mm (1") MDF.
I surfaced the upper sheet as per instructions, and put down a 12mm MDF sheet for a disposable spoilboard, having checked for regularity, on the theory that I would never have to surface the table again.
It has been 2 weeks, and today I cut an x- line at a depth of -1mm into the spoilboard to quickly eyeball small sheets.
Oh dear - the 1mm line actually disappeared in some places. So my table is no longer flat.
I have a perspex job coming up that is quite depth sensitive - grooves in perspex for silicone seals.
Does anyone else use MDF, and if so is it stable enough for the job? Maybe I need to think again, put down marine ply first, or something.
...Ideas?
(It has been raining here non stop for 3 days.)

Simon.
Noah's Art Signs and Designs
Ashburton
New Zealand

[rgbrown@itexas.net]

Gee David,

You mean there is a reason furniture, timber-frames, cabinets and boats are built minimizing the use of wood in the cross grain dimension? The next thing I expect is some fool to tell me that quartersawn material is more stable and there are things like compression grain, runout and knots in wood to deal with!

Simon,

The material and sealing tests on Aluthane, an aluminum filled poly-urethane is found here: http://www.epoxyproducts.com/. I'm not sure the product will work in Metric but, they might make a Metric version.

The plywood spoil-board I used was much more stable than the MDF tables I had built. On my "next" table, I think I will use two layers of plastic laminate ("Formica" in the Imperial world, I'm not sure of the Metric name)on 1-1/2" plywood, edge-band with plastic laminate, seal all the penetrations, machine the top, more laminate and then put the "spoil-board" on -

Of course, one might just buy a plastic, which would have its own set of problems, and machine that. Or, for about $10 a square foot (what does one call his foot in Metric?) one could buy slate that is machined flat and build from there.

Now, if we wanted to discuss some real interesting nit-picking, we could start a discussion on material expansion rates, how to bond them together and what the heat/cold/moisture problems would be. We would also need a conversion factor for the Coriolus effect into Metric.

Ron Brown

Diplomacy is the art of saying 'Nice doggie' until you can find a rock. - Will Rogers

[artisan]

Simon, for pretty solid stability, try making your first layer from a sheet of 1 inch polyprylene ( about $300.00) screwed on from undermeath and machine it flat. This will at least give you a stable platform to mount the spoilboard to. I have used a combination of the polypro and 1/2 inch MDF spoilboard(s) successfully for a year now. It's been much more dependable than the 3/4 inch MDF base I formerly used. You can use the Polypro as a spoilbord too....if your budget can handle it...good luck....D

[ron_cleaver]

Darrell,

Do you periodically flatten the MDF spoilboard? If so, how long does it last? What problems did you notice with the 3/4 in MDF base before?

I've been using a base of two 3/4 in MDF sheets with 1/4 in plywood sheet on top. I haven't had any problems until this year, partially because the ShopBot is located in a basement. But since all the rain started in the spring, the top seems to vary in size by +/- 1/16 in. So I've had to edit the homimg program almost daily to compensate.

[artisan]

I've had humidity problems Ron...just as you describe. I was using 2 pieces of 3/4 MDF a year ago. I now believe that the inch and a half combined total is just a little too much. I do periodically flatten the spoil board, but I've changed it out about 4 times this year already too. I don't have to do much surfacing on new spoilboards, because the 1 inch Polypro base stays FLAT! Therefore, I can use thinner MDF....which is easier to carry and install... for the spoilboard. I've even used 1/4 inch chipboard ($11.00 and FLAT)as a spoilboard for very precise HDU projects and 3/16 Komatex (PVC) as a spoilboard for Aluminum...where I flood the bit with soapy water. I've heard of others sealing the MDF to protect it from moisture, but I cut all sorts of materials... some of which I "flood" with water or lubricants... so I like being able to scrap the board when I no longer trust it.....Hope this helps....D

[rgbrown@itexas.net]

I wonder if the "Water-Proof" MDF is more stable than the standard stuff? The price I heard was $40 or so a sheet.....

Ron

[artisan]

Could be Ron B.....that would certainly make sense for the base at least...if you can find it.... I've also heard the glue in the waterproof MDF (Phenol-Formaldehyde) is nasty stuff to breath and the dust can cause a skin rash.... so I wouldn't use it as a spoil board....D

[artisan]

OOOPS! I just got an email about my earlier post for base material....the material is "Polypropylene"....not Polyprylene (no such thing).... and it's the white plastic stuff you see cutting surfaces made of in restaurants. A company called Piedmont Plastics stocks it....D

[gerald_d]

Be careful of assuming that plastics are stable, particularly for humidity. Nylon can absorb about 0.6% water causing swelling. If you think that 0.6% is very small, realise that it is about 1/2" over the length of a 96" table . . . . . . .

[jay_mack1@hotmail.com]

Hello ya'll

I'm getting ready to finish building my wood table, have seen joist hangers used. Any pros and cons about this use. I plan on using two layers of white melamine, finished on both sides.

Later adding storage rails to keep things under the saw.

[jay_mack1@hotmail.com]

Another wood table question:

1/2" bolts on the legs, is this a little much?

3/8" bolts look like they could handle that job and put the 1/2" as the levelers?

[bjwat@comcast.net]

Stickman,
I would suggest following the ShopBot plan to the T for building the table. It isn't a place that you want to cut corners. I have seen wooden tables in action and although they are adequate, you want to make sure that you have tight fitting joints and make sure that it is as stiff and perfect as possible. The additional beef of the 1/2 bolts will make a difference in spreading the torque of the bolt out.

I am not sure if the joist hangers will interfere with anything or not. I have a metal table.

-Brady

[gerald_d]

Stickman, for bolting wood, the washer size is much more important than the actual bolt size. A 1/2" bolt with a small washer has less holding power than a 3/8" bolt with a big washer.

[jay_mack1@hotmail.com]

I've assembled the table, awaiting the deliver of the shopbot, which is estimated at Tuesday. I'm going to post a few pictures of my wood table. I am working to level it out and square it up. I need to purchase a few longer bolts of the leveling feet. Garage floor has a little bit of drainage slope.

In squaring up my table, I'm really close to having it square. What I am considering doing and asking for suggestions. The shopbot wood table plan calls for 1 x 6 crossbraces. Would it work to put eyebolts at the four corners and place aircraft cable crosses with turnbuckles to pull the corners square? At them moment I have pulled it square with some ATV tiedown straps. I'm just thinking outloud. Any thoughts.

[jay_mack1@hotmail.com]

3211

[paul]

Hi Stickman

My original table was built the same way with the bolts in the bottom as leg levelling adjustment, but it wobbled around. I made up some 4 sided boxes ( ply or MDF ) that fitted tightly around the legs and about 6” high, once adjusted with the leg bolts you slide the boxes down to the floor and then bolt them through the legs. This give you a greater bearing surface on the floor than just a bolt head.
The expense of the aircraft cable is not really necessary, once you have squared the table with ATV tie downs and then fixed an 8 x 4 sheet as a table bed you can remove the ties….. The 8 x 4 will hold it square.
IMHO

Paul

[jay_mack1@hotmail.com]

Paul,

do you have pictures of your leg assembly?

StickMan

[paul]

Hi Stickman

I do not have any pictures of my old wood table, I now have a steel table which is exceptionally rigid.


Paul