Drill bits - is titanium worthwhile?

[David Thorpe]

The time has come when I have to replenish my stock of micro drill bits but I am not sure whether to go for titanium coated ones or ordinary HSS. The former are £1.25 each, the latter two for 99p. The main problem I have with micro drills is not that they become blunt, but that they break and I suspect that there will be no difference between HSS and titanium ones in that respect. That being the case, I'm minded to go for the cheaper HSS. I just wondered if anyone else has any views on this or has found titanium ones so superior as to justify the price difference? I should add that when using a micro drill bit I usually use a hand operated pin vice as I find electric mini drills too uncontrollable.

DT

[David B]

I find ordinary HSS bits adequate though I keep several of each size in stock.

Since I started using an Archimedes drill, which will take sizes up to 1mm, I have broken hardly any. Those I throw out are the blunt ones. I have disposed of my Eclipse pin vices and for larger sizes now use either a double-ended type or, more often, one with a ball which fits comfortably in the palm of my hand. The latter comes with several different sized collets.

I bought them all from Squires.

pin vices.jpg

[FCA]

99p for two looks a bit steep. Have you tried Arc Eurotrade? Much more reasonable. Usual disclaimer.

Richard

[Terry Bendall]

For sizes under 0.5mm I tend to use carbon steel because of the risk of breakages. I find these perfectly adequate for what I want and don't even use high speed steel for below 0.5mm. Over 1.0mm is another thing and I get HSS ones above 1.0mm. Titanium ones are good for larger work, but for much of what we do in 4mm scale, which is probably no harder then brass, HSS should be sufficient.

Terry Bendall

[David B]

I take Terry's point and hadn't really considered what my bits were other than they are not anything special. My smaller ones (under 1mm) most probably are just steel but might be HSS. I never use the smallest, under about 0.8mm, in a power drill. It's too strong and just breaks the bits.

Mine cost £1 a piece from the local model shop, a strong incentive not to break them!

[Philip Hall]

I have started to use HSS for most of my drills, partly because I have had so many 0.45 mm carbon steel ones where the cutting point is off centre. I have also found they blunt quite easily. Where the job allows (not often, I must admit) I have used my Proxxon vertical drill press, which accepts bits down to 0.3mm and seems quite kind to them, even the carbon steel ones although I usually only drill in brass and nickel silver.

Philip

[Terry Bendall]

I never use the smallest, under about 0.8mm, in a power drill. It's too strong and just breaks the bits.

It does of course depend on what your are drilling. I have used 0.3mm drills in my drilling machine and in the lathe successfully to drill holes in brass but you do of course have to be careful.

Terry Bendall

[David Thorpe]

I never use the smallest, under about 0.8mm, in a power drill. It's too strong and just breaks the bits.

Nor do I - but there again, I only have a cheap Lidl drill. It's fine for cutting or grinding, but lacks the precision required for fine drilling - too much wobble. I've often thought about buying a superior one, eg Dremel or Proxxon, but am not at all sure I'd use them any more than the Lidl one as I like the precision I get from drilling slowly by hand with a pin vice - like you, I've got one that has a swivel at the top and is comfortable to use. I'm also concerned by what I perceive to be the high minimum speeds of the Dremel and Proxxon models - the Lidl one can run very slowly indeed if required.

Anyway, thanks all for your advice and help. I've gone and bought the HSS drills together with an Archimedes drill. Normally I'd have got them from Squires, but their website has been down for the last few days. And thanks for the link to Arc Eurotrade, Richard - I'd have used them had it not been for the fact that I needed some .45 and .35 drill bits and they don't do half sizes.

DT

[David B]

I have a rechargeable Dremel my brother bought me a few years ago. I confess I never use it to drill with but use it a lot with an abrasive disc (my 'angle grinder') and a reamer bit, the latter for taking out the back of axle boxes before fitting them to W irons.

I much prefer hand drilling though there are occasions, like drilling out buffers, when I use a Proxxon bench drill.

[Mike Garwood]

I thought that when you drilled holes in different materials there was a recommended drilling speed given the diameter of the drill, for that particular material. Which is probably why I brake 0.3mm drills when using them in a pin vice..no matter the material. Or that could just be that I've fingers made of sausages!

There are some engineering folk on here, perhaps they'd be willing to comment on this.

Mike

[John Bateson]

http://www.amazon.co.uk/Vktech%C2%AE-10pcs-Tungsten-Carving-Engraving/dp/B00IMXHXGG/ref=sr_1_2?s=diy&ie=UTF8&qid=1418470929&sr=1-2&keywords=vktech+drill

They work out at 50p each as well, but since they come from HK they may well take a couple of weeks.

Just found these, been meaning to replace some broken ones for a while now. In a Proxxon MF70 or similar they perform very well.
Took me a while to remember that I should have been looking for micro-drills! (Sorry Terry)
John

[nigelcliffe]

Over some decades of doing small scale things, and picking up tips from others, the usual source of small drill breakages comes from two places:

1 - most common. Side angle pressure. This is very easy to generate with any hand-held device, be it powered, pin-chuck or Archimedean spiral. A small change from vertical and "ping" there goes a drill bit.
My personal preference for drilling is for the Archimedean drill, but taking a lot of care on not letting the top (free end) change position.
This is why a drill press will help no end, it keeps the drill bit perpendicular to the work. But only if the chuck in the drill runs reasonably true; a wonky £40 cheapo "garage" drill press will break a lot of small drills. It is possible to make a simple guide from some bits of scrap to keep a pin-chuck or Archimedean spiral vertical.

