Cutting circles with a DIY router jig

I'm moving things forward very slowly on the banjo making front, but as long as I'm doing something that will contribute to the overall goal, that's OK. So I've been re-sawing some wood (with mixed success) and stuff, and I also made a planer jig for my router (didn't work out too good).

Today I thought I'd have a go at cutting some circles in MDF with my router. At some point, I'm going to need these when getting the pot/rim circular, so I made a simple jig for my router. Basically, it's piece of plywood, to which the router is screwed, and there are holes drilled for pivot points into which I insert a nail. There are loads of videos of how to make much more professional versions of this type of jig on youtube, so there's not much point me going into further details.

The first problem I noticed was that on my el-cheapo router, you have to keep the trigger pressed with your finger whilst operating it, this meant some hand switching when turning the circle, it was pretty tricky keeping the cable out of the way.

Things to note:-

Make sure to have a piece of scrap under the material you are cutting, and drive the pivot nail right through into it. This prevents gouging the side of the disc when it comes loose from the sheet.
Make sure the bit is going to go all the way through the material
Use a narrow straight bit
Don't try to go too fast, make multiple passes

The router attached to the jig, the pivot nail is visible to the right of the router

The first disc I cut was an 8" diameter, and it came out pretty good, and damn close to 8" in diameter to boot. I was quite happy with it.

My first disc, 8" diameter for the banjo use

The next 3 discs were a success too, so all in all a job well done there .

2 x 11" and 2 x 8" diameter discs

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