Self Tapping Screws - Drill Size?

[Richard10002]

Hi,

 

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Any suggestions as to what I could be doing wrong?

 

Many Thanks

[Ex- Member]

Hi,

 

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Any suggestions as to what I could be doing wrong?

 

Many Thanks

 

Try here

 

http://www.scfastening.com/images/sheetmetalspec.pdf

 

 

 

[blackrose]

Hi,

 

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Any suggestions as to what I could be doing wrong?

 

Many Thanks

 

What thickness of plate are you trying to screw them into - and what material?

[bizzard]

Hi,

 

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Any suggestions as to what I could be doing wrong?

 

Many Thanks

If you measure the diameter of the screws thread valley that size drill would be ok for sheet metal,if screwing into softer material probably a touch under that again.

[Rebotco]

Hi,

 

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Any suggestions as to what I could be doing wrong?

 

Many Thanks

 

 

There's no correct answer to that question!

It depends on what the material is and its thickness.

 

Only with that information,can a correct answer be given.

[Radiomariner]

There's no correct answer to that question!

It depends on what the material is and its thickness.

 

Only with that information,can a correct answer be given.

 

Try on a test piece.of materials to be used. Drill small pilot hole and work upwards until best result achieved.

[gillian]

Hi... there is an answer to that question.... standard principle is pilot hole size should be same as core of screw... i.e. hold screw with drill bit in line to the light... drill bit to front and how much thread can you see sticking out behind drill bit.... make sense?

[Rebotco]

Hi... there is an answer to that question.... standard principle is pilot hole size should be same as core of screw... i.e. hold screw with drill bit in line to the light... drill bit to front and how much thread can you see sticking out behind drill bit.... make sense?

 

 

Yes, that is an answer - but not the CORRECT answer.

Nevertheless, that is indeed what I do for most everyday situations.

 

But in more critical applications that would be inadequate.

[gillian]

well, yeah, I agree if it is so critical but I suppose what was mentioned earlier is what material is being used and if it is that critical then a set of taps (not hot and cold) would be needed which would then define the pilot hole in the destructions.... I recall a 5mm thread needs a 4.2 mm pilot for example....

[Richard10002]

Try on a test piece.of materials to be used. Drill small pilot hole and work upwards until best result achieved.

 

That's what I did! 3.5mm too small, 4.0mm too big..... Don't seem to be able to get metal drill bits between 3.5mm and 4mm.

 

I'm fitting new fair leads to the handrail on the roof, for the centreline. I'm pretty sure the rail is the same steel as the top and sides, so probably 4mm.

 

Not a critical application, and I can work around it..... But if you buy some screws, you'd expect to be able to use a standard drill bit, and do the job in 5 minutes - wouldn't you?

[BEngo]

That's what I did! 3.5mm too small, 4.0mm too big..... Don't seem to be able to get metal drill bits between 3.5mm and 4mm.

 

I'm fitting new fair leads to the handrail on the roof, for the centreline. I'm pretty sure the rail is the same steel as the top and sides, so probably 4mm.

 

Not a critical application, and I can work around it..... But if you buy some screws, you'd expect to be able to use a standard drill bit, and do the job in 5 minutes - wouldn't you?

 

 

For a No8 self tapper into 3-5mm plate I use a 9/64 in drill. Drills don't have to be metric!

 

Lubricate the screw with a suitable compound like Rocol RTD or you may break it.

 

Try Chronos, J&L, Tracy Tools or any other of the model engineering suppliers for drills in all standard sizes, imperial and metric. 1.0-10mm the standard interval is 0.1mm and some are available at 0.05 mm interval. Imperial drills up to at least 1in grow by sixty fourths. The sheds, Screwefix etc. only have a very limited range, mainly because most woodscrews these days are engineered to not need to drill a pilot hole, counterbore, or countersink and are designed to be rammed in by a power tool. Ditto production self tappers, which come with a drill point.

 

N

[Rebotco]

That's what I did! 3.5mm too small, 4.0mm too big..... Don't seem to be able to get metal drill bits between 3.5mm and 4mm.

 

I'm fitting new fair leads to the handrail on the roof, for the centreline. I'm pretty sure the rail is the same steel as the top and sides, so probably 4mm.

 

Not a critical application, and I can work around it..... But if you buy some screws, you'd expect to be able to use a standard drill bit, and do the job in 5 minutes - wouldn't you?

 

 

Ebay's your friend! - Try this My link

[Robbo]

Bought some S/S self tapping screws sold as Nos. 6, 8, & 10, (3.6mm, 4.2mm & 4.8mm diameters).

 

What size drills should I use for each? 4mm seems too big for the 4.2mm screws, and a 3.5mm drill is way too small. Can't find a source of 3.75mm drill bits, which I'm guessing is what's needed.

