Newbie installs a mounting plate using one bit...
After reading countless articles, watching videos and taking valuable advice the very helpful folk here on the forums, I finally plucked up the courage to cut into my recently constructed router table top. I had a rather curious combination of bits - none of which seemed to "work together" - so I decided to do the whole job with a single bit, a guide collar and the mounting plate. I know there are other ways to do it - but many seem to involve several different bits, mounting plate templates etc. Given the simplicity of the method used, and the outstanding result that it produced, I thought it might be useful to share it here - just in case other newbies want to follow it.
Here's what I used:
• a 1/2" spiral downcut bit (size is somewhat irrelevant)
• a 40mm guide collar (size is somewhat irrelevant)
• the mounting plate
• 4 scraps of straight edged MDF, each about 8cm wide, long enough to surround the MP.
• double sided tape
• a small rectangle of MDF to support the router as it runs around the guides.
• jigsaw & drill.
Here's the method:
1. Locate the mounting plate on the router table, exactly where you want it to be.
2. Hold it firmly on the table, and draw tightly around the edge with a fine ((0.5mm) mechanical pencil. You want a very fine accurate line to measure off.
3. Calculate the offset between guide collar and bit : (external diameter of collar - diameter of bit) / 2. In my case, this was (40 - 12.7) / 2 = 13.65mm
4. Clearly I can't measure 13.65mm with a ruler, so I erred on the tight side and measured 13.5mm from the line created in step two above. Measure towards the outside of the mounting plate outline, very accurately - then use a ruler to very carefully join these marks. You should now have two rectangles drawn on the router table - one the outline of the MP, the other a rectangle x mm larger (on all sides) than the MP outline - in my case 13.5mm larger.
5. For a bit of insurance, I put two layers of masking tape onto the guiding edge of the MDF guides. Theoretically, this will cause the bit to cut inboard (ie inside) the MP outline - meaning that the recess will be too tight to permit the MP to drop in - however it's better to have it too tight (and be able to remove the tape, and run the cut again) than too loose.
6. Put two strips of double-sided tape on each MDF guide (to ensure good adhesion) then line up the MDF guides (with taped edges facing towards the centre) with the 13.5mm offset line created. Ensure that it's the edge of the actual MDF that sits exactly on the line - not the edge created by the tape. You may need to trim away a small sliver of tape from the edge of the guide, to ensure you can perform this very accurate lining up procedure.
7. Cut the small rectangle of MDF to size, so that it sits in the center of the MDF guides, whilst still allowing space for the collar to pass around between the MDF guides and the rectangle. This rectangle provides support for the router base plate, ensuring that it doesn't dip or tip while routing the recess. Use a few strips of double-sided tape to hold it in place.
8. Set the router plunge depth to a few mms, then position the router accordingly, plunge in and route a shallow channel all the way around, clockwise. Try to keep the same 'side' of the guide collar against the MDF guide - just in case your guide collar isn't concentric.
You can lift the supporting rectangle out and line up the MP on top of the recess to see how you're traveling - however I didn't, trusting my accurate measuring. I routed the channel to full depth (ie depth of MP, plus a mm to permit packing/height adjustment screws). I then used a drill to penetrate through (to the underside) on the inboard corners of the channel. I then flipped the router table top over, connected the 4 drill holes with a ruler - and cut away the centre with a jigsaw. The reason for leaving the MDF guides in place, was that there was a good chance the recess was too small for the MP - and it was. By leaving the guides in place, I could remove the 2 layers of masking tape from the edges, and run the router again - to shave off just enough to make it a perfect fit.
The result - the MP fits so perfectly (when applied by pressing it in by hand) that I can flip the table over and the MP doesn't fall out. The depth is perfect too - will just need a tiny shim - or height adjusting screws - which came with my MP. What could have been done better : the radius of the corners in the recess is ever so slightly different to the MP - however not enough to be of concern. I would have had to use a bearing guided pattern bit and MP template to sort that - neither of which I had.
If any one finds the above confusing, but would like to try the method, please let me know. I'm sorry that I didn't take any pics while underway (my camera is too expensive to put in that environment while working!) however I'm more than happy to create a few diagrams for any parts of the above that are confusing.
Last edited by matt1710; 01-23-2011 at 01:10 AM.