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how to measure temperature of a rotating drill bit
3

how to measure temperature of a rotating drill bit

how to measure temperature of a rotating drill bit

(OP)
I am trying to measure the temperature of a drill bit while drilling metals, I intend to pass the thermocouple through the one of its coolant holes , the problem is that the drill will be rotating and the thermocouple should send the temperature reading in a wireless way to the data logger ,is there such wireless method which I can use to capture the temperature while the drill is rotating. or is there any small wireless temperature sensors ?

I don't want to use a thermal/IR camera..

RE: how to measure temperature of a rotating drill bit

No there is no way to measure this directly. The direct rubbing, cuttings transport, rotation speed, coolant spray, and changing geometry of the entire system will prevent any success at direct measurement of the drill bit's temperature. Indirect measurement will have Heisenberg all over your ass too.

Why don't you do what everyone else does and just flood the contact area with enough coolant to preclude the drill ever overheating?

Keith Cress
kcress - http://www.flaminsystems.com

RE: how to measure temperature of a rotating drill bit

Are you at all uncertain about this Keith?? grin

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: how to measure temperature of a rotating drill bit

I'm sure NASA or someone insane enough to make their own drill bits could bore-drill them for a TC. Followed by heat treating them, coating them, using them, followed by wondering how the measured temperature equates to the actual cutting edges...



Keith Cress
kcress - http://www.flaminsystems.com

RE: how to measure temperature of a rotating drill bit

What size drill bits???

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: how to measure temperature of a rotating drill bit

Chuck up the material to be drilled and spin it against a stationary drill bit.

RE: how to measure temperature of a rotating drill bit

Unless the TC is located at the tip, you'd only be getting a shadow of the actual temperature. Nonetheless, if you are insane enough to do it, you could possibly wire up a thermistor to a small Arduino with a Bluetooth shield, and lots of silicone to keep it from flying apart.

TTFN
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RE: how to measure temperature of a rotating drill bit

Or make the following minor change:

I do n't want to use a thermal/IR camera.

RE: how to measure temperature of a rotating drill bit

David is thinking along the correct lines... drilling on a lathe is often spinning material with a stationary bit.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: how to measure temperature of a rotating drill bit

One other option would be to measure the temperature externally, i.e., move the bit to a fast TC or thermistor, grab the temp and move back. There are/were temp sensors that had response times on the order of a few milliseconds.

TTFN
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RE: how to measure temperature of a rotating drill bit

Could one use the interface between the bit and the drilled material as a thermocouple junction? And measure the voltage from the bit to the drilled metal?

RE: how to measure temperature of a rotating drill bit

Had a similar thought, 77JQX. It would have to be calibrated somehow (put a compression-loaded test sample of the two materials into an oven, and measure Seebeck voltage over a big enough temperature range), and the noise of the cutting interface making what is likely intermittent make/break contact would have to be filtered from the signal...but it might work. Passing the voltage across the rotating interface would be a challenge, but there is a simple method. We used this to measure strain gages on parts spinning in a lathe: simply let the leadwire out through the lathe headstock, providing enough length for the wire to twist/wind up and limiting the sample time to a fraction of what it takes to snap the leadwire (then rewinding the wire by reversing the motor between runs).

RE: how to measure temperature of a rotating drill bit

Great idea. I had a similar thought. Any two metals can make voltage. To save space in the cooling hole, only run one one wire down and spot weld it to the tip and calibrate. Of course that all depends on the drill tip being metal.

RE: how to measure temperature of a rotating drill bit

However, the problem is going to be that there will be an extremely tenuous electrical contact between the bit and the metal, potentially further compounded by anything like a coolant or lubricant.

Actually, another option is to build a slip ring around the drill head.

TTFN
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RE: how to measure temperature of a rotating drill bit

Quote (itsmoked)

Indirect measurement will have Heisenberg all over your ass too.

This weeks award for obscure humorous physics reference goes to... itsmoked! medal
lol

"Will work for (the memory of) salami"

RE: how to measure temperature of a rotating drill bit

I'm not sure I'd want to be the engineer designing the circuit for such a thermocouple... the noise would be atrocious.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: how to measure temperature of a rotating drill bit

One off the wall thing I'd like to try; bore a small hole along the drill's path in the test article, and fill it with insulated t/c wire. In the case of an iron article, maybe you could just use constantan. Then the passing drill flute would smear the wire into contact with the test article, however briefly, giving, maybe, a discontinuous thermocouple reading.

... yes, it would be a reading of the bulk test article temperature near the cutting zone, possibly not too different from a measure of the drill flute temperature somewhere near the cutting zone.



Mike Halloran
Pembroke Pines, FL, USA

RE: how to measure temperature of a rotating drill bit

In theory it would be a thermocouple. In practice it would be an electrically-noisy mess, and then the drill would rip the wire out the hole.

This thread reminds me of The Old Barometer Joke.

RE: how to measure temperature of a rotating drill bit

I agree that instrumenting a drill fixed in a lathe and rotating the test article is the most likely arrangement to produce usable data.

There are some problems.
Few lathes spin fast enough to get a drill flute up to optimum speed.

So, don't use it as a drill. Put it on the cross-slide, at say 75 degrees behind the axis, and use the instrumented flute to shave the face off a plate. The surface speed goes up as the drill is fed from the center, prebored hole, to the periphery, in a way that's independent of the drill diameter, but it can go fast enough to give data that will represent real drilling conditions with a fast spindle.

