Thread: Cheap drill bits?

I have had to hack into stainless sheet, and steel brackets, a few times lately away from the man cave.

Which means cordless drills, and struggling to drill correctly (speed, angle, pressure).
Which means I have killed a few drill bits.
Here is the corner of my favorite 8mm:
IMG_3475.jpg
whose corner I somehow lost yesterday, drilling through a bracket.


Don't have time to accurately re-sharpen it, and am missing a few other sizes:
IMG_3471.jpg

so a trip to Bunnings. And, $53 later, a 5.5, an 8.0, and a 9.0mm:
IMG_3472.jpg


The 9 is a Sutton Viper. Australian made. I figured 9mm is rarely used, so it would stay pristine.
The others are Kango, Chinese made. Tough HSS, supposedly M35 with a parabolic flute,
and 30%—50% cheaper than a Sutton.
The interesting thing is the tip grind:

IMG_3474.jpg



which has a little centre step (4 cutting edges). I'll see how long that lasts

I have bashed this into stainless flat bar, without a pilot hole but with cutting fluid, about 10 times.

The first few holes were good, but after that it started doing the tell-tale squeak of a blunted edge, and there was some build-up in the flute, just under the cutting edge. I found that I had to scratch that off with a ruler or similar.

Carefully hand sharpened the outside part (remember this has a small stepped point), and drilled another 4 holes this morning. The swarf looks OK:
IMG_3612.jpg

but you will notice it starts off very thin. Basically, this "mill finish" stainless (316?) is quite tough on the outside. I'm pushing hard to get the cut started. Once it is through the hard layer, handle pressure reduces, and the swarf is nice and thick. (until it gets to the edge underneath, where it punches out a little disc)


Maybe some metals just need Carbide

I also went to the big green shed yesterday to get myself some decent drill bits that will be used only on the pedestal drill. I bought a set of 29 Frost drill bits - only to realize when I got home that I had not looked properly at the packaging, and they were imperial sizes. Have debated whether to exchange them or not, but decided that today I'll go back there and buy a metric set as well. Both sets will live next to the pedestal drill and not be used for anything else - I have multiple other sets and miscellaneous cheap drill bits which I will put together for use with hand held / cordless drills etc.

I also wanted to get a can of cutting oil as mine is nearly empty. Bunnings didn't even know what I was talking about, but fortunately the other (much more expensive) Mitre 10 place up the road had one can of Trefolex left on the shelf.

The 8mm holes were too precise for the chef, so I had to drill some extra clearance.

(He keeps tightening one side of the u-bolt, then wondering why the other one won't move on the now jacked u-bolt!)



1) I tried the 9mm Sutton, in 3mm Stainless rolled flat (mill finish).

First, tried with a 3.5mm pilot, and then the 9mm. Lots of vibration, triangular shattered swarf:
IMG_3646.jpg
Even with cutting fluid, and Sutton branded at that, it was no better.

(Sutton Tools' Venom lubricating fluid is a medium viscosity metal cutting liquid for use in reaming, tapping, drilling and other metal cutting operations.)


2) I figured it was an issue with the pilot, so for the next few I tried without it.
No better. Lots of squealing. Starting to make triangular holes


3) Throw the drill in the Drill Doctor. Rough finish on the face, and split point seems too small, but the cutting edge is sharp.
Put the mill/drill down a few pulleys to the lowest speed (125RPM?).
Much better swarf:
IMG_3647.jpg
and even some nice spiral swarf from enlarging 8mm holes to 9mm, but that was all in 5mm stainless.
I'll try later in the 3mm again, to see if the Drill Doctor geometry works better.


So, from this limited testing, the cheap Chinese bit (with the stepped exotic grind) might work better than a locally made Sutton?
Or I might just be a bad tester of drills

Hi Nigel,

Try flattening the drill cutting angle a bit, maybe 130, 135 degrees and a slightly slower speed. The idea is to keep the drill cutting !

The ‘exotic grind’ is a sheet metal drill. It’s self piloting. They don’t stall the drill when they break through like a regular grind angle will.
We use that style a lot at work where everything is stainless. My experience with them is they work exceptionally well on sheet and anything sub 3mm, ok to 5mm and they generally suck beyond that. Also very easy to dull the corners of the major diameter because the temptation is to run the pilot flat cookie, of course when you break through the larger OD is spinning about 20million times faster than it should be to cut a 7/16 pilot for a chassis punch.

If you’re drilling it with a battery drill, low gear on the gearbox if it has one and get the weight onto it. At work I use Rocol cutting fluid, but that’s just because it’s what stores supply, does seem to work ok though.

Guhring make a decent cheap set for around $100. I need to grab another set quite good for around the home stuff. https://generaltools.com.au/product/...ric-drill-set/

Total tools have a special on a 75 piece set of P&N drill bits, most likely made in China like most things, but should still be decent quality and value at $69.95

P&N 2-13mm Metric M2 HSS-Bright Jobber Drill Set - 75 Piece 165399075 | Total Tools

Any tips on lining up drill bits in the drill doctor that have a split point? I have major issues lining up my P&N set. its a 135deg with splint point