Continued from Part 1
Having escaped from Colditz the garage and had a break, I returned to work on the circle cutting base.
I took the knob and tote off a Draper plane that I don’t use anymore since I bought some better planes.
I mocked up the offset/circle cutting base with the plunge base of my router and the plane knob and it looked OK, so I pressed on:
I used a center punch to mark the 3 mounting holes for the router base and drilled 6mm holes.
I used an old wooden chopping board as a sacrificial table as I’ve not made any more progress on my drill press table
I then realised I should have drilled the larger half thickness holes with the forstner bit first! This would have given the central point of the bit something to dig into and prevented the bit wandering.
It didn’t seem to cause too many issues, but I drilled the forstner holes first after that …
The holes provide a recess for the heads of the 3 screws holding the Lexan to the plunge or fixed bases of the router.
It took a few goes until I was happy I’d set the depth stop deep enough to provide clearance without weakening the base unnecessarily.
I then drilled the center hole for the router collet and a larger recessed hole at the narrow end to take the bolt for the knob.
I then marked out some center lines on the base (which would probably have been easier before drilling out the center hole …) and scored them lightly with a knife.
I marked every 5mm on the center line between the router bit hole and the knob (apart from where one of the mounting screw holes coincides with the line – I’ll have to drill those holes offset if I ever need them).
I was hurrying a bit by this point, so I’ve not made the neatest job of all the 3.2mm holes for the rolled pin center pivot.
(I needed to buy an extension bar for my socket set to enable me to use the bolt in the way I wanted with a self locking nut hidden inside the recess in the top of the knob and the shallow screw head recessed into the base. I got a new lock for the garage door at the same time to replace the one I’d had to cut).
Having removed the protective film from the Lexan I drew along the scored lines with a permanent marker and then quickly wiped away the excess from either side of the groove, so they are now clearly defined with a fine black line.
I’m not sure yet whether this crosshair will be any use …
The rolled pin is a nice firm fit in the 3.2mm holes
I think the 5mm spacing of the holes should give enough flexibility for my needs, as I can also vary the radius of the router bit to fine tune the radius of the circle.
At some point I’ll drill another 3.2mm hole into the top of the base so I can store the pin in it and lay the base flat.
Apart from the wobbly line of holes for the center pivot I’m quite pleased with how it’s turned out.
The 8mm Lexan doesn’t flex much and was a lot easier to work with than I was expecting.
Because I now have two of these routers I now have two plunge bases and two fixed bases, so I’m able to leave this base attached to one of the plunge bases, which is nice.
Update 06/04/2013: I’ve cut my first circle.
(I’ve also decided I should probably get 7, 8 and 9mm router bits to go with my 5, 6 and 10mm bits from Wealden, as this will give me the ability to fine tune the radius between the 5mm spaced pre drilled holes).
I drilled the center hole all the way through, so I could cut the circle from both sides, as this would avoid needing to waste a sacrificial sheet of ply or MDF for cutting on.
This meant I was able to use my Draper grip mat to hold the wood in place without worrying about ruining it when I broke through.
I had to plunge the router and cut full circle several times on each side.
I was expecting more issues on the final break through cut as the outer piece has nothing to support it,
The finish isn’t too bad, but there are “strata” where I’ve changed the plunge depth and flipped the wood over half way through to cut from the other side.
This circle formed the basis of an art project that my eldest daughter came up with last night just before bed time.
It has now been decorated with a face on both sides and some hair around half of the rim!