Sharpening TiN coated drill bits

[Garreth]

Hi !

Just a quick one !

Can / should you sharpen TiN coated drill bits ?

We use Dormer ones at work (not a production environment use general workshop) and the lads bin them when chipped or won't cut.

I reckon as they're basically a cobalt drill (I believe) you could re-use them , obviously losing the benefits of the TiN coating in the process.

Anyone have an opinion ?

If the answer is yes we'll have to get a new grinding wheel capable of doing the sharpening all the old ones are knackered - but thats a different story !

Thanks !

Garreth

 

[piman]

Hello Gareth,

I would personally, but I buy my own drills and it gets expensive to throw away once a drill blunts. I don't know if they are cobalt or HSS but I'd say re-sharpen.

Alec

 

[scott0031]

Hi Garreth,


The answer is yes you can sharpen them, Its really a totally wasteful to bin them. The steel we have in the world wont last forever, when it runs out people will say 'oh why were we so wasteful'.


If you are doing general work then using coated is really very close to a waste of time and money, its pretty much unnecessary the only real benefit is when doing hard to machine materials like exotics and stainless. choosing the correct drill geometry and flute type is much more important than any coating, even then in a general type shop its of little importance a standard decent quality jobbing drill will cover a multitude of sins.

What people forget is the tips of drill take a real hammering during a drilling operation, generally poor chip evacuation with gravity working against you all the time. That coating does not stay on the long at all (even with expensive tooling) that coating only works right on the edge of the cutting lip as soon as you see that coating slightly burnt or the metal underneath, the coating is done. You should question if you actually need coated at all. many people see coated as a standard must have, it totally is not. In the right environment coated tooling performs a lot, lot better.


My kind regards,


Scott

 

[Simon-]

Its not too difficult to sharpen by hand on a bench grinder. Granted they wont last as long as machine ground, and you will loose your tin coating but its economical imo.

You can get angle gauges i think to help you keep the 59 degree angle/side. (118 usually)
(i'm saying this because i'm not sure if you had a drill sharpening machine or not)

 

[Garreth]

Sound - thought I was right !

Have no issues sharpening drills - my old man worked for a company called Brierleys years ago that made drill sharpening machines. He could gring amazing angles, left hand cutters etc etc by eye, and he forced me to learn at an early age !

I'll true up the grinding wheel and crack on.

Cheers !

Garreth

 

[gordon stephenson]

first question, "can I come and empty your bins" I'm afraid I class Ti coated drills as snake oil, Yes it helps a little to carry some heat away from the cutting edge, but not enough to be really noticeable,For 17 years I worked at a plant actually making titanium sponge,(the raw material for further smelting) Titanium is not a hard material, in fact for aircraft engine use the softer the manufactured spec the better.Apart from that the drill bits will sharpen just fine,

 

[Hitch]

Sharpen them up. Buying new dormers everytime you chip and edge must be epensive. We have to make do with 500 drill bits for £12 type bits. Shocking quality.

I have a few odd TiN coated bits, dont really see a difference between them and a non coated bit of the same brand to be honest.


I sharpen them by eye, its not hard.
Now and then a non standard point comes in handy, for drilling sheet for example, flatten the angle a bit., or easier starting, make it a bit sharper....

 

[PhillipM]

first question, "can I come and empty your bins" I'm afraid I class Ti coated drills as snake oil, Yes it helps a little to carry some heat away from the cutting edge, but not enough to be really noticeable,For 17 years I worked at a plant actually making titanium sponge,(the raw material for further smelting) Titanium is not a hard material, in fact for aircraft engine use the softer the manufactured spec the better.Apart from that the drill bits will sharpen just fine,

TiN doesn't carry the heat away at all, it insulates the cutting edge slightly and acts as a high temperature lubricant to reduce galling. The trick with coated tools, is that you need to use more revs and a lot more feed and the chip itself will carry the heat away from the cutting edge and the tool will do a lot more work before it needs replacing, but you won't do it by hand.
And whilst titanium may not be hard, titanium nitride is not the same stuff.

However, coated drills are only really a benefit in deep holes, hardened steels, or as above - when used for production runs in high speed lathes/cnc machines - where the extra heat resistance and reduction in built-up edge pays dividends.
You can, however, regrind a batch in one go (135* and split points will probably serve you best for general abuse work) and then send them off to be re-coated if you prefer, there's plenty of places dotted around the UK that can re-coat machine tools.

 

[Rick]

Phillip, I'm in Rotherham also, do you know anybody local to re-coat?

PM if you prefer.

Many thanks.

 

[PhillipM]

I usually use WNT, but that's generally with a batch of machining cutters/mills at the same time to keep the price down, I'm sure there's some smaller shops around as afaik they outsource their coating to someone in Sheffield anyway.