Sagging Router Table

[Rick Hubbard]

My shop-built router table (the one I was sure would never sag) has, in fact, begun to sag (you can actually see it in the pictures attached).The table-top itself is 36 inches long and is constructed from two laminated pieces of ¾ in MDF and covered with laminate and hinged on the backside. The center of the table has sagged to the point that I had to adjust the mounting plate up 1/64 on the in-feed end and 5/64 on the out-feed end. With this arrangement and a feather board placed dead center over the bit, I can successfully route a long rail, but when I try to make a stick cut for the stiles, the insert catches the sled. The only way I can make the stick cut is to adjust the insert so it is flush with the table top (obviously a BIG pain). The obvious solution, I know, is a new top, but given the amount of effort I put into this one when a built it 3 years ago, I REALLY don’t want to launch into it again.
Does anyone have any suggestions on how I can compensate for this mess that doesn’t involve replacing the top?
Thanks

[David Weaver]

Is there any way you can joint hardwood boards, laminate them together, and screw and glue them to the top with recessed screws? That's what I did with mine, but it's not as old as yours is yet.

[Cliff Rohrabacher]

Wood will eventually accept some deformation from whatever stress you place one it over a long enough period. This is made worse by humidity.

I have considered a 1/8" thick steel or 1/4" aluminum plate ground flat (jig plate). I've also considered making one from Concrete with an inset for the router plate.

However the fact is that if you just make it from a couple layers of good lumber like Cabinet Ply or quality MDF and make it heavy it will not deform readily or at least not much. At least not for several years.

Compensation:
How about pouring a leveling compound on the top. Maybe one of those thick epoxy pour-on finishes that were so popular a decade or two ago. Any epoxy would do the job so long as you had the edges sealed up tight where you didn't want it to overflow like the outside and the inner plate opening.

Then when it's hardened up maybe take the meniscus around all the edges edge down with a hand plane

[Rick Hubbard]

I have considered a 1/8" thick steel or 1/4" aluminum plate ground flat (jig plate). I've also considered making one from Concrete with an inset for the router plate.



Hmmm. A concrete top. That is probably not an immediate solution to my problem, but it is certainly intriguing. I wonder how one might build such a thing? What do you suppose it would weigh?

[Rick Hubbard]

Compensation:
How about pouring a leveling compound on the top. Maybe one of those thick epoxy pour-on finishes that were so popular a decade or two ago. Any epoxy would do the job so long as you had the edges sealed up tight where you didn't want it to overflow like the outside and the inner plate opening.

Then when it's hardened up maybe take the meniscus around all the edges edge down with a hand plane

Actually, I had thought about that too, but with the T-Track and the imbedded aluminum miter slot in the existing table, it seemed to me that this might not be an effective remedy (incidentally, when I DO build my new top, there will be NO miter track and NO T-Track). What a mistake! What I want for my next top is just clean smooth "open space."

[glenn bradley]

I would have never thought my top would sag, it did. I now have the same top in a different cabinet. The underside of the top is framed with doubled 3/4" BB ply on edge about 2 1/2" wide.

Even though I was as careful as possible to get the frame flat, I still had to shim here and there to get the top flat across all directions. This of course meant I had to take the top off and on, off and on. But, within an hour or so I had it where I was happy and all has held for quite some time.

The rib pattern is sorta like this:

71637

You can see the table partially constructed here:

http://www.sawmillcreek.org/attachment.php?attachmentid=53969&d=1167612354

[Rick Hubbard]

I would have thought that two thicknesses of 3/4 MDF all encased in plastic laminate would have been sufficient to prevent sagging, but I guess not. Part of the benefit of the laminated was eliminated with the opening for the T Track and miter slots; then of course there is the opening for the router insert. The hinged top was perhaps not such a hot idea either.

Sooooo... I wonder what the IDEAL router table-top would look like?

[Chuck Lenz]

Can you shim it up under the top ?

[Jason Beam]

Rick,

You said it's laminated with formica on top, yes? Is it also laminated with formica on the bottom?

If not, you may not be getting sag, but warping due to moisture moving in and out at varying rates. If that's the case, it may be possible to adjust it's ambient humidity for long enough to get it to straighten itself back out. If that works, then you could laminate that underside to mitigate the moisture moving at different rates.

I'm a real stickler for equally treating both faces of a panel ever since i had 4 cherry pannels warp on me from leaving them stacked on one another. I did a similar thing to recover them, too :D


Edit: I just saw your latest reply while i was typing - i guess it IS sag. :(

[Rick Hubbard]

Can you shim it up under the top ?

