# PC 7539 and table sag -



## pb9003 (Sep 20, 2011)

Hi everyone, new guy here although not new to woodworking. 

I have a PC7539 mounted in my router table which was constructed of 2 sheets of 3/4" MDF laminated together, covered on both sides with laminate, and edged in cherry. The router itself is mounted to a Rockler aluminum insert which does not have a problem with sag. This is the second top I've made, and for the second time, this tabletop has sagged to the point that it's visibly affecting whatever I'm routing. I discovered this whilst routing beading for a bookcase I'm building, and now this problem has caused the bookcase project to come to a complete halt. 
I've read through some of the archives so I know some of you are using the same router (I had been considering selling it and buying a lighter-weight machine), but regardless of what I do I need to do something about the sagging top. I suppose my first question is whether or not I can fix the current top or whether it's even worthwhile to attempt a fix, and then the second question would be by what means do I stabilize a new or repaired top so I don't have to worry about the sag. If I make a new top I would consider sandwiching steel bar stock within the MDF, as suggested by Wally Kunkel in his tome on radial arm saws. If I attempt a repair to the current top I was considering just milling some hardwood ribs to attach to the underside of the table, removing the laminate from the underside somehow, and with glue and a heck of a lot of clamping pressure bringing it back to flat, but I don't know if even can get it to flat that way - there's about a 1/16" dip in the center of this thing. 

Suggestions? 

Sorry to be so wordy, but I couldn't explain in enough detail with fewer words.

Thanks in advance for your thoughts

Philip


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## Mike (Nov 22, 2004)

Philip, properly supported a single layer of 3/4" Baltic birch plywood with laminate on the top and bottom will not sag. This is how the Router Workshop table is built. I am testing some 3/4" phenolic impregnated Baltic birch with a 7518 on the oversized Rockler plate. So far so good.


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## Quillman (Aug 16, 2010)

"whether it's even worthwhile to attempt a fix,"
************************************
I think you've had it.
Moreover, @>17 lbs, you have the heaviest US router in history.
To minimize deformation & maximize flatness I use a skinny top (5/8" MDF) on top of 6 stout beams.
All in the same plane, supporting a 7518 x >10 years!


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## Cherryville Chuck (Sep 28, 2010)

Can you turn the top over and use the other side?

Pat hit on the answer. The temporary table I last built is only 1 thickness of 5/8 melamine coated particle board and I cut through most of that to put track into it and still haven't had a problem. Underneath is a ladder frame of 1 x 4 with crosspieces on either side of the opening. I also don't leave my router in the table when I'm not using it.


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## TomE (Dec 17, 2010)

One could take Pat's solution a step further and add a second skin below (torsion box) and configure a dust collection chute within the available channels between skins. Router can "breathe" and a goodly amount of dust that the fence port misses gets collected .


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## pb9003 (Sep 20, 2011)

Thank you, gentlemen, for your input. I guess I'll start making a new top today. 

Philip


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## Admin (Feb 13, 2012)

MDF = Most Definitely Faulty.

Has to be the WORST material ever developed, carcenogenic dust, reacts to humidity, cannot be resurfaced.

Use Baltic ply with laminate both sides

Regards
Ray


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## JOAT (Apr 9, 2010)

Yep, proper support underneath. I'm on my 3d or 4th homemade router table. None have sagged, and they all were made with 1/2" plywood tops. And well supported by a web of 2X4 pieces under, glued on edge. The latest version is probably 3-4 years old now. My first one was basically a learning experience and worked, but was too small, and actually kind of crude. So #2 was much better. Now I only make a new table when my needs change, not because the table has problems - in fact the last one was only made because I needed a larger top - the previous table was 5-6 years old at that point. 
I'd need to actually look at your present table top to determine if I thought it could be salvaged or not. That said, it it was mine, and I decided to try to salvage it, I would give it a shot, regardless - sometimes just the challenge is the most fun.


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## pb9003 (Sep 20, 2011)

Thanks Theo. Just 1/2" ply for the top? do you use an insert or just mount the router to the tabletop? I have some 3/4" birch (not baltic multi-ply but cabinet-grade) that I was going to double up. Under that I would put ribs for support.


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## mjdorsam (Nov 27, 2011)

Can you straighten the table with angle-iron? The Incra tables have angle-iron screwed to the underside of the table on either side of the router opening, to accommodate a PC7518/19. 

Just a thought.
Mike


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## Woodworker Shack (Nov 2, 2011)

How about leveling screws underneath each corner of the blue Rockler plate. Use 5/16" dia. threaded insert with a 1/8" screw at each corner of the plate. The center of hole to be drilled is to be offset 3/16" outward from the cutout to receive the Rockler plate. The insert is screwed through a drilled 1/4" dia. hole in the MDF base with small screw screwed from under the MDF base upward/downward to the Rockler plate as needed to level.


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## Mike (Nov 22, 2004)

This design has stood up to Hitachi M12's, PC 7518's and a Bosch 1619 for many years trouble free. The top is 3/4" Baltic birch plywood with laminate top and bottom. The base and supports are 1/2" Baltic birch plywood. Mine has been trouble free with a Bosch 1617 left in it for 7 years.


