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Herrman

Advice on high speed drill bits please

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Hi,

I keep buying drill bits, because I keep breaking them, I don't buy bargin-end of the market bits, I've gone for brands such as Clarkes, but them break all the same, even when drilling softer metals like ali. It could be that I'm ham-fisted, but I don't think my technique is totally to blame. Can anyone advise on what attributes to consider when buying drills- type of metal they're made from, coatings etc?

I've been looking at some Dormer drill sets on Amazon, discounted prices range from £50 to £90. Are these worth this sort money? It's difficult from the descriptions to work out what difference in quality the difference in prices reflects. I'm confused, so any words of wisdom you can offer will be gratefully received!

Regards, Herrman

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Hi Herrman,

You don't say how your breaking the bits, but I suspect you not drilling at right angles to the work piece and applying too much pressure...   To help with this it may be worth investing in a drill press, a cheapo Stanley press from Amazon will set you back approx. £40

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Most "cheap" drills (including Clarke) are Chinese imports and snap like carrots when you try to use them.

If you buy a set of Dormer drills (and they really are Dormer - not a Chinese clone with a label!) they may be more expensive to start with but they will last a long time (and can be resharpened).

You could try these folks:  http://www.tracytools.com/  who sell decent quality stock mainly to model engineers and vintage vehicle restorers.  They only sell decent quality tools - usually obtained from high class engineering companies when they sell off excess stock after a production run has ended. (usual disclaimer)

Coatings etc do not really apply to the amateur - they do make a difference if you are drilling 5000 holes in a production run and tool life is important - but we only drill a few holes with any particular drill on a project.

Julian gives good advice when suggesting a drill press - hand drilling metal is more or less certain to and in tears as you simply cannot hand-hold an electric drill steady enough.  Hand drilling metal is possible but will always be terribly slow as you cannot turn the handle fast enough!!

Talking of speed - amateurs often drill at far too low a speed.  If you look at drilling speed tables you will soon see what industry uses!

As to the rate of feed - this too is critical.  You must feed fast enough for the drill to cut.  Feed to slowly and the drill will rub and go blunt in no time.

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Apart from the quality of the drill bit, do you remove it often to clear out the the drill bit channels if these get congested there's no place for the material coming out of the hole to go, so the drill bit gets hot and will break.....

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Dormer bits are amongst the best, I won't use anything else; the steel quality is very good but if the ones you have are breaking then you have to determine why, are the pants and just break, is the bit snatching and snapping, are you moving the bit in the hole? Those sorts of things will break any bit Dormer included

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If you use a drill with a slipping clutch the clutch should stop the drill bit breaking when it jams, which is usually why they break.

Dave

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Some things are unfortunately a part of the learning process, and breaking drills I have found to be one of them.

It gets better as you get used to it. Then you learn new ways to break drills...

Richard

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I was wondering what diameter are the drill bits that keep breaking, and what other materials are you drilling, plus the thickness of the material?

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If you're getting through a lot of drills then you're probably doing something wrong.

At work we tend to buy general industrial quality HSS trade boxes

http://www.screwfix.com/p/titan-hss-drill-bit-set-170pcs/59953

and re-fill when a particular size runs low. Breaking drills is not an issue but I don't want to run out.

For critcal work on hard materials like stainless then a Cobalt HSS is used - but these are not cheap.

Edited by laser_jock99

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I use 135deg split points- no need for a pilot hole and work well when hand bombed. Cutting oil is crucial as is the mentioned feed rate and bit speed...

I have never used better bits than these, but they are hard(if not impossible) to sharpen. I use these http://www.norsemandrill.com/Jobber-Length.php

Edited by jetstream

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It's a common problem. More expensive drills are hardened in a different way so that they can bend. By a surprising amount in the past. These days they tend to be hardened along their full length and I suspect different alloys are used.

