Self Tapper Pilot Hole Sizes???

[exapp]

Hello,

Does anyone know of an online or downloadable list of pilot hole sizes for all diameters of self tapping screws under say 10mm.

i.e. if I have a 4mm self tapping screw what should the pilot hole size be for aluminium, fiberglass & wood???

Thanks in advance

Exapp

 

[fluffc]

There was once a list in the Screwfix catalogue, which I cut out and kept. Don't know where that is now.

The pilot hole should (generally) be the same diameter as the shank - that's the part between the teeth.

For Aluminimum the drill size should be ever so slightly larger; for fiberglass exactly the same size, and for wood the drill bit should be the same size too.

The disparity is due to the amount that the material will 'relax' after drilling.

All IMHO...

 

[pheonix]

No8 self tapper use a 4mm drill in fibreglass or 3.5mm in thinner materials ie thin sheet ss or ali
/forums/images/graemlins/cool.gif

 

[boatdoc]

If using size 8 self tapping screws in gel covered grp use 1/8" and csk the gel to stop it from cracking out.

 

[cliff]

Google came up with

this

and

this

You need to scroll down through both items to find type A self tappers or what ever type you are using.

--------------------

"Artificial intelligence is no match for natural stupidity"
sailroom <span style="color:red">The place to auction your previously loved boatie bits</span>

 

[alan17]

Can't tell you what size to use. I made up a guage which also serves as a drill stand. A section of scrap GRP drilled holds my drill bits and is easy to check if ST screw is a clearance fit or will thread in and grip.

 

[exapp]

I had found some of those imperial sizes myself. I'm trying ot find metric ones... Also I'm not jut looking for 4mm i just gave it as an example. I'm trying to find a table of sizes for all commonly used "small" self tappers in mm.

Regards,

Exapp