Drill confusion

I need to replace some drills that I've used for model making for years. I'm not sure what I should be looking for, though.
The existing drills are "high speed steel" drills and have a conical end out to the full drill diameter. Most of the drills I can find in DIY stores these days seem to have a double tip - a smaller conical tip of about half the diameter and a couple of mm high, followed by a flat shoulder out to the full diamater. They're probably great for general drilling, but they don't self center in a pilot hole and don't work very well for the hand drilling I do for most of my modelling work.
I guess both types have a different name, but I don't know what it is, and so I'm not sure what to look for (or what to avoid) on websites!
Can someone please enlighten me?
Thanks, Nobby
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On Wed, 30 Dec 2009 08:31:11 -0600, Nobby Anderson

What you're describing sound like wood drills used for dowel holes.
The 'engineering' type of drill you want is commonly know as a 'jobber'. However, you can now get this type of drill in stub length (jobber is 'normal length') and split point which saves drilling a pilot or dot punching first. TBH I think that split-point stub length drills are probably my favourite.
Have a look at this page for lots of info: http://www.drill-service.co.uk/Tools.asp?Tool 0000000000
Peter
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I second the vote for stub drills; I almost always start any hole below 6mm with a stub drill, especially if precise location is important. Unfortunately they are much less commonly available than standard length ones, and the only set I can find:
http://www.mscjlindustrial.co.uk/CGI/INPDFF?PMCTLG &PMPAGE&PMITEM=HS S-22000M
...is far from a bargain price. I have one of these, and a pretty comprehensive set from 1 - 6mm, but most sizes have been laboriously acquired.
Why-o-why do the makers/suppliers not produce decent 1-6x0.1mm sets at decent prices???
Failing this, get a decent set of jobber length drills. By "decent" I mean from a reputable maker, not a cheap unbranded set (they can be OK but are a bit of a lottery). Greenwood Tools often have reasonable offers, see e.g.
http://www.greenwood-tools.co.uk/ishop/728/shopscr75.html
Peter - did I miss the split point stubbies on the drill service site? (Good supplier though, used them myself once in the last year, but good stuff, good prices and good delivery).
David
--
David Littlewood

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On Wed, 30 Dec 2009 18:14:27 +0000, David Littlewood

No, not at all, mine came from J&L. I got one of there e-mail flyers last year, you know the sort of thing - 50% off if you buy 5 or more items - valid for 2 days, so I treated myself to a full set of the dormer stub/split/ticn drils for a bargain price. Only pain was typing in all the part numbers which took ages!
Details at the bottom of this PDF page http://www1.mscdirect.com/PDF/brochure/796497.pdf
Peter
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Thanks Peter.
David
--
David Littlewood

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On Wed, 30 Dec 2009 18:14:27 +0000, David Littlewood wrote:

It's not much trouble to make a drill shorter.
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Well if you shorten the drilling end it means regrinding the entire point profile again which is a hell of a lot of trouble if you don't have a drill grinder and if you shorten the shank end then the remainder will be all flute so you can't grip it properly and it'll still be too flexible. Maybe we have different ideas of what constitutes "much trouble" compared to spending a couple of quid on a proper stub drill.
--
Dave Baker



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writes

And, AIUI, the web gets thicker as you move away from the (original) point, so drilling requires more pressure (or you have to thin the web).
David
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David Littlewood

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On Fri, 1 Jan 2010 12:54:22 -0000, Dave Baker wrote:

Two hands and some skill/practice.
The o.p. said "laboriously acquired" - if you're going to labour, you might as well improve yourself. Grinding a drill point is a useful skill, not too difficult to aquire.
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(1) My words you are quoting, but I was not the OP.
(2) If you wish to spend half your life cutting down drills to make inferior substitutes, please feel free. Personally I am not so arrogant as to assume I can (effectively) make a 1mm stub drill as well as the manufacturer, despite having a decent March T&C grinder.
David
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On Sat, 2 Jan 2010 13:10:25 +0000, David Littlewood wrote:

Sorry; excessive zeal when snipping.

Having examined some drills fresh from the manufacturer, you might re-evaluate your capability.
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I was also under the impression that the webs became progressively thicker as the point is ground back, thus making the chisel end of the new point much wider and harder to push into the work.
Cliff Coggin.
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On Fri, 01 Jan 2010 17:18:08 +0000, Cliff Coggin wrote:

PMCTLG&PMPAGE&PMITEM=HS
Which can be thinned down on the grindstone when resharpening.
--
Neil
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That page has now been saved her to my favourites. Lots of good and usefull information, Thanks Peter :-)
--
Uffe Brentsen



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Uffe Brentsen wrote:

==What is the advantage of a coated drill? Surely the first time one touched up the point, the coating has gone? JW ==
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If you think about it for a moment you will realize that only the cutting lips do any work, when you grind the end of the drill you only grind the relief. The flutes will still have TiN coating, as will most of the lips, which after all does most of the work. Personally I like Guhring cobalt twist drills, which don't need any coating. T.W.
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Sounds good - advertising hype?
Julian.
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Nobby Anderson wrote:

They are, and they are good with a punched mark. Work well in most metals, but maybe not so good in wood.
They even work okay for drilling in the lathe (if the tailstock is properly adjusted, otherwise they break easily), and no center drill needed :)
but they don't self center in a pilot hole
Indeed, this is my main gripe with them. But apparently a single pass with no pilot hole is best for ordinary drilling, although if you want a stepped hole ...
and don't work very

Haven't tried hand drilling, but I'd have thought they would be okay?

