Circle-cut Moldings

High_Res ScrollI’ve returned to the Egerton tall clock this week to begin work on the hood moldings. Due to the dial design selected, this clock has a circular molding that is cut at an angle to fit to straight runs before it turns back the sides of the hood. I’m beginning with the arched section because it’s easier to produce a match when working on the straight runs, than it is to work up a perfect match on the arched section after the straight stock is made.

For this operation, I find it best to use my router along with a circle-cutting jig. You find the radius of the cut, which changes with each router bit used as you make the profile, then swing the setup as you make your cuts. IMG_1128For this clock, because there is a small added inlaid piece up the center of the hood, the arched molding is divided. That allows me to set up the stock as a pair of pieces instead a single piece with the entire arch cut. This translates into stronger moldings because there is no short grain where the piece can easily break.

In the photo above, you can see the setup. I have my router attached to a shop-made circle-cutting jig and yes, that is a drill bit I’m using as a pivot – no right-sized dowel in the shop. (Make do with what you have.) In the photo I’ve made the first pass, creating the thumbnail profile along the top edge of the molding. The workpieces are held with double-stick tape, as is the pivot platform.

The trick to this work is to properly set your router and the length of the jig to cut exactly where you need to produce the profile.IMG_1129 To do just that you need to accurately measure for the hole location (pivot point) on your jig. As you can see in the left-hand photo, you don’t need to be centered of your jig. As long as the measurement from the pivot to the correct edge of your router bit is right, your cut will be in the correct location. There are times when you’ll set to the far side of the bit and times when you use the near side to cut your profile.  Once determined, I use a bird cage awl to start my hole so the drill bit stays put as I drill. It takes some time to get the position just right, but it can be done.

IMG_1131The results are great if you use the correct router bits and get the setups just right. In the right-hand photo you can see the results of three passes using the setup. The first was the thumbnail. For the second cut I used a round-nose bit. The third cut was with a straight bit and it was simply to clear the material for the subsequent passes.

It was after the third pass that I realized I had used the wrong round-nose router bit. The width of the round-bottom trench was too wide for the profile as I had it drawn. You know what that means, right. Yep, start over. I’ll choose the right bits this time, and I think I’ll re-design the molding somewhat; I wasn’t thrilled with how it was coming out. Also, because it is time-consuming to accurately position the jig, I’ll switch to my Micro Fence circle-cutting jig which allows me way more accuracy as I work.

That’s my Sunday (another day in the shop, yeah). What are you planning?

Build Something Great!
Glen

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Filed under Jigs, Routers, Tall Clock

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