# Repetitive plunge router holes



## Bullerwell (Apr 17, 2018)

Making marble boards for my grandchildren. The game board measures 24 x 24 and requires about 160 holes for 1 inch marbles. I am using a plunge router, but I have to drill each hole freehand – and that is the problem. (1) Sometimes I get bit drift (which immediately ruins the board), and (2) I can’t always get consistently perfect alignment. A friend of mine uses a drill press (accuracy and depth) with a forstner bit. Drill press is unsuitable for my router bit and the forstner creates a dimple in the wood. The marble router bit I use gives a nicer hollowed out surface. Is there a jig I can make (or on the market) that would allow me to target each hole consistently with my plunge router AND avoid drift? Having to router 160 holes freehand perfectly each time is no fun. I’m a novice when it comes to woodworking. Your advice is appreciated.


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## woodnthings (Jan 24, 2009)

*You need a CNC machine ....$$$$*

*When I made reloading blocks and router bit storage blocks, I made a Master drill template with 1/16" or 3/32" pilot hole for each of the 50 holes. I then ran the drill through the template into the workpiece leaving a shallow pilot hole in the exact location for the larger bit.* I used a drill press and a twist drill bit, but the same approach could be used with plunge router. The issue is getting the bit centered on the small hole correctly, not easy to do because you can't see that well in the router opening.

If you pre-drill the holes to 1" then you have the same issue, but the chances of getting it misaligned are even greater. A brad point bit will center on a small pilot hole real well. Using a hand drill in a drill guide to keep it vertical will work. Your complaint with a Forstner bit is that the bottom of the hole is not flat, and that is so true. A flat bottom bit will not center on any hole, therefore a CNC would be used to control any X or Y axis movement.

I would experiment with different bits on scrap wood to see which combination work best. There is no easy answer that a home shop would be able to execute in my opinion. :sad2:

I used a two plate method for my router bits, drilling through the top plate then gluing it to the bottom plate leaving flat bottom hole:
The block is made from 2 same size pieces. There are 13 mm through holes in the top one, the bottom one has none. They are glued together, the edges sanded on the belt sander and then shellacked to seal them. MDF doesn't seal well on the edges. I chamfered the sharp corners and edges. The blocks measure 6" X 11" for those who want to make some.... Attached Thumbnails


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## andr0id (Jan 11, 2018)

Your holes look too shallow and rounded to firmly hold down a template. 

I think you should make a jig with some index holes that will eventually be cut off the edge of the finished part. Look at how some of the drawer peg templates are set up where a pin goes into the holes you've already made to line up the template to make the next row.

So your work piece will end up with small (say 1/4") alignment holes around the edges. Your template will have the needed 1/4" holes to fit in those as well as bigger holes to make the marble indents.

Alternately, you could make a bit more complicated jig using a T track.
You would clamp the work piece down and then slide the template along the track for each row or column.


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## woodnthings (Jan 24, 2009)

*Huh?*



andr0id said:


> Your holes look too shallow and rounded to firmly hold down a template.
> 
> *If you are referring to my photos, I did not show my drilling template with the 1/16" holes.... firmly hold down what template? you never saw it. The holes in the photos are 1/2" deep. Too shallow for what? *_:surprise2:_
> 
> ...


I don't get your reply, if it's directed at me. :|


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## mmwood_1 (Oct 24, 2007)

My grandfather made many Aggravation boards for all his grandkids and nephews/nieces, etc. They were a marble game and he used standard HSS drill bits on a drill press for the holes. They held marbles just fine and had the more rounded hole, rather than a straight sided forstner hole. I did a similar thing for golf balls in a display rack I did for someone a couple of years ago. You just need to experiment with the diameter and depth in proportion to the ball/marble size, but I think a 1/2" diameter drill bit might give you an adequately sized hole for a 1" marble to rest in. Or maybe a little larger.

The other option for using the router is to make a template that will work with using a guide bushing on the base of the router. You still have to drill the holes in the template on a drill press, but make them to fit the guide bushing. Then you can clamp the template onto your game board, plunge each hole in turn, and it will be totally repeatable for as many boards as you can manage to do. But that's a lot of holes to plunge cut.


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## Bullerwell (Apr 17, 2018)

OK, I see your point. Had actually not considered the standard HSS drill bits as a possible option. The router bit I have does such a nice job. Hate to give it up. A CNC machine is out of the question! Still, I'll give your suggestion a try, though the challenge there will be that with a board 24 inches wide, the drill press post will be problematic, getting in the way. And 'Yes', it is a lot of holes to plunge. Thanks for your responses here.


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## woodnthings (Jan 24, 2009)

*You can use a 3/4" countersink*

You would have to experiment to see how it worked with a 1/2" dia hole or a 5/8" dia hole then countersink/chamfer the edges. A drill press would give a consistent depth using the depth stop feature. Obviously, you can't use a 1" hole, but possibly a 7/8" dia might work.


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## Tool Agnostic (Aug 13, 2017)

As others have suggested, I would use a standard twist drills to make the holes. 
@Bullerwell likes the look of the straight sided, flat bottomed router holes. I have never tried it, but I wonder whether you can use the router bit in a drill press? It would run very slow compared with using it in a router. You could draw or print-and-glue a thin-line grid on the wood to help position the router bit for each hole. Is that a dumb idea?


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## woodnthings (Jan 24, 2009)

*Not entirely "dumb" just ....*

A flat bottom router bit like you will want to use will have no point to start it with, unlike a twist drill. It will dance all around aimlessly marring up the surface. A Forsnter, twist drill or brad point bit will have a pointy end to start the drilling operation. 

In my example, I drilled all the way thought the top 1/2" later of MDF and then glued a second layer on the bottom leaving a flat hole. The same could be done with plywood. Drilling or more precisely, "redrilling" an existing hole requires precision alignment when entering the hole with the second drilling operation. This is not easy to do and that's why I chose the 2 layer appraoch. :|


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## hawkeye10 (Feb 18, 2015)

I drilled these 3/4" holes with my drill press. I cut it into two pieces so I could drill it with the drill press and glued it back together. They were drilled with a Forstner bit.


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## TimPa (Jan 27, 2010)

use a straight edge clamped down to guide one dimension. a mark/tape indicator on your router against a yardstick can help you align the next dimension.


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