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Which bit?


Gunguy45's Avatar
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12-07-17, 01:31 AM   #1 (permalink)  
Which bit?

Ok, I'm confused and just getting more so, the more I look.

If I want a 1/2 moon shape...like this, "(" , on the edge of a board, so it mates relatively well with another board like this, "(", how would I do that? I mean, I don't have a custom molding tool and I imagine the heads for use on a table saw would be mighty pricey. I really would probably only do this a few times for a total of maybe 10ft, then it would just collect dust.

Is there a router bit that would give a relatively shallow radius on a 3/4" board? This is one tool I haven't used much except for roundover and straight bits. I know you can adjust up and down (to some extent) to use different parts of a complex bit, but I'm missing something, obviously.


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12-07-17, 02:35 AM   #2 (permalink)  
1/2 circle or 1/2 oval. If 1/2 circle you could put boards together and use a forstner bit in the center.

 
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12-07-17, 05:45 AM   #3 (permalink)  
How wide are the boards and how nice of a joint are you looking for? Typically of course you would have a pair of bits, one that would cut the concave and one that would cut the corresponding convex. If the boards are not too wide, and the fit just needs to be just somewhat close you could do as Pugs mentioned, and then get the corresponding board close with a router bit and/or a block plane and some sanding.

 
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12-07-17, 06:22 AM   #4 (permalink)  
How big are the half moons (radius) you want to create. If it's more than about 6" I would attach a router to a scrap of luan or thin plywood and put a screw through one end of the board to create a pivot point. Now your router can make round cuts of any radius you want and it can do the inside and outside radii depending on where you place the material your cutting.



Smaller radii arcs could be made with a circle template for the router's fence. It's basically a large circle cut into a piece of plywood to guide on the outer edge of the router's shoe. To figure the size of the hole in the template you need to account for your bit size and the size of the router's shoe.

 
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12-07-17, 06:52 AM   #5 (permalink)  
On the edge of a board....

If you are talking about a shallow convex / concave shape, look for concave / convex edging router bits.

If by "half moon", you mean a perfect 3/4" diameter half circle, that would be something like the MLCS #17063 and #18738.

This is the sort of thing you would probably want to do in a router table. It would be hard to do perfectly by running the router over the wood. (By hand)

 
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12-07-17, 07:03 AM   #6 (permalink)  
For straight boards, I prefer a tongue-and-groove joint.

 
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12-07-17, 07:11 AM   #7 (permalink)  
Gunguy what are you trying to do? If you're looking for complimentary edges like on a drop-leaf table there is a router bit set for that.
If you're looking to glue to boards together and want mating edges that don't shift, a tongue & groove works well and there's also a "V" groove set that's especially nice to create a slip-free joint--and works great from applying solid edging to plywood, too.

 
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12-07-17, 07:46 AM   #8 (permalink)  
Pilot Dane, I don't think that's what he's looking for in this case, but I like your circle cutter, and coincidently have that and a circle cutter for my band saw on the agenda for this weekend. In particular I like the fact that the router has a pocket, rather than having to remove to unscrewing the face plate and having to screw it to the template, so exactly what I had in mind. Curious though how your center is made. I was thinking of a center offset from the knob, with a piece that tightened in the groove when I twisted the knob, but looks like the knob on yours might be directly over your center marks, so assume that maybe you have a bushing that slips over the center? I've always improvised in the past, usually with a few blocks tacked to a piece of scrap of some sort to hold the router in place and then used a screw or nail to put the center where I wanted it, but seems that I have been doing more of that of late so time to make something more permanent.

 
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12-07-17, 10:41 AM   #9 (permalink)  
Scratch that, PD. Still like the one you made, and am undecided on how I am going to arrange the center for the bandsaw, but forgot that I had the one for the router under control. (Happens more as I get older.) In fact, going to have to look this evening, before I forget again and start all over, but pretty sure that I have the center pin for router made already. Probably similar to yours; just a bolt with a center turned on the back end of it.

 
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12-07-17, 04:38 PM   #10 (permalink)  
It's what I get for posting late at night. Yes, it's on the edge of the board. And yes, it is concave/convex...not an actual 1/2 moon. Circle cutting I understand, but have never had to do.

Here's what it's for (I solved it for this one project, but it's come up before and will again, I'm sure)....

I have an existing round nosed shelf made of off the rack pre-made boards from a home center. You know the type, particle board, front edge convex and finished, all other edges flat and unfinished.. I wanted to but another short shelf against it as tightly as possible, so that the pre-finished edges make an "L" shape. Thus I would have to make one flat edge concave to fit against the convex shape of the existing board. Sort of "spooning" if you will. If I was doing it from scratch, I would simply cut both on a 45 in the corner like a countertop, but one was existing and I was using leftover scraps for the short leg.

Since it was only a 13" section I needed to shape, I used a rasp that was very close to the right curvature initially, then a length of larger diameter pipe wrapped with 60 grit paper, and finally an actual piece of of the shelf board with a piece of 80 then 100 grit wrapped around it . And about 3AM I said that's as close as it's getting, paint and caulk will handle the rest.

I know, being a bit OCD for a project that only I will likely ever see or appreciate.

Thank you all for your thoughts. X, I actually have a kit that will allow me to convert one side of my table saw to a router table. I would use that if I had greater lengths to do I imagine...of course it would be in warmer weather and daytime..lol.


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