# Mitutoyo QuantuMike ratchet thimble and speeder mechanism



## tino_ale (Apr 25, 2010)

Hi guys,

Didn't want to hijack the other thread so, I'd like to ask my question separately.
Snip from another thread :



precisionworks said:


> +1
> 
> The reading on a mic is totally dependent on the pressure applied to the spindle, which is transmitted to the contact tip faces. Take a piece of ground stock like TGP shafting & mic it a dozen times - if the tip pressure is identical each time, the readings will all be the same. If some readings are too low or too high, keep working on technique until all readings are the same, or at least within +/- .0001".
> 
> I like the Mitu ratchet spindle & use it by clicking it three times for each & every reading. Some people don't trust a ratchet & prefer to rely on their fingertips, which can work better than any mechanical helper IF those fingertips have the experience to apply identical pressure each time.





gadget_lover said:


> Click it three times? That's like a torque wrench, tightening till it clicks. I never thought of doing it that way. It makes perfect sense.
> 
> I have always done it the wrong way; spin the thimble till it touches and then spin the little knob through a few rotations. That's obviously the wrong way. I wish the instructions had mentioned the right way to use it.
> 
> ...



Since I have a Mitutoyo QuantuMike on my way, I'm actually slightly confused about the correct measuring method to adopt.

The mic has a thimble (large rotating grip) and a speeder (smaller rotating grip). Until now my understanding was that the speeder was a very quick and coarse control, at 2mm/rev, while the thimble being the classic fine adjustment you use for final reading. Seems I got it wrong ?

Could anyone owning this mic make it clear what the measuring procedure is and what is the purpose of the thimble and speeder ? Besides, the pdf I have says they both have a ratchet mechanism.

Maybe this will become obvious when I get it in hands but a piece of advise never hurts 

Thanks!


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## gadget_lover (Apr 25, 2010)

The purpose of the ratchet is to allow you to use the same force every time. if you do not use the same pressure, then the caliper frame or the material you are measuring will deform differently, throwing off your measurement.

On a recent project I measured a bore as I roughed it, and was surprised to be able to see the marks where the expanding bore gauges were slid out of the bore. The metal was that soft.

According to the Mitutoyo web site, the thimble and the speeder have a ratchet. They make it sound like a way to vibrate the work into position. "The patented ratchet thimble mechanism* helps ensure repeatable
results by transmitting microvibrations along the spindle to the
contact face to provide a constant measuring force and encourage
good contact with the workpiece. "

It sounds like it's more of a torque sensing device to me.  On all of my mics the ratchet is only in the speeder. So I use the small knob to make the final adjustment and SHOULD only click it a couple of times. And it should be the same number each time to ensure the same pressure is applied.

Daniel


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## tino_ale (Apr 25, 2010)

Thanks for your reply,

So, you're using the main thimble to come close to the part, then finish with the small knob and click a couple times ?


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## wquiles (Apr 25, 2010)

On my QuantuMike I just use the main/large "timble" (or whatever is called) until it clicks once. It just works


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## tino_ale (Apr 25, 2010)

wquiles said:


> On my QuantuMike I just use the main/large "timble" (or whatever is called) until it clicks once. It just works


So there is a ratchet on the large thimble, thanks for that info 

What does the small "speeder" do ? Just the same but with a smaller diameter or ?


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## gadget_lover (Apr 25, 2010)

Smaller diameter = more revolutions per movement of your fingertips.

Daniel


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## tino_ale (Apr 25, 2010)

gadget_lover said:


> Smaller diameter = more revolutions per movement of your fingertips.
> 
> Daniel


That's all ?? :shrug:

lol

So I guess there's no room for headache here  I just need to tighten the thing down until it clicks twice


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## gadget_lover (Apr 25, 2010)

The larger diameter of the thimble will make it easier to set a particular setting. You do that so that you can use it as a gauge (for matching a part to a particular size) as opposed to using it as a measuring device.

Daniel.


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## tino_ale (Apr 25, 2010)

Thanks, perfectly clear.
Those Mitu are really nice pieces of equipment!


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## precisionworks (Apr 25, 2010)

> my understanding was that the speeder was a very quick and coarse control, at 2mm/rev, while the thimble being the classic fine adjustment you use for final reading.


