Correct size Pilot Hole for #8 screw

[cuggie]

Hey, I know it is a silly question but thought someone might know the correct size pilot for the PE #8 x 1" Deep Thread Pan Head Screws Black into MDF. for attaching the drivers.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=081-425

I just want to get it right since the tweeter is near the edge of the mounting hole. Almost done with the RB's. The paint job is not perfect but good enough for me.
cuggie

[mzisserson]

Re: Correct size Pilot Hole for #8 screw

http://www.engineershandbook.com/Tables/woodscrewpilotholes.htm

[Wolf]

Re: Correct size Pilot Hole for #8 screw

Hey, I know it is a silly question but thought someone might know the correct size pilot for the PE #8 x 1" Deep Thread Pan Head Screws Black into MDF. for attaching the drivers.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=081-425

I just want to get it right since the tweeter is near the edge of the mounting hole. Almost done with the RB's. The paint job is not perfect but good enough for me.
cuggie

Fow what it's worth, most drivers take a number 6/8, so I keep the 7/64" and 1/8" bits handy. Sometimes a little smaller bit for a #6, depending on the screws, but those are my most popular.
Later,
Wolf

[davepellegrene]

Re: Correct size Pilot Hole for #8 screw

If I don't know what size hole to drill. I usually hold the screw up to light. Look at the shaft of the screw, solid part without the threads. Hold a drill bit up in front of it, right against it, until you find one that is the same size. That way when you screw the screw in the hole only the threads bite. To small of a hole will mushroom out the MDF. To big of a hole you won't get a good bite.
Dave

[john trials]

Re: Correct size Pilot Hole for #8 screw

Safest route: Do a test in a scrap piece of MDF. Pick a couple of drill bits (I use Davepellegrene's method, or measure with calipers). Drill a hole with each bit, then drive some screws in. Pick the best one to use on your project.

[jclin4]

Re: Correct size Pilot Hole for #8 screw

If I don't know what size hole to drill. I usually hold the screw up to light. Look at the shaft of the screw, solid part without the threads. Hold a drill bit up in front of it, right against it, until you find one that is the same size. That way when you screw the screw in the hole only the threads bite. To small of a hole will mushroom out the MDF. To big of a hole you won't get a good bite.
Dave

This was what I was taught in shop class -- 'O so many years ago. I thought going with the smaller hole was being more conservative. But the logic of the small hole compressing/mushrooming out the MDF makes sense.

[davepellegrene]

Re: Correct size Pilot Hole for #8 screw

This was what I was taught in shop class -- 'O so many years ago. I thought going with the smaller hole was being more conservative. But the logic of the small hole compressing/mushrooming out the MDF makes sense.

I too will start with a smaller hole if not sure. I also found out the hard way if you drill to small of a hole in hardwood you end up twisting the head off of the screw. Especially the little ones. Hate that.
Dave