I have a set of number drills but haven't used them in years, I would suggest a decent brand metric drill set will be a better bet. Generally availiable in .05mm & .1mm steps so you can pretty well cover all options.

Tony

If you buy a set of either number or metric fractional drills buy a known brand as i have two sets that are a bit dodgy from the eastern provinces .

Can't complain really for the price as 90 % are ok but i was looking through my metric set that is .1 divisioned and stumbled upon the 9.6 and 9.8 drills that are both stamped 9.8 and measure the same !

Have the same issue with number drills from 40 up but so far the bigger drills have been fine .

Suppose you get what ya pay for !

Most you will never use so maybe just buy what you need ?

Ian

Edited By SLOTDRILLER on 14/06/2013 07:24:29

Edited By SLOTDRILLER on 14/06/2013 07:26:15

The sets i have are not too soft but rather brittle and the 5.0mm split up the middle !
If you look at a project and order what you need before hand there should be no hold up but i understand where you are coming from as everyone wants to use some wierd size drill for no rerason !

Ian

I think someone on the forum said " Buy cheap, buy twice!".

I've gone the eBay no brand cheap route, but never again!

I went through 5 x 4mm drill bits whilst fitting the roller shelves to my BH600G stand, and the remaining 5 soon after. They just snapped at the least provocation..

By comparison, I have a set of General number drill bits dating from the '70s and they are still going strong.

It's now name brand only, more expensive yes, but once only, unless I do something stupid.

Reminds me of a brand of metric sets I was selling in the '70s, from Taiwan, that I flung back at the distributor when a customer came into the shop, took a drill bit and bent it! I then did the same with another one, and everyone in the shop myself included, where goggle eyed before bursting out laughing, as this was up till then unheard off.

Nothing changes, except country of manufacture.

Geoff – Coffee time.

I remember dad being most disappointed, Via his woodworking magazine he bought a set of imperial twist drill, advertised as top class English made(he thought they would be better than the NZ made drills, they were cheaper). He put a drill in the Black & Decker, and started into a bit of wood(fairly hard), things did'nt feel right, pull the drill out of the work, the twist had reversed in an area about half way up the drill!! Ian S C

Another vote for Greenwood's Dormer drills.

Going back to the OP, it's not intended that you use drills to obtain an exact size hole. Generally if you want accuracy, ream it. If you're tapping, then the tapping size drill is open to quite a bit of latitude – very often you can get away with 50% thread engagement. Usually (it depends on the material and depth of tapping) you would go for 80% – 90% thread engagement, so just choose the nerest drill you have. The 0,1mm steps between metric drills will usually geive you what you want. Charts will show you what's needed.

Number drills are often useful to open up a hole "by a few tenths" to give you a better fit with a mating part, so it's good if you have both sets.

Many years ago at the Harrogate show, I bought a 115 piece set from Arc Euro. 1/16"- 1/2", plus a set of number, and letter drills. When i bought mine at about 10.30 am on the friday, they had two pallets full of these sets. Having got my bargain, i went back to find my mates in the cafe to tell them. The conversation was overheard by lots of others sitting nearby all of them got to their feet and headed to the Arc Euro stand. When walking past the stand a few hours later they were down to a single layer on one pallet. Up untill that time i had never used either number or letter drills, however i now use them very often. If i need a hole to be spot-on size, i use one to drill a few thou under then ream to finish. Cheers Derek. P.S. They are still in use every day.

I forgot to say that the reason for the big rush to buy the 115 piece set from Arc Euro **** £15.00 **** Cheers Derek.

Chris,

those look good! Do you have a link? The narrowed chisel point will make them easier to start on a centre punch mark. If it wears too much they can be gashed in again from the side with a very narrow wheel or perhaps with a Dremel in a jig.

I find that quality (Dormer) 4 facet drills start quite accurately without centre pops being needed. If I need better accuracy (less than a thou or so) then I start with a carbide spot drill.

I have a set of number drills that must be at least 40 years old, but hardly use them, I rarely use threads below M3, so I don't often need small drills.

For thread engagement I normally use 60-70%, may be a bit more for fine pitches. Of course that's another reason for using quality drills, they tend to cut on size.

Regards,

Andrew