Erich Weidner
02-07-2012, 5:27 PM
Well, ever since I saw that FWW article about Phenolic coated Plywood, my existing folding extension table had lost its luster. (Which was made of a sheet of melamine coated MDF) Especially as it serves double duty as my assembly table, cleaning up the stuck on dried glue was taking its toll on its once perfect surface (though it was still very, very flat).
When I recently (last month) sold my old TS and upgraded to a 3HP SawStop Professional, I was decided on building it out of a phenolic plywood top.
The plan was to have a 12" wide table which was bolted to the rear rail of the TS and with two diagonal braces attached to a steel angle which I screwed into the rear of the TS for support further than just at the point where it was bolted to the TS rear fence. (I adapted this from some plans I found online.) There is a second cut of the phenolic ply which is an additional 30" which is attached to the first piece via a piano hinge.
Here are the original plans so you have an idea of what I'm talking about: http://sawsndust.com/p-outfeed.htm
The only source I could find in Austin was Fine Lumber and Plywood (which is fine, this is were I buy my wood from anyway). A full sheet was in the neighborhood of $150. It never occurred to me to check it for being flat. It looked flat. It was $150, it must be flat... (For the curious it is "Finnform", manufactured for the concrete market)
For some reason no matter how much I planed the frame pieces they would wobble end to end when placed against my flat phenolic ply. The best reference I had was the table saw surface itself (which was serving as the work table for the larger of the two pieces of phenolic ply so I couldn't get to it), my Sjoberg workbench and a 2' steel straightedge. (I placed an order for some longer ones from Veritas, but it took several weeks for them to show up, more on this later).
By now I'm sure you figured out what it took me two weekends to get into my head. Indeed the plywood was not flat.
I assumed my 1-1/2" tall x 3/4" poplar frame (attached with pocket hole screws) would resolve this issue and suck everything flat.
After finally getting the 12" piece attached (and it does measure acceptably pretty flat at the edge which is bolted to the big rear "L" steel rail on the back of the TS, I prepared to finish the assembly and get to cutting sheet stock on the TS for the next project...
Fast forward four weeks to last night. With my wife's help I managed to get the "hanging" portion hung and screwed into the piano hinge. Today I went out after work, excited to get started on the pile of baltic birch ply earmarked to become a dedicated SCMS table!
First off, I did a few passes of boards with the saw off to make sure the outfeed table wouldn't pose any safety risks... I had deliberately dropped the first piece 1/16" below the actual TS surface, and aimed to get the 2nd piece about 1/32" below that to ensure no snagging of work being pushed on through the table saw. Well, the cup on this larger section of ply results in the rightmost edge being about 1/16" proud of the section it mates up with.
In the meantime, my Veritas 50" straight edge had arrived.
First I quietly cursed a bit then got back to work...
I've now pulled off the frame from the 48"x30" part, placed it back upside down on the tablesaw and checked it. Neither the frame, nor the ply is flat. Since the poplar is already painted, further planing on it is not an option. I'll consider it expendable and a lesson learned to get a better workbench for jointing... that is another story.
So now what?
Do I get aluminum (or steel) angle bars, or square tube (aluminum or steel) and try to force the plywood flat by screwing this/these in addition to, or instead of a new wooden frame?
Thicker wood? I'd really like to salvage this project if possible.
Photo of things as they stand now...
In the second and third photos I'm holding the straightedge "flat" against the left part of the ply, you can see the gap beneath the straightedge. About 1/8".
223022223023223024
I'm hoping someone has some suggestions.
When I recently (last month) sold my old TS and upgraded to a 3HP SawStop Professional, I was decided on building it out of a phenolic plywood top.
The plan was to have a 12" wide table which was bolted to the rear rail of the TS and with two diagonal braces attached to a steel angle which I screwed into the rear of the TS for support further than just at the point where it was bolted to the TS rear fence. (I adapted this from some plans I found online.) There is a second cut of the phenolic ply which is an additional 30" which is attached to the first piece via a piano hinge.
Here are the original plans so you have an idea of what I'm talking about: http://sawsndust.com/p-outfeed.htm
The only source I could find in Austin was Fine Lumber and Plywood (which is fine, this is were I buy my wood from anyway). A full sheet was in the neighborhood of $150. It never occurred to me to check it for being flat. It looked flat. It was $150, it must be flat... (For the curious it is "Finnform", manufactured for the concrete market)
For some reason no matter how much I planed the frame pieces they would wobble end to end when placed against my flat phenolic ply. The best reference I had was the table saw surface itself (which was serving as the work table for the larger of the two pieces of phenolic ply so I couldn't get to it), my Sjoberg workbench and a 2' steel straightedge. (I placed an order for some longer ones from Veritas, but it took several weeks for them to show up, more on this later).
By now I'm sure you figured out what it took me two weekends to get into my head. Indeed the plywood was not flat.
I assumed my 1-1/2" tall x 3/4" poplar frame (attached with pocket hole screws) would resolve this issue and suck everything flat.
After finally getting the 12" piece attached (and it does measure acceptably pretty flat at the edge which is bolted to the big rear "L" steel rail on the back of the TS, I prepared to finish the assembly and get to cutting sheet stock on the TS for the next project...
Fast forward four weeks to last night. With my wife's help I managed to get the "hanging" portion hung and screwed into the piano hinge. Today I went out after work, excited to get started on the pile of baltic birch ply earmarked to become a dedicated SCMS table!
First off, I did a few passes of boards with the saw off to make sure the outfeed table wouldn't pose any safety risks... I had deliberately dropped the first piece 1/16" below the actual TS surface, and aimed to get the 2nd piece about 1/32" below that to ensure no snagging of work being pushed on through the table saw. Well, the cup on this larger section of ply results in the rightmost edge being about 1/16" proud of the section it mates up with.
In the meantime, my Veritas 50" straight edge had arrived.
First I quietly cursed a bit then got back to work...
I've now pulled off the frame from the 48"x30" part, placed it back upside down on the tablesaw and checked it. Neither the frame, nor the ply is flat. Since the poplar is already painted, further planing on it is not an option. I'll consider it expendable and a lesson learned to get a better workbench for jointing... that is another story.
So now what?
Do I get aluminum (or steel) angle bars, or square tube (aluminum or steel) and try to force the plywood flat by screwing this/these in addition to, or instead of a new wooden frame?
Thicker wood? I'd really like to salvage this project if possible.
Photo of things as they stand now...
In the second and third photos I'm holding the straightedge "flat" against the left part of the ply, you can see the gap beneath the straightedge. About 1/8".
223022223023223024
I'm hoping someone has some suggestions.