Looking for alternative options for 3/4" spiral upcutting router bit - dog holes

[Bud Brinkley]

I want to precisely drill some new dog holes in my bench. I would like to use a plunge router to do this, but 3/4" spirals are hard to find and very pricey. It seems that I recall that you can use a 1/2" bit and a larger guide bushing and by rotating in a circle you can route a perfect 3/4" hole using a 1/2" bit.

Any tips or ideas would be much appreciated!

[Prashun Patel]

You could cut a 3/4” hole template in a piece of mdf and then use a pattern routing bit.

I do mine with a forstner. I start with a 3/4, go down about 1/2”, then switch to a half inch Brad point bit to hog out the middle, then come back with the 3/4 forstner. Nice clean sides and the forstner doesn’t have to work so hard..

[glenn bradley]

My recommendation is to buy the appropriate router bit. You will notice that the spiral bit will try to drill into the surface and pull the plunge down rather suddenly. And alternative that I used on my latest dog holes was Lee valleys three-quarter inch Bradpoint bit and guide. It was much more controllable although I’ve been satisfied with the results from both.

[Paul F Franklin]

+1 on the Lee Valley brad point. Particularly if you need deep holes as you will be limited in depth with a router. Their guide block lets you bore nice an straight with a portable drill so you don't have to muscle a bench top on a drill press.

But if you want to use the router, you can certainly do it with a template guide and a smaller bit. Just think of it as routing a mortise that happens to be round. You will need to take care that your template is nice and round as any defects will be reflected in the holes. And you'll want to use a thin template, say 1/4 mdf, to maximize your cutting depth.

Prashun's suggestion to use a pattern bit is also a good one. Advantage to doing that is once you have the holes part way done, you can remove the template and use the partial hole as the guide for the rest.

[Jim Becker]

While I use my CNC for this kind of thing normally, for those times when I've put dog holes in an existing bench, I used a combination of a Forstner bit for a clean start and a good quality spade bit (with scoring wings) to hog through the material with a board tightly clamped on the bottom to eliminate tearout. I would not use a router for this application unless you are only working with thinner material, such as for an MFT style surface from .75" or 1" thick material. (I do have a Freud 20mm cutter for that which strangely is only available with a .25" shank)

[Steve Wurster]

Are you against using a drill bit? I used this WoodOwl bit (https://www.amazon.com/gp/product/B0009OAJRQ) to drill the holes in the bench I made last year. Be aware however that this thing bites FAST! If you are not careful it can easily get away from you, go offline, and burst right through the bottom of your bench.

I used my drill press to make a 3/4" hole in a thick block of wood, and then used that as a guide for this drill bit to ensure everything was straight. I made the guide block wide enough that I could easily clamp it down when drilling the first set of holes close to the front of the bench, and then used a holdfast to keep it in place when doing the remaining holes. I used a piece of tape to mark the depth so that I would just barely get the point of the bit through the bottom of the bench when drilling from above, and then completed the dog holes from underneath. It worked great.

[Steve Rozmiarek]

Coming from the anti router bias that I've developed over the years and having a 5 1/2" thick top, I came up with a much more civilized way last time I did this. Just set a benchtop drill press on your bench, with a long drill bit, and shim it if needed to get the bit to just barely clear the bench at rest. I clamped it down with a cross bar, probably a good idea, and I got a bunch of bench dog holes with zero router drama.

I actually didn't have a bench top drill press when I did this, I took my floor model apart and substituted a shorter riser pipe for the job, but a benchtop model would save that effort. You may have to swing it to one side to clear the foot, or just drill a hole in the foot to.

Just an alternative.

[Richard Coers]

Curious if you have done any plunge drilling with a router. It's very easy to get something that I call a speed rattle. I get some kind of a resonance from the spiral or something and it gets a chatter in the hole. Not what I would call a precision hole after that.

[Warren Lake]

im not anti router or any other tool that has allowed me to do tons of work. Ive run up to 3" end mills in them but usually 2" Yes on the play Richard mentions, there is slop in up and down. Wrong tool for this job. The drilling stuff guys have mentioned. On the very old Ulmia benches i have they are rectangular and machined in during build before clamping, almost with a dadoe or radial arm then that butts up to the next board. Was it mentioned how deep has to be cut.

[Orlando Gonzalez]

I used a 3/4" end mill then finished it with a 3/4" Fisch brad point bit. Don't forget to have something underneath to prevent the hole from blowing out.

[Warren Lake]

no one mentioning the depth, its part of the question

[Bud Brinkley]

Thanks all for the great suggestions! The depth of my bench top is only 2 inches. I think the bench top drill press is a good idea, but would be a pain to actually set up and do in my case as I have an extended riser pipe on mine. I may look into getting a handheld drill bracket or something similar so I can use a forstner and brad point bit.

Thanks again everyone!

[Bob Cooper]

This is on my list to do...so I have a follow up question

for those that have used the LV Brad point big. How big of a guide did you bore on your drill press and do you try and hold it in place with a holdfast or something? Or can you just put a deep dimple where you want the hole, hold the block by hand and drill with the other hand. Also I assume you only go 1” or so deep and the. Remove the guide block and finish without it. My top
is about 3” thick

[Thomas McCurnin]

Nice jig for an auger style drill bit for 20mm holes,

https://youtu.be/M-NWq7j3lEw?list=ULQ6wigW_VX54

[Paul F Franklin]

This is on my list to do...so I have a follow up question

for those that have used the LV Brad point big. How big of a guide did you bore on your drill press and do you try and hold it in place with a holdfast or something? Or can you just put a deep dimple where you want the hole, hold the block by hand and drill with the other hand. Also I assume you only go 1” or so deep and the. Remove the guide block and finish without it. My top
is about 3” thick

I used the LV dog hole guide bushing as well as their BP bit. IIRC, the guide bushing presses into any board at least 1.5" thick. I had a chunk of oak left over from the bench build that I milled to be 1.5 thick by about 6 wide and 10 or 12 long. I have my dog holes spaced about 6" apart, so after I drilled the hole for the bushing, I drilled another hole 6" away from it. This let me drill the first hole, then slip a dog into it and slide the second hole in the guide block down over the dog. This positioned the drill bushing for the next hole with consistent spacing, as I leap-frogged the guide down the bench. I also sized the guide block and positioned the holes so they were the desired distance in from the edge of the bench. I clamped the guide block and a backer piece under the bench with two clamps. You do not want to try to hold the guide by hand. The LV bit was long enough that I could bore all the way through my bench even with the guide bushing, so I didn't bother to remove the guide half way. But you could.

[eta:] I forgot to mention...for dog holes that weren't along the edge of the bench, I clamped a stout board across the bench at the appropriate location, and then clamped my guide block to that.