Acrylic for Sub Base for Router

[George Bokros]

I have had several posts regarding a sub base for my DW611 router. I now plan to make my own out of acrylic. I am thinking 1/4" should be thick enough, your thoughtson thickness - 1/4" or 3/8"?

What should be used to drill the 1 1/8" or 1 1/4" hole in the center for the router bit, I am thinking hole saw. Forstner bit (I don't have one that large anyway) would not work well is my guess.

Thanks for your input.

[Matt Day]

1/4 would be fine but either will do.

For the hole a 1/8" doesn't make a difference I doubt. I'd make a template with ply or mdf using a forstner but then use a template router bit.

[Lee Schierer]

You would be better off using polycarbonate (Lexan) instead of Acrylic. Acrylic is rather brittle and can easily crack from pressure exerted by screw heads. Even the saw cut to make a round piece can leave stress points where a crack can start unless you polish the edges.

[Cary Falk]

I have never had a problem drilling acrylic with a forstner bit. Works great for the flat bottom for the screw holes.

[Mike Cutler]

George

Having done this many times, I would suggest, as Lee suggested, to use Lexan. It is much stronger and more rigid.
Me personally, I would go 3/8". It will gives you enough thickness to counter bore the screws. Forstner bits work well for this, and allow the use of a pinhead screw. A countersunk machine screw can crack the base. BTDT.

The hole saw works pretty well, but it is going to be slow. A lot of heat is generated and the material will melt and adhere to the hole saw. This will require that you stop and clean the material out of the teeth on the hole saw and then continue.

[George Bokros]

George

Having done this many times, I would suggest, as Lee suggested, to use Lexan. It is much stronger and more rigid.
Me personally, I would go 3/8". It will gives you enough thickness to counter sink the screws. Forstner bits work well for this, and allow the use of a pinhead screw. A countersunk machine screw can crack the base. BTDT.

The hole saw works pretty well, but it is going to be slow. A lot of heat is generated and the material will melt and adhere to the hole saw. This will require that you stop and clean the material out of the teeth on the hole saw and then continue.

Mike do you mean a pan head screw? A pin head screw is a security screw that requires as special driver.

[Dave Richards]

As for the holes for screws, don't countersink them. Counterbore instead.

If you use flathead screws, you can countersink the holes. Do that and mount the plate on the router with a centering pin in the collet. Bring the pin down to mark the plate so you can center the hole for the bit. With flathead screws in countersunk holes, the plate will align the same way each time you install it.

[George Bokros]

Thanks for the tips Dave. I was going to use the center of the arc I scribe for the one end of the base.

[Bradley Gray]

I made a base out of 1/4" Lexan a few years ago. I used a circle cutter in a drill press to drill the center hole as well as cutting the perimeter. Worked great.

[Rich Engelhardt]

George,
If you haven't gotten the material yet, I recommend HP Manufacturing in downtown Cleveland.
They are way East of all the downtown mess, at 3746 Prospect Ave.
They may even cut it to order for you!

[Dave Richards]

I would suggest drilling for the screws, marking for the center as I described above and use that center for an arc on the outside edge. It would be easier to let the router find the center since that will be important with larger diameter bits or if you want to use PC stye guide bushings.

[George Bokros]

George,
If you haven't gotten the material yet, I recommend HP Manufacturing in downtown Cleveland.
They are way East of all the downtown mess, at 3746 Prospect Ave.
They may even cut it to order for you!

Thanks Rich. I have not gotten any Lexan yet and to be able to get it locally is fantastic.

[George Bokros]

I would suggest drilling for the screws, marking for the center as I described above and use that center for an arc on the outside edge. It would be easier to let the router find the center since that will be important with larger diameter bits or if you want to use PC stye guide bushings.

Dave I have decided to use your suggestion on the centering pin. Having the bit in the center of the hole can be helpful / critical at times. And was planning to countersink and use flat head screws for the reason you cite.

[Dave Richards]

George, I think you'll find it works well that way. Since you are going to cut an arc on the end of the plate, it'll be useful to have the arc centered on the bit. Then if you run the router along a fence it won't be so critical that you keep the same point against the fence for the entire cut.

[Nick Decker]

George,

My situation is a bit different, but I just finished working on an acrylic plate for my Ridgid trimmer.

Like you, I found that the universal offset plates they sell are all for larger routers. I happened to have one of Pat's offset plates that he made for an old PC 690 that I no longer have. Yes, it's larger than necessary, but for edge profiles with a guide bearing (mostly what I use that router for) that's probably not a bad thing. So I decided to try to adapt it with new holes.

I don't have one of those centering pin/cone things, so I just eyeballed it. Should be OK, since I don't use guide bushings, etc.

Marking and then drilling the holes accurately was the hardest part, for me. Lets just say that two of the four holes needed a bit of enlargement.

The drilling itself was no problem. I adjusted my drill press down to 680 rpm, used an inexpensive Fortsner for the countersinks and a plain old Dewalt bit for the through holes. I did clamp things down for drilling, as I'm told the acrylic has a tendency to want to ride up on a regular bit. I also imagine the bits I used are not as sharp as they were before.

Anyway, hope some of that might be of use to you.