Joining boards for a workbench top

[Cliff Rogers]

G'day.

I am building a workbench out of Kwila & would like you opinions on joining the boards for the top.
They are 240mm x 45mm & it will have a 90mm x 45mm back board edge up across the back & another 240mm x 45mm apron across the front.
The plans say to just glue it & clamp it but I'd like something a bit stronger than that.
I could dowel it but I have an AEG plunge router that takes 1/4" bits &, althought I haven't used it very often, I have seen an idea in a book the shows a slot cut in both edges & a spline glued in place.
I understand it is also possible to buy a bit that makes a series of grooves on each edge that then fit together.
I know that it is also possible to cut a tongue & groove but I don't want to loose any width across the boards.

Thoughts/recommendations anyone?

What bits should I buy?

I would also like to use the router to clean up the end grain across the ends of the bench once it's complete.
I understand that a spiral bit would be good for this.
Given that the boards are 45mm thick & I only have a 1/4" router, will this work or will a long 1/4" bit flex too much?

I look forward to hearing from you.

[Rocker]

If you use wide boards for your bench top, you may have problems with the top cupping. Quality bench tops are usually made from laminations about 40 mm thick glued together with the grain running verticallly to minimise this problem. However, if you are not bothered by the possibility of cupping, you could use wide boards.

I don't think you need to be unduly concerned about the strength of the glue joint so long as the edges of the boards have been properly planed so that they fit closely together without any gap. Certainly if you added 3 or four 12.7 mm dowels the joint should be plenty strong enough.

I doubt whether a 1/4" router would be suitable for trimming the ends of boards 45 mm thick; I suggest a belt-sander, or else just a sanding block and a bit of hard yakka.

You might also consider the possibility of not gluing your wide boards at all, and leaving a 60 mm wide gap between them. My bench top is like this. The gap is useful since it allows you to use clamps in the middle of the top to clamp wood to the bench top.

[Stuart]

Double row of biscuits- similar principle to the groove & spline, but isn't continuous, and much easier, and much stronger than dowel. All other considerations aside- trying to break a double biscuited joint requires a sledgehammer, and even then it is a likely that the wood in the vicinity of the joint will fail as much as the glue line will split. And you won't loose any of your board width.

[dazzler]

Hey Cliff

Do you have a pic of your finished bench?

cheers

dazzler

[Paws]

I was told not to use dowels when joining together boards because when the timber moves it can use the dowels to break the glue joins. That made sense to me so I always use biscuit when joining boards. These add strength and also help align the boards when you glue together. If you do make your own biscuits I would make them out of ply rather than timber in case the timber was too expand or contract too much.

I can't explain this next bit properly but to avoid your bench top cupping too much I would make sure that when you first lay out the timber for your bench top you check out your end grain and alternate circle up, circle down, circle up etc. That will even out the cupping over the width of the top but not if individual boards cup.

I think it would be possible to trim the ends with your router. I haven't used a spiral bit before so cant comment but if you cut down from one side as far as possible you could then turn the top over and use a flush cutter bit to remove the rest of the waste.

[martrix]

Double row of biscuits- similar principle to the groove & spline, but isn't continuous, and much easier, and much stronger than dowel. All other considerations aside- trying to break a double biscuited joint requires a sledgehammer, and even then it is a likely that the wood in the vicinity of the joint will fail as much as the glue line will split. And you won't loose any of your board width.

I just glued up a top for a workbench out of 50mm thick Vic Ash using a double row of biscuits.:;

[Wild Dingo]

I dont know about that Paws... having used both dowels and biscuits for a joining boards I would RECOMMEND the use of dowels over biscuits anytime... the lining up of the boards with dowels is far better without any slop that can be had with biscuits and the dowel can be as deep or shallow as you like thus I THINK offering a greater amount of strength and better join than biscuits.... in fact IMO (In my opinion for what tis worth) one has far better control and the joining forces are better with dowels

Example... Jarrah table I made 18 years ago using dowels is still going strong while another Jarrah table I made less than 6 months ago using biscuits has come apart... now as a note on this one the factor most contributing to its pulling apart was the temperature variations within the house that the table lives in... these are pretty extreme... but that being said the first table has lived in homes from Carnarvon to Bunbury to Broome and in storage containers and sheds so its experienced major temp variations as well... but its still in one peice... this is but one example

The only time I will now use buscuits when joining boards is when I get to damned lazy to turn some dowels.

