Drill sharpening

[Kittyhawk]

I'm ok at sharpening twist bits - not great, but ok.
But it seems to me that if you want to drill a hole with precision then the point of the drill has to be exactly déad centre to enable the drill to run true. There is plenty of stuff online about cut angles and so on but nothing about centering the point. Most of the drills I use are under 6mm and I don't know how to easily get the point precisely centered, especially on the small ones.

 

[Distinterior]

When I need to do really accurate drilling in metal, for example, I pre drill the hole with one of these https://www.ebay.co.uk/itm/285556908284

 

[deema]

To drill true you need the drill centre in the centre, the cutting edges at the same angle, relief, and length. In other words perfectly symmetrical. I believe that this can only be achieved by a proper drill sharpener if you’re wanting the best accuracy. However, for drills under 6mm I wouldn’t bother and when you need the best accuracy use a brand new drill. You will need to ream to size afterwards.

 

[Jacob]

They can be filed or ground into a spur bit. Not difficult.
https://www.ukworkshop.co.uk/threads/tip-and-spur-and-brad-point-drill-bits.54853/

 

[Inspector]

I agree with Deema. The company I worked for had a guy that did nothing else but sharpen milling and drill bits. He was quick and could freehand sharpen, it was more economical to by new bits under 1/4".

I prefer 120º spotting drill bits over the centre drills recommended by Distinterior. With the starting hole made by a spotting drill the entire flute of the next drill bit engages and centres better. The only centre drills in the plant were for the manual lathe they used for repairs. Make sure you get the 120º and not the 90º spotting drills. Our machinists also used them to make a bigger hole than the drill size to have a chamfer after the drilling. Some examples in NZ you can look into if interested. There are Asian ones that would be cheaper through whatever online sellers you have.

https://suttontools.co.nz/products/spotting-drills-120/

https://www.sowatool.com/p/116354

https://webshop.iscar.co.nz/catalogue/product/1000003459

Pete

 

[Kittyhawk]

Thanks for the replies.
In retrospect I think I will just forget about trying to become a master drill sharpener.
Like probably everyone else I have a box full of well used drill bits and I will continue to sharpen these as best I can and used then on the non critical stuff, and buy a drill set of something like 1mm to 10mm sizes and set them aside just for the precision work. The stress of applying to the Child Bride for the release of funds for tool expenditure will be more than offset by not having the aggravation of trying to sharpen a drill bit properly anymore.

 

[Fergie 307]

I'm with Pete, small ones just aren't worth the bother. I keep a set of good ones in tapping sizes, and for accurate stuff, and loads of others for general use.
My eyes aren't what they were so no lomger sharpen free hand. I have a drill doctor which is really good once you get the hang of it.