I'm not sure what you have in mind, but one thing I thought about was placing pieces of 3/16 inch metal rod where the red lines are in the picture and then counterboring 1/4 inch lag screws through the top (where the green circles are) and into the table frame. I suppose I could tighten the lag screws to pull the ends down so the top would level out. I sure would miss my hinged top, though.

[Raymond Fries]

Picture this:

Remove the top and turn it upside down. Leave the hinges attached to the base.

Attach a 2 x 2 Oak or matching trim around the edge with the outside dimension the same as the base. This way, you can keep your hinged top.

Get some 1 1/2" steel angle iron to screw into the top similar to Glenn's suggestion. You could use shims where needed to flatten the top.

You could always spray it with Primer and then paint so it would blend in nicely with your table. BTW - It does look very nice.

Position the top and re-attach your hinges. If this works, you would just have a 1 1/2" higher table.

I hope something works out for you...

[Chuck Lenz]

I'm not sure what you have in mind, but one thing I thought about was placing pieces of 3/16 inch metal rod where the red lines are in the picture and then counterboring 1/4 inch lag screws through the top (where the green circles are) and into the table frame. I suppose I could tighten the lag screws to pull the ends down so the top would level out. I sure would miss my hinged top, though.
Yes Rick, thats kind of what I had in mind, but I know what your sawing. It's a tough call on what to do.

[Rick Hubbard]

Boy, there is nothing like having a bunch of good minds come together to try solve a problem. Thanks, everyone who made suggestions.:)

Short term, here is what I have decided to do:

Since the table-top also serves as the out-feed table for my TS, and is only about 3/8 inch lower than the saw, I don’t want to increase the height by very much. Also, I regrettably designed the top so it is exactly the same size as the base so there is no way to attach a hardwood apron around the outside edge. THEREFORE, I have contrived a remarkably whacko idea that will let me “get by” until I can engineer a new top. I am going to use a few dabs of modeling clay to level the top from end to end (it won’t take much) and then use a piece of ¼ inch MDF as an auxiliary top (which will be held in place by double-sided tape). I believe that after I have positioned my fence correctly I can butt the MDF up against the fence and push the board against the tape to secure it (or maybe even use some clamps). When it is necessary to move the fence I can move the MDF as well. This is admittedly pretty clunky, but will do for awhile, I hope.

Long term, I have another idea. I think I will have a machine shop build me a frame out of ¾ in square steel tube (drilled for hinges) and then attach a ¾ inch Baltic Birch top to it with screws from the underside of the frame. If the frame is welded and gusseted correctly, it should NEVER warp or sag. This time I am also going to allow for an overhang of about 1 ½ inches all the way around the top which (I think) will give me a way to clamp a fence to the lip. Most importantly, I will at last be rid of the miserable T Track and that useless miter track I imbedded in the existing top.

I am curious, BTW, about what your thoughts are regarding the steel frame.

[Chris Parks]

It is my guess that some tops are too heavy, due to our mania with thickness to prevent problems such as this. I can think of a couple of different ways to prevent it without all that thickness, the first make the top a torsion box, light and strong, the top sheet can be annodised aluminium and it would look great. I will try and describe the second so bear with me. Build a carcass as normal with the walls of the router cavity far enough apart to run two braces up to the top at about 60 degrees. These would support the top and prevent sag. Building a thick top only invites sag because the weight of the material is so heavy combined with the router. Rods running through the top will do little as they are not structurally strong. You can bend a rod easily, try that with a channel section, you can't.

The the ultimate table top is aluminium channel and skins (a torsion box), you could land a helicopter on it, glue it with Sikaflex, it will never need more than that. There are some things timber products don't do well and this is one of those things. Now the purists will detest all this but it will work and they can't deny that. I will now duck for cover.

PS. The aluminium torsion boxw will be flat due to the dimensional accuracy of the channel. Just don't go too heavy on the glue.

[Rick Hubbard]

Hi Chris-

I'm not sure I follow everything you say, but maybe I'm thinking in somewhat the same direction already.

The attached sketch is my vision of what the 2/4 " steel tube frame for the table top might look like. It is approximately 24" X 36" in size. I had thought about cutting 3/4 Baltic birch 27" X 39" (leaving room for 3/4" X 1 1/2" band around the bottom lip) and then routing the router insert into the plywood top. The top would be attached to the frame (from the bottom) with screws.

I guess you are suggesting something similar (using aluminum for the frame) and then covering the frame with with aluminum sheet secured with adhesive. Is that correct?

How would one attach the router to the top unless an insert was used? AND, I wonder how it would be possible to use an insert with the aluminum "skin"?

Questions, questions!!

