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Amateurs Night the saga continues

4114 Views 4 Replies 3 Participants Last post by  Benny LaBaw
I’m making a new sub-base for my router and thought some of you might find it interesting and or educational.

The methods I’ve used here maybe different then you have seen before but let me assure I have done this enough times to know it works and I have been happy with the results each time.

This time I am making a clear (acrylic) base for my trim router, the methods show will work for other type routers as well. Since my router is a Porter Cable I will be using that standard for the sub-base.

I have collected an oval shaped piece of acrylic from a surplus store, it was for something other then a router sub-base but it was cheap and clear the two things I was looking for. Now comes the surprise part of the project. I will be using my drill press to do the guide bushing cutouts and for drilling the screw holes.

I have a 1 3/16” forstner for the through hole and a 1 3/8” forstner for the step. I will also use a 1/16” drill to locate the other holes. The first step is to locate the center or desired location for the holes. Once that is done a center punch is used to locate the position of the drilling. One caution, a spring loaded auto center punch can create a stress crack or shatter acrylic so loosen the spring or use a light hammer with a conventional punch.

I use the 1/16” bit to locate the drill press to the point where I want to drill. You need to clamp the plastic down and make sure you have a backer board so you do not drill in to the table and make sure the board supports the plastic under the clamps so it is not cracked when you tighten the clamps. Adjust the table height so you can use both the 1/16” bit and the forstner bits without having to adjust the height again. Once everything is aligned drill the 1/16” hole.

Next we have to take a quick look at the portion of the guide bushing that will need to be flush with or slightly indented from the bottom of the sub-base. On the bushing I have it measured .108” thick. {See attachment 1} This I rounded to .110 then added another .005 and attempted to get the depth of the step at about .115”. Using the larger 1 3/8” bit I run the bit down to the point where it is making contact across the whole 1 3/8” diameter. This I use as my zero point and adjust the drill press to the depth of .115 (remember 1/16” = .0625, 1/8” = .125) I used a 7/64” inch bit (.109) as a spacer plus a hair.

I used my dial caliper to check the depth at about .112”, which I thought was close enough. Now it very important all through this process that you do not move the plastic or the table. I now move on to the 1 3/16” bit and drill the hole through. {See attachment 2} The plastic I used was ¼” thick so no farther modifications were needed.

{See attachment 3 for the sub-base with bushing inserted. Part 2 to follow……..


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Part two

The best way I know to match the new sub-base to the router is with a kit the many suppliers carry. It has a 1 3/16” disk with a ¼” hole in it, a ¼” shaft, and a set of pointed screws that fit in the routers sub-base mounting holes and some longer mounting screws. The kits are sold for a particular router as the screw sizes vary and as I mentioned this is for a Porter Cable trim router.

We will start with looking at the parts I have described. {See attachment 1) The idea is to use the pointed screws in the router base, pointed side out and adjusted to all the same height (count the turns). Next you mount the ¼” shaft in the router and the 1 3/16” disk in the new sub-base. {See attachment 2} (Sorry but I did not get the camera out until after the holes were in place but you should get the right idea.) Next the shaft slides into the disk, and you line up the sub-base how you want it to be. Then I tapped each screw location lightly with a plastic hammer, thus marking it. {See attachment 3} Having marked the locations you will be going back to the drill press and drill out the holes. It might be good to mark the bottom or top so you remember which way things are going. The “center” punches you have just done are on the router side so after drill them you must turn the sub-base over to do the countersink. I should point out that when you decide to do this it is safer to make the holes a little over sized and to counter-bore the screw heads so you can adjust the center easier. I went with the tapered fasteners but then I’ve done this a couple of times.

When the holes are done it is time to align the sub-base to the router. The sub-base must be centered to the shaft of the router to use guide bushings properly. Using the disk and shaft to center the sub-base while you tighten the screws does this. {See attachment 4}

In the last attachment you can see how much larger the new sub-base is compared to the original. The added size is what I need for a lettering project I’m working on. {See attachment 5}

I hope this was useful and clear enough, if not post questions and or comments. I would love to see how some other people do this as well.



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Ed san

Thank you for usefull infomations.
I tried to make sub-base.
A center hole is too small, I wonder.

I used 5mm acrylic plate. A little bit thin ? Next time, I try 8mm.
But I used a wide plate, so convienient I think.
I want table ...

As next step, I will try to make center hole for template guide.
But problem of friction-heat is not cleared when I use fostner bit.
Only makeing drill slow-speed is a good way ?

I were glad if you could teach me a good way to use fostner bit againt acrylic plate.


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Benny, Ed is no longer with the forum, he has been gone a long time. This is sad because he was a wealth of information to us all.
Remember this is for a palm router, not a full sized router like yours. The plastic will flex with the weight of your router. The router centering kit Ed mentioned is from Rousseau. It includes the centering disk, 1/4" centering pin and the correct size and number of Allen transfer screws for your router. You can order these online from Woodcraft.
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