# Half-round concave cut on a curved 2x8 semicircle



## Roberto1 (Aug 31, 2006)

Long post.
Hi, this is my first post and its a doozy. 
I'm converting a coverall building with the galvanized steel ribs into a greenhouse. I want to cut gussets for the ribs at the eaves where presently the rib is formed into an arc with a radius of about 8-10 in. The gussets would be cut out of a 2x8 or 2x10 material. The Idea is to conform on the inside with an arc and then extend the roof and wall lines till they intersect out over the arc making the roof and wall meet at the pitch angle.
I can cut the gussets OK on my bandsaw but I would like to router(?) the edge all along the arc to make it fit snug onto the top of the rib. This would mean I'd have to concave the arc of the gusset with a half-round profile to fit down over the round (top) of the rib.
I hope this makes sense. A simple diagram here would work wonders but I don't know how to get a diagram into the post, maybe I should draw it up, scan it to a file and attach it somehow. Can anyone enlighten me here? Just a shot in the dark.
The concave along the inside edge of the gusset would have to be a 3/4 in. radius or 1-1/2 in. half round.
Thanks .....Robert.
[email protected]


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## bobj3 (Jan 17, 2006)

Hi Robert

"A simple diagram here would work wonders" = yes it would. 
Also a picture(s) is worth a 1000 words... 
Just make the diagram then save it and then upload it to the forum same thing for a snapshot or two 
Just select edit on your post,then hit the item called Manage Attachments, then select the files you saved or snapshots and the up loader will do the rest.

Download Paint.net it's free and will let you draw a simple diagram. 

http://www.majorgeeks.com/download.php?det=4548

Paint.NET is image and photo manipulation software designed to be used on computers that run Windows XP or 2000. Paint.NET is jointly developed at Washington State University with additional help from Microsoft, and is meant to be a free replacement for the MS Paint software that comes with all Windows operating systems.

The programming language used to create Paint.NET is C#, with GDI+ extensions.

Paint.NET has many of the powerful features that expensive commercial applications have, including the ability to use layers.

This is the second semester that Paint.NET has been a project at Washington State University, and we have the goal of adding as much functionality as expensive commercial applications provide, but of course, for free!

Bj


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## labric (Sep 11, 2004)

Robert

I notice that you haven't yet been able to post a picture of your dilema and that you haven't got an answer to your problem.

I think I understand your problem and suggest that you need to think outside the box, or board, in this case.  

Instead of trying to accomplish the answer with one piece of wood gusset, the problem can quite easily be solved using two pieces as follows.

Firstly, cut 2 blanks of 2 X 8 nominal to the identical size, then temporary attach the two pieces together using long wood screws in areas that you will not be cutting into. Put a mark on the inside of the piece to indicate the two inside faces before attaching them together.

Next, cut the arc profile on your band saw on the 4 X 8 nominal blank. Now remove the temporary screws from the gusset. Both pieces will now be matched with the same cutting irregularities and identical profile and are now ready for routing.

Chuck up a 3/4" cove bit with bearing in your table top router and route along your arc on the inside face of the half gusset. Route the two pieces in a least 3 passes to the overall height of 3/4 +/- " height .

When routing is completed for both pieces, simply screw or bolt the two halves together and you should have the concaved arch profile that you are looking for.

The resulting gusset will be 3 +/-" thick and have a 3/4 "side leg, that will provide lateral support to the gusset. 

I am assuming you will be using U bolts or pipe hangers to attach the gussets to your metal framework.

I hope this simple solution is helpful and won't require you to pull out any more hair or lose any more sleep over your dilema and allow you to get on with your project.  

Route away.

  Ric


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## Mike (Nov 22, 2004)

Here is my suggestion: Chuck up a 3/4" coving bit in your table. Adjust your bit height so the bottom of the cutting edge is at the centerline of your wood. Adjust your fence to reveal part of the bit and make a pass. Flip your wood and repeat. Keep adjusting the fence and flipping the wood until you have removed the depth needed. Odds are when you try fitting it to the roof you will need to do some hand chiseling for deformities in the metal anyways.


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## Roberto1 (Aug 31, 2006)

Thanks Mike: I have no doubt that this method would work admirably for a piece of straight edge stock. However since I need to make the cove on the inside of a curved piece of stock (on the edge) it would not work as it requires the stock to follow the bit along the arc. 
The stock would only touch the fence at both ends of the curve. 
I think I will try making the cuts with a template of hardboard and backsetting it and then raising the bit and using a collet let the template follow the collet on the underside of the stock.
Thanks for the input though ...............Robert


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## labric (Sep 11, 2004)

Robert

I have some concerns as to what you may be attempting to do !!!!


> _raising the bit and using a collet let the template follow the collet on the underside of the stock_


I hope you mean "bearing or guide bushing" and *not* the  " collet "  as there is a good chance, that if you make contact to the collet, while the motor is powered up, it may loosen your router bit and cause either extensive damage to you, your router or both.

I am not sure you can raise the cove bit high enough to route properly while setting your router bit to the proper depth inside the collet as the shanks are fairly short to begin with, assuming you are using a 3/4 cove bit with top bearing?? Do not attempt to shorten the amount of shaft that goes into the collet as again dire consequences may result.

Hope I'm not too overly cautious here, but I would feel remorse if something were to happen that I could have prevented.

Please clear up any confusion and let us know how you make out with your project.

  Ric


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## Mike (Nov 22, 2004)

Robert, I misunderstood and thought you were cutting on the outside of the curve. Here is my suggestion: after you cut your inside radius attach 1/4" hardboard to both sides of your 2 x 8. Cut a smaller radius for a bearing guided bit to follow. Make a pass on each side and then increase the size of the radius, repeat until the template radius matches your wood. Easy enough?


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