Drilling / Countersinking Holes in Tablesaw rails

[Alan Lightstone]

I need to drill several holes in my SawStop tablesaw rails to install a cast iron router table. To have clearance for the Biesenmeyer type fence, I'll need to countersink the holes, just like the saw comes with.

My question is, how do I drill those countersunk holes in that steel? I'm assuming that my wood countersink bits can't do steel. Are their specific drill bits made for this task?

Also, is my drill press necessary for the task, or can a 36V Bosch cordless drill accomplish it?

[Don Zielinski]

Hi Alan,

Unless your countersinks specified wood only they are generally high speed steel and will be fine for the job. You do not need a drill press as the
countersink will follow the hole. The holes are probably 5/16 -3/8 so I would keep the drill speed under 500 rpm.

Don Z.

[Bill Edwards(2)]

Do you have a 1/2 inch or bigger twist drill (bit).

I would think it would provide the countersink you need.

(just guessing)

[Don Zielinski]

A large drill will work in a pinch but the point angle is too shallow. drills for mild steel are 115-135 deg and a standard countersink is 82 deg.

Don Z.

[Keith Westfall]

A large drill will work in a pinch...

But you won't get a very smooth countersink!

[zayd alle]

But you won't get a very smooth countersink!

Nor will your screw seat in the countersink due to the mismatched angles. Pay the $12 and buy a HSS countersink bit from Sears, even if you wear it out for just these holes.

[Lee Schierer]

Buy one of these countersink (http://www.amazon.com/General-Tools-195-1-2-Inch-Countersink/dp/B00004T7OQ/ref=sr_1_6?s=power-hand-tools&ie=UTF8&qid=1294853975&sr=1-6) bits at your local hardware store or big box for about $4. It will work just fine, if you drill by hand drill keep your drill speed down.

[Alan Lightstone]

That's the approach I took, Lee. What speed should I use? Is oiling the bit necessary during drilling?

The approach is to drill the center hole first, then essentially cut the countersink / smooth the edges, correct?

[John Coloccia]

Unless you're drilling through thin aluminum where it really doesn't matter, it's never a bad idea to lubricate your bits. Everything will just work better. If you try to use the countersink like a normal bit, you will probably be rewarded with a chattering cut. I prefer to countersink in metal with a slow speed and a higher than normal pressure. This will "lock" everything together and help to prevent the chatter. Once it starts chattering, you'll probably never get rid of it. You'll also never see it again once the bolt is in, so no big deal in this particular application.

[Lee Schierer]

it's never a bad idea to lubricate your bits. Everything will just work better. If you try to use the countersink like a normal bit, you will probably be rewarded with a chattering cut. I prefer to countersink in metal with a slow speed and a higher than normal pressure. This will "lock" everything together and help to prevent the chatter. Once it starts chattering, you'll probably never get rid of it. You'll also never see it again once the bolt is in, so no big deal in this particular application.

Chattering when countersinking on a drill press is also a function of the play between the rack and pinion gear on your quill. If there is much play, the countersink can chatter pretty easily. Unelss your drill press is really tight, you want to apply good quick downward pressure to a stop point and not try to sneak up on the desired final depth.

[Alan Lightstone]

Thanks guys. Great advice.

[Chip Lindley]

Countersinking has been well-covered. How about drilling holes in metal? Accurately finding where the hole center will be, comes first. Mark the spot with a prick punch. Then dimple that mark with a centerpunch. Now your bit will not wander and scar the surface! It will stay centered where you want it.

A drill press is nice for drilling OR countersinking. Feed pressure is steady and the depth stop can be set for uniform countersinks in every hole.

[Alan Lightstone]

Learned something new. Had to look up what a prick punch was. Why can't you just use the center punch?

[Alan Lightstone]

OK. Drilled the holes with the drill press - no problem at all. 7/16" Holes.

But when I tried the countersink (I got a Hitachi 5/8" titanium one at the BORG), it doesn't do anything. It just spins to its hearts content and doesn't cut into the metal (Despite pretty significant pressure).

What am I missing here?

[John Coloccia]

How hot did you get the steal when you drilled the hole? It's possible to harden the steal if you get it too hot. I doubt you did that but it's possible. Maybe this is a stupid question, but are you sure you're not up against a depth stop or the end of quill travel? I know I know...dumb question, but I figured I'd ask anyway.

[Alan Lightstone]

Not up against the depth stop or quill travel. I know, I looked just in case I was having a brain fart when I was doing it.

The steel did get a little hot. I did use drops of oil as I drilled the hole. I can't imagine it got hard enough to harden the steel. I was able to drill through it pretty easily with HSS drill bits.

[Kent A Bathurst]

Hmmmm....used the General countersink from Lee's post to do exactly what you are doing [except Delta rail, not SS]. Maybe the steel on the Uni is different alloy..........


We have the car in drive, and not reverse, don't we? :p


[Hey - I've done it - maybe there is one other fool out there as well]

[Alan Lightstone]

LOL. I don't know how to put my drill press in reverse, and it did drill the hole, so I'm thinking I'm in drive.

LOL. It did appear to be turning towards the cutting surface, FWIW.

[Alan Lightstone]

I just noticed something on the package of the Hitachi bit. It has two diagrams. One is a rectangular drawing - I think it refers to wood. The other is a pipe shaped object that says PVC. Is it possible that this drill bit isn't hard enough for steel? It says Titanium. Not sure which titanium alloy that refers to.

[Alan Lightstone]

Ooooh. Lowe's web site says for wood applications.

Do Lowe's or HD sell countersink bits for steel? This was the only one I saw at Lowe's.

[Don Zielinski]

Yes they do. Try to find a Hanson now made by Irwin. I have a few that I have been using for all types of metal that are at least 2o years old and still work fine.

[Lee Schierer]

Now that's your problem. Wood bits aren't generally hard enough for steel use, even when Titanium coated. The titanium is supposed to give you longer cutting life, but mostly they just charge more IME. Your bit is probably trash. Almost any hardware store will have a countersink for metal applications. Bits by Vermont American, Irwin, Hanson or General should all do the job. Avoid those with drills for pilot holes as they are generally for wood only.

[Tom Clark FL]

Any high-speed steel 82˚ countersink will work. Keep speed to around 100 rpm. If your drill press won't go that slow, use a variable-speed drill, and keep rpm way down.

Tom
retired machinist

[Alan Lightstone]

Did it on the drill press. Only went as slow as 500rpm. Wish I had seen Tom's post first.

It went reasonably well, although I stopped multiple times when it started smoking, despite keeping it oiled.

[Jim O'Dell]

Little late to the party, but my first thought was do any of the original holes in the SS fence rails already match up with the edge of the CI router table edge? CI drills much easier than steel. That's what I did when I installed my Biese fence on the contractor saw. Drilled the holes slightly over sized so I had a little adjustment built in, then used the factory supplied bolts to put it together. Jim.

[Alan Lightstone]

Never realized that cast iron was easier to drill than steel. Wouldn't have had to worry about the countersinking either. Could have just drilled via the existing holes. Oh well.