This is solely my experience others will differ of course... I only know what Ive experienced.

And if you want to go a double row of biscuits that would probably work too :doh: I just find them inadequate and dowels better just me I guess :roll:

[Paws]

Dingo, I agree that joining boards with dowels will add more strength and align your boards better, but I am about 90% convinced by the logic of what I was told, and also have a lot of respect for the person who told me. I get frustrated when using biscuits due to the slop in the holes cut but I get even more frustrated when my dowels don't line up, or the holes are crooked despite using a jig.

When I think about it I would guess that a laminated bench top would be more likely to come apart due to the temperature of its environment, the timber not being properly seasoned, it not being correctly secured to its base or a poor join between the boards to start with, rather than the use of dowels or biscuits. But I could very easily be wrong!

[Lignum]

I was told not to use dowels when joining together boards because when the timber moves it can use the dowels to break the glue joins. That made sense to me so I always use biscuit when joining boards.

Paws you are 100%correct. Talk to anyone who has restored/repaired old furniture and the number 1 problem is dowell joint failure but its mainly when end grain / long grain is concerned. Long againsed long isnt a problem because dowels and biscuits dont do much for strength.

The main problem is the orentation of the grain. When people use dowels they just insert them at random. When expansion takes place the cell takes in water and the cell wall compresses, when contraction happens the water leaves but the compressed cell wall means the cell is slightly larger and thay cycle takes place over and over. Unless its pure luck if you fluke good orentation, over time that extra compressin and collaps weakens the join. Tenons, biscuits and even dominos all move together beter. they still need matching if you are fussy, but generaly are more tolerant.

And for what its worth Cliffie :wink: i wouldnt even bother with any of it. A good quality glue just but joined (long grain to long grain) is just as strong as any dowel, biscuit or even domino:D

[rona]

Cliffy,
Have been reading above suggestions re joining your bench top. The 12 years I worked as a builder was divided into two areas, 3 years building houses from start to finish, and the remainder of the time, 9 years I was in the joiner shop making all types of joinery from windows, cupboards, entrance doors, tables chairs, church pews, notice boards, etc. Now in all that time I never used dowel joints I dislike them intently, they very seldom line up correctly, they break ,there is always one that is too long, etc Biscuits i have never used, so can't comment. We used to cut feathers of 3ply, or even 5 ply then put a saw cut(for the full length of timber) in each piece of timber to be joined (approx 1 inch or so cut in each board, feather 2 inches), then alternate the timbers so the grain went up and down to stop cupping, then glue firmly together. When I was teaching for 25 years, I applied the same rules with students and apprentices. I realize that what i was doing was not the 'norm', however I had very little trouble over the years with this method.

Regards,
Ron.

[martrix]

And for what its worth Cliffie :wink: i wouldnt even bother with any of it. A good quality glue just but joined (long grain to long grain) is just as strong as any dowel, biscuit or even domino:D

Agreed. But for me 99% of the time I will always use biscuits when joining/laminating boards. Mainly because I find them quick to machine and I don't have to worry about alignment of the boards when clamping. There is nothing worse than stuffing around getting boards etc level while clamping when you have very limited open time with yellow glue.
Its one less thing to worry about.

[Groggy]

Read the date folks, Cliff has probably rebuilt it (twice) by now :doh:

[Lignum]

Who has time to read dates:? He can just build another one:rolleyes:

[martrix]

Read the date folks, Cliff has probably rebuilt it (twice) by now :doh:

I knew that:C ...not:-


Who has time to read dates:? He can just build another one:rolleyes:

Yer Cliff, show us your benchtop. Should have it done by now!:q

[Paws]

Well if he has finished his bench by now I'd like to know what method he used to laminated the top and whether it has stayed in one piece!

[Cliff Rogers]

I'm back, phones & internet have been off for a week, what did I miss? :?

I'll get some pics on the weekend, it still doesn't have the vice in it yet? :rolleyes: