Finish for plywood top assembly table

[Todd Brewer]

I'm building a large MFT assembly table. I am using borg 3/4 maple plywood. I'm wondering what finish makes the most sense. I'm thinking Arm-R-Seal. Is that a good choice for removing glue, resisting wear and tear and can be refinished from time to time?

I see a lot of people use MDF and there are a lot of posts regarding MDF, not so much for plywood work surfaces that I can find. Maybe I don't know how to use the search function correctly.

Not sure why people love MDF, I read all kinds of posts about sealing and it swelling etc. But I don't want to get side-tracked on that issue.

If I coat it, should I do it before drilling the 20mm holes?

Thanks,

Todd

Edit: If MDF really is the way to go, I can do that, seems plywood is more stable and pretty darn flat.

[Jamie Buxton]

The advantage to MDF is that it is cheap. However, it does sag with time, so if you use it for a table you have to include supporting ribs or something to keep it flat. Me, I'd use plywood.

The objective of finish on a work table is to prevent glue from sticking. Darn near any wood finish will do this for you. Varnish, like armorseal, is a good choice. You can put it on before you drill the holes or after.

[Howard Acheson]

IMO, an assembly table top should be made as a 4" thick torsion box. That way you can be assured that it will stay flat over time.

That said, to answer your question about coating the top, I would use one of the following:

A film finish (lacquer, shellac, varnish, poly varnish) is not the way to finish a workbench top. A workbench is going to get dinged and film finishes will crack or craze or be otherwise damaged. Once a film finish is penetrated, it looses its effectiveness and adjacent areas begin to fail. No treatment or coating short of epoxy is going to make a soft wood benchtop harder. I much favor an "in the wood finish". Here are two that lots of folks find effective.

First, is an boiled linseed oil and wax finish. Sand the surface to 180 grit. Mix paraffin or bees wax into heated boiled linseed oil. USE A DOUBLE BOILER TO HEAT THE OIL. The ratio is not critical but about 5-6 parts of boiled linseed oil in a double boiler with one part paraffin or beeswax shaved in. Take it off the stove. Thin this mixture about 50/50 with mineral spirits to make a heavy cream like liquid. Apply this mixture to the benchtop liberally and allow to set overnight. Do it again the next day and again the following day if the top continues to absorb it. After a final overnight, lightly scrape off any excess wax and buff. This finish will minimize the absorbsion of any water and you can use a damp rag to wipe up any glue excess. Dried glue will pop right off the surface. Renewal or repair is easy. Just use a scraper to remove and hardened stuff, wipe down with mineral spirits using a 3/0 steel wool pad (a non-woven green or gray abrasive pad is better), wipe off the gunk and apply another coat of boiled linseed oil/wax mixture.

My personal preference is for an oil/varnish mixture treatment. Either use Minwax Tung Oil Finish, Minwax Antique oil or a homebrew of equal parts of boiled linseed oil, your favorite varnish or poly varnish and mineral spirits. Sand the benchtop up to 180 grit. Apply the mixture heavily and keep it wet for 15-30 minutes. Wipe off any excess completely. Let it dry overnight and the next day, apply another coat using a gray non-woven abrasive pad. Let it set and then wipe off any excess. Let this dry 48-72 hours. To prevent glue from sticking apply a coat of furniture paste wax and you're done. This treatment is somewhat more protective than the wax and mineral oil as the varnish component adds some protection from not only water both some other chemicals also. The waxing makes the surface a little more impervious to water so you can wipe up any liquid adhesive. It also allows hardened adhesive to be scraped off. Repair and renewal is easy. Just go throught the same scraping, wiping down with mineral spirits and reapplication of the BLO/varnish/mineral spirits mixture and an application of paste wax.

Both of the above treatments are quite protective but are easy to maintain and renew. They do not fail when the surface takes a ding.

[Shaddy Dedmore]

I went with Howie's second method, and used Watco danish oil from HD, and followed with paste wax. I can use a scrap block of wood to scrape off glue, it pops right off. I reapply wax after I use it a lot.

[Todd Brewer]

Many searches on the web turned up Watco danish oil, among others. Wasn't sure what would prevent glue from sticking but could be "renewable". Watco and paste wax sounds like the trick!

Thanks! Now my Sunday is not a complete waste. I can continue building my table and treat the surface later.

