Drill bits break.
How easily they break is proportional to how strong they are.
How strong they are is proportional to the cross sectional area.
Finally, how often they break is proportional to how easily they break *and* how often you use them.
As a result, when you buy a set of general purpose wood and masonry bits, you break all of the thin useful bits and are left with a load of fat useless bits. You then buy another set and start the whole process again, accumulating yet another family of fat useless bits.
If they sold sets of bits where the number of each size of bit in the set was inversely proportional to the square of the diameter and proportional to their usefulness, then you would get through them all at a roughly similar rate.
I imagine a quick survey of "usefulness" would find 2mm wood bits for pilot holes, 6mm wood bits for screw holes and 6mm/8mm masonry bits for red and brown plugs would be the most used and therefore require perhaps three times as many.
Here is a quick calculation of how many should be in a set based on this formula:
WOOD Size....Qty 13mm.....1 12mm.....1 11mm.....1 10mm.....2 9mm......2 8mm......3 7mm......3 6mm.....14 5mm......7 4mm.....11 3mm.....19 2mm....127 1mm....169
METAL Size....Qty 13mm.....1 12mm.....1 11mm.....1 10mm.....2 9mm......2 8mm......8 7mm......3 6mm.....14 5mm......7 4mm.....11 3mm.....19 2mm.....42 1mm....169
This must be a sensible distribution, because the maths says so.-- wagster, Oct 07 2008 Quickbits http://www.toolstat.../?r=s&feature=45454Looks like pisspoor quality, but sold in the UK. [UnaBubba, Oct 08 2008] Brazil nut effect http://findarticles..._20_160/ai_80747803 [hippo, Oct 13 2008] Yes, or the stores could stock replacement packs in a range of sizes to suit the curve. For example, the next pack down doesn't have a 13mm bit - but it does have a few extra 1mm and 2mm bits. The next has no 12mm, but extra 1/2/3/4mm ... etc. Each pack would have the same weight of metal in it.-- BunsenHoneydew, Oct 07 2008 Good idea - I have a set with two 1mm bits but one of everything else, so manufacturers have at least started to think along these lines, but it's not that great.-- hippo, Oct 07 2008 Size....chance of.....per .........breaking.....blue ......................moon 13mm.....169/169......1 12mm.....169/140......1.2 11mm.....169/121......1.4 10mm.....169/100......1.7 9mm......169/81.......2.1 8mm......169/64.......2.6 7mm......169/49.......3.4 6mm......169/36.......4.7 5mm......169/25.......6.8 4mm......169/16......10.6 3mm......169/9.......18.8 2mm......169/4.......42.3 1mm......169/1......169.0
Quite so sir-- BunsenHoneydew, Oct 07 2008 // accumulating yet another family of fat useless bits. //
Very like General Elections, then ?
Good idea by the way - for hobbyists. But machine shops tend to buy drill bits by the box of 100, all the same size ....-- 8th of 7, Oct 07 2008 Someone, somewhere, has done this calculation on the bit/attachment set I bought with my cordless Dremel. Will count it out later.
Also...mighty close to a "fibonacci tree" on those estimates. Well done!-- 4whom, Oct 07 2008 Good One, I feel your pain, Bro'. While we are at it can we have a couble of spare 13mm sockets in a socket set please? And an extra 8mm or two. Thanks Muchly!-- gnomethang, Oct 07 2008 Depends on what you're intending to use the equipment for, I would venture. I have a Ramset hammer drill (SDS chuck) that came boxed with 1 x25mm, 1 x 22mm, 1 x 19mm, 1 x 16mm, 4 x 12mm, 10 x 10mm and 10 x 8mm masonry bits, all with holding slots moulded into the box lining. Some manufacturers get it right.-- UnaBubba, Oct 07 2008 Absolutely!. But when I need a drill it is for piddly, fiddly little things stuck on air ducts etc. These are the ones more likely to break.-- gnomethang, Oct 07 2008 I have a piece of Black and Decker sh*t that comes with two soft driver bits that won't go in the standard bit holder, and a fool attached to the other end.-- wagster, Oct 07 2008 I like the idea, although there are sources out there that sell individual bits, even to residential/hobby users.-- MechE, Oct 07 2008 That's great, [MechE]... the idea is to pre-empt the need for buying expensive individual bits, which are three times the price per bit that bulk packs cost.
I will usually buy a packet of 10 of each size I need, say 2.5, 3.0, 3.5, 4.0, 4.5, 6mm because the little ones break so easily or you drill so many holes with them that they wear out. In those smaller sizes I buy QuickBits (6mm hex base) so they can be easily swapped in and out of the driver cups on cordless drills. Same applies to Phillips screwdriver bits, which tend to snap off in the screw head.-- UnaBubba, Oct 07 2008 Some guys I work with were complaining about just this today. The set should have extras of the more commonly used sizes as well (1/4" etc.).-- sninctown, Oct 07 2008 I love the Quickbits idea - have to find some of them.-- wagster, Oct 08 2008 I think I should invent the erectile drill bit, then. One size fits all, in a while.-- Ian Tindale, Oct 08 2008 [UB], it's possible to get professional quality hex-shank bits, and they're VERY good - but not exactly inexpensive.-- 8th of 7, Oct 08 2008 driller thriller +-- xenzag, Oct 08 2008 I have a cheap set (30 quid from Maplins of all places) that has, if I remember vaguely, a couple of 13mm bits, increasing to about twenty 1mm bits. Not really used it much yet.-- david_scothern, Oct 08 2008 [+], although I find I blunt 10mm drills as often as I snap 3mm ones.-- Srimech, Oct 08 2008 I can get good ones for about $2.50 each.-- UnaBubba, Oct 09 2008 If the bits were stored all together in a hopper, proportionally mixed, and sold by weight, it would work out the same in the long run-- BunsenHoneydew, Oct 13 2008 Not quite true, because of what is known as the "cereal box effect", where cereal packets always end up with a residue of fine, yucky bits in the bottom of them, due to natural sorting of the large items to the top.-- UnaBubba, Oct 13 2008 I thought the cereal box effect was where some other bastard fishes the freebie out first.-- Ian Tindale, Oct 13 2008 No, that's the "democracy" effect.-- 8th of 7, Oct 13 2008 [UB] That's more commonly called the "Brazil nut effect" (link)-- hippo, Oct 13 2008 Contents may settle in another country.-- Ian Tindale, Oct 13 2008 Coincidentally, I am tight (edit:right) now eating a bag of chocolate coated peanuts, raisins and brazil nuts. All the excellent brazil nuts are getting eaten first, having risen to the top, leaving only the second-class peanuts and raisins.
Damn the brazil nut effect!-- wagster, Oct 13 2008 //I am tight now eating // Having a little tipple too?
It's an effect used to advantage in panning for gold, where you deliberately shake the pan in such a way as to settle small items with higher specific gravity to the bottom.
Sorry, I called it "cereal box effect", it should have been "muesli effect" aka "brazil nut effect".-- UnaBubba, Oct 13 2008 halfbakery