 

Be lazy, get some SDS self tapping ones

 

http://www.ironmongerydirect.co.uk/Products/Screws_and_Fixings/Roofing_and_Self_Tapping_Screws/12514/Wing_Tip_Self_Drilling_Screws_For_Heavy_Section_Steel

[Grace and Favour]

That's what I did! 3.5mm too small, 4.0mm too big..... Don't seem to be able to get metal drill bits between 3.5mm and 4mm.

 

I'm fitting new fair leads to the handrail on the roof, for the centreline. I'm pretty sure the rail is the same steel as the top and sides, so probably 4mm.

 

Not a critical application, and I can work around it..... But if you buy some screws, you'd expect to be able to use a standard drill bit, and do the job in 5 minutes - wouldn't you?

 

Have you looked on Fleabay?

[RLWP]

For a No8 self tapper into 3-5mm plate I use a 9/64 in drill. Drills don't have to be metric!

 

<snip>

 

N

 

Or a set of number drills, which are metric sizes in an imperial series

 

http://www.ebay.co.uk/itm/HSS-DRILL-SET-1-60-NUMBER-DRILLS-WIRE-GAUGE-60-PCS-/300630944536?pt=UK_Home_Garden_PowerTools_SM&hash=item45ff002b18#ht_1927wt_905

 

Richard

[smileypete]

That's what I did! 3.5mm too small, 4.0mm too big..... Don't seem to be able to get metal drill bits between 3.5mm and 4mm.

 

I'm fitting new fair leads to the handrail on the roof, for the centreline. I'm pretty sure the rail is the same steel as the top and sides, so probably 4mm.

 

Not a critical application, and I can work around it..... But if you buy some screws, you'd expect to be able to use a standard drill bit, and do the job in 5 minutes - wouldn't you?

Try self tapping 'self tapper pilot hole sizes' into Google

 

Then try Ebay for drill bits, also it may be easier to cut the thread in the hole with a normal steel (case hardened) self tapper.

 

Edit: Helps to have a decent screwdriver bit, like a Wera or Wiha or something like that.

 

cheers, Pete.

~smpt~

Edited June 21, 2012 by smileypete

[Barry]

Or a set of number drills, which are metric sizes in an imperial series

 

http://www.ebay.co.uk/itm/HSS-DRILL-SET-1-60-NUMBER-DRILLS-WIRE-GAUGE-60-PCS-/300630944536?pt=UK_Home_Garden_PowerTools_SM&hash=item45ff002b18#ht_1927wt_905

 

Richard

 

That's close to tool porn that is

 

But where do you go when you break one?

[RLWP]

That's close to tool porn that is

 

But where do you go when you break one?

 

http://www.cromwell.co.uk/

 

Be careful in there, leave your credit cards behind

 

Richard

[Barry]

http://www.cromwell.co.uk/

 

Be careful in there, leave your credit cards behind

 

Richard

 

Oh I say!!

[bizzard]

If you break one,any good engineers supply shop should sell No-drill bits individually,especially if they supply to model engineers.

[Richard10002]

Or a set of number drills, which are metric sizes in an imperial series

 

http://www.ebay.co.uk/itm/HSS-DRILL-SET-1-60-NUMBER-DRILLS-WIRE-GAUGE-60-PCS-/300630944536?pt=UK_Home_Garden_PowerTools_SM&hash=item45ff002b18#ht_1927wt_905

 

Richard

 

Plenty of things to look at here, so thanks to all. I've looked at all the links and I'll revisit the job over the weekend.

 

Don't really understand the number drill sizes. The listing says something about wire gauge 1-60, but the wire gauge charts I've found say that No.12=2mm, and they get thinner as the number increases..... Doesn't really matter, just wondering

[RLWP]

Plenty of things to look at here, so thanks to all. I've looked at all the links and I'll revisit the job over the weekend.

 

Don't really understand the number drill sizes. The listing says something about wire gauge 1-60, but the wire gauge charts I've found say that No.12=2mm, and they get thinner as the number increases..... Doesn't really matter, just wondering

 

If it helps, I don't understand them either. A set of them is pretty useful though

 

Richard

[BEngo]

Plenty of things to look at here, so thanks to all. I've looked at all the links and I'll revisit the job over the weekend.

 

Don't really understand the number drill sizes. The listing says something about wire gauge 1-60, but the wire gauge charts I've found say that No.12=2mm, and they get thinner as the number increases..... Doesn't really matter, just wondering

 

 

Which Wire Gauge? There are loads of them- Birmingham, American, Standard (BS3737)....

 

A listing of the various drill sizes is here: Drill Sizes

 

N

[Richard10002]

Which Wire Gauge? There are loads of them- Birmingham, American, Standard (BS3737)....

 

A listing of the various drill sizes is here: Drill Sizes

 

That seems to match the drill bits in the listing - excellent! Looks like a set of bits worth having.

 

N