Why did my drill bit turn cherry red?

[Rich Engelhardt]

This is only semi WW'ing related.
I was installing some Pergo and had to drill into a concrete pad.
I used a 3/16" bit in my Bosch hammer drill and drilled about 9 holes w/no problem.

I ran into a situation where I needed to drill a 1/4" hole so I stuck a Bosch Masonry bit in and started to drill one of the 3/16 holes out to 1/4"
After a few seconds, I noticed the hole wasn't going anywhere and no cement dust was coming out.

I pulled the bit out and it was bright cherry red!
Instead of looking like drill bit, it looked like a pencil that had just come out of a sharpener.

The bit is pointed now like a pencil.

I can't even begin to guess what I ran into:confused:.

I'm positive that the bit was a masonry bit and I'm positive the drill was in hammer mode.


Weird!

[Judson Green]

Guessing you either hit a very hard rock or rebar. Or did ya somehow switch the drill into reverse?

[johnny means]

Pretty much to be expected. Like stated above concrete contains stone and metal. Once you dull a bit you're simply spinning against a hard surface. Switch out bits and keep moving. Are you using a true rotary hammer or a hammer drill? Smaller hammer drills tend to have this problem because they don't exert the same types of crushing force as a rotary hammer.

[Tom M King]

There's a reason the little sizes are available in packages of multiples. If you get more than two holes with one in old concrete, you are doing good.

They come in small packs, but also in packs of 25: http://www.homedepot.com/p/Bosch-3-16-in-x-4-in-x-6-in-Hammer-Drill-BlueGranite-Turbo-25-Pack-HCBG04B25T/203621542?MERCH=REC-_-PIPHorizontal1-1-_-NA-_-203621542-_-N

[Don Huffer]

you hit steel. buy a better bit.

Don

[johnny means]

you hit steel. buy a better bit.

Don

Like?

He was using a Bosch masonry bit.

[Greg R Bradley]

you hit steel. buy a better bit.

Don

Like?

He was using a Bosch masonry bit.

I agree on a "better bit" but that may require a better drill.

Hammer Drills only go so far doing concrete. Brick and concrete block, stucco, even gunnite is OK. The problem with concrete is the aggregate and sometimes the reinforcement. If you are going to drill concrete with a hammer drill and bits like those, you will need multiples. You may get 20 holes with a bit and then need 3 bits to do one hole. A hammer drill rotates a lot and vibrates to help work through masonry. If you hit a really hard piece of aggregate or rebar and you are spinning the drill, which is the only way to drill with a Hammer Drill, you will melt the bit very quickly.

Rotary Hammer bits work much better as the major drilling is done by much slower, but MUCH heavier impacts. The bit rotates just to give fresh material for the next impact and to pull the waste up the flutes.

Bosch makes both normal Rotary Hammer bits for concrete and the Xtreme series bits for concrete with rebar. They also sell actual Rebar Cutter bits designed to be used in SDS Rotary Hammers in rotary mode (no impact).

[Mark Bolton]

I will put a different spin on this. Sometimes when your enlarging a masonry hole the bulk of the brazed tip is not supported and only the edges are in contact with the hole. The brazed tip breaks off in the hole and now youll be forever drilling against and un-drill able shard left in the hole.

In this case no bit, and no drill, will give you any better results. The answer is to drill a new hole or if you must be in that location you have to dig the tip out of the hole.

[Mark Bolton]

Just for clarification, the only technical difference between a rotary hammer and a hammer drill is that the rotary Hammer generates it's own blows via an internal piston. You don't shove on a rotary hammer because it generates the hammer for you. A hammer drill however simply has two hardened impact discs that only create blows when you shove on the drill. Because the blows are so much lighter the drills generally rotate faster though most all are variable speed and will drill well at slower rpms.

All bits considered in my experience not many do a good job with rebar. You'll most generally wander off the bar (oval hole) unless you have a lot of bit embedded for support before you hit the bar.

[Rich Engelhardt]

My first thought was that I hit rebar. That seems to be the general consensus.
Although, breaking off the tip sounds very plausible also since the smaller bit drilled the first hole fine. It wasn't until I tried to enlarge the hole that I ran into a problem.

[Chris Fournier]

I will put a different spin on this. Sometimes when your enlarging a masonry hole the bulk of the brazed tip is not supported and only the edges are in contact with the hole. The brazed tip breaks off in the hole and now youll be forever drilling against and un-drill able shard left in the hole.

In this case no bit, and no drill, will give you any better results. The answer is to drill a new hole or if you must be in that location you have to dig the tip out of the hole.

I think that this is the likeliest scenario. If you hit steel, there would be no guessing about it.

I have used hammer drills successfully and many times with bits up to .75" in diameter, through stone and concrete.

[John Downey]

I will put a different spin on this. Sometimes when your enlarging a masonry hole the bulk of the brazed tip is not supported and only the edges are in contact with the hole. The brazed tip breaks off in the hole and now youll be forever drilling against and un-drill able shard left in the hole.

In this case no bit, and no drill, will give you any better results. The answer is to drill a new hole or if you must be in that location you have to dig the tip out of the hole.

Yep, that's what I think it was too. If the bit had been a Vermont American or something of that order I would be less certain - I've had the carbide come off of those under normal use. Never had it happen with a good bit like a Bosch.

The key is that this was not normal use.

[Greg R Bradley]

Vermont American is a Bosch Company for many years - Now one of Bosch's lower end tool "brands" along with Skil. My 30 year old set of twist drills from Vermont American are excellent quality.

Hard to make assumptions about brands and quality. As the brands merge some may stay good until the tool is redesigned, taking its place in a company's matrix of brands.

Sometimes there are big surprises within a brand. For example, Dewalt twist drills are pretty poor. Their SDS drill bits are VERY good. Their flute design on the larger SDS Max bits worked very well drilling down into newer concrete. It seems to now be copied by Bosch on their new Xtreme SDS bits.

[John Downey]

Being owned by Bosch doesn't make their stuff any good in and of itself. Last Vermont American bit I had was probably 5 years ago and they were still of marginal quality then. When nothing else is available I buy them to get the job done - sometimes that happens when I'm in one of the rural hardware stores around here. Given the choice I don't buy their junk.

[Jim Matthews]

Can you get a vacuum onsite?

That could extract some debris,
at the least.

[Vince Shriver]

What about a magnet?