The pointy ones are sometimes called bullet-point drills.
I don't know of a definitive term for the ordinary ones - twist drill, or jobber's drill maybe, though the pointy ones are sometimes called twist drills, and jobber actually refers to the length of the drill.
-- Peter Fairbrother

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Thanks to all who answered - bullet-point drills are indeed the ones I don't want and jobber drills I do. SOmeone mentioned stub drills as maybe being a better alternative because they were shorted than jobber drills, but I sometimes need the length of a "standard" jobber drill and don't use them enough to justify two sets, although in many cases the shorter length would indeed make the drill easier to manipulate for hand drilling.
Thanks for all the information,
Nobby
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Standard length general drill bits are called "jobber" drills where the length of the fluted section is about 10x the drill diameter so they'll drill a hole 10D deep. That's actually far longer than most jobs need except perhaps for woodworking. For instance when are you likely to want to drill a 5" deep 1/2" hole in steel?
Stub drills are shorter, more rigid and less likely to wander for precision work so you get a straighter hole but that would only be relevant for machine drilling. For hand drilling your hand is going to wander a damn site more than any drill bit. Both would normally come with a 118 degree end which doesn't self centre but copes adequately with most normal materials.
Unless you're working with exotic materials another set of HSS jobber drills should do you fine. You can get a set to 1/2" for as little as a tenner if you shop around. Often you'll find them titanium coated these days but the vanilla ones have always worked fine for me.
You could of course invest in a drill sharpening jig if you have a bench grinder to work it with and sharpen all your old ones but I've never had much luck with mine. A resharpened drill never seems to work quite as well as a brand new one in my experience but that's probably because either I'm doing it wrong or my old sharpening jig is crap.
Maybe that's another question for the masses. Do any cheap sharpening jigs work really well, especially on small drill bits?
What I also have in my collection of oddments is a couple of solid carbide jobber drills of about 5mm diameter which a mate donated to me many years ago which are brilliant for pilot holes, especially in tough materials. They cut through anything like a hot knife through butter. It's far quicker to run a carbide drill in first and then take out the excess with an HSS than try to drill to size from scratch with HSS. Saves wear and tear on the HSS drills too.
If you're hand drilling through metals, especially steel, the biggest mistake most people make is to run the drill too fast and burn the point out, especially if your drill only has one speed. On a mill or lathe you'd normally be running at under 1000 rpm and well under for say 1/2" drills or bigger. Electric hand drills might run at up to 3000 rpm which is far too fast except for very small drill bits or for drilling wood, plastics or maybe aluminium. When in doubt less speed and more pressure is the way to go rather than the other way round and you can make a drill bit last for ever if you're careful with it. A decent variable speed drill is therefore a good investment. 500 to 800 rpm is a good starting point for general drilling in steel.
You'd be astonished how much faster you get through iron or steel at low speed and with high pressure on a milling machine or lathe than you would ever manage with a high speed hand drill and low pressure using the same drill bit. A bit of cutting oil usually helps too. If you're burning drill bits out on a regular basis then excessive speed and insufficient pressure is probably the reason. My two sets of HSS drill bits are 20 or 30 years old and most of them are still sharp even after that many years of regular use on the lathe and mill. I generally only ever blunt one by doing something stupid or hitting a hard spot in something. I'm always happier to knock the speed down and take a few seconds longer on the job but not hurt the drill bit than rush through a job and blunt a tool.
What you probably don't realise if you've never used big machine tools is just how much pressure a light pull on the handle is actually putting onto the job and just how little pressure you generally achieve in hand drilling. A normal pull on the quill handle of my mill might be putting 50 to 100 lbs of force on the drill bit which would be the equivalent of someone with a hand drill using most of their weight rather than what you probably do which is just push with 10 or 20 lbs force. Plenty of pressure never hurts a drill bit but too high a speed will kill one in seconds. In fact you can't really sustain the required pressure in hand drilling for long because you'll get tired too quickly. Even one of those cheap jigs which converts a hand drill to a drill press would be worth considering if you're doing lots of work but it'll never be as good as a proper drill press or milling machine.
--
Dave Baker
Puma Race Engines
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