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Machining large stock for pergola Knee brace.

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Markvk

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Hi All,

Long time no post! Im building a pergola in my garden. Its a fairly chunky construction. Im using 125mm posts and double rafters for the construction. I want to make some decorative Knee braces to fix to each post which will slot between the rafters fixed to each side of the posts.

This means that the stock for the brace will be 125mm wide on the decorative/shaped face. I was planning on making a template and using a bearing cutter on my table router, but the longest cutter i can find is 50mm ideally i need a 75mm bearing cutter , but i cant find one.

The alternative would be to machine it in 2 halves and glue them together but its more time and hassle. does anyone know where i can buy a 75mm cutter or have any suggestions how i can efficiently make the braces that ive described?

Thanks in advance for your help.
 

Sgian Dubh

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use a bottom bearing on the template then a top bearing on the previously routed curve
Surely that has to be impossible? If the part is 125 mm thick and the template sits on the face that's 90º to the 125 mm thickness then the only option is to use a top bearing bit to follow the template, and to rout from one side, then move the template to the other side and repeat.

In any case, I don't think this is a cut I'd try to do with an inverted router in a table because you're generally committed to trying to take a full 75 mm long cut in one pass with that cutter from Wealden. I'd prefer to use a guide bush arrangement which could be set up for an inverted table router. But a guide bush lends itself readily to a hand held plunge router fitted with one used with a template offset from the required profile, and using that 75 mm long cutter. That way you can plunge a bit at a time until you get to the maximum depth of cut possible. If necessary, the final cuts to reach a bit left at the mid-point could be achieved by removing the guide bush and using the profile already cut in the wood as the template for the cutter's top bearing. Slainte.
 

Cabinetman

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Richard, he said it was the decorative side that was 125 mil wide, personally I wouldn’t do it with a router at all, I would cut out the profile on the bandsaw and as it’s for the garden I would use sanding disc machine and the bobbin sander. Ian
 

johnnyb

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surely its (thin) template on the bottom rout then top bearing along the routed profile. bandsaw to within 1/2 mm of the profile. to me a better way would be with a template and a follower slightly in front of the bandsaw ala brian boggs.
I've made loads of round and shaped windows using a table router in 3 inch stuff. just use spiral bits and go steady and careful.
 

Inspector

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Richard, he said it was the decorative side that was 125 mil wide, personally I wouldn’t do it with a router at all, I would cut out the profile on the bandsaw and as it’s for the garden I would use sanding disc machine and the bobbin sander. Ian
I would almost do the same up to the point of sanding. I would smooth the surface with a spokeshave and scraper in the areas the grain is difficult. I could see using the router if you had dozens to do but for 8 or so the hand tools would suffice.

Pete
 

Markvk

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Hello gentlemen.

it was my intention to use my bandsaw to remove most of the material and then finish with the template cutter. ideally i need a top and bottom bearing cutter 75mm.

i got the idea from this video,


i just need to find the cutters, i will call wealdens on Monday. I have 32 to make some im looking for speed BUT SAFE! If i cant find a top bearing cutter then ill think about making a box jig an just reverse the work on the router table
 
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Inspector

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You do have the option of using a guide bushing in the router base. There are long cutters made for milling machines with 100mm cutting edges that could be used in a beefy router with care. You would want a HSS 2 flute slot cutter for aluminium. Light cuts with multiple passes.

Pete
 

Markvk

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You do have the option of using a guide bushing in the router base. There are long cutters made for milling machines with 100mm cutting edges that could be used in a beefy router with care. You would want a HSS 2 flute slot cutter for aluminium. Light cuts with multiple passes.

Pete
Thanks for that Pete, if i understand what you are suggesting, i would need to make up a box template, and the turn the work over and machine from top/bottom edges? The same process as using just a bottom bearing cutter?
 

Sgian Dubh

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Richard, he said it was the decorative side that was 125 mil wide, Ian.
Are we in agreement, or disagreement, Ian? As I understood it he's looking to create something like a decorative knee brace or corbel type form with curves and steps across material that's 125 mm thick, something similar to the image/video link Markvk put up in a later post, see below.

I was assuming the bulk of the waste would or could be removed with a bandsaw, with the router used essentially for cleaning most of the job up. Slainte.

 

Cabinetman

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No, you’re right Richard I reread what he said and I had misunderstood, anyway I still wouldn’t use a router ha ha. After all it is only for the garden and a Bobbin sander would deal with that no problem.
 

Markvk

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No, you’re right Richard I reread what he said and I had misunderstood, anyway I still wouldn’t use a router ha ha. After all it is only for the garden and a Bobbin sander would deal with that no problem.
But i dont have a bobbin sander...... But i do have a router 😜
 

Sgian Dubh

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surely its (thin) template on the bottom rout then top bearing along the routed profile. bandsaw to within 1/2 mm of the profile. to me a better way would be with a template and a
Ah, johnny, now I think I see why I misunderstood you. You seem to have reversed the terminology I'm used to for bearing guided router bits.

The description 'top bearing bit' is normally given to bits where the bearing is nearest the cutter's shank, the part that goes into the collet, commonly described as something like a top bearing flush trim bit.
And the descriptor 'bottom bearing bit' generally applies to a bit with a bearing at the exposed end of the cutter, i.e., furthest from the collet, and commonly described as a bottom bearing flush trim bit.

I apologise if I've got your meaning wrong. Maybe I'm just being dense. Slainte.
 

Sgian Dubh

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No, you’re right Richard I reread what he said and I had misunderstood, anyway I still wouldn’t use a router ha ha. After all it is only for the garden and a Bobbin sander would deal with that no problem.
If it's a one-off, I agree a bandsaw and a bit of chiselling and sanding (bobbin sander or not) would suffice. But if there are several I'd go with a router, as I described earlier. But I do have a lot of router experience and know how to set up for safe operation, in both hand-held and inverted in a table mode. A 75 mm long cutter used at its maximum length is not one to mess around with in either set up if you're at all unsure of what you're doing. I've no idea how experienced and confident Markvk is with router set up and use. Approach this routing task (if you decide to go with it) with great care Mark if you're not very experienced around routers. Slainte.
 
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