RT circle jig solves template dilemma

[johnpipe108]

I needed to upgrade my router mounting plate to accept removable center inserts, as I bought a slot-cutter which wont fit the original 1-inch center hole. My dilemma was how to make a 4 inch circular template to use with a PC guide.

After a bit of brainstorming, I came up with this jig, consisting of a piece of 1/2 inch MDF with a 1/4-20 FH for a pivot, screwed into an undersize CS'd hole in the MDF, and attached the piece to a length of miter bar to allow easy adjustment of the radius of the cut. A scrap support piece is clamped on the right of the cutter.

A backing block with a matching pivot hole in the center is used to rotate the MDF pieces over the cutter; the block is large enough to cover the cutter when in use. The pieces to be cut are affixed to the backing with double-stick tape.

The stack of finished pieces shown here are the new, replaceable center inserts, to allow for zero-clearance on any size cutters.

Machining the router-mounting plate after the fact to now accept inserts was a bit of work. The polycarbonate material does not take kindly to machining, and the swarf has to be manually removed often; the finished recess and some of the swarf are shown in the photo:

I cut the center out with a nest-of-saws hole saw; it didn't come out on center, but as long as it doesn't interfere with a bit, then OK, else I'll trim it up.

 

[cskipper]

that seems like a very clever solution. I also wondered if they sell them out of metal and such because of marketing or durability.

 

[Will Goodwin]

Hi John,
The jig was a great idea....can you post some pics of everything set up so I can get a better understanding of how it all comes together? I'm not sure what the stack of mdf circles are used for. :eusa_thin

Will

 

[Glennbear]

Seems like a fine piece of engineering to solve a dilemma, I do have a question regarding the plate machining:

"Machining the router-mounting plate after the fact to now accept inserts was a bit of work. The polycarbonate material does not take kindly to machining, and the swarf has to be manually removed often; the finished recess and some of the swarf are shown in the photo:"

What did you use to machine the recess? was it a VS router? I am thinking a lower speed on the bit would eliminate the swarf problem. The reason I ask is that I have some polycarbonate projects in the future.
Thanks.

Glenn B.

 

[DavidF]

Nice fix! Did you need the piece of mitre bar? Why not set the rad just by Clamping the mdf with the pivot to the table top?

 

[johnpipe108]

Hi John,
The jig was a great idea....can you post some pics of everything set up so I can get a better understanding of how it all comes together? I'm not sure what the stack of mdf circles are used for. :eusa_thin

Will

The stack of circles are finished disks for making center inserts; this was the second use of the jig, the first was to make a cutout-template for routing the polycarbonate to accept the disks. The square piece of MDF on the left is the backing, with a finished disk stuck to it. I'll see about more pictures tomorrow.

 

[johnpipe108]

Nice fix! Did you need the piece of mitre bar? Why not set the rad just by Clamping the mdf with the pivot to the table top?

That could be done, but I had just purchased the miter bar and it was easier to just use it, as it's simpler to slide the miter bar with fingers at each end to adjust the pivot. If I didn't have it, I'd just clamp.

 

[johnpipe108]

Seems like a fine piece of engineering to solve a dilemma, I do have a question regarding the plate machining:

"Machining the router-mounting plate after the fact to now accept inserts was a bit of work. The polycarbonate material does not take kindly to machining, and the swarf has to be manually removed often; the finished recess and some of the swarf are shown in the photo:"

What did you use to machine the recess? was it a VS router? I am thinking a lower speed on the bit would eliminate the swarf problem. The reason I ask is that I have some polycarbonate projects in the future.
Thanks.

Glenn B.

Bosch 1617EVS, with a 1/2 shank 3/4 inch straight bit; I probably should have slowed down the speed, but I was too concentrated on the operation to remember to do that

 

[johnpipe108]

Re: RT circle jig -- more pix

The stack of circles are finished disks for making center inserts; this was the second use of the jig, the first was to make a cutout-template for routing the polycarbonate to accept the disks. The square piece of MDF on the left is the backing, with a finished disk stuck to it. I'll see about more pictures tomorrow.

Here is a mock-up of the set-up as it was used to make the template that was later used for routing the polycarbonate router mount (as it's a mock-up it is shown without the clamps). The template being made-up is under the backing-block, affixed with carpet-tape outside the cutting radius, a support-piece of wood is on the right of the cutter, and the block is turned 360 degrees counter-clockwise to make the cut:

Here the block has been lifted off the pivot, with the template still affixed, leaving the waste-piece behind; the support-piece of wood to the right is removed to better show the cutter and waste:

HTH, John