With regards to the torsion box design, I have read much about that. I'm building a version of the Ron Paulk Ultimate Workbench. Its a torsion box design but with all the openings in the frame and not a lot of frame structure, I'm not sure how effective it will be. It's a one piece design instead of two halves. I will build a robust structure below to keep it flat. But that's another subject for another thread.

[Lee Schierer]

I have a BORG plywood extension table on my TS that gets used for assembly. It is finished with 3 coats of oil based polyurethane. PVA glue doesn't stick to the surface and if the surface gets messed up you can always sand it and apply another coat of poly. Glue sticks even less if you occasionally apply a coat of Johnson paste wax to the surface.

[Todd Brewer]

With regards to paste wax, are there any issues with the wax transferring to the workpiece, thus potentially causing a finishing problem for the workpiece?

Also, so far I've only found Minwax paste wax, not Johnson, does it matter?

Thanks,

Todd

[Mike A. Dawson]

Many searches on the web turned up Watco danish oil, among others. Wasn't sure what would prevent glue from sticking but could be "renewable". Watco and paste wax sounds like the trick!

Thanks! Now my Sunday is not a complete waste. I can continue building my table and treat the surface later.

With regards to the torsion box design, I have read much about that. I'm building a version of the Ron Paulk Ultimate Workbench. Its a torsion box design but with all the openings in the frame and not a lot of frame structure, I'm not sure how effective it will be. It's a one piece design instead of two halves. I will build a robust structure below to keep it flat. But that's another subject for another thread.

Would love to see how your version turns out! Are you making any changes to Ron's design? I've had my plans for a couple of months now and am anxiously waiting to build it! I just don't have a way to do the dadoes right now.

[Lee Schierer]

With regards to paste wax, are there any issues with the wax transferring to the workpiece, thus potentially causing a finishing problem for the workpiece?

Also, so far I've only found Minwax paste wax, not Johnson, does it matter?

Thanks,

Todd

If you are using solvent based finishes the wax poses no problem at all. It could cause issues with water based finishes; however, you will be wiping off the majority of the wax and just leave a thin film. I've never had a problem, but I use a roll of rubber shelf liner under the work to protect pieces when I sand them on by work bench. Any transfer from a buffed wax surface is likely to be very minimal.

Min Wax paste wax is good. A can will last you for years. The last time I found Johnson paste wax it was at one of the Borgs, but you can also find it in supermarkets.

[Andrew Joiner]

With regards to paste wax, are there any issues with the wax transferring to the workpiece, thus potentially causing a finishing problem for the workpiece?

Also, so far I've only found Minwax paste wax, not Johnson, does it matter?

Thanks,

Todd

I'm big on testing this for your self. I did. I was concerned that the paraffin wax I rub on my planer bed, saw fence, and saw table was rubbing off onto my stock.
I rubbed paraffin wax heavy onto 2 scraps, glued them and yes poor glue joint with PVA as you'd expect. I was amazed that 2 scraps rubbed onto a freshly paraffin waxed planer bed did not rub off enough to make a failed glue joint. The same was true for buffed Johnsons Paste Wax.
For finishes I don't ever see a problem. All surfaces I finish never touch anything but sandpaper and finger tips. They would never slide on a waxed surface prior to finishing.

[Todd Brewer]

Would love to see how your version turns out! Are you making any changes to Ron's design? I've had my plans for a couple of months now and am anxiously waiting to build it! I just don't have a way to do the dadoes right now.

I used all 3/4" plywood. The long sides have 5 openings instead of four. I didn't like 24" between supports. They're about 18" on center now. I didn't do the half rabbit/dados. I did full width rabbits/dados. Biscuits to attach the bottom to the frame. I modified it so I will have 1 1/2 " clamping around the perimeter (top is 4' x 8', frame is 45" by 93"). Not a metal fastener in it and it is very strong, but does flex but I have not attached the top yet. Still, I don't expect it to be totally rigid. It is large and does not have a lot of torsion box cross members. We'll see. I'm building it as a single 4' x 8' unit instead of two halves. But I can cut it in two if it proves to consume too much space. I'm going to build my own base/legs. Haven't figured that part out yet. Currently trying to accurately drill the top. 20mm on 96mm grid. I have the "middle version" of the Festool LR32 system. I've made two attempts but accuracy is not 100%. I'm going for my third attempt. Approaching it differently this time. Hopefully, third time is a charm.