[Chuck Lenz]

Rick, one question I have is, on the backside where your hinges are is the top laying on the frame or are the hinges holding it up some ?

[Rick Hubbard]

Hi Chuck-

When I assembled the table I clamped the top to the frame and then installed the hinges (which are springloaded fire-door hinges to make it easy to lift the top).

I'm not in the vicinity of the table right now, so I don't know if something has shifted, but the top SHOULD be resting on the frame.:D

[Phil Thien]

Hi Chuck-

When I assembled the table I clamped the top to the frame and then installed the hinges (which are springloaded fire-door hinges to make it easy to lift the top).

I'm not in the vicinity of the table right now, so I don't know if something has shifted, but the top SHOULD be resting on the frame.:D

Chuck is onto the answer here. For the top to sag, it needs to "pucker" up at the corners. If you can conceive of some way to hold it down at this corners, it will be harder for the center to sag. Just make sure the four corners are held firmly against the cabinet and the center should take care of itself.

[Chuck Lenz]

One other thing that I just noticed when looking at one of the pictures Rick, is the face of your fence looks like it is pushing down on your router plate on the left side and possibly causeing it to dip. You may want to take the fence off and check the bottom for flatness and make sure that isn't bowed causeing your table to dip. I'm really starting to think the answer is the fence. If the fence is flat and true on the bottom it should keep the top from saging. Much like a beam support, except it's ontop.

[Ken Stevens]

Rick: can you expand on why you consider the T-track and mitre track to be "miserable"? Does it relate to weakening the top and thus contributing to the sag? Won't you lose some functionality without at least the mitre track?

Thanks.
Ken

[Mike Goetzke]

I like your hinged top but to remove the sag you will probably need to shim it and clamp it down good when in use.

I built a RT into my TS using the infamous Delta warped extension tables. I actually had two replacements sent out and even the best one was bowed down in the middle even w/o a router.

Here's the final result:

http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/th_IMG_0902_1_1.jpg (http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/IMG_0902_1_1.jpg)


This is the bottom - I added a few support bars:

http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/th_IMG_0677_1_1.jpg (http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/IMG_0677_1_1.jpg)


Cabinet w/o top:

http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/th_IMG_0675_6_1.jpg (http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/IMG_0675_6_1.jpg)


I had to add shims to level the top:

http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/th_IMG_0678_9_1.jpg (http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/IMG_0678_9_1.jpg)
http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/th_IMG_0679_3_1.jpg (http://img.photobucket.com/albums/v212/mbg/Unisaw%20Cabinet/IMG_0679_3_1.jpg)

In my case, you can see from one of the photos above I used pocket screws to hold the top to the cabinet. These screws provided enough load to straighten out the table. It's been almost a year since I built it and it's still very flat.

Hope this helps???


Mike

[Rick Hubbard]

Rick: can you expand on why you consider the T-track and mitre track to be "miserable"? Does it relate to weakening the top and thus contributing to the sag? Won't you lose some functionality without at least the mitre track?

Thanks.
Ken

Hmmm. Am I expressing some dissatisfaction? Yes, I guess so. For one thing, the T Tracks are just a hair short of being perfectly flush with the top (write that off to my own ineptitude, I guess). Anyway, they often "catch" just a tiny bit and that seems to telegraph to the piece I am routing, so there is frequently a slight dimple in the machined surface. This is usually when the piece catches the T Track on the out feed side.

As far as the miter slot, I can't think of even once when I have needed it (usually a coping sled, or something similar, gives better stock control). Mostly it is just a place to store spare sawdust, in my judgement.

I have seen setups where the router table is locked down to the lip of the table and that seems much preferable to me.

And, yes, as you suggest I DO suspect the T Track slots have compromised the integrity of the top. For one thing, when the fence is secured to the track, it places pressure on the MDF substrate and creates some distortion. For another thing, the MDF into which the track is imbedded is essentially unsealed which makes it pervious to moisture (the same for the miter track, I think).

Maybe what I'm looking for here is just an excuse to build a new top! Ya think?

[Jim O'Dell]

From the pictures, it looks like the top sits down on another flat surface? If so, this won't work. If there is some space, or if some relief slots could be cut, the some angle iron screwed under the top should pull it back flat. I suppose you could take the top off run some 1" deep slots across the bottom and sink the the angle iron into that channel. Could probably daddo a shallow area for the angle iron to recess into the top so it wouldn't change the height of the top at all. It would weaken the top some where it would be thin, but the angle iron should more than compensate. Only problem with this idea is the t-track might be in the way. Angle iron could be notched at that point though to allow it to work. If you are going to junk the top anyway, this might be a quick-n-dirty temporary fix. Jim.

