Drilling Perpendicular Holes w Spade & Forstner Bits?

[Steve H Graham]

I'm going to reveal my shameful secret: I can't drill holes perpendicular to my work.

I was putting bench dog holes in my bench top, and I figured I would try the trick I saw on a Youtube video. I would put a V-shaped notch in a thick batten and use it to support the bit so it cut straight. Then I realized this will not work for spade OR Forstner bits. I could have used a Silver & Deming bit, but I hate to ruin them on wood.

I got out a Craftsman gadget with two springs on it. It's supposed to hold the drill at a fixed angle to the work while you drill. Apparently it doesn't. I have one hole that looks like it's a solid 5 degrees off vertical.

So what's the answer?

[Jim Dwight]

My Ryobi cordless drills have little levels on them. They help. Holding a square up to the drill to sight against also helps. If I really have to drill straight and can't use the drill press I dig out a parallel rod guide. It has a separate chuck. Works well but it's one more thing to manage. Another good way to make a bunch of holes perpendicular would be to use a plunge router.

[Kent A Bathurst]

Set wood blocks at 90*, so you can see plumb in 2 directions. Get in position where you can sight along the bit/shaft v the references and start drilling - less than Warp 4 - keeping it sighted in.

Stand up a bevel gauge if you have one angle that is not 90*.

Or - use bevel gauge @ 90* and / or squares - whatever - for reference.

I have tried 2 of those gadgets where you mount a drill to use as a guide-type-drill-press-mimic-thing. Never held true. Must be something out there, but this is a rare event, so I just take my time and do it carefully.........

[Eric Schmid]

Plunge router seems like the right tool for your job. You could do the layout on a template so you're not practicing on your table. The template can be a strip of plywood that you drill/route the layout holes in. Lay it out on the table and trace the holes with a pattern bit on a router. If you've got a drill press the template could be made on there. Two parallel rows on the template will give registry points for parallel rows on the table.

[Mike Schuch]

I have a 30 year old little bench top drill press pretty much worthless for anything but... I have swung the table out of the way, lowered the head, and cut out a hole in the base. It did an excellent job on perfectly perpendicular bench dog holes.

[glenn bradley]

I fought non-perp dog holes for the last time and switched to a plunge router.

[Roy Harding]

http://www.busybeetools.com/products/drill-mate-accu-milescraft.html

i did one bench with a plunge router, and one with a drill guide as at the link. Both worked. I'm on my iPad, so I couldn't post a proper link, you'll have to copy and paste the link.

[Ken Andersen]

Modify your v-block so it can accommodate the cutter portion of your forstner or spade bit while the shaft of the bit rests in the v. Here's one way to do that: Make a backer board for your v-block. The backer board thickness should be slightly more than the total length of the cutting portion of your bit. Mount the v-block so the bottom of the v overhangs the edge of the backer by at least the radius of the bit.

[Kent A Bathurst]

I fought non-perp dog holes for the last time and switched to a plunge router.

Dunno why I did not think of that. Ignore what I said. Go with Glenn.

[Keith Outten]

A plunge router seems to be the best answer in this case as mentioned.

Another option is to borrow or rent a magnetic drill which are made primarilly for metal drilling so they are generally very heavy duty and accurate unless they are worn out. You can lay a large piece of flat bar on your wooden table top and use clamps to hold it securely to the top. At that point you can engage the mag drill magnet to the plate and drill your holes.

We have discussed magnetic drills here before as they offer a means to drill holes without the drill bit to column limit you normally have with a drill press. Very large holes are possible using hole saws, mag drills are made for this kind of work.
.

[Jim Wheeler]

I'm not sure how drilling wood could hurt a Silver and Deming drill that is intended for metal, but be that as it may...
You could use the shop-made guide with the v-shaped notch to drill a small pilot hole first with an ordinary twist drill or brad point bit. The spade bit will follow the pilot hole, if you're careful - as will the Forstner if it is one with a brad point.

Btw, rather than a batten with a v-shaped notch, I like to use a hardwood batten that has been drilled on the drill press to form a perpendicular guide. I've even used such a guide to drill dowel holes with good results.


Jim

He who welds steel with flaming pine cones may accomplish anything!​

[Brian Tymchak]

... I like to use a hardwood batten that has been drilled on the drill press to form a perpendicular guide. I've even used such a guide to drill dowel holes with good results.
​

this is what I did to drill dog holes. My bench top is 3 1/2" thick so my plunge router wasn't going to cut it. I grabbed a scrap of 8/4 Ash long enough to span the bench top width-wise and drilled 3 holes on the drill press in the exact spacing I wanted across the bench top. Then clamped that pattern guide onto the bench where I wanted and drilled the holes using the guide to stay straight. I also clamped a board on the bottom of the bench to minimize tear out as I was using a twist bit. I used a trim router to put the very lightest chamfer I could on the tops of the holes to eliminate any future splintering.

[ryan paulsen]

I haven't used these, but am considering them for when I build my bench:

http://www.leevalley.com/US/Wood/page.aspx?p=72602&cat=1,41637

[Robert Engel]

I haven't used these, but am considering them for when I build my bench:

http://www.leevalley.com/US/Wood/page.aspx?p=72602&cat=1,41637

Drill the dog hole strip before you laminate the top and you can make a nice job of it on the drill press.

