how to secure sacrificial MDF?

[matmac]

Hi
I've made the base for a work bench and i have a solid top to go on and then i want to put a sacrificial piece of MDF on, but i don't want any pieces of metal on the surface so screws and nails out. Any idea's will be much appreciated thank you.
Matt

 

[marcros]

I would suggest double sided tape.

 

[Grahamshed]

Double sided tape was my first thought as well.

 

[CHJ]

For ease of removal I would use counter bored screws and flushed MDF plugs.

 

[Hitch]

How about counter bored nylon nuts and bolts? Then if you should catch it, minimal damage should occur....

 

[adidat]

For ease of removal I would use counter bored screws and flushed MDF plugs.

i did this and just filled up the voids with hot glue gun and then pared them flush

adidat

 

[AndyT]

If you want the top to be easily removable in future, glue or sticky tape would not be good.
You could use long screws up from underneath the solid top, measuring carefully so that they don't come more than two thirds of the way up into the thickness of the MDF.

Another way would be to place your MDF in position, then drill strategically placed 8mm holes, and glue dowels down through the MDF into the layer below. When the glue has dried, cut them off flush. I don't think they will spoil the appearance too much!

When you want to replace the MDF, just drill out the dowels from above and the top will lift off ready for the replacement.

Yet another idea would be to put a strip of wood along each of the four sides, as deep as the combined thickness of the solid top and the MDF, and then screw through it horizontally into both layers.

 

[Phil Pascoe]

Use counterbored brass screws - any damage would be minimal if you did hit them.

 

[Benchwayze]

Hi Matt,

If you really must cover a nice bench-top with MDF, then make the top out of MDF full-stop.

But if you really want a sacrificial sheet, make it 18mm oversize all round.

Screw 18mm square battens along the underside of each edge of the MDF. (No need to have them full length.)
You can then drop the MDF board in place and it will be held by the battens against the bench. You can remove it at will.

This will enable you to have the MDF there when you are using any liquids that might stain or damage the top, but you will be able to see your nice new bench when you are using tools. You'll soon learn to avoid serious dings and/or nicks, by always using a cutting-block when chopping out, and a square of scrap under your bench hook when sawing. You could even screw a square sacrificial 'plate' to your bench-hook.) It's just a case of remembering to do these things. A bench is made to be worked at, not just gazed upon.

It isn't for me to tell you how to approach woodworking, but I try not to be too uptight about my bench-top, whilst at the same time having due respect for it. So whilst I try to be careful, I don't mind the occasional little ding. (Yes I know the first few will hurt; But only your pride. Not the bench!)

It works for me...

HTH

 

[adidat]

Hi Matt,

If you really must cover a nice bench-top with MDF, then make the top out of MDF full-stop.

But if you really want a sacrificial sheet, make it 18mm oversize all round.

Screw 18mm square battens along the underside of each edge of the MDF. (No need to have them full length.)
You can then drop the MDF board in place and it will be held by the battens against the bench. You can remove it at will.

This will enable you to have the MDF there when you are using any liquids that might stain or damage the top, but you will be able to see your nice new bench when you are using tools. You'll soon learn to avoid serious dings and/or nicks, by always using a cutting-block when chopping out, and a square of scrap under your bench hook when sawing. You could even screw a square sacrificial 'plate' to your bench-hook.) It's just a case of remembering to do these things. A bench is made to be worked at, not just gazed upon.

It isn't for me to tell you how to approach woodworking, but I try not to be too uptight about my bench-top, whilst at the same time having due respect for it. So whilst I try to be careful, I don't mind the occasional little ding. (Yes I know the first few will hurt; But only your pride. Not the bench!)

It works for me...

HTH

whilst a good idea John this could be rather problematic when it comes to using the vice (depending on how your vice is set up)

adidat

 

[Hudson Carpentry]

My way would be battens as edging around the sides of the top of the bench which then allows you to slip a piece of MDF on the top. If the edging is built into the bench any vices wouldn't be affected.

 

[paulm]

My way would be battens as edging around the sides of the top of the bench which then allows you to slip a piece of MDF on the top. If the edging is built into the bench any vices wouldn't be affected.

Yep, ditto, did that with my bench, raised lipping all round and lay in a sheet of thin ply, mdf or whatever, works great.

Cheers, Paul

 

[Benchwayze]

:mrgreen:

Hi Matt,

If you really must cover a nice bench-top with MDF, then make the top out of MDF full-stop.

But if you really want a sacrificial sheet, make it 18mm oversize all round.

Screw 18mm square battens along the underside of each edge of the MDF. (No need to have them full length.)
You can then drop the MDF board in place and it will be held by the battens against the bench. You can remove it at will.

This will enable you to have the MDF there when you are using any liquids that might stain or damage the top, but you will be able to see your nice new bench when you are using tools. You'll soon learn to avoid serious dings and/or nicks, by always using a cutting-block when chopping out, and a square of scrap under your bench hook when sawing. You could even screw a square sacrificial 'plate' to your bench-hook.) It's just a case of remembering to do these things. A bench is made to be worked at, not just gazed upon.

It isn't for me to tell you how to approach woodworking, but I try not to be too uptight about my bench-top, whilst at the same time having due respect for it. So whilst I try to be careful, I don't mind the occasional little ding. (Yes I know the first few will hurt; But only your pride. Not the bench!)

It works for me...

HTH

whilst a good idea John this could be rather problematic when it comes to using the vice (depending on how your vice is set up)

adidat

This is true. It would need a false set of jaws maybe, to keep the top of the vice level with the surface of the sacrificial sheet. However, as I don't cover my bench when I am working with tools, the problem doesn't present itself. :wink:

BTW: My battle-scarred old bench is undergoing renewal, so I have offered it to the bonfire for the jubilee beacon lighting! :mrgreen:

 

[baldpate]

In my experience (I put a thin mdf sacrificial surface on a bench - 4mm mdf) it doesn't take much to hold the sacrificial surface to the bench top against overall lateral motion - if the underlying top is flat, you have the whole pressure of the atmosphere holding it down! I think the same would be true of thicker mdf sheet, if that is your intention. I used small, countersunk brass screws around the edge of the bench - and I probably used more than necessary for this purpose. When I made the bench, I was also concerned about the sacrificial surface being pulled upwards when extracting bench dogs; but in practice I haven't found this to be a real problem (see comment below about distortion, though).
I must say that I have subsequently found that thin mdf is less than ideal. It's not very resistant to abuse. Two or so years on the surface is looking rather sad - stained, battered and generally somewhat dog-eared. When I eventually replace it, I shall try to source some oil-tempered hardboard, preferably slightly thicker (5/6 mm ?). Failing that, I'll use thicker mdf and treat it with yacht varnish (something I've done successfully to the existing surface as a remedial measure).
The other issue I found with mdf sacrificial surface is that after a while you get a raised rim around the most-used dog holes - the result of lateral pressure against the bench dogs and hold-downs. That's because I drilled the dog holes after applying the surface layer, so the holes in the sacrificial surface were the same diameter as the hole in the main bench below; thus the dogs/hold-downs bear sideways against the surface layer, so distorting it. You end up with little raised bumps, which are annoying. I subsequently enlarged the holes in the sacrificial surface by a few mm all round , so that any 'bulging' sits well below the table surface. Worth considering from the outset.