I was drilling some 1/2" holes today in some 3/8" mild steel today (for the
base clamp of a drill press stand I am putting together), and was wondering
about drill bit temperatures.

I'm using "Rapid Tap" as a cutting fluid, and when it starts to smoke off, I
stop and put some more on. I am keeping my chips/spirals from getting to
the straw colored stage, and measuring the bit (HSS) temperature with a
non-contact thermometer tells me that my bit is at about 160F.

At what temperature should one limit a HSS drill bit to in order to prolong
the life of the bit? Does anyone have any numbers?

Thanks,

Jon

"Jon Danniken" wrote in message
...
I was drilling some 1/2" holes today in some 3/8" mild steel today (for the
base clamp of a drill press stand I am putting together), and was wondering
about drill bit temperatures.

I'm using "Rapid Tap" as a cutting fluid, and when it starts to smoke off,
I stop and put some more on. I am keeping my chips/spirals from getting
to the straw colored stage, and measuring the bit (HSS) temperature with a
non-contact thermometer tells me that my bit is at about 160F.

At what temperature should one limit a HSS drill bit to in order to
prolong the life of the bit? Does anyone have any numbers?

Thanks,

Jon

It depends on the grade of HSS. Good-quality drill bits, typically made of
M2, can tolerate around 1000 deg. F without losing temper. But don't try it,
because, especially with drill bits, the hottest part of the cutting edge
typically is hundreds of degrees hotter than the bulk of the tip, and a
non-contact thermometer isn't likely to catch it. If the extreme edge is
just starting to turn blue, you've hit the limit, even though that's a few
hundred degrees cooler, theoretically, than the steel can tolerate.

The trouble is that a lot of cheaper drill bits are made of M50 or something
like that, and the Chinese "equivalent" can't take much heat at all. It
typically contains no tungsten and it doesn't really precipitation-harden
very much.

Any decent HSS can take turning straw color, or somewhat darker, with no
problem. If it doesn't, it's junk steel.

--
Ed Huntress

More than a little bit.

--
WB
..........


"Jon Danniken" wrote in message
...
I was drilling some 1/2" holes today in some 3/8" mild steel today (for the
base clamp of a drill press stand I am putting together), and was wondering
about drill bit temperatures.

I'm using "Rapid Tap" as a cutting fluid, and when it starts to smoke off,
I stop and put some more on. I am keeping my chips/spirals from getting
to the straw colored stage, and measuring the bit (HSS) temperature with a
non-contact thermometer tells me that my bit is at about 160F.

At what temperature should one limit a HSS drill bit to in order to
prolong the life of the bit? Does anyone have any numbers?

Thanks,

Jon

Wild_Bill wrote:
More than a little bit.

So you thinking like 200F or 300F would be fine? Higher?

Just kind of making sure I don't bork my spendy bits.

Jon

If these are decent bits, I wouldn't worry about the temperature at all
when drilling the holes you are talking about. If you are drilling at
600 to 700 rpms or less, and if the bit is cutting (not just turning in
the hole), you should be able to keep drilling until you get through the
hole. The only thing that would make me stop drilling those holes would
be if the shavings started to clog the bit and drag the drill motor
down. But that's not likely in that size of hole. One shot of your oil
or whatever should be enough.


Pete Stanaitis
---------------------

Jon Danniken wrote:
Wild_Bill wrote:

More than a little bit.


So you thinking like 200F or 300F would be fine? Higher?

Just kind of making sure I don't bork my spendy bits.

Jon

I was just making use of the word: bit.

Ed H has presented info regarding quality HSS steel. You won't rapidly wear
out good quality drills when using a good cutting lubricant.

I'm more particular about a clean drilling area, than about drill cutting
edge temperatures. Rust and dirt can can dull cutting edges.
I think you're using new steel, so that shouldn't be much of a problem with
this project.
Beware of hard spots in cheap materials such as OBF old bed frame angle
iron. Hard spots can occur in new stock, but they're fairly uncommon.
Hard spots can quickly wipe out the cutting edges of a sharp drill.

It may be useful to use a cutting lubricant dispenser bottle, like a poly
lab-type wash bottle. These bottles don't need to be tipped upside-down to
dispense liquid, making them very easy to use for cutting lubricants because
they don't distract the user from the operation of the machine.
The spouts on the wash bottles easily direct the cutting lube to the actual
cutting area.

With a handy dispenser, you can keep drilling instead of letting up on the
feed pressure.
A small amount of cutting edge rubbing can take place as a drill is allowed
to retract from the cutting area during drilling.. this rubbing is more
detrimental to the cutting edge than heat, IME.

Once good chip flow is achieved, I generally keep the drill cutting all the
way thru.. while adding small amounts of cutting lube to the hole with the
dispenser bottle in my other hand.

Eventually, the drills are going to need sharpened, so be on the lookout for
the type of tools or equipment you'll want to use for sharpening.

There are a lot of good fixtures and sharpening machines available.
Developing a reliable hand sharpening technique with a bench grinder is
about the lowest cost method available.

--
WB
..........


"Jon Danniken" wrote in message
...
Wild_Bill wrote:
More than a little bit.

So you thinking like 200F or 300F would be fine? Higher?

Just kind of making sure I don't bork my spendy bits.

Jon

Wild_Bill wrote:

It may be useful to use a cutting lubricant dispenser bottle, like a
poly lab-type wash bottle. These bottles don't need to be tipped
upside-down to dispense liquid, making them very easy to use for
cutting lubricants because they don't distract the user from the
operation of the machine. The spouts on the wash bottles easily direct the
cutting lube to the
actual cutting area.

With a handy dispenser, you can keep drilling instead of letting up
on the feed pressure.
A small amount of cutting edge rubbing can take place as a drill is
allowed to retract from the cutting area during drilling.. this
rubbing is more detrimental to the cutting edge than heat, IME.

Thanks Bill. I was considering putting together what could be called a
"pulsed mist" device, but I like your idea of a wash bottle better.
Hopefully I can source one of those locally.

Once good chip flow is achieved, I generally keep the drill cutting
all the way thru.. while adding small amounts of cutting lube to the
hole with the dispenser bottle in my other hand.

Eventually, the drills are going to need sharpened, so be on the
lookout for the type of tools or equipment you'll want to use for
sharpening.
There are a lot of good fixtures and sharpening machines available.
Developing a reliable hand sharpening technique with a bench grinder
is about the lowest cost method available.

Aye, that is a skill I would like to learn. Don't think it will happen for
this job, but if I end up buying another $30 bit I'll probably have a go at
it.

Jon

Ed Huntress wrote:

It depends on the grade of HSS. Good-quality drill bits, typically made of
M2, can tolerate around 1000 deg. F without losing temper. But don't try
it, because, especially with drill bits, the hottest part of the cutting
edge typically is hundreds of degrees hotter than the bulk of the tip, and
a non-contact thermometer isn't likely to catch it. If the extreme edge is
just starting to turn blue, you've hit the limit, even though that's a few
hundred degrees cooler, theoretically, than the steel can tolerate.

The trouble is that a lot of cheaper drill bits are made of M50 or
something like that, and the Chinese "equivalent" can't take much heat at
all. It typically contains no tungsten and it doesn't really
precipitation-harden very much.


Any decent HSS can take turning straw color, or somewhat darker, with no
problem. If it doesn't, it's junk steel.

Ah, thanks Ed, I hadn't thought of the leading edge being hotter.

The bits I'm using are American, Chicago-Latrobe actually (my local supplier
has them for a very good price). I'll go ahead and keep my eye on the chip
color as my best indicator.



Jon