Cutting a tight curve on a thick bit of wood, with a bandsaw.

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rich1911

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I have to make 4 replacement ends for roof joists.

They are 175mm high, 100mm wide, so quite chunky.

This is the profile:

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Not sure if my Record bandsaw would make a 100mm cut. I tried a bit of 20mm and it can cut this profile but the tight corners had to be done in a few nibbles. I guess a narrower blade might help.


I'm not sure if I should try and get some 175x100 wood from the timber merchant and have a go, or cheat a bit and cut some 20mm planks and glue them into a stack of 5 for each joist end!

I have 4 of these to do.

Any suggestions welcome!
 

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A narrower blade should work. Can't remember of the top of my head but ,there are listings of what radius cut you can achieve with various widths of blade. There are even some blades that have serrations on the back edge to allow you to get round a tighter radius - not sure how good they are, having never used one :unsure:

Failing that, use a template and go in from each edge with a router cutter to give crisp edges. You can then take out any fillet that might be left in the middle with the bandsaw or some sort of pad-saw, before cleaning up.
 
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What model of Record bandsaw ? It is the number of teeth, blade width and blade material that need to be correct. You could give Tuff saws a ring for blade advice and at least you are then on track. Do not use Record blades as they are really brown stuff .

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I don't really want to depress the OP but it will need a fairly hefty saw to do that in a sensible amount of time.A pilar drill would probably be the sensible way to get the notch at the bottom of the image and then saw in from the outside to join the profile.It looks almost inevitable that there will have to be several relief cuts from the outside to very close to the line and the removal of the waste in stages.Hoping to get around that curve without the bottom edge wandering might just be possible,but I wouldn't count on it.I would be happy to get quite close and then clean up the shape on my bobbin sander.Lacking a bobbin sander,it can still be done but it will take longer.Which also applies to gluing up several boards and waiting for the glue.

The advice to use a router for the cleanup may be a good path to follow.I have seen the common 1/2" worktop trimming cutters at a good price and used from each side,you could bet a good result it the template location was precise.I would still hope to remove as much waste as possible with the bandsaw.
 
Well I found a narrower blade for my saw and tried a cut into the old wood. Went through it a lot better than I expected and made tighter bends of course.

The machine is a RSBS12 so quite small. Blade looks to be about 6 TPI.

I have a length of 175x100 on order so I'll give it a go soon.

It's right up on the roof so doesn't have to be super clean. I've got a bobbin sander which will help tidy the cuts up a bit...

I'll give it a go and see what happens!

Thanks for the info.

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I would draw it out and find the largest drill bit to cut out the big rad then it should be simple cuts on the bandsaw to finalise then clean up.
 
you just need the right blade, I'd do it with a 14tpi thin blade like 1/4" should cut through it no problem, ideally tuffsaws blade.
 
I agree with Phill, This is a simple profile, don't make it difficult on yourself.
Remove the bulk of the wart with the proper sized drill bit first, The remainder of the waste can be taken care of wit a series of small strait cuts. Finishing with a router and template would give the best finish results.
Just my opinion
 
the above swinging a big joist around would be a huge pain. use a 30mm Bush or a deep profile bearing guided template bit and a jigsaw for taking off the bulk.
 
I'm not surprised that a 6tpi blade works.I use them up to about 7 inches thickness.Too fine tends to clog and make slow progress.I confess to being startled by a recommendation for 14 tpi as I have gummed up 8tpi in 4 inch thick timber and would expect it to be more severe with finer teeth.
 
I would be expecting you need to use something with at most 6TPI for that sort of thickness. I’d be very surprised if a 14TPI didn’t end up just burning.

I get my blades from tuffsaws and Ian there gives outstanding advice if you contact him by email. There is a guide on the axi website as to TPI for different thicknesses, and I think there’s a pinned post in the general woodworking forum here on blade suitability which has a helpful spreadsheet thing on
 
I cut several 8cm thick, 13 cm wide discs in sweet chestnut using a Basa 1 which is about the smallest you can get. As everyone else has said, use a narrow blade with few teeth and take it slow.
 
Sharp/ new blade is key. I have done similar decorative ends with a long Bosch jigsaw blade, not perfect but plenty good enough for a roof and bringing the tool to the work is a lot easier than a big piece on a band saw.
 
I had some intricate porch supports made in 2.5 inch wood a few years ago, and they were cut entirely on a hugh band saw by a pattern maker at a local foundry. They had the right tool and a skilled man, it cost me very little.
 
Hi again, thanks for the tips! Just to clear up the 'swinging a joist about', yes its for a joist, but the ends of the joist were rotten so I have already cut them off. I'm just replacing a 200mm long section right at the end of the joist where is pops out under a dormer. It's not supporting anything at this point.

So doing it on the bandsaw would be fine.

I'll have a go at one this weekend hopefully....
 
These canopy supports were cut on a bandsaw from 2 1/2" pine and didn't need a touch of sanding or further shaping, but they were done on a huge bandsaw with a blade like a G string by a foundry pattern maker.
porch.JPG
 
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