2 - less common. Clogging on flutes. Depends on material, but some do grab a lot and can break a drill bit. White-metal can be awful for this. Constant removal, some lubrication (choice of which depends on material) helps.


I'd be cautious about a lot of high-tech sounding drill bits. They are often left-overs from PCB drilling machines used in automated factories. Great for drilling PCB, but not that good on other materials, and often very brittle, so prone to break even more easily than normal steel bits.



- Nigel (very part time 2mm scale scratchbuilder of locos )

[Tim V]

I don't break a lot of drills, so don't source vast quantities. Important thing is that they are sharp. I also use the vertical attachment on the Unimat for most small drilling.

[Terry Bendall]

I thought that when you drilled holes in different materials there was a recommended drilling speed given the diameter of the drill, for that particular material.

Yes there are Mike, but for what we normally do, they don't really apply. It is possible to find tables of speeds for drills but they are unlikely to include the sizes used for 4mm work. The rule of thumb is that the larger the drill, the slower the speed.

Terry Bendall

[Guy Rixon]

The rule of thumb is that the larger the drill, the slower the speed.

Isn't the recommended speed (for drilling a given material) linear with the diameter of the drill? I.e. based on a constant, linear speed for the fastest-moving part of the tip.

[Mike Garwood]

I thought that when you drilled holes in different materials there was a recommended drilling speed given the diameter of the drill, for that particular material.

Yes there are Mike, but for what we normally do, they don't really apply. It is possible to find tables of speeds for drills but they are unlikely to include the sizes used for 4mm work. The rule of thumb is that the larger the drill, the slower the speed.

Terry Bendall

So conversely, the smaller the drill bit, the faster the speed to drill at? Just wondering or am I stating the blindingly obvious.

Mike

[Chris Mitton]

The rule of thumb is that the larger the drill, the slower the speed.

Isn't the recommended speed (for drilling a given material) linear with the diameter of the drill? I.e. based on a constant, linear speed for the fastest-moving part of the tip.

I'm no engineer, but it does seem reasonable to me to suppose that, for any given combination of material and cutting tool, there will be an optimum cutting speed, which will need to be attained at the outer extremity of the drill bit. In which case the angular speed (RPM) of the drill isn't linear with its diameter, it's inversely proportional.

To be more precise, if V (metres/sec) is the cutting speed, then V = angular speed (in radians/sec) x radius of drill (in metres), or put another way,
RPM = V x 1000 / ( π x 60 x Diam in mm )
If you want to assume the optimum speed should be reached at the middle of the cutting edge, ie half the drill is cutting too fast and the other half too slow, double the answer.
Doubtless the engineers out there will tell us a few values of V for various combinations.....

HTH
Regards
Chris

[Simon_S]

It's probably of no help at all but for a time I worked on air-bearing spindles used to drill very small holes in PCBs; for a 10 thou hole, the spindle speed was 120,000 rpm Tolerances on the journals of these spindles were quite fine too at 0.00005" (half a tenth of a thou).

[45609]

Re drilling speeds. Read pages 90-93 of this.

Model Engineers Handbook

No doubt you'll find other interesting stuff in there too.

[Tim V]

I have the second edition, this nicely updates that!

[Terry Bendall]

Re drilling speeds. Read pages 90-93 of this.Model Engineers Handbook

Thanks for that - some useful information. I had not appreciated the idea of reducing the speed for drills smaller than 1.0mm. For those who want to use some sort of power drill the challenge will be to find a drill that will reach the recommended speed and if this is not possible then do the best you can. As mentioned earlier, for what we are doing it wont make a great deal of difference.

Terry Bendall

[derekrussan]

The last batch of Microbox Drills I had from my normal supplier were Titanium Coated and to be honest not very good quality, some being soft and would bend, others being blunt. I have since found out that products from some mainstream trade suppliers are having the same problems. So now I have managed to souce a much better quality of Microbox which I am differentiating from the rest by describing them as "Jewellers Quality" and sell for £10. The feedback on these is very good and they retail at about the same price as the mainstream ones that I am hearing poor reports about. The Titanium coated ones are being cleared off at £5.

The conclusion is the quality matters more than a coating.

Derek

Eileens Emporium

[DougN]

Derek. The last box I purchased here in Australia mid last year were steel. Most of the ones I have used were all blunt at source. So it is not just your supply. I think this may be a general problem at the moment. Which ever factory they are comming out of, seems to only be producing duff drills.

[Philip Hall]

Whilst these Microboxes are very good for getting a selection of drills, invariably only a few sizes break or wear out at a time, so I just replace those. Buying a new box regularly seems to me to be a bit of a waste, although they are useful for storing the various sizes, particularly the ones not often used.

For years now I have also kept sizes from 0.3mm to 1.0mm (in 0.10mm steps) and a few larger ones ready to use in pin vices. This saves having to look out a drill and fit it to a vice each time. I grant you this may seem extravagant (and I have two complete sets, on two different workbenches!) but I built up the collection of pin vices over a number of years as the idea grew on me.

Philip

[Guy Rixon]

Could the blunt drills actually be second hand, like the ones mentioned above by Nigel? (I've had some of those in the past; mine weren't blunt but were fragile.)