Question about pilot hole size for screws

[Jeff Skory]

Do any of you have any rules of thumb for how big pilot holes should be for screws? I have run into a couple of situations where my guess was apparently too small.

The first was when I was trying to attach some brass hinges to a small box. The box is made out of white oak (very hard stuff). I got the screw in about 1/2 way and it broke. I made the next pilot hole a little larger and got about 3/4 of the way in before the screw broke.

I blamed the screws that came with the hinges as being of poor quality and have not bought replacements yet.

Then yesterday I was putting some 1 inch screws through a piece of the same white oak which I used for a fence on my cut-off sled. I managed to snap one of those large screws in half.

After some trial and error with a scrap of the oak I figured out which size works.

But in the future I would like to avoid breaking screws inside of my workpieces.

Any hints?

Thanks,

Jeff Skory

[John Christiansen]

Do any of you have any rules of thumb for how big pilot holes should be for screws? I have run into a couple of situations where my guess was apparently too small.

The first was when I was trying to attach some brass hinges to a small box. The box is made out of white oak (very hard stuff). I got the screw in about 1/2 way and it broke. I made the next pilot hole a little larger and got about 3/4 of the way in before the screw broke.

I blamed the screws that came with the hinges as being of poor quality and have not bought replacements yet.

Then yesterday I was putting some 1 inch screws through a piece of the same white oak which I used for a fence on my cut-off sled. I managed to snap one of those large screws in half.

After some trial and error with a scrap of the oak I figured out which size works.

But in the future I would like to avoid breaking screws inside of my workpieces.

Any hints?

Thanks,

Jeff Skory

I'll usually just hold the drill bit up against the screw until I have one that will cover or almost cover the shank of the screw without covering the threads. It also helps with dense or hard wood to lubricate the screw with something. I will use bees wax, Ivory soap, parrafin, paste wax..... whichever one is handy.

[Michael Campbell]

I'll usually just hold the drill bit up against the screw until I have one that will cover or almost cover the shank of the screw without covering the threads. It also helps with dense or hard wood to lubricate the screw with something. I will use bees wax, Ivory soap, parrafin, paste wax..... whichever one is handy.

Soap will corrode certain screw types, so be careful there.

Here's a good link to pilot hole sizes: http://www.woodmagazine.com/media/screwchart.pdf

[Jim DeLaney]

General rule of thumb is that the pilot hole should be just slightly bigger than the core, or solid portion of the screw - usually just over half the actual diameter of the screw itself.

For brass screws, you could make the pilot hole a bit bigger yet, but what I do - with good success rate - is to drive a steel screw of the same size into the hole first, and let it make the threaded hole for the brass one that follows. Also use beeswax or parafin wax on the screws to make them go in easier.

[Fred Voorhees]

I would agree with Jim's post. I have used steel screws of the same size to "thread" the hole before using brass screws. Brass is notoriously soft and I have had the displeasure of having one or two break within my project. Not fun. :mad: That is when I made a post myself on another woodworking board and was informed about using steel screws. Works like a charm and I also use an old candle to lubricate my screws. I used to use soap, but was told that soap actually attracts moisture and therefore rusts up screws.

[Mark Singer]

Here is a link for tappered drills...they are great for fine brass hardware also use a steel screw first..as Fred suggested here is a link:
http://www.leevalley.com/wood/page.asp?page=32334&category=1,180,42240&ccurrency=2&SID=

[Jeff Skory]

Thanks all. Great information. I'll give those suggestions a try and also visit the sites that were referenced.

[Bob Powers]

I use a chart from www.deltawoodworking.com/table/charts/boring.html. It's titled Pilot Hole/Shank Clearance Hole Boring Recommendations.


Do any of you have any rules of thumb for how big pilot holes should be for screws? I have run into a couple of situations where my guess was apparently too small.

The first was when I was trying to attach some brass hinges to a small box. The box is made out of white oak (very hard stuff). I got the screw in about 1/2 way and it broke. I made the next pilot hole a little larger and got about 3/4 of the way in before the screw broke.

I blamed the screws that came with the hinges as being of poor quality and have not bought replacements yet.

Then yesterday I was putting some 1 inch screws through a piece of the same white oak which I used for a fence on my cut-off sled. I managed to snap one of those large screws in half.

After some trial and error with a scrap of the oak I figured out which size works.

But in the future I would like to avoid breaking screws inside of my workpieces.

Any hints?

Thanks,

Jeff Skory

[Bob Powers]

I use a chart from www.deltawoodworking.com/table/charts/boring.html. It's titled Pilot Hole/Shank Clearance Hole Boring Recommendations.
Does anybody have an idea why I can't get this URL to say /table/charts?

[Michael Campbell]

Does anybody have an idea why I can't get this URL to say /table/charts?

The posting software shortens the URL when it considers it "too long". If you click on it though, it goes to the page you specified. (However, that page doesn't exist, even so.)

[Don Stanley]

Been there, done that! You have good advise from others here. FWIW here's the technique I use on non-taper screws. Measure the shank (between the threads) with a dial caliper. Find the drill bit with neareast size, usually maked in thousands on the drill bit box.

Wood screws have a tapered shank. Get a set of tapered drill bits for best results.

I lubricate stuburn screws with candle wax. Keep two big candle in the shop, just for that purpose.

[Chris Padilla]

For cheap and easy lubrication, try out the wax ring that are used on toilets.

I warm one up slightly and ease it into a buttercup or cool whip container...lasts quite a while.

[Jeff Skory]

Been there, done that! You have good advise from others here. FWIW here's the technique I use on non-taper screws. Measure the shank (between the threads) with a dial caliper. Find the drill bit with neareast size, usually maked in thousands on the drill bit box.

Wood screws have a tapered shank. Get a set of tapered drill bits for best results.

I lubricate stuburn screws with candle wax. Keep two big candle in the shop, just for that purpose.

Don,

I hadn't thought about tapered drill bits. I have seen them in the catalogs but never really knew when you would use them. I am assuming that it helps give an even fit across the entire length of the screw. I take your advice and purchase some.

Jeff

[Jeff Skory]

For cheap and easy lubrication, try out the wax ring that are used on toilets.

I warm one up slightly and ease it into a buttercup or cool whip container...lasts quite a while.


Chris,

That just sounds wrong! :p

[Chris Padilla]

Jeff,

The tapered bits often come with a countersink and stop and are relatively cheap. Start at Grizzly...I think you can get 5 or 6 of them in a package for under $25. I'm sure you can find others that are more expensive but the cheap ones have worked well for me for a couple years now.

Yeah, I reread my wax ring post--it does sound a bit, er, wrong! :)

[luke bronco]

This web site has a good chart for pilot holes on it for sizes 0 thur 24 plus a good source for those hard to find screws you could have um made here. hope it helps http://www.oemfasteners.net/My_Homepage_Files/Page10.html

Luke