[Rick Hubbard]

One other thing that I just noticed when looking at one of the pictures Rick, is the face of your fence looks like it is pushing down on your router plate on the left side and possibly causeing it to dip. You may want to take the fence off and check the bottom for flatness and make sure that isn't bowed causeing your table to dip. I'm really starting to think the answer is the fence. If the fence is flat and true on the bottom it should keep the top from saging. Much like a beam support, except it's ontop.

I think I see the same thing you are looking at. The part of the fence that looks like it is pushing down on the insert is actuually just lyin loose on it. The fence itself seems to be perfectly flat. In the picture you can see that it is resting on the insert and on the left side (out feed side, not visible in the photo) it is resting on the edge of the table. The gap you see between the main fence and the table top is the amount of sag there is in the table.

[Chuck Lenz]

I think I see the same thing you are looking at. The part of the fence that looks like it is pushing down on the insert is actuually just lyin loose on it. The fence itself seems to be perfectly flat. In the picture you can see that it is resting on the insert and on the left side (out feed side, not visible in the photo) it is resting on the edge of the table. The gap you see between the main fence and the table top is the amount of sag there is in the table. Is there sawdust under the fence ? I would think that your fence should be able to pull that sag out. The router plate looks a little high on the left side. I just noticed that the track on the left side of your table is far away from the insert, if it were closer like the right side is it would have a better chance of pulling the sag up, if it is a sag and not just being pushed down. I hope I'm not bothering you with all this.

[Chris Parks]

I would use aluminium open channel, the extrusions are readily available, it is light and easily worked and you could do it yourself. The top sheet could be anodised and it would look trick (the trendy word for the week). With aluminium you can use as much framing as you want due to its ease of use and lack of weight. I would just make the internal frame stringers parallel with an external perimeter frame. I have not given the router attachment much thought, how about this. Leave the frame surrounding the router opening exposed and make your attachment plate out of whatever. Cut the exposed frames down to the attachment plate thickness and it will drop in flush. This will need to be refined as you go, but the general idea is there. The result will be a good looking, light and flat table that will never move, you could jump on it and the thing wouldn't bend. I tend to think of the unusual as you can see. You could trim it in timber around the edges, glue laminate to it and no one would know what was underneath if you wanted. Your TS top isn't timber for a good reason and router tops shouldn't be for the same reason.

[Don Stanley]

Hi Rick, I had the same problem from the get-go when I built my table. Same size and material you used. On inspection, it was obvious the drawer dividers on my cabinet were not flush with bottom of top. The combination of the big PC-7518 and router lift caused it to sag! My solution was to shim the drawer divider walls, and add additional bracing around the router.

http://www.ncwoodworker.net/pp/data/852/3_Topremoved.JPG

If you look close you can see there are two cross braces - in front of, and behind the router. A picture is worth a 1000 words! Here's a link to my album for more pictures.

http://www.ncwoodworker.net/pp/showgallery.php?cat=852

-Don

[Rick Hubbard]

Hi Rick, I had the same problem from the get-go when I built my table. Same size and material you used.
-Don

Hi Don-

Other than the top's dimensions and material, there is no comparison between your work of art and my utilitarian clunker. Do you actually USE this? I'd be worried about getting it dusty, or something. VERY IMPRESSIVE.

Anyway, thanks for chiming in. Several other folks seem also to think part of the problem may be the contact point(s) between the top and the frame.

Nevertheless, I think I'm going to abandon this particular top and start over. I can fix it up enough to "get by" while I'm dreaming up something else.

I'm going to stop at the local machine/welding shop today and get some advice from them on an integrated metal frame for the top.

[Bill Hylton]

Rick,

Can't tell you why your tabletop is no longer flat.

I'd suggest building a support frame. You're a woodworker, so make it out of wood. Use well-seasoned, straight pieces about 3/4" x 2 1/2", and assemble the frame with rabbets and dadoes. Do the glue-up on a surface you know is flat--like your table saw top--and be sure that clamping doesn't twist the frame.

If you want to try rehabbing the top you've got, remove it from the table, turn it upside down and set it on a flat surface on blocks--one at each corner. Pile weight on the center and let it sit. Check with a straightedge periodically. When the top is flat once again, attach the support frame.

On the other hand, it may be just as expeditious to make a new top. I'd say you should nix the slots and grooves and even the mounting plate. See the photo.

The photos show my current alpha table, built a couple of years ago. The top is two 1/2" pieces of MDF, glued and screwed face to face. I cut a hole for the router base through one piece before glue-up. The router is attached directly to the top; motor drops out easily for bit changes. (I'm finishing up a table with the same sort of frame, but only a single piece of 3/4" MDF.)

