Bracing 3/4" phenolic sheet by embedding 1/4" steel bars?

[Matt Armstrong]

I have a 27x36" phenolic router table sheet that i need to reinforce so it doesn't sag. A thought of mine was to route a 1/4" deep x 2" wide groove in several spots on the underside and then epoxy in a piece of steel or 6061 of the same dimensions. My goal is to prevent sagging over time... will this work at all or is it a horrible idea?

[george wilson]

Can't you just screw on a piece of metal to the bottom?

[Chip Lindley]

+1 on *screw on a piece of metal...*

IF you brace across the router table frame, you can shim as needed between the phenolic and steel, to achieve max. flatness. 2" angle iron is some stout stuff! Two pieces of 2" angle running the 27" depth, roughly 12" apart, dividing the 36" length into thirds, should give you a router table that will NEVER sag!

[Chuck Saunders]

IF you can increase the depth in the direction of the sag you will see much better results. 1/4 inch will not provide hardly any benefit. On the other hand if you could route a 1/4 inch groove 1/4 inch deep and epoxy the 1/4x2 strip in, you would have far more rigidity.

[Matt Armstrong]

+1 on *screw on a piece of metal...*

IF you brace across the router table frame, you can shim as needed between the phenolic and steel, to achieve max. flatness. 2" angle iron is some stout stuff! Two pieces of 2" angle running the 27" depth, roughly 12" apart, dividing the 36" length into thirds, should give you a router table that will NEVER sag!

So the entire piece of phenolic is supported 2" in, along the 36" dimension... so the unsupported "chunk" is actually 23x36. Can I just take two pieces of angle, 23" long, screw them onto the bottom of the phenolic, and then set the whole thing back in place and be good to go? If so, that sounds pretty good to me...

[Matt Armstrong]

IF you can increase the depth in the direction of the sag you will see much better results. 1/4 inch will not provide hardly any benefit. On the other hand if you could route a 1/4 inch groove 1/4 inch deep and epoxy the 1/4x2 strip in, you would have far more rigidity.

wait... what? 1/4" is not enough, but 1/4" should work?

[David DeCristoforo]

"wait... what? 1/4" is not enough, but 1/4" should work?"

Read what he said. 1/4 X 2" laid flat... weak. 1/4" X 2" on edge... strong... get it?

[Bill Huber]

I agree with Chuck but I just don't think steel is the answer. I have the same table and it is supported by 3/4 inch plywood on edge and the largest unsupported area on the table is where the plate goes.

The way I look at it if it sags in that small of and area then the table is not worth having anyway. I have had this set up for 2 years and the router is been in the table the whole time I it is not sagging.


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[pat warner]

Steel (6061?) at 1/4 over your length will not buy you much.
Moreover, if the metal is not milled (and extrusions are anybody's guess), expect to introduce a deformity = to the trench, the metal and the substrate itself. Phenolics have outrageous flatness and uniformity in thickness specs. Might wind up worse than doing nothing at all!

[Matt Armstrong]

Argh... I'm just getting sick of creating my tools rather than using them! OK - I guess I should probably go back to the drawing board. sigh sigh sigh

[Myk Rian]

How thick is the phenolic? Perhaps glue 3/4" MDF to the underside?

[glenn bradley]

Bill's got it. Plywood can be ripped true. Mine are double 3/4" ply ribs on edge. Maximim span anywhere on the table is about 14" IIRC.

121150

The foil tape compensates for irregularities in the top found once tightened down.

http://www.sawmillcreek.org/attachment.php?attachmentid=116927&d=1240946204

[Chip Lindley]

I have a 27x36" phenolic router table sheet that i need to reinforce so it doesn't sag..... My goal is to prevent sagging over time...

Matt, Matt Matt!! 90% of the things We worry about, NEVER HAPPEN! Unless your 3/4" phenolic RT is now unusable because of sag, Umm...."If It Ain't Broke Don't Fix It!"

If your RT is of the design Bill Huber provided pix, I feel you are worrying in vain! (UNLESS...your shop is within the *tractor beam* of ET's Mother Ship!) Use the table and Make Something!

[Mike OMelia]

How thick is the phenolic? Perhaps glue 3/4" MDF to the underside?

MDF? I don't think so. That stuff has no stiffness.

If you use angle iron, it should be machined flat (milled). I guess you could use aluminum, too. This aircraft grade:

http://www.mcmaster.com/#aluminum-angles/=2dmx3g

But I cannot imagine Phenolic that thick bending, especially combined with Bill's table.

Mike

[michael osadchuk]

I doubt that a 3/4" THICK piece of phenolic is going to sag because of the router weight.

michael

[Matt Armstrong]

The router table is actually mounted on aluminum rails which are bolted to the extension rails of my unisaw... so it's an extension table

[Mike Cutler]

Matt

Everyone, myself included, tends to go way overboard in their thinking sometimes. If you have 1/4" by 2",: "L" stock for support, and it was flat along it's length, you would do just as George Wilson suggested and simply screw it to the bottom. Bedding it in epoxy can make for any slight distortion along it's mating surface.
What you may try and make is a "torsion box" top similar to what Bill Huber has detailed. Your router would be suspended in the middle of the field and the torsion box would surround it. The torsion box doesn't need to be thick, only 3 or 4 inches total including the thickness of the top and bottom. Use a high quality ply and screw and glue it.

