Best material to make a router table top

[William C Rogers]

I have built a router table and glued formica using contact cement. The problem is I have flatness of 0.010 to 0.20. Is this too much, or is there a better material or way to glue the formica to get better flatness?

[Bill White]

I made mine from sink cutouts I got from the a local cab shop. Glued two of 'em back-to-back. Added 3/4" wood edge banding to trim the edges. Flat, free, and stable. How good is that?
If ya don't have a cab shop nearby, buy a small post formed countertop from a borg and cut it to size (2 pieces). Glue 'em up and band.
I forgot to add that I used the Veritas circular phenolic router plate from Lee Valley. Excellent install instructions. Went in right the first time.
I've had a 690 and a Freud VS router in the plate. No sag at all.
Bill

[Andrew Joiner]

Router table tops don't need to be flat.

Since 1973 I've made my router table tops out of mdf or plywood.I found out it was hard to keep them flat, but a top that had a slight crown or upward curve was accurate. Now I put a slight crown in the top with hardwood ribs under the top.I make the crown adjustable with screws so I can "push up" just the right amount of crown.

Lee Valley makes a steel top with a crown. This is the theory behind it and it works for simple shop made tops too.

This is from the Lee Valley website:
"Many router tables claim to be flat, and some even are, until you mount a router to them and they suddenly become concave. Each Veritas® router table top is a 16" x 24" steel plate that has been hand tuned to have a slight upward curve. This curve is specifically set so that the weight of the router cannot deform the router table to concave. When used with routers up to10 lb, the Veritas router table top will always be slightly convex, with the highest point adjacent to the bit, so your depth of cut will always be exactly as set. Because the plate is steel, it will not sag over time, as many laminate tables will."

[Bill Huber]

Router table tops don't need to be flat.

Since 1973 I've made my router table tops out of mdf or plywood.I found out it was hard to keep them flat, but a top that had a slight crown or upward curve was accurate. Now I put a slight crown in the top with hardwood ribs under the top.I make the crown adjustable with screws so I can "push up" just the right amount of crown.




I think it depends on how you mount the table to the supports. I have a flat router table, it has 3/4" plywood on edge that is just under each side of my router plate. Then I have the same on each end of the table. I have shimmed the plywood all the way across until all were flat, then I put the table on and it has been FLAT for the last 4 or 5 years with no problem.

So I really think it would depend on how you mount the table and the plate you are using.
What is not in the picture is the cross braces to make sure the plywood would not bow.

226042

[pat warner]

Looks like best material has been chosen already for tablesaws, drill presses, jointers and planers etc. Ground cast iron.
Ground aluminum jig plate (http://patwarner.com/images/drilling1.jpg) is just as dear. It's all down hill from there.
10-20 mils surface variability: As bad as it gets, might as well use boltsawn rough maple.

[Andrew Joiner]

So I really think it would depend on how you mount the table and the plate you are using.What is not in the picture is the cross braces to make sure the plywood would not bow.Yes, Bill good point. I built a large MDF workbench top sorta like your description. My experience is nothing stays dead flat, so I shimmed my benchtop to flat, but it's adjustable with shims and screws for the future.On router tables a slight crown is better than any sag.

[Don Morris]

I've had thick MDF that was doubled, that was OK. Had 3/4"plywood that was shimmed flat, but I made a design flaw and eventually it bowed. I got a great deal and now have a solid phenolic Bench Dog top and it's super. If I had all the money in the world, I'd like one of those real expensive cast iron tops like my TS, but I don't. But once in a great while I take a chance on a jackpot when I feel wild and reckless.

[Myk Rian]

This is woodworking, not metal working.
Use what you have.

[glenn bradley]

I assume you mean 0.02 and not 0.20. Point-oh-one and point-oh-two I can live with. Point-two is over 3/16" and would make my router table pretty useless. Like others I built a good supporting rib structure and shimmed for level and have never had a problem. This design followed a commercial outer-edge supported double 3/4" laminated MDF table that sagged after about a year. Took me awhile to figure out how my measurements could be so far off. They weren't off at all at the bit but, the sag created an uneven path of travel past the bit that yielded an unusable result. . . doh!

[Chris Parks]

This is woodworking, not metal working.
Use what you have.

So you would build a timber TS? There is no reason to go to a thick top if some thought is put into the engineering that will support that top. Of course a top that is unsupported and made from the usual MDF etc will sag over time, gravity will soon win out. It needs support at the centre of the table or as close to it as possible where all the weight is. Put a modern big router with a lift in there and it weighs a lot. Look at how to get support in there and the material choice is largely irrelevant as the support does not depend on the top being stiff enough not to bend.

[Bruce Seidner]

I picked up a $25 Craftsman direct drive table saw on Crag's list and while the wings are aluminum the main table top is cast iron. With the wings removed and the motor and guts removed I am soon taking this to a machine shop that will cut out the top for my plate. (I am using the motor to make a disk sander.) The cost of the new cast iron tops are dear, but look around and find a dead or near dead TS or put a TS out of misery like I did and re-purpose this top for a router top.

[Carl Beckett]

I dont like Aluminum. Over time it seems to always 'gall' on me and bugger up. Most aluminum fences or surfaces I will be pushing material across I put a layer of uhmw on (I have a roll of adhesive backed material - ok, Im not sure if its Delrin or UHMW or Teflon). For fences its great, for a table top I would prefer formica.