The QuantuMike is different, as the ratchet works from both the large & small sections of the handle:







Most other mics have no ratchet on the thimble, so the thimble is used to get within a few thousandths of the part diameter & the ratchet on the speeder closes until contact, plus three clicks. With this mic, both the large & small sections can be used for final contact.


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## tino_ale (May 12, 2010)

I just got my Mitutoyo QuantuMike and been playing around with it .

It's ability to pick-up small measurement differences is amazing, and you soon realize NOTHING around you is even, parallel, square etc. Even supposedly precise parts hardly stand a chance to show up perfect with a mic.

Well I picked up my SPY007. It has two large flats on each side. I was impressed that across the whole surface of these flats, the mic would pick-up a difference of only 0.010mm (less than 0.0004"). So up to now I can say my SPY flats is the post precise feature I've found on objects surrounding me.

BTW the speeder is nothing more than a reduction of the diameter of the rotating thimble. Both parts basically act as a single part. The ratchet mechanism of course works with both and I like it a lot.

One question though : when I set the zero, if I screw slowly until contact, then click three times, I will not get the same zero than if I screw faster. If I screw faster it is like the surfaces are pushed harder against each other and there is some resistance to unscrew.

I guess the slow motion is the way to go, but I was wondering how you make sure you got the correct "zero" ?


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## precisionworks (May 12, 2010)

Sounds like dirty contact faces ... this happens sometimes to my Mitu digital & stops as soon as the faces are cleaned. The easiest way to clean them is to take a sheet of bond writing paper called "100% cotton rag", fold the paper in half and lightly close the spindle while drawing the paper between the faces. Do this a few times with the spindle closed enough that a slight drag is felt. The cotton rag paper cleans & polishes the faces, and will give the mic a consistent zero.

It doesn't take much junk on the anvils to mess the zero up, as the mic is reading 10 millionths of an inch in the last decimal place.


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## tino_ale (May 13, 2010)

Thanks but I've cleaned the faces and it hasn't changed anything.

Actually since it is my first mic I am not even sure if it is normal.

when the faces are coming closer, if I spin the thimble slowly until they make contact, then click three times, I always get the same and consistent zero. While unscrewing the thimble, the faces separate with no resistance.

Now, if I spin the thimble quickly when the faces are coming close and touching, they "hit" each other. At this point I get a negative measurement. Also there is some resistance to unstuck them.

I believe the inertia of the thimble press the faces against each other much harder then if I screw slowly and click normally. The resistance to unscrewing must be due to the small deformation of the mic.

This is not a problem but I wasn't aware of the fact that the speed at wich you spin the thimble when the faces make contact would change the measurement. But it kind of make sense though.


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## Anglepoise (May 13, 2010)

tino_ale said:


> Actually since it is my first mic ................
> .



You bring the two measuring surfaces of the mic together very gently and slowly and then..... if you want, let the ratchet click 3 times.
When you come in too fast, you are tightening too much and the ratchet mechanism cannot 'back off' . 
Old timers never had ratchets or clickers and it was all done by feel
but if the ratchet is used correctly, you are guaranteed perfect repeatability.


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## 65535 (May 13, 2010)

WHen you "slam" the anvils together you get the spindle and anvils to start compressing and the C arm to start bending, probably not preeminently or to cause damage, but it will through off your reading because they are that precise.

Realistically you don't need the ratchet, what you want is the anvils to barely close on the part and just be touching the serface, you start putting pressure on the parts and things bend which throws off your reading.


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## KC2IXE (May 13, 2010)

Want to have some fun with your new mic?

Put the Mic away in a cool dry spot overnight (well, a few hours will do - enough to get the mic down to room temp

Gently close and zero the mic 

Open the mic a turn or 2, and HOLD the mic in your hand by the C frame for say 10 minutes - now close the mic and take a reading. Yep - below zero! Why? Because the frame got larger from the heat of your hand!

People do NOT want to believe how small .0001 of an inch is. Whenever someone tells me "Oh, I work to .0001 tolerances, I ask the question "Oh, what temp - and what do you use for climate control in your shop?"

(Back when - I used to work on the hvac system for a place that DID work to those kind of numbers - the shop was kept at 68 degs +- 1 deg, and no more humidity change than 5% (can't remember WHAT the percentage was) and all the air was 100% fresh air, electrostaticlly precipitated - aka a low level - (maybe class 100-200) clean room. Not quite bunny suit level, but...)


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