To mount the frame to the top, I used machine screws. Drilled holes through the edges of the frame, used a transfer punch to transfer locations to the top, drilled 13/64" holes through the top, then tapped them for 1/4"-20 screws. I did this after applying the laminate to the underside of the top, but before applying it to the top surface. Did that after drilling and tapping the holes.

The frame is birch, as is the edge banding. Formica on the top surface, backer (a.k.a. balance sheet) on the underside.

More info on this table and other router table construction issues in Woodworking with the Router.

Hope you get your problem solved. Maybe this will be of some use to you.

Bill

[David DeCristoforo]

As usual, I am inclined to say something like "What did you expect with MDF?". But I won't. Instead I'll suggest you use two layers of 3/4" MDF or "Melamine". But don't just stick them together. Rout or cut 1/4" wide 1/2" deep dados in the pieces and imbed 1/4" X 1" steel "stringers" when you bond the pieces together. I have used this method on long melamine shelves ("back in the days" when I would actually consent to work with this stuff). I was able to make 6 - 8' long shelf spans that you could sit on without noticeable sag. Heavy? Well.....yeah.....

[Rick Hubbard]

Evidently I’m not content with just pestering Creeker-Folk with my router table-top woes. I've escalated!

I ducked out of work early this afternoon and visited the director of the machine tool lab at the university where I work. He was interested in the mechanics of the entire problem, but was pretty short of time, so he gave me the name of a guy at a fabrication facility near where I live. I spent an hour or so describing my problem and sharing with him some of the suggestions the Sawmill Creek correspondents have made, and we have come up with a “working concept” for a killer, sag-proof router table-top.

The point of departure will be a metal frame, or web, that permits the router plate to be attached directly to the metal frame. The table top itself, plywood or MDF, will attach to the metal frame but will be independent of the router plate (the opening in the table-top will fit around the router plate and the plate will be adjustable with set screws on the underside of ears on the web that will permit the plate to be adjusted to the geometry of the table top). I guess this would make it easy to change tops too (in case the old one gets dusty or something :D ).

The plan is then to attach the metal web to the base using ball bearing pillow blocks for both ease of lifting and to provide additional adjustment points for the entire assembly.

My next step is to provide exact measurements for the base. He also wants to have the router and plate in hand so we can transfer everything to his CAD program.

Not counting the material I choose for the table-top itself, I’ll have about $225 invested in this project. I think that is a heck of a bargain. This is the third router table I’ve built in the past 7 years and frankly, I’m tired of messing around with it all. I just want something convenient to use and dead-flat (good looking would be nice, but nothing else in my shop is that way so why start a trend?).

[Bill Huber]

Rick, see the post I just made, it may help you with the table surface in the future.

http://www.sawmillcreek.org/showthread.php?t=65192

[Phil Thien]

The point of departure will be a metal frame, or web, that permits the router plate to be attached directly to the metal frame. The table top itself, plywood or MDF, will attach to the metal frame but will be independent of the router plate (the opening in the table-top will fit around the router plate and the plate will be adjustable with set screws on the underside of ears on the web that will permit the plate to be adjusted to the geometry of the table top). I guess this would make it easy to change tops too (in case the old one gets dusty or something :D ).

I'd make two, sell one on eBay and probably make enough $$$ to cover the costs for both.

Sounds like a helluva router table is on the way. :)

[Ryan Gentry]

Rick, I will echo Mr. DeCristoforo's comment regarding the use of steel stock epoxied into matching dados between 2 pieces of quality MDF or ply.

It sounds like you have a working solution that will be really nice, but just in case it doesn't pan out or you ever have a need for another really strong, flat surface in the shop, keep this idea in mind. It really works.

This style table top is referred to as a Mr. Sawdust Table in many circles. Google it sometime. Named after Wallace Kunkel, author of How to Master the Radial Arm Saw. The process does make a really nice table, excellent for radial arm saw tables, router tables, table saw extension wings, etc.

Good luck and hope this helps.

[Jim O'Dell]

As usual, I am inclined to say something like "What did you expect with MDF?". But I won't. Instead I'll suggest you use two layers of 3/4" MDF or "Melamine". But don't just stick them together. Rout or cut 1/4" wide 1/2" deep dados in the pieces and imbed 1/4" X 1" steel "stringers" when you bond the pieces together. I have used this method on long melamine shelves ("back in the days" when I would actually consent to work with this stuff). I was able to make 6 - 8' long shelf spans that you could sit on without noticeable sag. Heavy? Well.....yeah.....