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## bobj3 (Jan 17, 2006)

Hi 

I will 2nd. Mike's post,but add a note, no beams are needed most put the router in a cabinet and the inside wall parts of the cabinet will support the router just fine like below ..just like the OP table also.

Deluxe Router Table..Improved - YouTube

==


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## TomE (Dec 17, 2010)

The Sagulator - Shelf Sag Calculator


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## pb9003 (Sep 20, 2011)

The leveling screws are in and properly adjusted, but the sag is across the 34" width. I suppose I could use the leveling screws to make the plate in the same plane as either end of the table, but that's not the answer. The sag cannot be removed by screwing angle iron or wood ribs to the bottom - the 2 layers of MDF just don't have enough structural integrity and quickly either allow the screws to pull out (if installed from the underside), or pull through (if installed from the top down through the layers into hardwood ribs). I believe the correct answer here is to make a new top, design and materials to take into account the weight of the router (~18lbs) and the fact that I'm too lazy/forgetful/just don't want to be bothered- to remove the router between uses. Note that the plate itself has not sagged, just the MDF table itself has sagged. My bad - poor design, poor choice of material.


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## paduke (Mar 28, 2010)

I also had difficulty with a large top. The center wasnt sagging the ends were lifting I straightened mine using 3 1/2" wide 3/4 plywood on edge.


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## pb9003 (Sep 20, 2011)

*exactly what I tried!*



paduke said:


> I also had difficulty with a large top. The center wasnt sagging the ends were lifting I straightened mine using 3 1/2" wide 3/4 plywood on edge.


but due to the design of the cabinet under the table I couldn't pull the 6" or so of each edge flat due to drawers underneath. Seemed easier to make a new top than to modify/remake the cabinet, so that's where I'm going with this. However, I'm using 2 layers of birch ply with 1/2" steel rods between the two layers, set in epoxy. Positioned so it won't interfere with the cutout or a sliding track, I cut dadoes into the ply to hold the steel bars, added epoxy to hold them in place, then put the 'sandwich' together with glue & screws, formica top & appropriate edging still to be done. Basically followed the Wally Kunkel idea for radial arm saw tabletops. So just in case Sears or someone comes out with a 35hp router weighing 400 lbs (but still running on 110v, naturally) I'm good. :blink:


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## JOAT (Apr 9, 2010)

pb9003 said:


> Thanks Theo. Just 1/2" ply for the top? do you use an insert or just mount the router to the tabletop? I have some 3/4" birch (not baltic multi-ply but cabinet-grade) that I was going to double up. Under that I would put ribs for support.


Yep, 1/2". Insert, also 1/2". My first tabletop mounted the router to it, and was a real bear for changing bits. Second had an insert. Underneath the top is a real spiderweb of 2X4 pieces, which is the real secret. 
My present top is three piece, plus the insert. I was just winging it when I made this one, as I wanted an insert that was quick and easy to remove and insert, but would lock in and not move. Not sure if I have any pictures, but I'll describe what I did, then look for pictures. 
The back piece is rectangle about 6-8" by the width of the top, maybe 18-20". Hmm, I probably couldn't have told you how I made the top after I made it, let alone now, so I'll just wing it. The insert is slightly wider than the router, with about a 1 1/2" hole for the bit, and three holes for the screws to hold the router in. Then the part that butts against the back of the top is maybe 1" or so longer than the router base. The right rear corner of the insert is cut at an angle, so when I rout out new inserts, they go the same side up and fit perfectly. Then toward the front both sides are angled in slightly for a couple of inches, then cut straight toward the front, the leading edge is then even with the top. Then the two sides, that go on each side of the insert were cut to fit the angles of the insert very nicely. And I have no clue how I did that but it worked out nicely. I may have made the cuts with the scrollsaw. The insert is supported by 2X4 pieces, which also support the back and sides, overlapping I suppose you could say. I can pull up on the front of the insert, then lift it out, router and all, then it's easy to change bits, or whatever. To put it back, just set the back of the insert in place and lower the front in. Takes about 2 seconds either way. And with the multiple, and identical, inserts, I can put routers and different bits in those, and have a different bit installed in the top in about 30 seconds. I have 5 routers as I recall. That's as well as I can explan it just now, so I'll see if I can find some pictures to make it a bit clearer.


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## JOAT (Apr 9, 2010)

OK, found two pictures of my router table top. It's been so long since I've thought about it, I got the description a bit wrong, but I think the pictures are pretty self explanatory. I hope. If any questions, feel free to ask. Now that I look at the pictures, I realize the top was actually quite easy to make and put together. The insert fits quite closely and locks in place nicely, with the weight of the router holding it down. In the photo on the right you can barely make out that I left a gap in the 2X4 supports that just lets the router move thru to take out or put in. It looks too like each side of the insert is a bit different, so if the correct side is not screwed to the router, it won't fit and the insert must be turned over.


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