Twist drills - HSS, Titanium coated or Cobalt?

[Paul Narramore]

Bit by bit I am loosing some of my twist drills in the smaller sizes. HSS is almost certainly what I have already and generally suits me for my metalworking jobs but should I now go for Titanium coated or Cobalt? Which is 'better' and why?

 

[Rorschach]

What do you drill? Pointless wasting money on fancy drill bits if you don't drill "difficult" materials.

Also, if it ain't broke, don't fix it, why do you feel the need to change?

 

[MikeK]

I don't bother with the titanium coated drills. I sharpen my drills when needed, and this removes the thin TiN coating, which turns the drill into a HSS drill. I have a few HSS drills for general use in soft metals, but for harder metals, such as stainless steel or cast iron, I use only cobalt drills with plenty of lubricant. Excessive heat destroys the cutting edge, so lubricant is required.

The TiN coating allows the drill to last longer than HSS drills under the same conditions, but is not recommended for aluminum. I learned this the hard way when drilling some aluminum extrusion and the swarf bonded to the cutting edge. I put the drill in my "to be sharpened" bin, where it will become yet another HSS drill. I finished the drilling with a HSS drill without any problems.

I have a drill speed chart next to my benchtop drill press so I can match the speed to the material and drill size.

 

[Paul Narramore]

What do you drill? Pointless wasting money on fancy drill bits if you don't drill "difficult" materials.

Also, if it ain't broke, don't fix it, why do you feel the need to change?

Because I was wondering about any advantages to buying ‘better’ drill bits, if there are any. I drill mild steel, aluminium and stainless steel. Whatever is found on motorcycles

 

[Paul Narramore]

I don't bother with the titanium coated drills. I sharpen my drills when needed, and this removes the thin TiN coating, which turns the drill into a HSS drill. I have a few HSS drills for general use in soft metals, but for harder metals, such as stainless steel or cast iron, I use only cobalt drills with plenty of lubricant. Excessive heat destroys the cutting edge, so lubricant is required.

The TiN coating allows the drill to last longer than HSS drills under the same conditions, but is not recommended for aluminum. I learned this the hard way when drilling some aluminum extrusion and the swarf bonded to the cutting edge. I put the drill in my "to be sharpened" bin, where it will become yet another HSS drill. I finished the drilling with a HSS drill without any problems.

I have a drill speed chart next to my benchtop drill press so I can match the speed to the material and drill size.

Thank you Mike

 

[Rorschach]

Because I was wondering about any advantages to buying ‘better’ drill bits, if there are any. I drill mild steel, aluminium and stainless steel. Whatever is found on motorcycles

If you are drilling stainless on a regular basis then 5% cobalt drills will be worth the extra money.

If it were me I would have a set of Cobalt and reserve them for the stainless and then get a cheaper set of plain HSS for the aluminium and mild steel, be better from an economy point of view in the long term.

 

[AJB Temple]

I do exactly that ^. I have a set of good quality cobalt that I reserve for steel work, and HSS generally bought in cheap sets for day to day. I also have a set of top notch Fisch foresters and various specialist framing drill that are quite pricey.

This is a decent 5% cobalt set without spending silly money: https://www.amazon.co.uk/gp/product/B000R9Z5CM/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[Phil Pascoe]

https://www.ukdrills.com/drill-sets/99pc-cobalt-magazine-drill-set-for-metal
I haven't got this particular set, but I have others of theirs that are fine.

 

[dannyr]

I'm not a cutting tool expert, but 5% cobalt sounds like a cheaper version of M42 - does it keep its edge as well?

Re the metals on motorbikes -- could be cast iron, variants on mild steel, aluminium, high tensile steel, zinc alloy, many quite different stainless steels, even titanium and some metal composites on pricier machines.

 

[disco_monkey79]

Ditto the comments re reserving cobalt drills for tricky materials, and using HSS for "every day".

For what it's worth, I have some branded cobalt, and some cheapo unbranded Toolstation cobalt ones, and they both cut equally well.

I do find they can snap the cutting edge quite a bit more easily than HSS, but I am also a c@ck-handed buffoon.

 

[Paul Narramore]

Thanks everyone for your advice.

 

[sploo]

My $0.02: good quality cobalt drill bits in the sizes you use most regularly, and make sure you use an appropriate cutting fluid or compound. Total game changer. Life's too short for swearing at cr*p drill bits

 

[John Hall]

One point is the quality of the bits….loads of cheap companies are advertising their bits as Tin coated, cobalt etc, but are still using inferior materials….basically as with most tools, you get what you pay for. It’s worth buying good tried and tested makes, like Dormer, Presto , Titex etc…it’s a good idea to keep an eye on EBay, boot sales etc for good named quality bits at a fraction of the cost new, that just need sharpening. It’s also worth reading up on drill speeds and sharpening angles, cutting fluids etc.. for different materials, which make cutting easier and prolongs the cutting edge…Sharpening bits, when you get the hang of it is quite therapeutic.

 

[bushwhaker]

Brief classification:
HSS-R ...low level (Roll-forged)
HSS-G ...better heat resistance
HSS-E ...best (or HSS-co, M35) 5% cobalt
M42. 8% cobalt

 

[Phill05]

The better quality of HSS every time you can grind the edge to suit the work, grind a coated and you have lost the coating except in the flutes.
For the tougher materiel you can grind a carbide masonry drill I have drilled through leaf springs from a lorry before no problem.

 

[akto]

Makita do a good range of hss bits in fractions of a mm, their cobalt set is also vfm.

 

[Sandyn]

in the past, I got the 5 pack HSS bits from Screwfix, they are very good, you can also get a trade pack, but it's mainly 2 to 4mm I use most.
I also have a good set of cobalt drills for more demanding drilling and a set from UK drills. 1 to 13mm in 0,5mm steps.

 

[thetyreman]

Life's too short for swearing at cr*p drill bits

good point....

 

[Ttrees]

Glad the liddle ones are worth buying, along with cheap titanium nitride ones good too.
Recently bought some fancy cobalt bits, just for hardened stuff.

Cheap bits are good for learning to sharpen on.
Took me sometime to figure out what I was doing wrong
(using a method similar to AvE but with a bench grnder)

Not seen folks mention this, but having the grinder on a low bench meant I was stooping and not presenting the bit low enough on the wheel for the clearance right behind the edges, but was grinding plenty of clearance to the back of the bevels.

How to know if you're grinding behind the edge to give enough clearance,
is to, along with a small bit of relief, try and get a smile shape on the bevels, you might find holding lower down on the wheel that this is easier.
Chances are that you will be grinding right behind the edge that way.

Likely worth knocking up a wee jig, this works grand,

And this one too, which is handy if you're table has a dip....
Not a sure way whatsoever to detect runout though

Tip from this mornings reading
Find a long bit, roll it on the bench to check for wobble and align the bit with something
even the table tilted 90 or whatever, and a soft mallet might get you by,
obviously after you've already knocked out the arbor and chuck already,
and no tooling to check properly.