# Trimming plywood



## amckenzie4 (Apr 29, 2010)

I built myself a cabinet out of 3/4" plywood to hold my SCMS, and I discovered once I'd put everything together that my cuts were off -- I need to take about 1/16 of an inch off the sides to get them to match the level of the chop saw's deck. 

What's the right way to trim plywood? If it were solid wood, I'd try a planer, but it didn't cut very well on the scrap plywood I tested with. Should I just use a power sander with some coarse sandpaper, or is there a better trick?

Thanks in advance.

-Alex


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## cabinetman (Jul 5, 2007)

amckenzie4 said:


> I built myself a cabinet out of 3/4" plywood to hold my SCMS, and I discovered once I'd put everything together that my cuts were off -- I need to take about 1/16 of an inch off the sides to get them to match the level of the chop saw's deck.
> 
> What's the right way to trim plywood? If it were solid wood, I'd try a planer, but it didn't cut very well on the scrap plywood I tested with. Should I just use a power sander with some coarse sandpaper, or is there a better trick?
> 
> ...



That is a predicament that is likely from not doing a good layout or planning, or not measuring correctly. Dry fitting before assembly may have been a tell tale. 

It seems you could just add 1/16" onto what ever has to be flush. Shearing off a layer of plywood is a PITA. I don't like doing it with a planer. Sanding, even with a belt sander is a PITA. You might be able to take it down with a wide belt sander if available.

But, in this case if the sides don't line up, it may be easier to add onto the mating piece(s).


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## firehawkmph (Apr 26, 2008)

Alex,
Belt sander would easily do it. Also, why not put a piec of laminate under your saw to shim it up instead? Just another option.
Mike Hawkins


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## Ghidrah (Mar 2, 2010)

Aluminum step flashing


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## amckenzie4 (Apr 29, 2010)

It's certainly an error in either my measurement or my cutting -- I'd never used the new table saw before building this, so I may very well have gotten a few things wrong. It's close enough that it wasn't really clear to me until I'd gotten the whole thing assembled. Shimming the saw may be the best option; I'm not quite sure why I didn't think of that. The two sides of the cart are identical, so lifting the saw would solve the problem completely. I don't have a belt sander yet, so that's not as easy an option as I'd like. I do have some 1/16 hardboard, though, so that may be the right solution.

This is actually my first attempt at building something that requires tolerances this close (I've done a fair amount of "knock it together out of two-by-four and call it good" sort of rough work, but nothing precise), so I'm fairly pleased to have only been off by a sixteenth of an inch; the only other mistake I made was in clamping, so the cart is just barely out of square. It's close enough to be solid, and a bit of sanding will leave it invisible, but now I know I need to be more careful next time. It's pretty basic -- sides, top, and bottom made of 3/4" AC plywood, with the bottom rabbeted to accept the sides, and the sides dadoed to accept the shelf, and the joints glued and fastened with brads from a pneumatic nailer. I put a couple of cross-pieces top and bottom of pine 1x4, since I had it handy, and the thing is remarkably solid. I'll eventually add a middle shelf (or maybe a drawer), and that should make it even more solid. The whole thing is set on a mobile base built from 3/4" plywood and a set of retracting casters from Woodcraft (which I can't find on their web site for some reason). Overall, I'm pretty pleased.


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## WoodRic (Jun 17, 2009)

www.woodcraft.com

Are you wanting to cut the "edge" down 1/16" ?
I think the guys are assuming you're talking about taking it off the face.

There seems to be some confusion about just exactly what you need to trim. It sounded to me like you needed to trim an edge down a hair, and that's pretty easy.

A router with a trim bit should do it in pretty short order.

Oh, and congrats on the new project. It's a good feeling when you've reached into new territory, and it comes out that good. Way to go!


