Working with old plywood...

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Forum topic by tyskkvinna posted 07-19-2011 05:08 PM 2123 views 0 times favorited 18 replies Add to Favorites Watch
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1310 posts in 3158 days

07-19-2011 05:08 PM

I have a surplus (and by surplus I mean “100+ sheets”) of 4×8 plywood that was produced somewhere between 1970-1975, I think. Maybe a little earlier but definitely not any later… It was part of a subfloor so it has nail holes around the edges but that is mostly confined to just the perimeters of the wood. I am fairly certain it is some kind of pine/birch mashup thanks to the colour and smell of the chips when I make them. It is also unique plywood (at least compared to what I’ve ever used)- the top (and bottom) layers are just as thick as the rest of the layers, which is just under 0.12”. The whole thing is a hair over 0.75” thick. 0.7559” my calipers told me…

There are knots (which are actually really pretty in this context) and a lot of the inner layers have voids. The wood sands up magically smooth.

If you aren’t familiar with the stuff I do, it’s not just straight cuts—I do a lot of engraving, contouring, sculpting, etc.

I want to take this “bad wood” and turn it into pretty things. I have lots of plans already.

My questions:

-What are your favourite ways to work with voids? Sometimes it will be a “surface void” so I need to fill it so it will be smooth and look interesting. I am primarily sealing/staining this rather than painting, but I of course am not expecting the surface repairs to be invisible. Was kind of aiming for a contrasting effect. I know epoxy and sawdust/glue methods work well for small voids, but there are usually big enough for me to stick a #2 pencil into easily.

-And what about the “inside voids”? I’ve made quite a few cuts where you can see under the top layer is a void. I would prefer to fill it so that it remains stable. Usually it is in the middle of engraving, so filling it and ensuring that the engraving stays in-tact is kind of tricky. I can’t go back and re-engrave it so whatever I do will be done by hand.

-What is a good grit to start out with when I sand this stuff? It’s kind of fuzzy and flaky (not unlike the generic ply surface you’d find at HD) but it DOES get smooth and pretty with some elbow grease. I tried starting at 100 and it was too fine, but I feel like going down to 60 or 80 and I’m also scratching up the surface more than its worth. Suggestions?

-- Lis - Michigan - -

18 replies so far

View rance's profile


4264 posts in 3332 days

#1 posted 07-19-2011 05:36 PM

I like to recycle as much as the next person but I’m realizing that sometimes there are better alternatives when it comes to my personal projects. I think what you have is called CDX. Not really useful for a ‘finished’ project, mainly due to the massive voids. It is good if you need to build a shed or something like that but I’d a-void filling those kind of voids. Have you considered selling it on CL and parlaying that into good-wood-money?

If you choose to use it, try cutting the edges proud of your intended cut line, fill the void with epoxy, bondo, or joint compound. Once dry, cut to your final cut line. Joint compound can’t be good for your saw blades though. Same procedure for the inner sections but not quite as easy. You want to get the void filled before you get to your final shape. If you are carving, I’d go the bondo route.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View ksSlim's profile


1286 posts in 3062 days

#2 posted 07-19-2011 05:47 PM

Take an electronic stud finder for a drive over your material to locate voids before laying out cut lines.

-- Sawdust and shavings are therapeutic

View tyskkvinna's profile


1310 posts in 3158 days

#3 posted 07-19-2011 05:58 PM

On my local CL I would be lucky to get between $1-5/sheet. That doesn’t really buy that much “good wood”.

I’m also not going to design things around the wood. It would be one thing if I was making solid panel built things, but I do engraving and sculpting. Not an option.

Which leaves me back to my original question. ;) How to work with the voids the best way possible.

-- Lis - Michigan - -

View Waldschrat's profile


505 posts in 3607 days

#4 posted 07-19-2011 06:06 PM

I agree with rance.

If you are trying to recycle material because its environmentally friendlier, that is a good reason. But if you really calculate it out, the time and energy (electricity) not to mention stuff like epoxy and bondo or whatever, with a low grade plywood, you would more than likely be better off, and quicker, if you sold it or used it for something else where the voids do not matter, than trying to fill all the holes and whatnot.

There are machines that look like a biscuit cutter that cut a oblong “canoe” shaped whole that you can plug with solid wood. That’s probably the most economical way of doing the work… but the machines are expensive. Maybe you can borrow such a machine from a local cabinet maker, I think that would be the quickest way.

-- Nicholas, Cabinet/Furniture Maker, Blue Hill, Maine

View Sawkerf's profile


1730 posts in 3240 days

#5 posted 07-19-2011 06:07 PM

That sounds like CDX which was (is) essentially “junk” for anything except subfloors, sheathing, etc where you needed structure but didn’t worry about appearance.

When new, the stuff can twist, cup, bend bow, and warp like crazy. Since yours was nailed down for several years, it’s probably pretty stable.

The stuff can be “interesting” if you don’t mind dealing with the fillers, etc. The panels in this planer stand were made from some 3/8” CDX that I recycled from a large shipping box. It’s fine for shop use, but I wouldn’t use it for house furniture. – lol

To respond to your second post, I wouldn’t mess with it. IME, that stuff is way more hassle than it’s worth.

-- Adversity doesn't build reveals it.

View Swede's profile


191 posts in 3190 days

#6 posted 07-19-2011 06:14 PM

I would take similar material and make wood filler pieces and glue them in.