Technique needn't have much to do with breakages. The main one is speed. Taking an extreme watch maker types are likely to want a lathe that will run at say 4,000 rpm or even faster. While holes can be drilled in principle at any speed they will only accept a certain amount of cut per revolution so if they tried to drill a hole at 100 rpm they would have to feed it in incredibly slowly, same at 4,000 rpm actually with very fine drills. Also using the same analogy but little to do with technique the tail stock and headstocks on the lathes they use are aligned to very fine limits. It will also remain aligned as the drill goes into the work.  If they were not aligned like this the drill would have to bend at some point as it went into the work. The fact that it has bent will also mean that the hole wont be straight. Poor sharpening can cause drills  to wonder as well.

The main thing technique wise is drilling into centre punch dots or holes started with a centre drill and using a feed rate to suit the speed. If the drill pulls off centre as it starts to cut one fix within limits might be to lift it out and cut again and so on until it doesn't. This will help but not completely fix the problem.

In terms of what is being used to drill the hole making sure the drill is square to the surface of the work is the most important thing. If the bearings in a pillar drill are loose this probably wont help, same with lathes. I break drills in wood sometimes well sub 1/8in dia using a battery powered drill, I never do with an old elu  mains powered one. Expensive battery drill too.

On a lathe it's not too difficult to make a test mandrel out of ground silver steel if a dial test indicator and a fixed steady is available. Hold one end in the most accurate way possible with a collet or chuck, it might be a good idea to check for run out. Then hold the other end with the fixed steady and get that running as true as possible, no deflection on the DTI. The steady should close to the end. Face the end and centre drill it. Bought test bars will be drilled in a depression on the end to protect them. Don't drill in too far. An and angled ledge of say 1mm or so is plenty, that way the drill will self centre the hole in the bar. Reverse the bar and do the same to the other end. It can then be used between centres to check and adjust the tailstock alignment with the DTI. They can also be bought with a morse taper on the end.  Personally I feel parallel ones between centres are better.  It's important to use the DTI in a way that allows it to be moved across the diameter of the test bar both horizontally and vertically to measure at the highest points. There are some magnetic based mounts about that have an articulated arm. By testing with the tailstock barrel at 2 extensions how well that aspect is set up can also be measured. Shims can sometime fix problems. Minor errors can be removed with morse taper reamers - sounds awful but this is usually done by holding the reamer carefully in a 3 jaw. Extending the barrel of the tail stock say 1/2 way and pushing it along the bed onto the reamer. This works with heavy tails stocks as the weight causes the hole to self centre, the reamers are stiff. On light weight set ups it might be better to do the same thing followed by clamping the tailstock and advancing the barrel a touch. It's not possible to remove much metal this way as at some point the morse socket will be too big. If some one is unsure of what they are doing they could wreck their lathe. I've done it a couple of times following advice from a fully fledged tool maker. Not clamping the tail stock  is an important aspect. They all say that as silly as it sounds. It's really a method of correcting thous not gross errors.

John

-

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Hi,

To begin with, sorry for the delay in responding to your replies- I've been away for a few days.

Wow, thank you all for your thoughts and advice- through reading your replies I've learned more about drills and drilling technique in the last few minutes, than in the previous 40 years!

 

Julian: I think you're right about drilling angle and the pressure applied- I tend to push harder when the going is tough, and I think this results in the drill going over to one side. A drill press sounds like a good investment for jobs that can been done on the bench.

 

Roger: Your tip about drilling speed may explain why I need to apply so much pressure- I did wonder if high-speed drilling was causing the bits to overheat, so I've been running at low speeds. I'll increase the drill speed to see if I break fewer bits! I brought the Clarke drills through a local independent retailer, who recommended them, admittedly they didn't cost a fortune, but I thought they'd be better than they turned out to be. I've decided to bit the bullet and go for the Dormer set, it'll be interesting to see how they perform.

Tinker1947: Thanks for the tip about clearing out the channels- it's a good point, and perhaps I've not been doing this often enough.

 

Colin: Thanks yes, the bits were snatching and snapping, hopefully increasing drill speed will stop this happening.

 

Dave: Thanks for the tip about drills with slipping clutches- I think my drill has one, but the smaller diameter drills still break.

Richard: Yes, despite following the good advice offered- I'm sure I'll find new and innovative ways to break them!

