How to slightly enlarge a bench dog hole

I made a workbench from some gluelams I got for free. It is quite substantial, being about 5 inches thick; very solid. I drilled some bench dog holes in it, and then I bought a holdfast.
Unfortunately, even though the holdfast was described as 3/4" diameter, it's really a bit larger, and I need to enlarge the dog holes by about 1/8". I saw one technique where you grind the shoulders of a spade bit at 60 degrees and proceed carefully down the holes to enlarge them. Does anyone have better ideas?
Also, I initially drilled too many holes. Any thoughts on plugging them? I might just glue in some dowels, but someone might have a more elegant idea.
Thanks,
scritch
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On 10/12/2013 11:27 AM, scritch wrote: ...

I'd use a twist drill (carefully) -- it'll follow the existing holes more readily than the spade bit will.
Or, the really clean way would be to glue in a waste dowel and redrill as wanted w/ a Forstner.

Use a dowel for the bulk but cut some matching grain plugs 1/4" thick or so to mate up with the surface if want the appearances...
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"scritch" wrote in message
I made a workbench from some gluelams I got for free. It is quite substantial, being about 5 inches thick; very solid. I drilled some bench dog holes in it, and then I bought a holdfast.
Unfortunately, even though the holdfast was described as 3/4" diameter, it's really a bit larger, and I need to enlarge the dog holes by about 1/8". I saw one technique where you grind the shoulders of a spade bit at 60 degrees and proceed carefully down the holes to enlarge them. Does anyone have better ideas?
Also, I initially drilled too many holes. Any thoughts on plugging them? I might just glue in some dowels, but someone might have a more elegant idea.
Thanks,
scritch
I would plug the holes with a dowel and then redrill with the proper sized fostner bit WW
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wrote:

I'd use a twist bit and take it slow like dpb suggested. Or if you want to use a Forstner bit drill the desired hole size in a piece of scrap and then clamp it to your bench to be the guide for the Forstner bit to get it started. After you get deep enough you will no longer need the guide and it can be discarded.

This is an easy fix! Go to Harbor Freight and get one of their recently inventoried "Negative Kerf" drill bits. They're fantastic!! :-)

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On Sat, 12 Oct 2013 12:27:27 -0500, Gordon Shumway

That's what I would do, even with a twist drill. The hole in the "guide" scrap can be drilled at the same time. I'd probably use hardboard for the guide.

Should have used a portable hole.

https://www.youtube.com/watch?v=dI-I8DQD4LI

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On 10/12/2013 12:27 PM, scritch wrote:

--
Jeff

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On 10/12/2013 10:30 AM, woodchucker wrote:

Best idea yet! I ordered up two, too. Then, in a flash of inspiration, I turned a bunch of tapered plugs which I pounded into the holes I don't think I need. They will make the top smoother and can be tapped out from below should I need a new hole.
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You might use an "Oops" arbor with two hole saws.. Lee Valley Tools sells them. I'm not sure that a 1/8" difference is enough to use smaller to larger hole saws, but you could visit an LV store and find out.
http://www.leevalley.com/en/wood/page.aspx?pR518&cat=1,180,42316
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No idea if it is better but if you don't want to enlarge the holes, shrink the holdfast. You could take it to a machine shop or if you have something you can chuck it in - lathe, drill press, etc. - you could do it yourself with a stone.
Personally, I'd send it back. If they say 3/4 I expect 3/4.

You could get some epoxy, thicken it with talc (so it will be white/grey and opaque) and swirl in different colors. Personally, I'd just use the dowels :)
--

dadiOH
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On Saturday, October 12, 2013 11:27:38 AM UTC-5, scritch wrote:

I would use the drill press to drill the proper sized holes in a substantial piece of hardwood. Then I'd clamp that hardwood to the proper position above the old holes and use it as a guide to enlarge the holes.
Mike
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"scritch" wrote:

Return the defective dog(s) and make your own,
Start with 3/4" x 3/4" x 8" maple or white oak piece.
Setup router table with a 3/8" round over bit and fence with stops.
Machine a "dogbone" with 3/4" round in center and 3/4" x 3/4" x 1" ends.
Cross cut "dogbone" into two (2) equal pieces that become your bench dogs.
Lew
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On 10/12/2013 12:27 PM, scritch wrote:

should be grinding away at the holdfast to make it the correct size (or return it for one that is correctly sized). Other tools you might acquire in the future will want the dog holes to be the correct size and there is no way you are going to shrink them retroactively.
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On 10/13/2013 10:44 AM, BenignBodger wrote:

Excellent point.
I use dogs from veritas and holdfasts from Garmercy... all fit the same hole.
--
Jeff

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I would not permanently glue in dowels. I would make expanding plugs that could be removed. Buy dowels that are snug fit. Cut to length. Drill a h ole in the center of one end for a countersunk wood screw. Using a thin ke rf saw, cut down the middle of the screwhole (lengthwise) about 1/2 to 1/3 the length of the screw. Insert the dowel in the excess hole, insert screw and tighten. The screw should cause the dowel to expand, securing the dow el in the hole. Might be a good idea to heavily coat the top end of the do wel in parafin or candle wax in case glue or paint gets on it.
On Saturday, October 12, 2013 11:27:38 AM UTC-5, scritch wrote:

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*snip*

If they're not in the way or you're only bothered by the look, I'd consider leaving them. If you add a vise to your bench, especially one without a quick adjust, more holes is a good thing.
Puckdropper
--
Make it to fit, don't make it fit.

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wrote:

I made my dog holes with a router and bearing guided router bit. They ended up perfectly square to the table. You could enlarge an existing hole by drilling an enlarged hole in a scrap piece and clamp that scrap over the existing hole, then enlarge with the router. Once the hole is started, you can go deeper in stages if the router bit is not long enough.
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