After a long absence(of about a year and a bit!) I have finally resumed work on my first canoe.I know I might be being picky but I'm just about to mould the edges of my strips and(lucky me) I have two options.I can either go with a 3mm radius cutter or opt for a slightly flatter 4mm radius.(for both beads and coves)Could anyone tell me which would give me the best result for my joins?before I end up using my strips for kindling!! my strips are 6mm thick.
Many Thanks
Alick
exactly what radius should i have on my bead and cove strips
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alick burt
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woodworker
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radius on strip edges
The radius should be half of the strip thickness, so 3mm should do it. You could use the 4mm as well though. The whole point is that the cove radius is the same as the bead radius, and centered on the thickness of the strip. good luck! 
radius of half thickness not a good idea
I have copied below my post from an earlier dicussion. I don't think any of the cutters made commercially specifically for 1/4 inch strips have 1/8 inch radius.
I have been using the same set of cutters for 20 years and I just went to the shop and got out the calipers and measured the diameter of the bead/cove. It confirmed what I had suspected. The radius of the cutting profile is 3/16. This is as it should be. If the radius of the cutter is half the thickness of the strip you get a very deep cove with fragile edges. Also when strips meet at an angle with this situation they must either break the inside edge of the cove or leave a gap between the two strips. There is no way these strips can meet cleanly except straight on.
With the larger radius profile, coves are not as deep, edges are not as fragile and strips can meet cleanly at much greater angles. It is really not that difficult to center the strip with the cutter profile. I always saw a few scrap strips from a piece of pine to use later for centering the jig. Since these scraps were sawed with the same set up as the batch of strips they are exactly the same thickness and can be used for adjusting the bead/cove jig.
I have been using the same set of cutters for 20 years and I just went to the shop and got out the calipers and measured the diameter of the bead/cove. It confirmed what I had suspected. The radius of the cutting profile is 3/16. This is as it should be. If the radius of the cutter is half the thickness of the strip you get a very deep cove with fragile edges. Also when strips meet at an angle with this situation they must either break the inside edge of the cove or leave a gap between the two strips. There is no way these strips can meet cleanly except straight on.
With the larger radius profile, coves are not as deep, edges are not as fragile and strips can meet cleanly at much greater angles. It is really not that difficult to center the strip with the cutter profile. I always saw a few scrap strips from a piece of pine to use later for centering the jig. Since these scraps were sawed with the same set up as the batch of strips they are exactly the same thickness and can be used for adjusting the bead/cove jig.
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woodworker
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1/8 inch radius works fine for me......
A radius half the thickness works just fine. The two pieces rotate, and after sanding there is one joint line and no gap. Everyone has their own preferences, always more than one way to skin a cat i guess! On the other hand though, my strips are a fat 3/16 thick, but not much less than 1/4. And you also can use a 1/8 radius bit set and set your fence to cut a little shallower. 
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woodworker
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alick burt
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radius of cutters for beads
Thankyou for all your replies I think i'll go with the 4mm option as it will leave me with less fragile corners on the cove cut! :smile