Im curious how anyone measures 'flatness'. Its not that easy without a CMM. You can lay a straight edge across it in numerous places and try feeler guages to pick out the low spots.

But even this doesnt represent function. I could have a very small spot that was low for example, that any practical work piece would span so it wouldnt be a problem (remember a plane is defined as three points and if a rigid work piece it will only touch on three points at any one given time).

High spots are the enemy though - I like to take these down.

For the record - my router top is two layers of MDF with shellac. Well supported underneath (structure is everything), with a benchdog insert. (and note the insert was less 'flat' than the MDF was - at least until I worked it all down).

.020?? Depends on where that was and how it affected a cut like a stile/rail set. If it directly translated to .020 mismatch to the mating, without repeating such that I couldnt compensate by a setup adjustment - then ya it would bother me.

Maybe a question should be (instead of debating absolute flatness): What test cuts can we do to determine if a router top is flat enough for PRACTICAL purposes?

A stile/rail set cut?
A long straight groove to fit the edge of a mating board? (or tongue and groove?)
Sliding dovetail?
Or drawer dovetail (like incra or something)?

If none of these cuts have an impact on functionality - then why care about how flat the table is??

[Tom Clark FL]

Maybe a question should be (instead of debating absolute flatness): What test cuts can we do to determine if a router top is flat enough for PRACTICAL purposes?


If you build in some support around the router then you table will stay flat enough. This table is over 25 years old and does everything expected of it.

[Justin DiValentino]

I dont think Ive seen torsion box mentioned yet. I was under the impression this was the best way to get a flat surface thats resistant to sagging

http://lumberjocks.com/assets/pictures/projects/187790-438x.jpg

[jonathan eagle]

Are you guys concerned about flatness of the whole table? As long as the plate is flat and very slightly proud of the table, I don't see the issue. The cut should be registered relative to the bit which should be registered to the plate.
Maybe I'm missing the concern.
Jonathan

[Bill Huber]

Are you guys concerned about flatness of the whole table? As long as the plate is flat and very slightly proud of the table, I don't see the issue. The cut should be registered relative to the bit which should be registered to the plate.
Maybe I'm missing the concern.
Jonathan

I am, I want the whole table to be flat, if I am running a long board I don't want to have to try and keep the board flat just on the plate. The board will be at an angle to the tool if not flat on the plate and not be making contact with the table on the right side. Then when you cross the mid point of the board and holding it down on the out feed side the angle will change direction. I want the board to be at a 90° at all times.

If you have a 3 foot long board and have a crown in the table you will have to keep the board flat on half the width of the plate to start your cut, then you will have to keep the board flat on the other half of the plate to finish the cut. So if the table is flat all the way you don't have to worry about it and you can just run the board.

[Van Huskey]

This begs the question, how flat is flat enough across the entire table? I have never given it much thought and as far as I know all my tables are flat enough but I have never felt the need to check them.

[Bill Huber]

This begs the question, how flat is flat enough across the entire table? I have never given it much thought and as far as I know all my tables are flat enough but I have never felt the need to check them.

I think that .00000001 is flat enough....... well maybe not that flat but I use a .0015 feeler gauge with my steel Lee Valley straight edge and that is what I shoot for.

[Van Huskey]

I think that .00000001 is flat enough....... well maybe not that flat but I use a .0015 feeler gauge with my steel Lee Valley straight edge and that is what I shoot for.

.0015 is pretty darn flat, especially since the spec on the short Lee Valley straight edge is .001 over its length. I am not arguing that is "too" flat since if you can get it there it is excellent! Like I said I have never checked but prior to this thread if I had checked I would have been happy if it was .005 over the length.

[Bill Huber]

.0015 is pretty darn flat, especially since the spec on the short Lee Valley straight edge is .001 over its length. I am not arguing that is "too" flat since if you can get it there it is excellent! Like I said I have never checked but prior to this thread if I had checked I would have been happy if it was .005 over the length.

I have the 36" straight edge and it is .0015 over the length, so I could not be flat to .0015 but it is as close as I can get it. I guess I could be off by .0030 but I think that will work for me.
It is not easy to do, I have worked on this for the last year or so. I check it and if I find that it is off I then put in some shims, leave it for month or two and then check it again, I think it takes some time for the table to settle down to the shims.
At this point I am real happy with my table, it does have one little low spot about 3" in from the out feed side and the low area is about 1 1/2" long so I think it must be a bad spot in the table.

[Van Huskey]

Count me impressed! I have seen a lot of blanchard ground machine tops that weren't that flat.

[tyler mckee]

If it cuts accurately and consistently, I really don't care.

[Myk Rian]

So you would build a timber TS? .
Excuse me? What dark hole did you drag that out of?

[William C Rogers]

Thanks for all the response. Yes I did state incorrectly, should have been 0.001 to 0.020 and not 0.20. The reason I was checking it was I installed the incra LS fence system and had to modify the table. I added an extension so I could used it like a conventional table instead of putting the fence along the 52 inch length. I am going to be doing some cabinet rail and stiles. I am also guessing the drum sander will get rid of most mismatch. I intend to leave .040-.050 to sand off with the drum sander. The top is 2 inch thick hardwood 32 x 50 I got from a cabinet shop about 30 years ago. Before I used it, it was about 0.005 out of flatness before I glued the formica. I don't remember checking after until now.

Bill