Interesting idea about imbedding the steel. I'll have to think about that before I join the 2 pieces of my top together. My 3/4" plywood grid on the base varies in size from 7 X 9 squares to 10 X 13. Jim.

[Richard Butler]

Hmmm. A concrete top. That is probably not an immediate solution to my problem, but it is certainly intriguing. I wonder how one might build such a thing? What do you suppose it would weigh?

I would do the steel city thing and get a granite top. Concrete is corrosive due to the limestone.

[J. Scott Chambers]

I would do the steel city thing and get a granite top. Concrete is corrosive due to the limestone.

I always thought concrete was corrosive due to the ash.

Wonderful idea about embedding the steel, and the wooden frame underneath. Both give me ideas about finishing mine.

[Cliff Rohrabacher]

Hmmm. A concrete top. That is probably not an immediate solution to my problem, but it is certainly intriguing. I wonder how one might build such a thing? What do you suppose it would weigh?

I have been diddling with the idea of Concrete as a work surface for a while. The though process has caused me to look at concrete in an altogether different light.

What would a 3 inch thick concrete top weigh? A lot. Which fact standing alone is a good thing as it'll dampen vibration.

I'd look at two ways to make one.
1.) Try the old school method pouring into an open mold/frame and trowel the top to get a nice flat true surface using two fixed guide boards on either side of the frame and a dead flat troweling board.
or
2.) pour it upside down into a reverse pattern mold like they do when they are building kitchen counter tops.

Then I 'd seal it with Epoxy. I think there are some that can be applied to fairly fresh concrete.. The counter top people use waxes and oils to finish fresh concrete.

[Rick Hubbard]

What would a 3 inch thick concrete top weigh? A lot.

To be (somewhat) more precise, I calculate that a 36" X 24" X3" concrete top would weigh 225 pounds (based on a weight of 4,050 # per cubic yard). The opening for the router (12" X12") would reduce it somewhat, to 187.5 pounds.

By contrast, 3 inches of MDF same size, with the same size opening would weigh 56.25 pounds (based on a weight of 45 # per cubic foot, a typical Plum Creek Timber QC density).

The differential then is a whopping 131.25#!

I'm not sure what you would get for the extra weight, but it would need to be a lot, I'd think.

[Rod Sheridan]

I'm interested in the solution from an academic point, however having seen too many problems with router tables, I gave up on the entire process and purchased a shaper.

This thread does have some interesting plans of attack.


Regards, Rod.

[Rick Hubbard]

I'm interested in the solution from an academic point, however having seen too many problems with router tables, I gave up on the entire process and purchased a shaper.



Actually, in the midst of all this angst over my table-sag, that same thought popped into my head, too. It proabably would indeed be a lot simpler just to ante up for a shaper. Conversely, it is not in my nature to walk away from a challenge as long as their is a reasonble chance for FAILURE :D .

This entire matter, it seems to me, is a perfect specimen of such an "opportunity."

[Mike Heaney]

in the midst of considering how to update my Craftsman router table, I'm trying to make sense of the options out there. I'm wondering where the Lee Valley metal top (which is sort of like a huge router mounting plate) fits into this discussion:

http://www.leevalley.com/wood/page.aspx?c=2&p=41793&cat=1,43053,43885

hope this helps!

Mike

[Ed Beers]

It's going to be hard to weld up a frame as flat as you want. I suppose it can be ground or machined flat after welding but all of this sounds like a lot of work and expense. I would lean toward some bracing and shimming.

Ed

[Rick Hubbard]

It's going to be hard to weld up a frame as flat as you want. I suppose it can be ground or machined flat after welding but all of this sounds like a lot of work and expense. I would lean toward some bracing and shimming.

Ed

The fabricator who will be doing this (unless I can con the Machine Tool Lab at work to do it for free) specilaizes in retrofitting paper-making machinery. Their tolerances are "aerospace tight " according to both the fabricator and our Machine Tool lab Director here at the university. It will be no work for me, but yes, it will be a little spendy. Under the circumstances, however, I am willing to fork over the dough to get EXACTLY what I want:) . Of course, when SWMBO finds out about it, I may be sleeping outside under the porch for awhile, but I guess that's all part of having a fun hobby, right!

[Rick Hubbard]

in the midst of considering how to update my Craftsman router table, I'm trying to make sense of the options out there. I'm wondering where the Lee Valley metal top (which is sort of like a huge router mounting plate) fits into this discussion:

http://www.leevalley.com/wood/page.aspx?c=2&p=41793&cat=1,43053,43885

hope this helps!