Don't get frustrated with having to build your own tool setups. It's an odds on bet that you can build something just as good as you can buy, and it will be suited to you. My router table is 2'x4' and supported like Bill's and built like a tank.
I never had much success with extension wing tables and finally just made a dedicated table. I do a lot of big stuff though and needed the extra support. I actually would be better suited having a shaper, but.......

[Chip Lindley]

Matt, I had been led to believe that your phenolic top was mounted on it's own base!

I would have to see your "aluminum rails" attached to the Unisaw to determine how best to meet your *No-Sag* expectations. Seeing how your phenoic is attached (and where) to the Unisaw rails would let me make a more viable judgement on how to support it! Show me the PIX!

I'm a great fan of TS extension table RT's! They put all that vacant acreage to work! I would go to great lengths to help a TS/extension/RT kinda guy! The free-standing RT guys are on their Own! LOL

[Matt Armstrong]

Matt, I had been led to believe that your phenolic top was mounted on it's own base!

I would have to see your "aluminum rails" attached to the Unisaw to determine how best to meet your *No-Sag* expectations. Seeing how your phenoic is attached (and where) to the Unisaw rails would let me make a more viable judgement on how to support it! Show me the PIX!

I'm a great fan of TS extension table RT's! They put all that vacant acreage to work! I would go to great lengths to help a TS/extension/RT kinda guy! The free-standing RT guys are on their Own! LOL

OK - I'll take you up on this. Let me snap some pics when I get a chance (I'm at work) and I'll post them up. You make a good point about full disclosure. Thanks!

[Matt Armstrong]

Pics attached. You can see in the 2nd pic one side of the 2x2 aluminum angle and the extension table legs holding it up on the end...

[Matt Meiser]

Just rip some lengths of 3"x3/4" or so hardwood of your choosing, joint one edge flat if needed, and glue and screw the 3/4" edge to the underside to provide support. If that sags on you you are putting way too much weight on there.

[Chip Lindley]

Well Matt, your extension table is pretty solid as-is! The Biesemeyer and aluminum angles will prevent any sagging along the front and back rails.

Your only concern will be across the 28" depth of the table. I honestly doubt 3/4" phenolic will sag over 28"!!

But, to be safe, I would attach two more pieces of 2x2 alum. angle between the existing pieces. One at the extreme end ot the table which is totally unsupported across the 28" width.

The other 2x2 at approximate center of the table, just *behind* your router opening. Do not attach these to the phenolic, but with 2x2 brackets bolted at a R.angle to the ends of the 2x2.

This will make a very sturdy frame beneath the phenolic which can be shimmed exactly as you wish.

[Matt Armstrong]

Well Matt, your extension table is pretty solid as-is! The Biesemeyer and aluminum angles will prevent any sagging along the front and back rails.

Your only concern will be across the 28" depth of the table. I honestly doubt 3/4" phenolic will sag over 28"!!

But, to be safe, I would attach two more pieces of 2x2 alum. angle between the existing pieces. One at the extreme end ot the table which is totally unsupported across the 28" width.

The other 2x2 at approximate center of the table, just *behind* your router opening. Do not attach these to the phenolic, but with 2x2 brackets bolted at a R.angle to the ends of the 2x2.

This will make a very sturdy frame beneath the phenolic which can be shimmed exactly as you wish.

Can you provide a link or a pic to what the bracket would look like? I'm not clear on how this would work or where to buy these brackets...

Thanks to everyone for their help so far! I need to clean up my shop. I just got my jointer a couple days ago so I've just been jointing random 2x4s for fun. I realized that there's an upper limit to how much fun you can have with the jointer... :(

[Cliff Rohrabacher]

You want a Permanent Sag Proof under table?
Concrete.

Somewhere I read that Concrete is how MM keeps vibration down in their machinery.
I have no clue of this is true but Machinery makers do use it and some use a rubberided concrete cause it works even better.

[michael osadchuk]

Can you provide a link or a pic to what the bracket would look like? I'm not clear on how this would work or where to buy these brackets...

Thanks to everyone for their help so far! I need to clean up my shop. I just got my jointer a couple days ago so I've just been jointing random 2x4s for fun. I realized that there's an upper limit to how much fun you can have with the jointer... :(

....Chip will answer but I suspect that the "brackets" that he is referring to are simply cut off pieces from the same 2" by 2" right angle aluminum used for the brace (and which you appear to have used on the long sides of the phenolic to bolt it to the fence system rails......one side of the bracket is bolted to the vertical side of the existing longitudinal 2" by 2" right angle aluminum and the other side of the bracket is bolted to the right angle aluminum being used for the brace....... you could also bolt the horizontal side of the aluminum brace to the horizontal underside of the the longitudinal aluminum right angle pieces use flat metal stock the same thickness as the 2" by 2" right angle aluminum as filler stock between the bottom of the phenolic and the top of the aluminum cross braces.....

.... but again, I would first query whether 3/4" phenolic is going to sag... if the phenolic you have is paper or cloth impregnated with binder throughout the entire 3/4" thickness (and not some thin phenolic sheeting on either side of a non-structural filler like foam) it shouldn't sag.... and if phenolic that strong sags, 2" aluminum right angle stock may not be strong enough to "lift" the phenolic and you may need to use steel right angle stock for the cross bracing...

good luck

michael