Is thick plywood too bouncy for workbench top?

[tomnewby]

I've had a slow morning in the office and have put my time to good use by googling for information regarding workbench tops. Unfortunately I cant find an answer to my last remaining questions.

I know how I want to make my base, but the top has left me confused. The base will be as wide as the top, so that the top is flush with the top stretcher, however it will be shorter to allow overhangs for front and tail vice.

I also know what I dont want.

I don't want to build a solid laminated wood top like the traditional benches. I dont get enough time in the shed to do that. One day I'll get to it.
I don't want MDF or a solid core door with an MDF centre. I plan to use dogholes and being a messy bugger I'm odds-on to spill something and have the thing swell up on me. Also its bloody ugly. I know that doesn't worry some but me it does. Also my "shed" is actually the enclosed (by vertical slats with gaps) underneath of a raised QLD'er, so it gets all the moisture from the humid Brisbane summer.

So what I have been investigating is using plywood. Its stable, good performer with moisture, cheap, and fast to make into a bench top.

Here's the plan. I want to get a 2440 x 1220 sheet of 25mm exterior hardwood ply cut it in half and laminate it. I'll then attach my 9 1/2 inch Record vice and add one further sheet of 25mm (this will allow me to hide the vice bolts/screws).

I figure hardwood will be more durable, exterior version more moisture resistant, and a triple stack of 25mm will give plenty of weight.

The questions I have are:

Would this still be bouncey?? I use mainly hand tools.
Is it possible to attached an apron to the front and ends, to the "side" of the plywood, ie onto the plys?

Any help for those in the know would be greatly appreciated.

Cheers
Tom

[Wongo]

Tom,

I quite like the idea, so you have my approval there. 75mm of ply should be solid like rock, not bouncy. And yes, you can definately attach an apron to the front and ends. Glue or screws will work just fine.

I also like the idea of adding a thin layer of timber on top, say 5mm. It would make the surface a lot tougher. Unfortunately I have never had a chance to explore such idea, maybe you can do it for me.

[tomnewby]

Hmmm.... how would that 5mm on top work? do you mean like a veneer or something thicker, like say 5mm of tas oak or similar?

I dont have the gear to rip that thin or lengths that long so i would have to be able to buy it.

[tomnewby]

For the aprons I was planning to counterbore and use lag screws and glue, and then plug the hole so I have a flat surface.

[Wongo]

Hmmm.... how would that 5mm on top work? do you mean like a veneer or something thicker, like say 5mm of tas oak or similar?

I dont have the gear to rip that thin or lengths that long so i would have to be able to buy it.

It would be good if you could do it. Otherwise, don't worry about it.

[BobR]

You might consider screwing a sheet of masonite over the top. Will make it smooth, protect the ply, and can be replaced when it becomes messy.

[tomnewby]

Thanks Bob,

I might have a look at that option... I'll see how the surface of the ply comes up after I give it some finish. Either way it will be alot better than the particleboard bench top i'm using now. The bench I use was there when I bought the house and is attached to a frame built from 70 x 35 pine framing timber. Its up against one side and the rain comes through the slats onto it and its starting to come apart fast.

Tom

[munruben]

Sounds to me its got the makings of a great bench.

[Wizened of Oz]

Hi Tom
What you propose will make a great bench. I think you could get away with less.
I made a fold-up bench for No.2 son (he has a small shed). It is actually a blatant copy of the folding gateleg bench sold by Carba-Tec. Had to be light enough to fold but still sturdy. It is one thickness only of 19mm ply with 2 more thicknesses 75mm wide laminated around the edges and along the lines of dogholes. A hardwood lipping all around completes it and it has front and end vises.
Bolted firmly to the shed frame it is a sturdy bench.

[GraemeCook]

Hi Tom

75 mm of plywood would be one hell of a benchtop.

You have lost me on one point. You don't like MDF but you accept Bob's suggestion of a masonite skin. IMHO masonite is crappier than MDF, but each to ones prejudices.

I am not convinced that 5mm solid timber would be robust enough for a benchtop - certainly not the way I work. Perhaps a sacrificial 5mm plywood skin would be acceptable?

Cheers

Graeme

[tomnewby]

My thinking regarding 75mm is that I really want to be able to cover the vice bolts. And I think 50mm is sufficient to attach the vice to without causing the overhange to sag.

I guess I could go thinner on the last sheet... perhaps 18mm... I was going to buy two 2440 x 1220 sheets, and use 1 1/2 on the bench top, and then use the rest for a smaller bench i want to make for my thicknesser and eventually a small benchtop jointer (perhaps...) I coudl still do that with a 18mm sheet....

But then I thought.. what the hell!! they always say you should over-engineer your bench.

[Wongo]

Tom, a heavy workbench a good workbench. 75mm of ply is best.

[SilverSniper]

Hi Tom,

Thanks for the PM, I sent a reply before reading your post, and I have some additional comments below.

I too wondered about attaching the apron to the sides of the laminated top (38mm solid core door on two sheets of 19mm MDF). What I did was clamp the bench top in position on top of the carcase, and planed it together with the top rail so that it was totally flush all the way along both sides. Then I glued the two 30 x 200mm side aprons to the laminated top (using Keiberit Pur 501), and then bolted the apron to the top stretchers of the carcase. This seems a bit unconventional, and I was concerned about seasonal movement, but so far, all of the joints have remained tight.

The advantage of doing this, there is no way I will get any sag at either end, where I have my vises. The ends are supported by the 2 30mm x 200mm aprons

I agree that MDF looks a bit better than masonite, but both seem to look ok if they are surrounded by an apron made of halfway decent timber - its the apron your eye will notice, not the benchtop (there are some pics of masonite tops somewhere on this forum that also show this).

As I mentioned in my PM, I expect that one day, my door will wear through or become scratched or dented. When that happens, I will rip off the top layer of ply and replace it with something tougher. So far, its held up fine. I cheat a bit, for messy or rough work, I keep a couple of large nylon chopping boards on the bottom shelf of the bench, and I pull them out and do my damage to them.

If it were me, I wouldn't bother using ply for the bottom layers, MDF is bloody heavy and two layers underneath your top layer might do as good if not better job than the ply (just gut feeling, not a timber expert)

cheers

Tom
Attachment 97359

[bsrlee]

Masonite is MUCH more water resistant than MDF - the 'old time' way of preparing Masonite as wall sheeting was to hose it down all over, let the water sink in, then nail it up to the studs. The wet down & drying made the Masonite taut over the wall studs.

Try the same thing with MDF and it will swell up & go fuzzy, and if it keeps getting damp it will delaminate & collapse.

I'd say screw down a Masonite top layer then give it a coat or two of Polyurethane. When it gets chopped up, just unscrew it, turn it over & use the old sheet to mark the screw & dog holes then screw the new sheet on.

[Malcolm Eaton]

If you are going to use masonite as a sacraficial skin or layer, use tempered Masonite as it is a very hard surface. Masonite comes in standard grade and tempered grade.
The standard grade is quite soft and therefore prone to ware. In the old days when I was on the tools we always used tempered Masonite for the removable layer, it would last for up to 1 or 2 years dependant on the abuse.
Mac