Best way to machine off one side of a large wood beam, in situ?

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rich1911

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Looking for ideas on how to clean up a large wood beam, in situ, on our house.

It has some patchy rot on one surface due to close contact with rotting wooden cladding boards and lack of ventilation.

The beam is about 3m long and 120cm wide, 120cm thick. The rot has gone in maybe 40mm at the worst point.

I want to 'face off' the front so it's flat and level, removing all the soft wood. Then I can place on a repair piece.

I can't easily remove it to plane it off.

I have made a jig that allows me to run a router along the front of it (holding the router sideways against the beam using a guide bush). This works but I need to make a longer version as at the moment I can only cut 350mm by 14mm on each pass and then I need to move the jig, so its a bit slow.

Another option is to place another beam on the back of it, bolted through and then just chew the rot out of the front of the beam with a burr. Treat it and then leave it rough. I would have to place packing onto it for new cladding boards to go over the top.

Thoughts?

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20220611_165734 (Medium).jpg
 

DBC

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Chisel then buzzer then beltsander would be faster. Maybe paint rot hardener on the bad bits first too.
 

MARK.B.

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Could you just screw/hot glue a couple of battons/lats top and bottom the full length of the beam instead of your jig and then just use the router to remove the material in between ?. If you make up a temporary larger base plate for your router from some ply, then you could remove the lot or the majority without needing to move the battons/lats.
 

Spectric

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The obvious is not always obvious to everyone, improvement and advancement can be achieved through critique. Unfortunately some of my woodworking cockups are way to obvious and I find joining wood is much harder than joining metal.
 

Sideways

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Hmmm.
Metabo paint shaver / planer is a corded tool - effectively a handheld spindle moulder block - that will work right up to an edge and take 0.3mm cuts at a time.
It doesn't sound much but it's a hell of a powerful thing. Just sweep it back and forwards and it will take the surface down in a fairly controlled manner.
Designed for sor stripping paint on flat surfaces, it's incredibly quick and almost too aggressive.
Replaceable carbide tips in case those old nail holes are as bad as they look.

I suggest it mainly because the cutter goes right to the edge of the tool. I can't think of anything that will cut as close to your ceiling.
 

Doug71

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If you have an SDS drill with rotation stop/hammer only you can get wood chisel bits for them which cut through wood like butter and can be surprisingly accurate in use. I use them for things like removing rotten cills from old windows.

Many brands available, but here is a cheap example from Amazon

 

Spectric

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A good weld laid in properly should not require any finishing touches except painting, the only time I have taken a grinder to a weld is to remove one that needed redoing. I suspect that was done with a MIG, it has a very laid on look like a crawling caterpillar rather than a laid in look where the parent metals have been fused with a shallow cap.
 

Valhalla

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Looking for ideas on how to clean up a large wood beam, in situ, on our house.

It has some patchy rot on one surface due to close contact with rotting wooden cladding boards and lack of ventilation.

The beam is about 3m long and 120cm wide, 120cm thick. The rot has gone in maybe 40mm at the worst point.

I want to 'face off' the front so it's flat and level, removing all the soft wood. Then I can place on a repair piece.

I can't easily remove it to plane it off.

I have made a jig that allows me to run a router along the front of it (holding the router sideways against the beam using a guide bush). This works but I need to make a longer version as at the moment I can only cut 350mm by 14mm on each pass and then I need to move the jig, so its a bit slow.

Another option is to place another beam on the back of it, bolted through and then just chew the rot out of the front of the beam with a burr. Treat it and then leave it rough. I would have to place packing onto it for new cladding boards to go over the top.

Thoughts?

View attachment 137572 View attachment 137573
I would make the metal framework wider than the beam and build a cross sled that the router can sit on and traverse the beam from top to bottom (and vice-versa). Something along the lines of my (poor) dwg. The cross sled could be made out of timber which would be both lighter and quicker I would guess.

Cheers
 

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rich1911

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I would make the metal framework wider than the beam and build a cross sled that the router can sit on and traverse the beam from top to bottom (and vice-versa). Something along the lines of my (poor) dwg. The cross sled could be made out of timber which would be both lighter and quicker I would guess.

Cheers
Good idea, but I forgot to say the beam doesn't have parallel sides...
 

rich1911

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How about closely spaced vertical cuts with circular saw and chisel used to knock out waste.
There's nothing to run the saw on. The surface of the beam is not flat. (my fault, I went digging into the rot before I thought more about what I was doing...) I'd still need a jig. But yes, it would maybe be quicker...
 

rich1911

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Welding's a craft skill. You need to know the how and why of it, then do enough of it to build up the dexterity.
He'll get better with practice.
Too right! I am using a very old cheap mig and I just wanted to see if the jig would work...
 

rich1911

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Could you just screw/hot glue a couple of battons/lats top and bottom the full length of the beam instead of your jig and then just use the router to remove the material in between ?. If you make up a temporary larger base plate for your router from some ply, then you could remove the lot or the majority without needing to move the battons/lats.
Not easy as the beam is not parallel. Also I cannot afford to lose too much depth. I need 60mm of depth from the base plate of the router... in the worst place on the beam...
 
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