It sounds they snagged and he was using a rather large drill with lots of inertia.
Opening up a large hole by just 2mm, and with a bit with two cutting faces isn't as easy as it may look. The drill will purchase unevenly on each side causing the bit to alternatively snatch either side.
A reamer or indeed any bit with multiple cutting faces would have been easier.
Think it's like all these brands where the actual tools are sourced from different makers. I recently bought a Silverline 'Helicoil' kit which I used in steel with no problems. A genuine one from my local tool shop plus the correct drill would have cost 4 times as much.
I also have a Silverline threaded rivet tool which works just fine - and appears well made.
FWIW, the special size drill in the thread kit had a very well ground dual angle tip. Which enlarged 10 holes in 15mm plate to take the threads nicely with no signs of distress. But I was using a slow speed in a drill press. But it wasn't an ordinary HSS drill.
In article , Nightjar To open up a hole that is not far off the finished size, you need
Which would explain the three flute drill in a 'helicoil' set I bought recently.
However, for MHM's purposes (probably just enlarging a hole to take a fixing not yet made) an ordinary twist drill will do the job. It's not exactly a precision task.
Now why could I see your post coming from a mile away?
On Thu, 30 Jun 2011 10:04:58 +0100, Nightjar To open up a hole that is not far off the finished size, you need
The ones I've used have steep tapers between one step and the next so are pretty much ideal for this sort of job. But IIRC TMH stated earlier in this thread that that's what he'd wanted but Toolstation didn't have them.
a half-inch countersink would have done this job nicely.
Hence my alternative suggestion of a file and patience.
Colin Bignell
Bouncing about the hole, hitting only on the tips of the cutting edges quickly knackers the drills, as he found. There is also a risk of the drill snatching in the hole and spinning the workpiece, if it is not firmly clamped down.
Colin Bignell
That's the problem - not knowing if it'll be good or bad. I recently bought a small, rotary, wire brush for the drill to remove old paint in the corners of an angle iron frame. The brush is Silverline and, after use on 3 - 4 sq. cm., is about half gone! It was cheap to buy but extrapolating...!
Preferably an odd number, then it won't chatter (bounce) diametrically.
ISTR seeing 3-flute bits somewhere.
Bit OT: I'm about to enlarge a hole through the wall from 22mm to 25mm - that could be interesting.
Even with an SDS masonry bit you may still have fun with the drill bit snagging:-)
It will depend on the hardness of the bricks and the power of the drill. Enjoy.
All fluted cutters bounce to some degree and usually create a polygonal hole with one more side than the number of flutes.
Bob
As a "foreman" you would obviously be the expert on that...
Ah well, unbeliever seems to have a bit of a thing for our Dave, and you know where the bitterness of unrequited love can lead. How sad does your existence have to be before stalking and trolling one individual seems worthwhile?
It would not be so laughable if he ever actually posted anything remotely useful himself.
That works ok when the pilot is about the size of the quick on the next drill size. Its much harder to control the feed when the two holes are similar in size like here.
Yes - it looks as if it's a constant diameter polygon, like 20p and 50p coins.
You "Unbeliever" are a nasty person, please crawl back under your bridge. And Stay There.
Baz
Also a very good technique for drilling thin sheet.
Baz
Ask Dave - he spends much more time trolling urc than anything positive here. Well, I say trolling, but there's nothing subtle or skilled about it.
urc? uk.rec.cantbelieveitsnotbutter ?
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