Workbench Build - a few questions

[PlacidCasual]

Hi Guys

I'm building a basic workbench from a 2.4m by 0.7m sheet of 25mm ply.

I'm using some 75mm square posts for legs with stretchers and I'll be putting 2" by 4" skirt all the way around. So the edges should be good a rigid the trestles whilst not my ideal should do the job adequately. The stretchers should allow me to put in a low shelf.

My queries are around dog holes and support holes in the legs.

Will 25mm ply be adequate for 19mm (3/4") dog holes strength wise?
Also any advice on how to cut such large holes I tried using a 22mm auger in my drill to cut waste out for my mortice joints and it just jammed as my corded electric hand drill lacks the oompf (or my cheap augers are blunt).

Also vice holes and leg holes is 19mm (3/4") the normal size for these if I want to support something vertically in bench vice or use the travel on a tail vice to clamp a large piece on the worktop?

PS thanks for any advice in advance.

 

[Tasky]

Will 25mm ply be adequate for 19mm (3/4") dog holes strength wise?

About as good as the dogs/holes in a B&D Workmate, I should think... Depends how heavily you want to lay into them.
For these and vice-mounting, I'd personally look to laminate up something at least 2" thick from normal timber, but that's just me...

Also any advice on how to cut such large holes I tried using a 22mm auger in my drill to cut waste out for my mortice joints

Thinner drill/auger bit?
Spade bit?
Can you not just chop the mortises with a chisel? It doesn't take long, even in 4" thick wood.... it's kinda fun, too!!

 

[PlacidCasual]

I am cutting the mortises by hand, slowly.

My problem is more making a decent job of the dog holes. Will a Forstner bit take less torque and be clean?

As to worktop thickness I could always bond another sheet of ply or MDF to my worktop.

For the vice heads I’ll make if different wood and decently thick.

Thx for the advice though.

 

[Phil Pascoe]

I don't think you'd gain much with a forstner over a decent auger - both of course won't get you far if they're blunt. If your dog holes are in line you could always reinforce the underside with a 4" x 2" (or 1") rather than a sheet. Think about whether you wish to mount a drill stand, morticer or anything when planning your holes - kill two birds with one stone.

 

[PlacidCasual]

Good point on the 2"by4" a strip under the dog holes might be cheaper and easier.

With regard to mounting things like drills you mean set my holes so I can clamp through to the base?

Are there any goo rule of thumbs for dog hole spacing along there line? Or is it best related to the tail vise travel?

Progress, another mortice completed last night 2 of 6 done. Hopefully complete them all over the weekend.

 

[PlacidCasual]

Hi Peeps

Thanks for all the earlier feedback.

I have finished the build of my workbench now. It has a birch ply top 25mm thick sitting on 18mm OSB to give me a top thickness of 43mm. The apron is 145mm deep and 45mm thick on the front and RHS, the LHS may need adjusting and doesn't have an apron at the moment but the trestles are braced for rigidity. The top is 2.4m long by 0.7m deep. The worktop height is 0.89m.

Overall I'm quite happy with it, I haven't placed any dog holes yet or any vices. I have an old Record 53 (if memory serves) that I plan to fit as a front vice. I'm not planning a tail vice just at the moment. Although I haven't positioned my bench yet I'm concerned I may have made it a touch too wide but I'll see how I get on.

The ply surface is relatively soft would anyone care to suggest how I finish it? I was thinking a varnish of some sort just to harden the fibres of the ply. Although my last project made with birch ply was Osmo wax oiled and that has nice finish.

 

[custard]

The ply surface is relatively soft would anyone care to suggest how I finish it? I was thinking a varnish of some sort just to harden the fibres of the ply.

It's as hard as it'll ever be. In the context of a workbench the choice of finish won't make any difference. Besides, there's an axiom in finishing that says never lay a hard finish over a softer finish or substrate. Finish with something that'll prevent glue sticking, but won't make the surface too slick...or don't bother finishing at all, it's not really a big deal either way.

 

[PlacidCasual]

The birch ply is overall very firm it is just the face layer that seems easily blemished.

I'd been doing a little mooching on the Axminster site and was thinking something like this might be appropriate.
Polyvine Heavy Duty Wood Varnish

Failing that I do have some Osmo oil leftover that has finished other birch ply nicely for me.