Mike

Hi Mike-

These guys are defintely on the right track, I'd say. The main reason I did not give this much consideration is because of the size. The working surface of my table-top is ~24X36, so I would prefer not to go smaller, especially since the base for the table is all 6/4 maple, kind of like a work-bench. THAT I defintely don't want to rebuild!!

For my purposes there are a couple of other drawbacks:

I can't see an easy way to hinge the top. That is another feature of my existing table that I don't want to give up.

The second drawback (related closely to the first) is that it apparently necessary to completely remove the top from the cabinet every time it is necessary to change bits. I'm not fond of that idea.

The BEST thing about this system is the wide variety of insert rings. That is terrific. Other router plate manufacturers should take note, it seems to me.

[Mike Heaney]

I had not picked up on that- assumed removal of the rings would allow sufficient access for above the table removal (I generally use a PC892 in my table and with my current set up I can easily change bits from above). Think I will send an email off to Lee Valley to query this, as it would be a deal breaker for me too! I suppose one would also need to drill a couple of holes in the top to facilitate above the table height and lock adjustments- I am assuming that this will not adversely impact the overall strength of the table.
Good luck on your major undertaking- its beginning to sound like it would be easier to acquire one bed of an old iron very wide jointer- that at least would guarantee flatness and stability...hmmmm.. maybe combining routers on the end of jointers rather than the end of table saws makes more sense...!:rolleyes:

[Cliff Rohrabacher]

I always thought concrete was corrosive due to the ash.

Wonderful idea about embedding the steel, and the wooden frame underneath. Both give me ideas about finishing mine.

It is the ash I believe.
However, sealing it with epoxy solves for that.

[Cliff Rohrabacher]

I'm not sure what you would get for the extra weight, but it would need to be a lot, I'd think.


I'm a big fan of heavy. It dampens vibration, prevents equipment from suddenly moving when being used, and it just feels good.

[Cliff Rohrabacher]

Actually, I had thought about that too, but with the T-Track and the imbedded aluminum miter slot in the existing table, it seemed to me that this might not be an effective remedy (incidentally, when I DO build my new top, there will be NO miter track and NO T-Track). What a mistake! What I want for my next top is just clean smooth "open space."

Yah I have pondered the T track issue and never used it.
Currently my Router table is a tiny thing off the end of the cast iron top of my slider and I can use my slider fence on it with ease. So that essentially mooted the issue for me. However, I have a grand scheme to build a three station router table (some day before I die) and I'll likely be revisiting the idea of fence guide slots again.

[Rick Hubbard]

I spent the week-end working on building a mock-up of the steel-framed router table-top I am planning to have fabricated. This was a worthwhile exercise, since the original drawing failed to account for sufficient table width to accommodate the hinge-ears at the back of the table. I also did away with the V-Web design.
Pictures are attached;
The first picture is of the bare frame. The second shows the frame with a “top” and the third shows it with the phenolic plate in place.
I’m still working on a design that will allow the “hinges” visible in the first picture to use torsion springs to work as a lift assist.
The frame should weigh in at about 37 pounds (not counting the wood top). That compares nicely with the existing 1 ½ inch MDF top that weighs 34 pounds.
I’m thinking of tapping ¼ inch bolts into the part of the frame under the insert and using them both to support the insert and to provide fine adjustments to assure the insert and the top are always flush. Any thoughts about that strategy?

Rick

[David DeCristoforo]

... I gave up on the entire process and purchased a shaper.

The best "solution" yet.

[Chris Parks]

A couple of comments if I may. I can't see the logic in embdedding a metal frame in a timber or an MDF type top. It is not going to add thing for the effort involved, you don't embed a torsion box frame do you? As I said earlier I would use an aluminium frame due to its easy workability, you could rivet and glue the torsion box frame and then glue the sheets to it.

The insert rings could be made by anyone at home and rare earth magnets used to hold them in. Yeah, I know they are all mechanically locked but I just dont see why, or rather I do as historically the have been used in timber tops and that is how to best hold them in. Put 4 small rare earth magnets in one and drop it onto a ferrous base and it won't come out. The rings themselves could be made out of PTFE using holesaws. The inner hole is all that varies and you could custom make your own as needed. They mightn't look as pretty but is that the point? I suppose it is to some.

The Lee Valley top looks like they have recognised the problem at last, it could be hinged at one end by bolting it to a crossmember using CS bolts from the top and putting pins in the end as pivots into the xmember. It will be intersting to see how his turns out, I am in the process of planning mine at the moment and might get some ideas from his. The fence is the next thing that needs adressing, they are either very basic or over complicated for no good reason, we need a middle path here.

