Wood vs Steel Table

[tucker-52@charter.net]

Whoa!!! Those steel tables went FAST!!! I'm soon to be ordering a new PRT96, and I've made up my mind, with the help of this forum, on all the bells and whistles except for the table itself. I'm an accomplished carpenter, so I've been serious about building my own wood table. But looking at how fast those steel tables were swept up, I don't know! I would like to hear from anyone/everyone who has built his or her own wood table for the Shopbot....Wood you do it again? (No pun intended.) What are the advantages other than cost? What are the disadvantages? Are you happy with them? Any and all input will be much appreciated here. Mark

[odysseywood@home.com]

Mark
I have had my ShopBot about 3 years now. While waiting on the ShopBot to be delivered I built my own table from wood. I started with the basic plan from ShopBot and made some modifications.
After 3 years of fairly heavy use I am more that satified with the wood table. In the 3 years I have squared the machine one time and that was because of my own stupid mastake. If I had it to do over again I would build another wood table. If you are intrested in the modifications I made to the ShopBot plans drop me an email and I will send you the details. For your information I am using a 3.25 hp PC router and 90% of the time I am cutting 3/4" MDF.

[beacon14]

Our table is made of 3/4" plywood, doubled up to 1 1/2" thick. We more or less took the Shopbot design, substituted plywood for solid 2x6's, increased the widths (imagine 2x12's made of plywood), and screwed the whole thing together. It has worked with no problems for 2 1/2 years. To level the table, we remove the worn-out old platen, surface the top edges of the plywood struts, then install a new 3/4" MDF platen.
Not sure what the steel tables run these days, but the time to build was not insignifcant, so I can't comment on cost-effectiveness. If you have more time than money, it is probably less expensive.

[david_fisk]

We've had a wood table from the beginning. We used the wrong kind of wood in the building of it, so we've had to add a lot more to beef it up. If we had to do it again and hopfully we will. It will be a steel table. From reading posts on this forum, it sounds like you could build a steel table for a little more than a wood one and you have one less thing to look at when it comes to troubleshooting. A great table top is two 3/4 pieces of mdf glued together. This helps reduce a lot of vibration. Use glue in the construction of your table It will act more as a unit that way with less vibration.

[rgengrave@aol.com]

I had a wood table for the last 4-5 years and would stick to wood because I have never had a problem with anything.

I am going to build a new table with some new idea's I have to make things simple, and it will all be in wood.

Ron V

[tucker-52@charter.net]

Thanks to you all. A wood table it shall be, with two sheets of MDF(3/4") glued together for a top.
I like the idea of using 3/4" plywood, laminated together, to make a 2"x whatever. Plywood is stronger and more weather resistant than any natural wood, and it's relatively cheap. I already knew all of this. Just testing you guys! (I'm impressed!)

Mark

[gerald_d]

Strange that nobody talks of mixing wood & steel.

My choices for the components would be:

A. The table top: Wooden board with fine ply's or a very high density "glued-and-compressed-sawdust". Stability with different moisture levels would be the main factor, followed by affordability for replacement. I don't want to feel too sorry for the table top, because sometimes I want to drill a clamping hole through it.
B. The legs: Concrete will be the most stable, but impractical for ever moving the table. Wood doesn't appeal to me because I know that good stable billiard tables have monsterous legs. Steel columns feel good because I am a metalworker and because they are very common for holding up long-life structures with low maintenance (Bus shelters, sky-scrapers, airport terminals, etc.)
C. The long X-rail bearers: The x-rails from ShopBot are steel, so I just feel that is better to clamp steel onto steel. No issues of differential rates of thermal expansion, or drying wood shrinkage, causing the rails to maybe curve.
D. Cross-members under the table: If I have long steel x-rail bearers and I know that the distance between the two x-rails is absolutely critical, then I am going to weld steel between them. The V-rollers are very sensitive for the exact spacing between the x-rails (and y-rails for that matter). If the spacing is out, the roller simply climbs off the rail to compensate. (Suspect that this is a cause of many of the erratic squareness problems, because it is not always the same roller that lifts off first. . . . )
E. Diagonal bracing: Steel or aluminium, any old scrap will do. this can be bolted or welded.