 

Phil: Thanks, it's generally the smaller bits (5 mm) that break when using them on mild steel and ali.

 

Gerry: That's for the link to Norseman drills. These look really good quality and tempting, but I was unable to find a complete set when I searched the Amazon UK site

Laser_jock99: Yes, I think at times my technique leaves a lot to be desired- especially having read some of the advice given above! I like the idea of bulk-buying the bits- it's frustrating when one breaks and invariably I don't have a spare of the same size.

John: Many thanks for the wealth of advice you've provided- it makes me appreciate there's more of an art to drilling than I'd realised, I'll certainly put your guidance to good use in the future.

All: I've bit the bullet and ordered a Dormer set though Amazon- hopefully a combination of good quality drill bits and improved technique will result in fewer bits being consigned to the recycle bin!

Thanks again, Herrman

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I second what Jetstream says about oil.  If you are cutting metal dry you are very likely to break a drill.

Machine shops use soluble oil (which is mostly cooling water) but for small scale work any kind of oil is better than nothing.  For example, ordinary 3-in-1 easing oil works.

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Hi Sporadic,

Many thanks for drawing my attention to this tip. I have to confess that I've never used oil when drilling, but will do in future. I note what you say about 3-in-1, but are specific drilling oils available for DIY use?

Regards, Herrman

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Cutting oil is expensive can be very messy.  It is available from Model Engineering suppliers in sensible amounts of around 1litre - however many will not post it as it is flammable so it is often collection only.  One litre will last you many years!!  A good alternative is spit - seriously!  It works well.  For Brass and Aluminium you can try rubbing the drill bit with a candle - the wax warms and acts as a lubricant.

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I bought 5ltr of cutting oil from Morris Lubricants mail order some time ago. The price is very reasonable and 5ltrs will probably out last me. I mostly use it on my lathe - a smear on final cuts on nasty stuff such as stainless or silver steel applied with kiddies paste brushes from a £ shop. I prefer the wooden handled ones. It's ok on taps and dies too but I generally just use ordinary solid hand soap.

It or any oil really shouldn't be needed drilling ordinary materials. The thing to look for is the end of the drill pulling in some direction when it engages with the work. If that happens small drills are likely to break. If the drill is brought down on a centre punch mark slightly to one side even that will tend to pull a drill. Once it's pulled it's bent and things get worse as it goes further into the work. The drill will also pull if it isn't square to the surface of the work. It's worth checking drilling machines for that problem also loose spindles.

Clogging drills up with swarf will break them too - deeper holes in aluminium can be a problem as can drilling several holes in one go - it's very good at melting and sticking to drills and lathe tool especially parting off tools. It can be flicked off with a scriber. Little else seems to shift it.

John

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Edited by Ajohn

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For aluminium we use pure white tallow which stops it clogging sanding discs and works well with drill bits too.

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I'd rather have a budget drill press with reasonable drill bits than premium drill bits and no drill press...

Once you use a drill press, you will wonder how you managed without one. If you have got the space, don't get a mini one get a mid sized taller one as it will come in handy on occasion.

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If it helps, I never use oil when drilling. Not down at the sub millimetre sizes or up around 1", or in between

I do use a pillar drill though, or the lathe. I suspect that's what is making the difference

Incidentally, soft materials cause more trouble than steel, so I'm not surprised you break drills in aluminium

Richard

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Hi Roger,

Many thanks for the tip about using candle wax- I often drill aluminum so that tip will come in handy!

Regards, Herrman

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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

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Hi Phil,

Many thanks for the tip about using tallow- an interesting alternative to candle wax. When I 'Googled' tallow I found it can be purchase through Amazon. I was fascinated to see how many other potential uses it has- got to be worth investing in a tub, I can see it coming in handy elsewhere in the home!

All the best, Herrman

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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

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Hi Richard,

Many that's for your reply.

I've learned a lot about metals and drilling through this thread, and although it's obvious my technique is in need of refinement, it's reassuring to now know that softer metals can be so problematic. I'll certainly be acting on your (and other responders) advice, by investing in a press.

All the best, Herrman

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