Butt joint in long boards

[georgemharris]

Hiya folks,

Long time lurker and reader.

I’ve recently made some kitchen worktops, and had difficulty getting the butt joints totally square and true. I’ve got a set of shelves to make in the same ash timber, and also need to butt joint them as staves to make them long enough (2x 2.5m lengths at 250mm wide, 30mm finished thickness).

I had a good long play around with my processes to try and find the best method for getting a proper 90 cut both side to side and up/down.

I’ve got a beautiful old metabo 250mm induction motored mitre saw, fettled to cut at 90 in test pieces (25mm thick or so soft wood, and in ply panels flipped to test alignment). I’ve also got a newer hitachi 216mm chop saw that’s also bang on 90 in thin test pieces.

The problem seems to occur when I’m cutting thicker bits of timber. The ash worktops I made ended up being 41mm. It seems that it’s the thickness that causes some deflection somewhere. A cut in the middle of a plank, where I pull the chop saw all the way towards me before bringing it down, on the metabo, gives a very-close-to 90 cut, but when done to trim a piece to length, with only a few mm to cut off, the blade seems to deflect and I get a slightly uneven cut (the leading edge is shorter than the back edge).

If I try the gradual slicing method, I end up with a deflection in the middle, giving me a concave cut across the width of the plank.

I also tried using a shooting board with the hand plane, to trim the joint, but the plane bogged down in the ash, (almost full width of the plane blade, so not entirely surprising, and I don’t have a low angle jack plane) and I ended up with a worse cut than off the chop saw.

Does anyone have any suggestions?

I’ve got a SIP 01332 10” table saw, which has a mitre slot and guide, didn’t try that as when I first did a test with it a couple of years ago when I got the machine, there was too much play in the slot to get an accurate 90. I’ve got the sliding carriage, but not fitted it, having no need for cutting boards, yet.

I’ve got a friend who’s got a dewalt radial arm saw, that I could probably borrow and set up, but would like, if possible, a more permanent solution than this...

thanks in advance folks.

 

[Luke Barnard]

Hey,

You could aim to make the faces complimentary rather than each being bang on square. If you have the space either side of the saw, you could clamp both within the blade kerfs distance of each other. Then when you cut through them they should match well even if they are not each perfectly square. Or you could so similar with a router and fence clamped across one of the worktops.

 

[mr rusty]

Yes, router and fence taking a fine finishing cut, or a track saw.

 

[Transit80]

If you want to get the edges nice and straight why not use a straight edge of some kind and a router with a 30mm guide bush and 12.7mm cutter. Measure back from the edge of the board at both ends approx 10-12mm and place your straight edge on the marks and clamp down tight then when you put your router with the 30mm guide bush against your straight edge it will take approx 2-3mm off the edge of the board, take it slowly at around 5mm per cut and you should be OK.
Hope that makes sense.

Chris

 

[Racers]

I do the ends of wooden work tops with a straight edge clamp and a router. You can space the clamp with a sheet or two of paper between it and the router to get a nice fine cut.


Pete

 

[georgemharris]

Many thanks for the replies already!

Just to be clear; I’m not cutting the edges of worktops already prepared.
I’m making worktops/long shelves, from staves. It’s the ends of the staves that I need to butt (flawlessly, ideally) up to each other.

However, Luke’s idea reminded me of the edge jointing method I learned from Paul Sellers; to put both pieces alongside each other in the vice, plane the edges, and then put them together. Any error will be matched by its opposite.

Perhaps I could do this with my table saw, by flipping one stave 180deg so any deviation in cut would be matched by its partner that’s out of phase, so to speak. I’ll have a go at that and see what happens.

...)

 

[peter-harrison]

I would butt join the staves using dominoes or whatever, and then machine the 2.5m lengths. That way it doesn't really matter how square your cuts are (within reason!)

 

[georgemharris]

A

I would butt join the staves using dominoes or whatever, and then machine the 2.5m lengths. That way it doesn't really matter how square your cuts are (within reason!)

Aye, used biscuits, to help align, but it’s not alignment that’s the issue, it’s getting the same level of exact fit as the long joints. They almost disappear, and it looks, to my eyes, a bit lacking in professionalism if the butt joints aren’t as clean.

thanks!
George.

 

[Inspector]

Read up on making scarf joints. You can use a hand plane or if you like noise, a router in a jig. Then you have wood that is joined as one and almost as strong. It is good enough for sailboat masts and wings of airplanes.

Pete

 

[LBCarpentry]

Many thanks for the replies already!

Just to be clear; I’m not cutting the edges of worktops already prepared.
I’m making worktops/long shelves, from staves. It’s the ends of the staves that I need to butt (flawlessly, ideally) up to each other.

However, Luke’s idea reminded me of the edge jointing method I learned from Paul Sellers; to put both pieces alongside each other in the vice, plane the edges, and then put them together. Any error will be matched by its opposite.

Perhaps I could do this with my table saw, by flipping one stave 180deg so any deviation in cut would be matched by its partner that’s out of phase, so to speak. I’ll have a go at that and see what happens.

...)

This is what I would suggest if you wanted the most bang on-ness.

Also, have you ever used filler gel designed for floors?? Works wonders

 

[Racers]

Many thanks for the replies already!

Just to be clear; I’m not cutting the edges of worktops already prepared.
I’m making worktops/long shelves, from staves. It’s the ends of the staves that I need to butt (flawlessly, ideally) up to each other.

However, Luke’s idea reminded me of the edge jointing method I learned from Paul Sellers; to put both pieces alongside each other in the vice, plane the edges, and then put them together. Any error will be matched by its opposite.

Perhaps I could do this with my table saw, by flipping one stave 180deg so any deviation in cut would be matched by its partner that’s out of phase, so to speak. I’ll have a go at that and see what happens.

...)

So its butt joints on the ends of staves.

If you butt the boards together and run a hand saw or circular saw down the gap they will fit together, it’s called kerfing in.

Pete