Of course I am biased to steel because I can weld and have metalworking facilities. BTW, my glue (welding) dries a lot quicker than the stuff the woodworkers use
But I would never consider a steel working top (unless I plan to have many jigs and fixtures screwed into holes that musn't wear out)

Maybe one should also wonder why ShopBot see their way clear to offer a "steel table", but don't offer wooden tables . . . . .

[Wdyasq@yahoo.com]

"Plywood is stronger and more weather resistant than any natural wood,"

The Myans and older Central American cultures built tombs of wood in damp humid areas that are still viable. Live Oak mallets will outlast any 'plastic' mallet I have seen. Lignum Vite and maple shaft bearings will both outlast steel shafts they hold in alignment. Wood is used in billiard tables because of it's stability.

All that defending of wood done, if I were to build a new table it would be of welded steel with a wooden cutting surface........

Ron Brown - wdyasq@yahoo.com (mailto:wdyasq@yahoo.com)

If Stupidity got us into this mess,
then why can't it get us out? - Will Rogers

[bill.young]

Ron,

Spoken like a true boatbuilder!

[gerald_d]

Come on Bill, what would you do for your next table? Can see you laughing on the sidelines here . . . . .

[bill.young]

Gerald,

You steel guys will never turn me to the Dark Side!

In reality, though, I've got to admit that a steel table has a lot going for it. My first ShopBot table was made from 2x4's and 2x6's, but it moved too much with temp and moisture changes. My current table frame is laminated out of 3 layers of 1x12 pine, glued and screwed, with doubled 2x12's lagged together at 90 degs to make legs. It's good and stable, but it would have been a whole lot quicker and easier to just bolt a steel table together.

Alright, alright, I admit it...if I had to do it over again I'd probably do a steel table!

I hope you're satisfied...I'll never be allowed in the WoodenBoat Show again :^)

Bill

[billp]

Bill, You could always veneer it....

[danhamm@abccom.bc.ca]

Hey Bill,
you are on the slippery slope now...you mite as well get a can of asimilated wood grain paint on hand!!! "grin"

[danhamm@abccom.bc.ca]

Hey Bill,
you are on the slippery slope now...you mite as well get a can of asimilated wood grain paint on hand!!! "grin"

[gerald_d]

However, if I had to build my own boat, then I would go for wood, no question about that! Probably paint it metallic silver afterwards though. . . . .

[Wdyasq@yahoo.com]

Gerald,

You could always veneer it with Aluminum foil.....

Actually they are doing 'bottoms' of resin and copper powder for the past 25 or so years with very good success.....

[sea_nc@bellsouth.net]

Forget about wood and steel...how about fiberglass? The ideal ShopBot has a *fiberglass table* that also has a center console and rod holders and can do 35 knots offshore. :^) (yes, Bill, I'm stirring the boatbuilding pot here)

Actually, I'd agree with Bill on the steel versus wood table issue. My first ShopBot table was made of wood (2x8's) and was rock solid and easily customized (for storage space underneath), but the temperature and humidity in the southeast US caused the wood to change daily. I never noticed any significant problems in the X or Y directions, but the Z zero position on top of table changed with humidity. We switched to a steel table when we upgraded ShopBot. No regrets. The steel table was quicker to assemble and much more resistant to temp/humidity changes in Z direction.

Where wooden tables are appropriate, several people have suggested gluing and laminating plywood (increasing both strength and assembly time). It might be worth looking into engineered wood (GlueLam? LVL?) to get the strength of laminated plywood while reducing assembly time.

Boatbuilders: If you paint a shopbot table with copper bottom paint, where do you put the bootstripe??

David

[billp]

David, just below the dust scuppers...and don't forget to use a barrier coat between the steel table and the copper paint...

[tucker-52@charter.net]

OK, now I'm REALLY confused! I already have a 24' pontoon boat. Let's see,...if I remove the console, fabricate some concrete legs and...ahhh,
nevermind!