My father made cabinets and trim for his house out of scrap when he moved in over 40 years ago.
I have worked on jobs where we took birch plywood made cabinets and they were painted.
It isn’t always the wood but the skill put into the making.
One person can take scrap and make furinture the next can take quality wood and make scrap.

Don’t let them discourage you.

-- Swede -- time to make some sawdust

View David Kirtley's profile

David Kirtley

1286 posts in 3170 days

#7 posted 07-19-2011 06:37 PM

I would just live with it. For show sides, you can laminate a 1/8 or 1/4 of something pretty.

-- Woodworking shouldn't cost a fortune:

View Kjuly's profile


311 posts in 3457 days

#8 posted 07-19-2011 06:57 PM

Hi Lis,
Durham’s wood putty will work. It’s a water based putty the sands pretty easy. You can mix it pretty thin, so it’s easy to push into the voids. It does shrink a little so you may have to apply a few coats. Durham’s does not take stain very well but you can mix in a water based dye to add some color. Because it is in power form there is a long shelf life as long as the can is sealed.
Oh yea…it’s cheap. $4.00 for a one pound can.

-- Keith, Charlotte, MI

View Jim Jakosh's profile

Jim Jakosh

21504 posts in 3277 days

#9 posted 07-19-2011 07:16 PM

First of all , if the wood sands real smooth with out a lot of effort, I don’t think you have a C or D surface. More likely a B surface. Lots of voids might have been the way they made it in the 70’s

If you were going to paint it, Durham’s water putty would fill them just fine. But you are going to finish them with stain and varnish so you want all wood in that area. If they are on the surface, you could cut a round hole in with a forstner bit and then plug it with a glued in round piece. You could go all the way through and put in a piece from the original plywood from a good area-take care in matching grain patterns. That would work for internal voids too, but I bet you don’t see the internal ones until you cut through the surface. Is it possible for you to cut the whole project about 90% deep and then plug all the void areas and then reset the part in the machine to the original position and cut it to full depth?

It’s a CNC so you could redefine your zero points if it is out of position a bit.

Good luck , Lis…...................Jim

-- Jim Jakosh.....Practical Wood Products...........Learn something new every day!! Variety is the Spice of Life!!

View dbhost's profile


5767 posts in 3404 days

#10 posted 07-19-2011 07:30 PM

I am thinking shop projects and cabinet carcasses are likely candidates for recycled CDX. I have a bunch of 3/8” CDX I pulled from my attic (poor initial attempt at decking by the builder). I keep it around for window covering in case of another hurricane…

-- Please like and subscribe to my YouTube Channel

View Mark's profile


1807 posts in 3446 days

#11 posted 07-19-2011 07:53 PM

make rustic projects…like little things as in a stepping stool, mail boxes, etc. People love restored wood projects. The more dinged up the wood is the more character it has

-- M.K.

View rance's profile


4264 posts in 3332 days

#12 posted 07-19-2011 08:30 PM

To fill inner voids, use a hole saw to cut down 1/4” deep. Then set your router bit to cut out the middle. Then cut out exotic disks(wenge, cocobolo, purpleheart, etc.) and insert them. Sand flush & Bob’s yer uncle. Oh wait! make the cutouts 1/2” deep, add the exotic inserts, then with 1/2” inserts you can carve into them.

Oh, and 100 grit on the basic plywood! :)

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Don W's profile

Don W

18988 posts in 2739 days

#13 posted 07-19-2011 10:13 PM

CDX stands means its c grade on one side and d grade on the other. X is for exterior (although its open to interpretation. Don’t leave it out for too long) so try to pick the best side. It shouldn’t have as many voids.

Typically the stuff I build with it is shop or exterior work, so I don’t fill the voids. If a piece is showing I pick a section that doesn’t have any voids if possible. If you must fill it, anything you would typically use will work. I’ve even used joint compound if its going to be painted.

If its the end it can be a little more frustrating. At time it will affect the structual integrety, but its also smaller gaps. Again, fill it with what you’d like, depending on the desired finished look.

I don’t agree that this stuff isn’t worth your time, but I do agree it’ll never make fine furniture. On the other hand, rip open your couch and look at some of the crap that’s in there. Where there’s a will, there’s a way.

-- - Collecting is an investment in the past, and the future.

View BertFlores58's profile


1698 posts in 3094 days

#14 posted 07-20-2011 02:56 AM

Hi Liz,
You got your CNC… you can cut circular or square (depending on your choice and size of the voids) pieces of the same plywood and make it also thinner nearly half of the plywood thickness) then you can inlay it on the void. In the long run, this would be the easiest method because we are talking about 100+plywood sheets. Use of router for the inlay recess (CNC can be used but limited to its capacity), thicknesser (for proper thickness of the inlay pieces), and CNC or router to shape circular patches of plywood. Gluing will be later and use of tape and vacuum freeze will do. I had suggested this because you got the first ply which is thick .12”.

Just be careful cutting those little pieces specially if you use scroll saw. Hope this will help.
God Bless,

-- Bert

View tyskkvinna's profile


1310 posts in 3158 days

#15 posted 07-20-2011 05:06 AM

There were some actually useful responses here, thanks guys. I’m going to play around with the suggestions and see what works best for my applications. I think the durhams could actually be kind of cool if I tint it.

People DO love recycled/upcycled wood, which is my main motivation here. I want something that is a good quality when I’m done, with a solid, pretty finish but was also obviously recycled.

I had not thought about plugging just the surface layer.. that’s a really neat idea. I will report back on how it works.

-- Lis - Michigan - -

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