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Discussion Starter · #1 ·
I'm newbie to woodworking and have a question that I couldn't find an answer to on the internet.

I find when making plastic base plates it's difficult to drill the center hole perfectly centered with the edges.

The closest method I have found is to:
- Make a blank base plate with outside dim's to size
- Attach a piece of 3/4" wood to the blank
- Use template bit to route the wood to exact size of the blank base plate
- Using dial calipers mark the center on the wood.
- Clamp the assm'y to the drill press table
- Use a Forstner wood bit to drill the center hole thru the wood
- When the bit reaches the blank base plate, Stop
- Put water in the hole that is in the wood(to cool the plastic while drilling)
- Drill the plastic center hole

The result was the center hole was off center .010" for a .020 side to side misalignment.

Being a newbie, I don't know if I'm trying to be a perfectionist, or the misalignment will cause issues.

My question how close is close enough?

Thanks, in advance.

Rout1101
 

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Marine Engineer
Doug
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Rout,

Welcome!

It really doesn't matter where the hole is in relation to the center of the base plate. Unless you are using template guides on the plate, the bit placement doesn't matter. You are guiding wood against the fence or against a bearing guide on the bit, so that is the reference point.

If you want to use template guides, you will need to make sure the router is centered exactly on the hole in the plate.

There are alignment tools you can use if you need to center a router to an alignment bushing. The one below is a bit fancier than the plastic one I have

https://www.amazon.com/Bosch-RA1151...=2025&creative=165953&creativeASIN=B004Z8SM6M
 

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David - Machinist in wood
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Welcome to the forum! Add your first name to your profile so it clears the N/a in the side panel and so we'll know what to call you. Add your location, as well.

Photos showing your setup may help. How much runout does your drill press chuck have? How concentric is the Forstner bit?

Unless I am missing something it probably doesn't matter that the center hole is off a tiny amount. It's just for bit clearance anyway, right? As long as it's large enough to handle your bits then it's probably fine.

David

Edit - we were typing at the same time, Doug! Same basic response, though. :wink:
 

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welcome to the forums N/A..

use your old base plate for OD sizing and screw hole placement...
a transfer punch is just the ticket for getting the screw holes exactly where you need them...
mount the plate to the router...
plunge rout the center hole a straight or mortise bit that is of the same diameter as an on hand fostner bit...
NOTE: the bit you use must be rated for plunge cutting...
take the plate off...
move to the drill press...
load the fostner bit into the DP..
insert the bit into your plate's hole..
clamp the plate down...
swap the fostner bit to size you desire...
bore away...
return the plate to the router w/ the holding screws barely snug...
center the plate w/ your centering cone..
tighten down the screws...
 

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As Doug stated it's not important that the hole be centered in the plate. It is important if you ever plan to use guide bushings that the router be centered in the hole but since you are making your own plate I'm not sure that you planned on machining the plate to accept guide bushings. If you machine the plate to accept guide bushings then the through hole will only allow you to use bits up to 1" diameter. I made my own plate but I machined it to accept the snap in rings from a Grizzly plate I had so that I have a large opening for big bits and the smallest insert ring allows me to use guide bushings.
 

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Yeah, what they all said. :)

If you do need to find the center, chuck a V bit in your router and raise the router up in the base so the V bit wont touch the new plate. Then mount the new plate, turn the router on and very slowly lower the router until the V bit just digs into the plate, maybe 1/64th of an inch. You now have a mark at the center of the plate and can drill a perfectly centered hole. This works best for plunge routers. Don't use this technique if the router is loose in the mount when lowering it. I've done this several times.

Though, a better way to go is find a friend with a CNC machine...
 

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The attached shows a good method of centering a baseplate on the router.

If you just need a baseplate with a clearance hole in the center, drill and c'sink the appropriate sizes at the locations marked with the setscrew points.

If you need a baseplate to use with a guide bushing, you will need to drill the 1.375" diameter counterbore for the guide bushing and a through hole for the threads and then use a centering guide - there are both conical and disc versions available - to center the plate with the router spindle and then mark the hole locations as shown. For this application, it is more usual to use either button head or fillister head screws so would require you to drill the through hole which gives a slight clearance with the body of the screw and a counterbore to suit the head of the screw. This allows you to check the location and recenter the baseplate to the spindle as required.
 

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As much as as I like to make as much as I can, if you need to use guide bushings then I'd be inclined to buy the plate for my router. Different routers use different methods for the guide bushings. A quick example is my Bosch 1617EVSPK which requires an adapter to use the PC style of bushings. Sometimes it's just easier to buy the needed part. But you've certainly gotten good information. BTW, welcome to the party JJ!
 

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I have made several plates from either phenolic, Lexon and I made one from aluminum also . I use the router itself to make the center hole. I use the original plate as a template to bore the mounting holes them mount the plate to the router and use the router with a 1/4" bit and lower the router into the new plate to make a perfectly centered hole. Then I use a fly cutter in a drill press to enlarge the hole and create the step needed to accept porter cable style guide bushings.
Hope that helps it has always worked well for me.
 

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I have made several plates from either phenolic, Lexon and I made one from aluminum also . I use the router itself to make the center hole. I use the original plate as a template to bore the mounting holes them mount the plate to the router and use the router with a 1/4" bit and lower the router into the new plate to make a perfectly centered hole. Then I use a fly cutter in a drill press to enlarge the hole and create the step needed to accept porter cable style guide bushings.
Hope that helps it has always worked well for me.
I did it a bit differently. I marked the center of the plate and then drilled either a 1/4" or 1/2" hole through it so that I could put one of my router centering pins through it. Then I clamped the pin in the vise on my milling machine and just turned the plate by hand as I milled the stepped recesses for the Grizzly insert rings. That way I knew I could stay perfectly concentric to the center hole I drilled.
 

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welcome to the forums N/A..

use your old base plate for OD sizing and screw hole placement...
a transfer punch is just the ticket for getting the screw holes exactly where you need them...
mount the plate to the router...
plunge rout the center hole a straight or mortise bit that is of the same diameter as an on hand fostner bit...
NOTE: the bit you use must be rated for plunge cutting...
take the plate off...
move to the drill press...
load the fostner bit into the DP..
insert the bit into your plate's hole..
clamp the plate down...
swap the fostner bit to size you desire...
bore away...
return the plate to the router w/ the holding screws barely snug...
center the plate w/ your centering cone..
tighten down the screws...
I attached my router under the table and just turned the router motor in it’s mount which raised the bit and cut threw the surface .
This about sums it up as how I go about it. I use an old router plate and use it to mark screw hole placement. Once I screw it to the router, I plunge (slowly) a bit through to cut the hole. I use a flute bit. It gradually makes the hole bigger.
 
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