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Herrman

Advice on high speed drill bits please

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Hi Stuart,

Many thanks for your post. Though reading yours, and comments in other replies, I can see that a drill press will be a worthwhile addition to the toolkit. I'd be the first to admit that I'm no master craftsman, and while a bad workman blames his tools, the right tools for the job can can turn an indifferent workman into a better one. I shall be clearing some bench space in anticipation of the arrival of a new press!

Regards, Herrman

A poor workman blames his tools, a good workman avoids poor tools

Richard

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Hi John,

Many thanks for your reply.

Your thoughts on drilling aluminum are most interesting- because it's a softer metal than steel, I'd always thought it should be easier to drill, and was therefore perplexed by the difficulties I experienced. What you say about keeping the drill square makes sense- it's when when drilling in tight spots, where it's difficult to keep the drill straight and steady, that I have a tendency to snap the bits.

Thanks again, Herrman

"Drilling in tight spots" - This can be helped or even solved by using "long series" or even "extra long series" drill bits.  These are, as their names suggest, longer than the "regular" size that most people are used to.  They are specifically designed to reach into awkward places as well as their other function of allowing holes to be drilled to greater depth.

You can make an approximation to a long series drill by brazing an extension piece to a normal drill (taking care not to overheat the drill and soften it thus rendering it useless) or by getting a piece of round steel rod and drilling it axially with the drill you want to use.  the drill bit can then be glued into the hole thus produced making a temporary "long" drill  that shouild suffice for a few holes at least.

For completeness you can also buy "stub drills" which are considerably shorter than normal.  These are often used when a short, stiff drill can be "self started" into a simple punch mark.

I hope no-one is trying to drill into a punch mark!  Unless the mark is of greater diameter than the flat "point" of a drill (look at one about 1/2" or 12mm and you can easily see the flat or straight "point") the drill will surely wander when you try to drill a hole.  There is a way around this as well - the use of "four facet" sharpening the drill to produce a real "point" on the drill that will self start dead straight into a flat surface without a punch mark.  These things are best read about in books on drills and drilling http://www.amazon.co.uk/Drills-Taps-Dies-Workshop-Practice/dp/0852428669 is a good one for the amateur who wants some basic theory (usual disclaimer)

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I have an old set of Dormer that I brought from the UK and have had for years, they have been excellent and have been sharpened more times than I can remember. I also have a set of drills by Hitachi as most of my power tools are by them and I have to say they are very good indeed, though they were not cheap. I also use their SDS drills for concrete and only snapped one and that was my fault, the other bits have drilled hundreds of holes in granite type rock and still keep going.

I think the general rule is if they cost a bit it is normally because they are good, It is a bit like Wera bits for screwdriving, they cost but they last.

alan

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I drill into punch marks

Richard

Me too. There is always some wonder fix around that should fix all problems what ever they are.

The fact is that a centre punch mark will pull a drill for the simple reason that it has slightly less work to do where the mark is. If the drill is centred on it all is ok. One school of thought suggests light centre punch marks another sort of average what ever that is. With rather small drills that bend easily the punch even needs to be held vertically when it's used.

There are drills about that can be used on a lathe without using a centre drill first. It's interesting to note that if the tail stock is accurately aligned with the headstock and the end of the work is squared off and smooth ordinary drills are ok used like this too. There is no reason why they should wander if they are sharpened correctly. Bad practice, centre drills are used first. These work because they are designed not to bend and are perfectly happy within reason just cutting on one side. When they do that the work is rotating so they form a hole which is on centre - some people break the tip of the smaller sizes because the tailstock is too far out. Switch to a don't need the centre drill  types and given some reason to bend such as the tail stock being out or the surface being rough or out of square and they will. Exactly the same factors apply how ever a hole is drilled - so much for giving them funny ends. That's why square to the work was mentioned along with them. They are an un needed fix as far as small drills go and in larger sizes the ordinary types are far more tolerant so who needs them really.

While it is a good idea to have drills that can bend some what without breaking there isn't much point in expecting this to totally fix problems with deeper holes or aluminium melting and sticking to the cutting edge. It just helps when they have low diameters. One aspect of why bent drills have problems is that they don't cut very well on the sides. 

One important aspect is that they are sharp. A jig can be bought to do this on an off hand grinder also other things just aimed at just sharpening drills. Not sure just how good the later are if they are affordable especially as small diameters need precise re regrinding. The accuracy needed relates to the diameter.

:embarrassed: Must admit I have an ebay box that contains maybe 10 of each size in 0.1mm steps up to something like 3mm dia that I use rather than resharpening.  I haven't bought a box of drills for a very long time. I have one box that I only use for holes that will be tapped or reamed, 2 actually to cover the size range. Another that I just use for run of the mill stuff and sometimes over a period of what is must be well over 10 years some small ones break and I top them up from the ebay box. That's why I bought it but these break more readily than the ones that were in the box. These are not terribly good drills, sizes can be a little off but I suspect the main problem is sharpness. What I should have done probably is buy specific sizes of some where like this

http://www.drill-service.co.uk/

Jobber drills unless something specific is wanted. Or some where else similar. There may be cheaper sources about and some that sell them in packets with several in.

John

-

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I drill into punch marks

Richard

And me.

I was taught basic machining several years ago and every hole was marked either with a centre punch or a centre drill before drilling.

(A centre drill is a very, very short drill with a smaller point sticking out of the end)

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