[mikejohn]

I'm all at sea with some of your recent posts!
I would like your opinions on one thing,however.
I hope to take delivery of a SB in the near future, delivered in Europe
It appears to me that there is likely to be savings having atable built locally, particularly when you take into account the shipping costs.
What is the likely material costs of the metal parts?
How easy it is to fabricate the table?
My son is a welder/fabricator, will I need his help?
I work with wood, heavy metal to me is a horrible type of music

[steve]

Mike, I built my own steel table here in the UK because of the carriage cost of the steel table.Shopbot supply you the plans and it is a very straightforward construction apart from in the USA they manufacture 6"x2" steel channel while here in the UK they only manufacture 6"x3" which makes it a little more difficult. What I did was use 4"x2" channel with 2" box section bolted on top then welded at intervals, it works great if you want more precise details let me know. By the way we did try cutting 1" off the 6x3 with plasma cutter but the channel just buckled, wouldnt use timber in europe the changes in humidity are too high and timber just not stable enough. My table cost about £150 approx but it takes a long time to drill all the holes required if your son is a welder you could likely do away with a lot of the bolts and just weld together.
hope this helps
regards steve

[gerald_d]

Mike, the so-called recent posts are more than 1 year before yours


Steve, I would be a bit careful to say "just weld it together". You saw what happened when you applied heat to your channels - they started distorting. Welding will have the same effect, particularly if you apply too much welding.

Mike, I would personally still go for the welded steel table frame (with wooden top). If your son knows how to keep everything straight and square, and does not have too heavy a hand with the welding gun, then he can build you a fine table. For the 6x2 channel, you can ask a guillotining/folding shop (called a plateworks or boilermaker shop in the UK) to cut and bend it for you. This will need quite a big cutting and folding machine, but they are around. Steve also found a practical solution.

If things do distort a little, it should be no worse than the guys with wooden tables . Shopbot supplied me with a packet of shims for final tweaking when you screw the x-rails down.

[mikejohn]

Thanks for the response.
I gather what we are trying to achieve is a stable, firm, solid table that the x rails can be screwed to with precision (and no bending).
I guess, also, the table needs to be heavy to absorb vibrations and movement during operation.
A block of concrete 4 feet by 8 feet by 3 feet high sounds perfect!

[gerald_d]

Now you are talking!
(except when you want to get underneath to tighten nuts or fit vacuum systems . . . . .


Mike, the x-rails by themselves (as supplied by ShopBot) are very flexible - they will easily droop by 1/2" just under their own weight if you pick them up in the middle. You need something stable under them to keep them straight and parallel to each other. The concrete/steel/wood that the customer supplies is seldom perfectly flat and true and that's why you get a packet of shims, and a whole heap of instructions of how to finally get the right result.

[mikejohn]

Thanks again for the quick answer.
If I can construct, or have constructed, a well made table, need I fear assembling and tweaking my shopbot?
Everyone (or almost everyone) on this forum seem to love there shopbots. Some users seem reluctant to do much finishing after the piece comes off the shopbot, or want to do on the SB what could be better done on a saw or sander. Also, there seems to be a desire to plug in the shopbot, switch on the computer, and off we go.
I am fortunate AutoCAD is my daily bread and butter, CorelDraw is no stranger, and even DOS based programmes are in daily use.
Mind you, I've downloaded the software, and the DOS programming does take me back a few years.
If you remeber a language called LOGO, it's a bit like that.

[Only fear and comon sense holds me back]

Why not think way out of the box and consider suspending a steel frame on heavy cables with turnbuckles to pullys in the rafter(s), then to a heavy duty crank where you could lift the whole thing so you can sweep under it. Great for us shopbotters that don't have a lot of floor space. Assuming a rigid framework, adustment can be made with the turnbuckles. Now it may sway a little but who cares, it all sways together and think of the dampening effect on vibration. Only part of my tounge in my cheek.

[gerald_d]

Mike, I am Germany till next week and if you mail (mailto:gerald@scapenotes.com) me your phone number, I could have a chat with you.

"Only fear and comon sense holds me back", I have seriously thought of fitting a trailer axle under our SB, giving it a towbar and lights, and making it street legal. Good for country fairs....and doing the boatbuilder's job in his shop, so that HE can clean up the sawdust and dispose of the scrap. . . . . .