[Rick Hubbard]

A couple of comments if I may. I can't see the logic in embdedding a metal frame in a timber or an MDF type top. It is not going to add thing for the effort involved, you don't embed a torsion box frame do you? As I said earlier I would use an aluminium frame due to its easy workability, you could rivet and glue the torsion box frame and then glue the sheets to it.

Hi Chris-

Nothing embedded here at all. The "top" (what ever material that may ultimately turn out to be), simply sits on top of the frame. The purpose of the metal frame is to to a.) increase rigidity, b.) transfer vibration to the cabinet and, c.) isolate the inherent stress between the table-top and fence (which I now believe contributed significantly to my original problem).

I fail to be convinced that the torsion box you described earlier would be effective at items b and c although there is no question that it has acceptable rigidity. Morever, I am following closely the recommendations of credentialed engineers, so (no offense) I'll give the nod to them.

Rick

[Chris Parks]

Hi Chris-

Nothing embedded here at all. The "top" (what ever material that may ultimately turn out to be), simply sits on top of the frame. The purpose of the metal frame is to to a.) increase rigidity, b.) transfer vibration to the cabinet and, c.) isolate the inherent stress between the table-top and fence (which I now believe contributed significantly to my original problem).


Rick


Rick, I am only addressing the sagging problem. Now do tell what you believe is happening in item C before I stuff up mine!! You can isolate vibration with carefully placed anti vibration blocks if you feel that is needed. The embedded reference was to an earlier post.

[Rick Hubbard]

Hi Chris-

With respect to the “inherent stress” remark, I have begun to suspect that a major cause of my sagging problem may have had to do with the T-Track embedded at each end of the table top. I had installed the track about 1/32 lower than the surface of the table-top. I THINK (but can’t prove) that the fence pulled upward on the T Track when locked in place (and the fence is almost always locked in place). Since the T Track is attached to the table top material, I’m fairly sure that this is what really caused the sagging problem. In a way, I guess you could say that that the center of the table did not sag, but that the ends curled upward. I’ve got an idea that I can eliminate that problem with this new table by machining a slot in the metal frame (and completely through the table top surface) so the anchor bolts slide inside the steel tubing and therefore apply no pressure to the table top material itself.

Rick

[Alfred Toy]

Hmmm. You did use a precision straight edge (http://www.leevalley.com/wood/page.aspx?c=1&p=56676&cat=1,240,45313) on both the table and the fence? Is the fence straight and flat? Seems to be a bit of overkill to get a flat table. Maybe you could get your engineers to mill you a steel table.

[John Clark-COLORADO]

I can't see an easy way to hinge the top. That is another feature of my existing table that I don't want to give up.

The second drawback (related closely to the first) is that it apparently necessary to completely remove the top from the cabinet every time it is necessary to change bits. I'm not fond of that idea.

Lee Valley/Veritas, it seems, have already addressed these issues; see http://www.leevalley.com/wood/page.aspx?c=2&p=41796&cat=1,43053,43885

That big steel plate looks like a pretty attractive router table top.

John

[Ed Peters]

under the top. Firmly fastened at each end with a couple of t-nuts along their length, you should be able to generate sufficient pressure in just the right spots to reverse the deflection by sending bolts through the t-nuts to press against the underside of the top.

Next top............NO MDF. Insufficient density, no cellular structure.

Ed

[Chris Parks]

To resurrect this thread, have you got it completed yet Rick?

[Ed Kowaski]

Didn't see this thread first time around.

Two layers of MDF with plastic laminate on both sides can be a pretty ridgid flat surface. It is in fact a torsion box of sorts. The plam needs to be attached with a hard non creeping glue line, not contact cement, not PVA. Urea resin works well, epoxy may be ok. Just like in solid wood work, let all the materials reach a common % of moisture before laminating or it will warp.

[Rick Hubbard]

To resurrect this thread, have you got it completed yet Rick?

Hi Chris!

It is done! I will head up north to get it next Wednesday. I hope it turns out the way it is supposed to!

Rick

[Basil Rathbone]

Two sheets of BB plywood, 2 1/8x3/4 cold roll flat bar cut to the width of the table, dado a 3/8x1/8 groove into the top/bottom of the ply, epoxy the bars and white glue the ply. Clamp it up really good on a REALLY flat surface and put some weight on the middle.

This is way of making the classic Wally Kunkel (Mr. Sawdust) RAS table but it works great on any table. It will never warp or sag.......although never is a real long time.

[Chris Parks]

Rick, can you post some pictures with a rundown of how it goes?

[Rick Hubbard]

Rick, can you post some pictures with a rundown of how it goes?

Yes, I will be sure to do that. I think I am going to need some advice about mounting the T-Track (for the fence), so maybe I can depend on others to give some input.

Rick