Suggestion: figure out where your vise will go before you drill the holes to avoid having holes that end up over the vise frame (how do I know that?)

[Reinis Kanders]

I just used that bushing, worked great.


I haven't used these, but am considering them for when I build my bench:

http://www.leevalley.com/US/Wood/page.aspx?p=72602&cat=1,41637

[John Donofrio]

this is what I did to drill dog holes. My bench top is 3 1/2" thick so my plunge router wasn't going to cut it. I grabbed a scrap of 8/4 Ash long enough to span the bench top width-wise and drilled 3 holes on the drill press in the exact spacing I wanted across the bench top. Then clamped that pattern guide onto the bench where I wanted and drilled the holes using the guide to stay straight. I also clamped a board on the bottom of the bench to minimize tear out as I was using a twist bit. I used a trim router to put the very lightest chamfer I could on the tops of the holes to eliminate any future splintering.

This is basically how I did it but would instead use thicker hardwood as Brian did.

http://www.sawmillcreek.org/showthread.php?196969-Post-production-roubo-build-thread&p=2044119#post2044119

[Al Launier]

If the plunge router doesn't have enough travel to completely drill through the bench top, drill to finish depth with a hand drill. The finish drill will follow the pilot hole through the enire depth of the bench top.

To avoid any drill chatter when entering the hole, drill a starting hole in a board, align the board to the previously drilled hole in the bench top with a dowel, clamp board in place, remove the dowel & then drill through the starting hole through the bench top.

[glenn bradley]

If the plunge router doesn't have enough travel to completely drill through the bench top, drill to finish depth with a hand drill. The finish drill will follow the pilot hole through the enire depth of the bench top.

To avoid any drill chatter when entering the hole, drill a starting hole in a board, align the board to the previously drilled hole in the bench top with a dowel, clamp board in place, remove the dowel & then drill through the starting hole through the bench top.

Al makes a good point and I should have elaborated. I use a template . . . the example pics are an assembly table top but, you get the idea.

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I drill about an 1/8" deep with a Forstner and use dogs to align the template for the next position. I do all the positions.

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I then use the dimple in the Forstner hole to center a 7/16" twist drill and drill all the way through (back you work). This removes the bulk of the spoil and makes the router work very quick. I then plunge all the holes as deep as the router will go, again I use the shallow Forstner holes to line things up.

Then I flip the top over and use a 3/8" flush trim bit from the opposite side. The bearing rides in the routed part of the hole and flushes the 7/16" through hole perfectly. Sure it takes a few more steps but, I forget all about the extra effort years from now when I am still using nice perpendicular dog holes.

Many ways to skin the cat and lots of good suggestions here.

[ian maybury]

Think this is one of those situations where the devil is in the detail, and a hole is more than just a hole.

Perhaps it's been said already, but neither a Forstner nor a spade bit is self guiding - especially the former. Both can drift off line unless held vertically over clamped work as in a drill press - and even then some movement could be possible.

The various drill stands don't have a whole lot by way of stiffness or accuracy, and are not much use unless tight and the base clamped down.

My preference is for a good quality brad point such as a Colt, Lee Valley or a Famag HSS-G - they have a proper cylindrical body/fluted section, and as such can be guided pretty accurately using a guide block with a correctly aligned and sized hole. It might also be possible to use a router to start the holes/to create a guide bore - and finish with a brad - but the router cutter might deliver a smaller hole than the brad needs if it is to enter it and be guided. They also have very sharp spurs that on a top quality item will deliver an absolutely clean entry, and a pretty good exit too.

The chances are that there may be some power augers with a screw tip that would do a decent job too, but I haven't yet had one that was controllable enough. (most are made to self feed pretty aggressively to blast through roof timbers and the like when running cables or pipes)

As before the other consideration that needs testing/thinking about is the actual hole diameter a given drilling method will produce.

Chances are that a holdfast like the Grammercy one (which is a great product) will not grip so well in a bench top much over 2 1/2in thick if the resulting hole diameter is close to nominal 3/4in size. It'd need testing, but on a very thick top it's even possible that a 20mm hole might work well - and permit usefully heftier dogs and 20mm dia Euro work holding hardware as well......

[Steve H Graham]

A plunge router! That seems so obvious! That would have been so much easier.

[Greg Hines, MD]

Heres another way to do it:

https://www.youtube.com/watch?v=lo6Ondv9L98&list=PL06ACC20F47E7FE39&index=21

[william watts]

Heres a jig that guides a forstner bit. I used it to drill perpendicular holes for mounting capitals on bed posts. The spacers allow chips to clear, my shop helper/wife held the shop vac, this worked fine, don't know if you can get a forstner bit long enough for a work bench.

I built my work bench in the last century. Back then the thinking was that dog holes should be tilted about 2 * toward the tail vise to firmly hold the work down to the bench or maybe it was so the dog would be perpendicular under pressure.....so long ago memory is fuzzy. Has that thinking changed? Dog holes are square pie r round.




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