Of pilot holes, counter sinks and the like

Exile_D

benevolent tyrant
Charter Life Member
Benefactor
Joined
Dec 17, 2016
Messages
8,661
Location
On an accident prone boat (CLT)
Rating - 100%
21   0   0
So I made the mistake of using the internet to search about drilling the proper size pilot hole and using counter sinks. There seems to be some disagreement, depending on which random website you land on, to the correct size of the drill bit for a pilot hole. Gets even more fun when you throw in hardwood, softwoods and tapered vs. straight bits, lol!

In the past I just used a very small drill bit to drill a pilot hole and then a drill bit about the size of the head of the screw to take out just enough material for the screw to sit flush. I realize the error of my ways now, but unfortunately can't seem to find a consensus on the best size bit for any particular screw size.

Should I just stop looking online and just line up the bit and screw so I get a bit close enough to the size of the screw root/minor diameter?

Also, do woodscrews like the GRK R4 really eliminate the need for pilot holes?
 
In softwood I use a drill slightly smaller than the screw shank, in hardwood I drill the same size as the screw shank. If I’m just putting together a utility piece from 2x4 and plywood then I often don’t drill a pilot.

I’m not sure it’s right, just what I do.
 
Never ask the internet anything like that.

Personally I don't usually drill pilot holes unless I think what I'm putting screws in might split. And then I usually drill just to line things up right.

You could look through the McMaster Carr catalog and see if the pages on screws recommend a pilot hole size.
 
In softwood I use a drill slightly smaller than the screw shank, in hardwood I drill the same size as the screw shank. If I’m just putting together a utility piece from 2x4 and plywood then I often don’t drill a pilot.

I’m not sure it’s right, just what I do.
It's never failed you though, has it?

I mean, I think the best way to be more sure you don't split the wood is to drill a pilot hole equal to the full diameter of the threads... but what you're doing will probably work at least as well. :)
 
I don't use one in soft woods usually but in hard wood I go with a bit just the diameter of the screw minus the threads. The purpose of a pilot hole is to guide where the screw goes, and to a lesser extent, prevent cracking of the wood.

If it's a countersink issue just get the countersink bit for the screws you're using. #8 for #8 screws and so on.

If you are doing a project with a lot of screws like a deck you would be well suited to buy a wax toilet seal from the plumbing section. They are pure beeswax and just drag the tip of the screw through the wax and you'll be amazed at how easy the screw goes in.
 
This thread reminded me of one of the key lessons from my high school shop class. Take a punch and make a small indentation where you want the hole to go. If you do, the drill bit will go right to it. If you don't it will dance around the surface and scrape it up.
 
A ma ford single flute countersink needs no pilot hole for wood. It cuts better with no pilot hole, in wood.
Also for wood, I use just under minor diameter for soft, and a few thousandths over minor Dia for hard wood.
 
It's never failed you though, has it?

I mean, I think the best way to be more sure you don't split the wood is to drill a pilot hole equal to the full diameter of the threads... but what you're doing will probably work at least as well. :)
You are correct that you’ll never split the wood if the pilot hole is the full diameter of the screw threads. The only real problem with that approach is that the pilot hole is the full diameter of the screw threads. Screw has to bite into something.
 
I used to have a poster from I believe Popular Mechanics that had screw and bolt sizes, listed tap drill sizes and I believe it had pilot hole sizes for soft and hard wood and nail sizes.
 
Well now you have gone and asked the question on the internet....

I would go with Scsmith42's recommendation first. Those are a little pricey but the deal for perfect counter sink.

I have used what ES44AC linked for years and they work fine. However; the counter sink can be inconsistent but you get pretty close and the bit is typically tapered which generally isn't a problem dependent on depth.

If your bit was too small in say hardwood, you will know because it will leave a gap, back the screw out and drive it in again. Things should tighten back up.
 
Back
Top Bottom