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## woodnthings (Jan 24, 2009)

*Let's see a photo?*

Seems like the suggestions to raise the saw by adding a thin piece of laminate would be the best solution. If the saw gets bolted in place then a washer or two underneath will also work. Large 1/2" ID washers are about 1/16" thick, 5/8 ID 's about 1/8 or 3/32nds. 
You have no pictures yet so this would be a perfect time! :thumbsup: bill


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## amckenzie4 (Apr 29, 2010)

I'll get some pictures tonight, most likely... if it's not raining, probably a shot of the whole workshop, too, since it's finally close enough to useable that I'm willing to have people see it. 

WoodRic had it right -- the side board extends above the top shelf, so I need to trim 1/16" off the edge of a piece of plywood. I do have a router, though not a very good one, so I may look into figuring out how to use a trim bit on it. The router I have has no built-in way to follow an edge, and no easy way to attach a guide, so I'm stuck with clamping a rail to the workpiece and running the router along it.

Or I may just check to see if my hardboard is the right dimensions: it should be close, and I know it's 1/16" thick, but I'm not sure it actually would cover the top, which is what I'd prefer. If it works, that's clearly the easiest way to get it working.


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## cabinetman (Jul 5, 2007)

amckenzie4 said:


> WoodRic had it right --



How you word a description may determine the answers you get. If it's necessary to figure out what you mean, it may not be what you mean. For example, you said:


_I built myself a cabinet out of 3/4" plywood to hold my SCMS, and I discovered once I'd put everything together that my cuts were off -- *I need to take about 1/16 of an inch off the sides to get them to match the level of the chop saw's deck.* 

What's the right way to trim plywood? If it were solid wood, I'd try a *planer*, but it didn't cut very well on the scrap plywood I tested with. Should I just use a power sander with some coarse sandpaper, or is there a better trick?

Thanks in advance.

-Alex_ 

When you say sides, that could mean sides, not ends of panels. Suggesting using a planer indicates reducing the thickness of a panel, not trimming the end of a panel.

I'm suggesting this in a constructive nature to help describe what is wanted. When making a post, read it back to yourself and see if what was said is totally clear to be understood. This is helpful when sketches or pictures aren't included.


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## WoodRic (Jun 17, 2009)

amckenzie4 said:


> WoodRic had it right -- the side board extends above the top shelf, so I need to trim 1/16" off the edge of a piece of plywood. I do have a router, though not a very good one, so I may look into figuring out how to use a trim bit on it. The router I have has no built-in way to follow an edge, and no easy way to attach a guide, so I'm stuck with clamping a rail to the workpiece and running the router along it.


Pick up a trim bit. They're the ones with a bearing on the end. The bearing will follow the shelf, and take that little bit off the edge of the wood.

-> The router would be held against the side, with the bit over the top edge. The bearing would ride against the top shelf, and that sets the height for the cut. If you're careful, you can get it nearly perfect this way.

OR... if you have a belt sander, you can take 1/16" off the edge of a piece of plywood REAL quick & easy.


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## amckenzie4 (Apr 29, 2010)

cabinetman said:


> How you word a description may determine the answers you get. If it's necessary to figure out what you mean, it may not be what you mean.


Yep -- that's what I get for posting first thing in the morning.  I'll try to be a bit more clear in the morning, or at least wait until I'm a bit more awake.



WoodRic said:


> Pick up a trim bit. They're the ones with a bearing on the end. The bearing will follow the shelf, and take that little bit off the edge of the wood.
> 
> -> The router would be held against the side, with the bit over the top edge. The bearing would ride against the top shelf, and that sets the height for the cut. If you're careful, you can get it nearly perfect this way.
> 
> OR... if you have a belt sander, you can take 1/16" off the edge of a piece of plywood REAL quick & easy.


Thanks -- I'll stop on the way home and pick up a trim bit. Since I don't have a belt sander, that sounds like the best option. Or I could pick up a belt sander, but I don't think my finances would take that this week.


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## WoodRic (Jun 17, 2009)

amckenzie4 said:


> Thanks -- I'll stop on the way home and pick up a trim bit. Since I don't have a belt sander, that sounds like the best option. Or I could pick up a belt sander, but I don't think my finances would take that this week.


Yep, trim bits are cheaper. 
Just be sure you get a trim bit, and not a pattern bit. The difference is a trim bit has the bearing on the end, and a pattern bit has the bearing on the top.

