How do you cut a narrow slot in timber?
Discussion
I am trying to make a garden pergola/shade frame thing to go over a patio. I want to use some of these post feet to attach it firmly to some concrete I've put in the ground. A timber company suggested they could cut the 8mm-wide slots required for this, but on giving them more details, they've said they can't do it. I also wanted to use some of these timber frame beam hangars for the horizontal pieces to make it aesthetically pleasing, but they give me the same issue of needing a 6mm slot in the beam.
I've considered a router, but can't find long enough bits to get the depth required (approx 60mm cut depth to get a cut across a 125mm post (cut from either side)). I can't think of another method that will give the accuracy of cut required. I've considered using two pieces and then sandwiching the metal piece between them, but then how to you cut the recess to accept the metal 'blade'? How does it get done 'properly'?
I've considered a router, but can't find long enough bits to get the depth required (approx 60mm cut depth to get a cut across a 125mm post (cut from either side)). I can't think of another method that will give the accuracy of cut required. I've considered using two pieces and then sandwiching the metal piece between them, but then how to you cut the recess to accept the metal 'blade'? How does it get done 'properly'?
Multi tool to cut the sides and chisel out the middle?
https://www.screwfix.com/p/dewalt-dwe315sf-gb-300w...
https://www.screwfix.com/p/dewalt-dwe315sf-gb-300w...
You could do it with a mortice chisel:
https://www.amazon.co.uk/Narex-NAR811208-Premium-M...
https://www.amazon.co.uk/s?k=mortice+chisel&cr...
https://www.amazon.co.uk/Narex-NAR811208-Premium-M...
https://www.amazon.co.uk/s?k=mortice+chisel&cr...
Prawo Jazdy said:
How does it get done 'properly'?
The whole post is laminated! Prior to gluing and screwing the post together, you make a 3 or 4mm rebate at the end of the post to accommodate the bracket. Easily done with mere hand tools.The other advantage of a laminated post is there's less chance the wood will "move", over time.
Obviously not much help if you've already bought the timber.
Drill some holes with a bench drill.
Join them up with a saw?
It might be an idea to rout shallow slots both sides of the post, then join the slots with a handsaw.
That might ensure the slot ends up in the right place?
The 'Dave' method might be to heat the bracket red hot then introduce it to the post.....
Join them up with a saw?
It might be an idea to rout shallow slots both sides of the post, then join the slots with a handsaw.
That might ensure the slot ends up in the right place?
The 'Dave' method might be to heat the bracket red hot then introduce it to the post.....
Prawo Jazdy said:
I've considered using two pieces and then sandwiching the metal piece between them, but then how to you cut the recess to accept the metal 'blade'? How does it get done 'properly'?
A third, 8mm bit of wood sandwiched between the two pieces where the blade isn't? Glued and bolted, it should be strong enough, but might not look as pretty as a single piece.If you don’t have too many to do and don’t want to go mad buying power tools, a rip saw and mortise chisel will do the job. If you want to go down the power tool route a 1/2 router and carbide, plunge, up cut bit will do the job. A 1/2 router with a 75mm plunge capacity will give you the ability to handle 150mm, coming from both sides, irrespective of the length of the bit. Other more spendy options are are a bench Morticer and chain morticer.
KTMsm said:
For a Pergola - I'd be using a chain saw
If you don't have access to a suitable bandsaw then this is the way to do it.With a bit of care you can do quite a tidy job. Use a square to mark out the slot accurately all round and then cut each face individually by holding the saw at the right angle. You can then join the cut faces to get the slot nice and accurate.
Practice on an offcut first.
Thanks for such a bunch of useful replies. I haven’t bought the timber yet, so I could potentially get laminated timber, but I might end up wasting a load more time trying to CAD what I want in order to get a quote, and then discover it’s prohibitively expensive, what with being bespoke parts?
The post foot I linked wasn’t actually the one I bought - just identical in principle, but I can’t see any installation instructions. Where did you find that?
A deep cut router bit was mentioned, but the narrowest I can find is 9.7mm. I can borrow a decent 1/2” Makita router, and have tested the idea with a 9.7mm bit (only cutting a shallow slot though, as it was only a 20mm bit), and it seemed like a tighter fit is needed. If anyone can point me to a deep 8mm and 6mm bit, I’m all ears! I assumed they didn’t make them because they might snap really easily. The router has a 1/2 to 1/4 reducer with it if that helps.
Failing that, the “rout as far as you can and then saw/drill/chisel the rest” might be the way I’ll have to do it. I’ll have 12 to cut in all, so that could get really tedious…
Thanks again for all the suggestions.
The post foot I linked wasn’t actually the one I bought - just identical in principle, but I can’t see any installation instructions. Where did you find that?
A deep cut router bit was mentioned, but the narrowest I can find is 9.7mm. I can borrow a decent 1/2” Makita router, and have tested the idea with a 9.7mm bit (only cutting a shallow slot though, as it was only a 20mm bit), and it seemed like a tighter fit is needed. If anyone can point me to a deep 8mm and 6mm bit, I’m all ears! I assumed they didn’t make them because they might snap really easily. The router has a 1/2 to 1/4 reducer with it if that helps.
Failing that, the “rout as far as you can and then saw/drill/chisel the rest” might be the way I’ll have to do it. I’ll have 12 to cut in all, so that could get really tedious…
Thanks again for all the suggestions.
speedking31 said:
Liamjrhodes said:
Would a circular saw not work? Cut lots of lines close to each other then chisel out the rest
The post base you linked to literally has this method in the installation instructions. Just make sure you bolt the feet down before attaching the posts 
Circular saw, or if the OP has a table saw that would be even easier.Out of interest, are you wanting the slot all the way through the wood so as leave the bracket exposed on each side or for a hidden pocket to completely conceal the bracket "tongue"?
I've used almost identical brackets on a couple of similar projects and like I said earlier did a pretty clean job with the chainsaw.
It's also worth pointing out that the brackets provide very little racking strength to the structure; there's a lot of leverage on the small unbraced metal tongue so there's no real requirement for a tight fit - they really only locate the post base and provide resistance to uplift. This then means the structure obviously needs to be braced and rigid in it's own right unlike most traditional builds where they sink the post in concrete.
I've used almost identical brackets on a couple of similar projects and like I said earlier did a pretty clean job with the chainsaw.
It's also worth pointing out that the brackets provide very little racking strength to the structure; there's a lot of leverage on the small unbraced metal tongue so there's no real requirement for a tight fit - they really only locate the post base and provide resistance to uplift. This then means the structure obviously needs to be braced and rigid in it's own right unlike most traditional builds where they sink the post in concrete.
Edited by Snow and Rocks on Wednesday 24th July 23:19
jardinec said:
Circular saw cutting half the post depth from both sides should work.
If the kerf of the blade is not wide enough (it might be) then multiple cuts.
This would be my thoughts. Maybe a panel saw to square the last half inch out by hand afterwards.If the kerf of the blade is not wide enough (it might be) then multiple cuts.
Or use a difference base!
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