That may not give a representative temperature, because it removes friction from the drill's chisel point from the situation, and also whatever heat is associated with dragging the flutes against the drilled surface. ... but maybe you wouldn't want those contributions included anyway.



Mike Halloran
Pembroke Pines, FL, USA

RE: how to measure temperature of a rotating drill bit

Not necessarily that noisy. If the OP uses a 100 ohm PRT, that might be pretty reasonable, given that he could filter the signal ad nauseum.

The problem with instrumenting the article is that the article, being metal, is essentially a giant heat sink. It's probably going to be nowhere near the temperature of the bit.

TTFN
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RE: how to measure temperature of a rotating drill bit

(OP)
Hi Guys thank you all for your answers , I have already found a way to measure the drill bit temperature when drilling but I am not sure if it will work 100% . I will use a wireless data logger that is connected with a thermocouple which is welded on the drill bit tip , this wireless data logger which is attached to the thermocouple can transmit the readings to a receiver connected to my laptop,

now the problem is that I am worried that when I attach the wireless data logger to the rotating spindle it wont be able to send the measured readings or even wont be able to record anything and send to the receiver due to the high rotational speed or the high vibrations caused while drilling the material ?!!! what do you think guys ? how possible is this to happen?

Thank you all for your comments smile

RE: how to measure temperature of a rotating drill bit

Survival depends on the particular design of the data logger, and how and where it's attached to the spindle.
So far I have detected no clue about which data logger you intend to use,
or which spindle you intend to use,
so I can't conjecture.

Mike Halloran
Pembroke Pines, FL, USA

RE: how to measure temperature of a rotating drill bit

Unless the data recorder is home-built, I don't see any problem. Commercial data recorders are used for shipping environment logging and on-vehicle environment recordings, which include massive shocks, and vibration environments so large that humans wouldn't stand it for more than a few minutes.

TTFN
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RE: how to measure temperature of a rotating drill bit

We still don't know the drill diameter or the nature of the material to be drilled.

As a point of reference, the optimum rpm for drilling a 1/4" hole in aluminum is somewhere near 18,000 rpm.
... so I wouldn't just assume that any old data logger will survive.

Mike Halloran
Pembroke Pines, FL, USA

RE: how to measure temperature of a rotating drill bit

Quote (khalchris )

I have already found a way to measure the drill bit temperature when drilling but I am not sure if it will work 100%

I hate to burst your bubble khalchris. Are you not realizing that NOTHING YOU DO will get you the correct temperature?

The temperature at the cutting faces is going to be different by hundreds of degrees from wherever you're sensing at. If you've somehow contrived to put the sensor right at the cutting edge in contact with the material you've completely invalidated its readings because it isn't cutting it's just rubbing.

As the tool cuts into the workpiece how the heat leaves the bit changes dramatically because the material starts changing its thermal coupling to the tool and the conduction cross section changes.

Keith Cress
kcress - http://www.flaminsystems.com

RE: how to measure temperature of a rotating drill bit

@khalchris

Have you? (found a way to do that measurement)

What speed are you running the drill bit at?

Typical drills will not accept the unbalance that a transmitter causes. Or, the transmitter will not accept the forces caused by rotation.

So, what dimensions are we talking about? What speeds? What temperature are you interested in? The tip's temperature or the stem's? Or just about any temperature that you happen to read? Is this a real problem? Or something you just thought would be interesting to discuss in general?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: how to measure temperature of a rotating drill bit

I like the idea of using the drill-work interface as a thermo-couple. That may be the best way by far to measure the temperature at the interface. The contact between a cutting drill and the material is intimate and the noise generated may be much less than expected. You may insert insulating material between the work-piece and the vise.
This is worth a try.
Why do you want to know the temperature??

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: how to measure temperature of a rotating drill bit

Regarding the transmitter but without comment on sensor placement:

Maybe not totally relevant, but this thread made me think of the pressure transmitters in my car's wheels. They survive an awful lot of shock while running maybe 1000-ish RPM, and report pressures on the road. They're about $50 per wheel.

Of course, you're not measuring pressure -- but a similar temperature device seems possible to me. A spinning drill seems like a calm environment compared to slamming a pothole at 70 mph on the I-85.

Best to you,

Goober Dave

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RE: how to measure temperature of a rotating drill bit

Car wheel, ~1000 rpm, radius ~12.5 inches, ~355g.

Drill given 18,000 rpm (?), ~9200g per inch of radius.

I recommend safety goggles.

RE: how to measure temperature of a rotating drill bit

Well, I didn't comment on the mounting hardware... In the car wheel, the transmitter is contained. But I would wear safety goggles too!

Best to you,

Goober Dave

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RE: how to measure temperature of a rotating drill bit

If it's a "wireless" (once upon a time, we used to call this "radio") system, the circular motion should impart a nice Doppler tone.

RE: how to measure temperature of a rotating drill bit

You might want to look at WISP (wireless identification and sensing platform) technology. The drill bit thermocouple leads could be run back to the processor/transceiver module near the bit chuck. Since these tend to be very small devices, building an antenna loop and electronics into a mechanically balanced housing shouldn't be difficult.

The WISP module can be read with an RFID reader. The distances involved will be a few centimeters at most.

http://en.wikipedia.org/wiki/Wireless_Identificati...

RE: how to measure temperature of a rotating drill bit

I'd take a step back and ask the question 'why?'.
Understanding the answer to that one might provide a little more background as to how to solve the issue.

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