They do take a little bit of practice though, so be careful with that.


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## amckenzie4 (Apr 29, 2010)

WoodRic -- I've got a fair amount of scrap, so I should be able to work it out without ruining anything too valuable. Thanks for the warning, though.


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## ash123 (Mar 14, 2010)

Straight edge & router w/ flush trim bit.


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## amckenzie4 (Apr 29, 2010)

The trim bit did the job perfectly! Thanks everyone -- I'll post pics sometime today, so everyone can see exactly what I was talking about. I actually used the saw in the cart last night, and it worked well, so I'm pleased. I'm not quite done, though: I started adding a set of "wings" out of leftover plywood, but I still need to add the support on the right, and attach the wing and support on the left. And I'll probably build in a drawer for storing blades, wrenches, and the like.

Thanks again!


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## amckenzie4 (Apr 29, 2010)

*Pictures!*

As I mentioned in my last post, it's not quite done, but it's close, and it's now usable. Here's what it looks like in the poor light of my garage at night. (Well, poor for seeing color -- it's bright enough to work in, but the fluorescent tube lights really mess with the camera.)

















The piece I was having trouble with was the side, where it rises above the shelf the saw sits on. I set the shelf about a sixteenth of an inch low, so it was too high for a long piece of wood to sit on the saw. 

The curved cutout in the top front of the sides is so the blade can make mitre cuts out to its max; without the cutouts, the arm attached to the table couldn't swing all the way. The clip you can see on the back is holding the support for the wing in place -- I didn't finish that last night, but I wanted to take the pictures anyway. And as you can see, I'm short enough on space that the bottom shelf is already full! (I'll probably swap the compressor for a shop-vac, though -- make it a bit easier to hook it up to the saw, not that it helps all that much.)

Thanks again for all the help!


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## mdntrdr (Dec 22, 2009)

Looks great! :thumbsup:

If that compressor fired up while I was making a cut, it would scare the 
SH*T out of me! 

I would definitly move that! :yes:


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## WoodRic (Jun 17, 2009)

Looks good! Nice job.


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## amckenzie4 (Apr 29, 2010)

mdntrdr said:


> Looks great! :thumbsup:
> 
> If that compressor fired up while I was making a cut, it would scare the
> SH*T out of me!
> ...


Thanks! And there's not much chance of the compressor firing up unexpectedly... I don't use it all that often, so it gets drained and unplugged when I'm not using it. Besides, it's small enough it only takes about 2-3 minutes to come up to pressure, which is about as long as it takes to get the nailer out and load nails in it. 



WoodRic said:


> Looks good! Nice job.


Thanks!


I'm especially pleased since, as I mentioned, it's the first thing I've built that really required precision. It gives me hope that I might actually be able to build nice things one of these days! 

Next up, once I've got the wings built on this, is a box for router bits. I've got two bits, I might as well have a safe way to store them, and any others I acquire! And I think I have everything I need except hinges already in my scrap bin, if I build something small... Then a drill-press stand, and a smoother workbench would be a plus. Hmm.... I guess I don't have to worry about making fine furniture any time soon. Just getting a working shop is going to take some doing.


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## WoodRic (Jun 17, 2009)

amckenzie4 said:


> I'm especially pleased since, as I mentioned, it's the first thing I've built that really required precision. It gives me hope that I might actually be able to build nice things one of these days!
> 
> Next up, once I've got the wings built on this, is a box for router bits. I've got two bits, I might as well have a safe way to store them, and any others I acquire! And I think I have everything I need except hinges already in my scrap bin, if I build something small... Then a drill-press stand, and a smoother workbench would be a plus. Hmm.... I guess I don't have to worry about making fine furniture any time soon. Just getting a working shop is going to take some doing.


I think many of us spend our early build time building the shop itself. It's a great place to practice, and expand. While I doubt anyone would put any fine furniture in there, you'll find that you do use a lot of the same techniques.

So practice away, it's all to your benefit. Not only do you get some good woodworking experience, but you improve your shop while you're at it.


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