SELECTING A SUBBASE
Routers for hand use require some sort of subbase. There are safety & control problems without them. Whether you choose to use the OEM plate, one of mine or one of the competition's, you should be using one. For the multitude of router apps, there are usually subbases to accommodate. They differ in size, shape, material and thickness. They are commonly made of metal and plastic, though MDF, masonite, plywood, and fabric (phenolic laminates) are just as common. This discussion is about Acrylic.
Why bother with anything but the OEM (the mfg's) plate? Well your router should sit flat on the work without rocking. It if it rocks at all, the cutter will chatter the profile as you cut and you've lost the precision element of routing. Moreover, you may now have to sand where a mill finish might have done. Bakelite subbases (still common) are rarely flat and the new polycarbonate plates found on most new routers are not machined, they're cast. They have high spots here & there and their collar counterbores are sloppy, shallow, sometimes proud and out of round. To complicate matters, few castings are machined flat. So given a misshapen subbase and a casting that is not flat, you get a router that won't sit flat. For average work (non-joinery) I would not necessarily buy a new plate, I would wet sand the face of a "rocking" casting however, as no plate will sit flat on a poorly milled casting.
My subbases (plates aka) are either round or offset, supplied in a thickness that matches its application stress, and made of Acrylic. I make them. They are not farmed out; you have me to blame for success or failure. I supply them with either of 2 cutter holes. One sample uses the default diameters (1-3/16" x 1-3/8") of the PC 2 piece collar guide system (the inventors of the collar guide/bush). The other cutter hole is through and 1.75" for standard routers, (~1.56 or 1.62 for trimmers). I can also mill a cutter hole to your specification.
These plates are designed to get you collar guide service (inexpensively) or to simply replace a plate you no longer need. They are not easily center able. They are ~1/4" thick, a full 360 degrees of circumference, and cut to match the diameter of your machine. One size does not fit all. The plate has been made from templets that combine the 3 diameters (screw hole circle, cutter hole and plate) to ~ + or - .005". Some are bigger (DeWalt) than their castings to manage instability. All screws (supplied), because of plate thickness issues, are either 82 or 90 degree Phillips flat head machine screws. Machines deployed with round plates, are generally used for inside work where support/stability is not an issue. Moreover, inside work is usually small cutter work. And, as such, a collar guide cutter hole (1-3/16") is not a compromise. For larger cutters use the 1.75" cutter hole model.
This plate is for dovetail/boxjoint fixtures. The plate is oversized (7" or 7.6"), .350" thick and counterbored for the PC collar guide system. It will not deflect on your dovetail templet. Moreover, this plate is precisely center able. The screw holes are oversized & counterbored for flanged button head screws. Depending on the diameter of your guide ring it is possible to center this plate within .001" of its guide bush diameter. Use this plate on your dovetail templet systems or on templets where the router is well supported & precision paramount.
These plates are essentially designed for outside work where stability is an issue or on templets where router support is scarce. Their classic applications are bearing guided profile routings, such as rabbets, round overs, or decorative cuts on the edges of stock. Few routers have more than 40% of their casting on the work whilst outside routing the ends or edges. In my view, my plate (or one like it) is essential for safety and quality of cut. The router can remain flat down on the work, even around corners where there is never more than 25% of the router on terra firma. Try these corner cuts with a round subbase and expect compromises and safety issues.
The offset plates are supplied with 1.75 cutter holes for nominally sized bearing guided tool bits. A collar guide option can also be enjoyed with the same fastening and centering system used with the precision round plate above. The collar hole samples are center able. The plates are made from 12mm (.472" min.) stock and designed for each of the most common fixed base castings, (Milwaukee, Bosch, PC and DW). Tho they will fit on most plungers, I make them only for the DW plungers, 618, 625 & 621. One word of caution: Offset plates less then 12mm (~.450") thick will deflect when overhung on outside cuts. A subbase that bends is a safety risk.
These plates are offset subbases cut to order. 1/2 the business end of the plate has been milled away and the stability of the offset design is essential. I typically waste 3/16" of the plate to ~ the centerline of the cutter hole. This allows the router (with a 3/4" cutter) to approach and mow down anything in its pathway that is 3/16" proud or less. Trimmer (small routers) plates are too thin to be made into surface trim plates. A thicker plate is an option. All other offset plates can be made into surface trim plates. Trimming down proud hardwood trim around plywood is the most popular application for this accessory. The cutter hole is 1.75".
My subbases are all Acrylic, colorless, transparent, provided with either of 2 cutter holes, fully machined, supplied with all hardware, safe and ready for use.
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Copyright © 2009 Pat Warner
Last modified: Mon Aug 30 06:15:21 PDT 2010