drill bits

[andpartington]

hi
i have tried many different types of drill bit over the years from dormer ones to b&q’s finest but find after about 6 months (or sooner) they start to loose there edge and soon be come as blunt as a badgers back side. I have tried the sharpeners but they have never made a good job of making the size hole that the bit is supposed to make, if you see what I am chatting on about!

So what I would like to know

What drills do you use and how long do they last?

Do you resharpen yours and if so how?

thanks Andy

[ron]

Andy
I only bother sharpening the larger sizes, small sizes are so cheap nowadays I usually buy a dozen of the common sizes, and chuck them when they're blunt.
Ron

[chameleonrob]

If I remember rightly, a drill bit (or any cutting tool) will last about 8 hours of constant use, at the correct speed, after which it needs sharpening. cut the speed by half and it would last 4 times as long. The problem you're having is that after sharpening the tip of the tool is no longer central so one cutting edge cuts less than radius it should and the other cuts more. the easiest way of dealing with this is to either use new drill bits for critical holes or put a pilot hole in first. With care and practice you can sharpen drill bits by eye and hand on a bench grinder right down to about 3mm dia but the larger the easier! I normally bin small drill bits rather than sharpen them but it is useful to be able to sharpen them when your last one breaks 10 minutes after the shops shut on a bank holiday and you need that size drill to carry on all the work you had planned, its happened to me, frequently

[SteveW]

Andy,

I can never throw anything away if it can be fixed in some way. I also keep too many things on the off chance I'll know how to fix them one day.

Some years back I bought one of those plastic drill sharpeners powered by the usual hand electric drill but is was always too noisy to use. I finally mounted it with its own induction motor and it works a treat.

One clamps/aligns the bit in a little plastic chuck that has a built in cam. The action is to push it into an articulating holder against the rotating stone and rotated it stop to stop. The cam rocks it putting the cutting rake on. It works from around 3 to 6.5mm and you get bits back to new. I keep meaning to rebuild it in metal (one day) to get above/below 3-6.5mm.

The real easy way is the DAG Brown Four Facet method using his published special jig. This uses a set of collettes to hold each drill bit and a block with two angled holes, one for the cutting edge the other for the rear clearance and a base with a diamond abrasive on it. The jig allows the 180deg rotate and end-stops to ensure symmetry

Two facets each side equals four.

[andpartington]

thanks for the info

what is the best brand money can get are the wouth it

thaks
andy

[ron]

Hi Andy, Dormer used to be the best, but I don't think they're worth the extra, I use cheapos from Screwfix, by the dozen as I said before, they are as accurate as any, last reasonably well if not abused, if I want an accurate hole I double drill it and if I want a really accurate hole I use a reamer.
Ron

[chris vine]

Hi,

Try J and L, industrial supply,

0800 66 33 55, they will send you a catalogue. I use Guhring from them. They are so cheap that these may be cheaper than the rough stuff from else where.

I find that for milling cutters etc, Presto make are cheaper than old second hand junk from the purveyors of second hand rubbish at the exhibitions.....

Chris.

[Nigel Bennett]

Arc Euro Trade (www.arceurotrade.co.uk/ ) offer drills in small sizes, stupidly priced at about £1.25 for five for the 1,5mm sort of size. Made in China, TiN coated. At 25p each, why bother re-sharpening? They usually appear at ME exhibitions, and I've bought quite a stock of the regularly-broken sizes over the last couple of years. Usual disclaimer.

[gwrfan]

Nigel,

Silly question I know (considering the price of these drils), but are they any better/worse than HSS bits? Do they snap like carrots, or actually last longer? I currently pay about 60 pence per drill from my local supplier, so I will make a purchase!

Thanks for the 'reminder', I just found I have a copy of their catalogue!!

Geoff

[SteveW]

Guys,

I bought a set of ArcEuro' Ti coated drills at an MEX a while back at a very good price but on close examination my FAR more expensive Dormer set were FAR FAR better made.

They all work OK but no two were ground to the same spec. and are best for raw metal clearance only. However, that's all you need most of the time. So I sort of got a good deal.

[Tim Bayliss]

I've found, by bitter experience, that the quality of point grinding is very important. I purchased a 'bargain' tripple set (numbers, letters & imp) from screwfix many years ago & had to regrind every one before they would cut! Not so much of a bargain. Always look at the evenness of the lands & that there is a good clearance. I believe HSS is HSS but if you don't have a good drill bit grinder the better grind is worth a bit extra.
By the way I picked up a very good 1.5-10mm set, well ground, from Lidl a bit back for 10 Eurobucks. A genuine good bargain.
Tim