Thread: Micrometer "feel"

Originally Posted by Mark Rand

The problem isn't often the part that's being measured (although thin walled hollow sections can be fun), it's the micrometer itself. A 1" mic is reasonably stiff, just because of it's small size. When you get to a 36", they're made of liquorice. Even though they're made with larger sections, they are still flimsy in comparison.

If we use the German DIN standard DIN863 for micrometer accuracy as a guideline then the larger the micrometer the larger the allowance for deformation.It's the second one on this link, last column.
http://www.f-m-s.dk/DIN862+863.pdf
It's even given which specified force is used (10N). That's where the ratchet comes in handy as a micrometer ratchet normally gives 5-10N

Basically it comes down to, who ever is going to use the mic should calabrate the mic. Thats why most shops have mics for every guy not 1 mic for everyone, because everyone's "feel" is alittle different. Three people measure the part 3 people should get the same reading using thier own mics. Once you start talking in .ooo1's it's hard for 2 people to use the same mic and get the same measurment.

Originally Posted by racen857

Basically it comes down to, who ever is going to use the mic should calabrate the mic. Thats why most shops have mics for every guy not 1 mic for everyone, because everyone's "feel" is alittle different. Three people measure the part 3 people should get the same reading using thier own mics. Once you start talking in .ooo1's it's hard for 2 people to use the same mic and get the same measurment.

Not in any company I know. Are you saying that the machinists you know either can't or don't know how to use a micrometer?

Your micrometer might show 0.0001" but that doesn't mean it's that accurate.

If a company can afford to give every machinist all the micrometers they need then surely they can give them ones that have a ratchet?

"Your" company sounds like Anarchy Inc.

Gordon

Originally Posted by Gordon B. Clarke

"Your" company sounds like Anarchy Inc.

Gordon,

There are people in the world who do not agree with you.

They have an absolute right to express their views without being subjected to derisive comments.

This is a community of equals, sharing their views and experiences, which can differ widely.

If you can't control the civility of your responses, I can.

- Leigh

For those advocating the general use of the micrometer ratchet... to take it a logical step forward - surely your in-house micrometer ratchet mechanisms should themselves be checked, cleaned, and calibrated, i.e. all to be precisely equal to each other in applied torque for a given reading??

If not, why not?

Yes, I'm stirring. But it could also be a serious question. I can't remember the last time I used the ratchet on a mike - when I have, they seem to require a little too much torque, and are mechanically simplistic - more like an afterthought than a real solution.

(edited to clarify) Of course micrometer ratchets aren't adjustable, and therefore can't be calibrated. A machinist can learn to 'feel' the amount of torque which gives an exact reading off a gauge. A ratchet can't, as it's just a rudimentary mechanical device whose only job is to replace (unskilled) human variability with a degree of consistency.

Do you always get a perfect reading using the ratchet when measuring a standard gauge? Just asking.


Shaggy

Each individual micrometer has its own friction device. Therefore each micrometer can have a different torque limiting value.
It makes no difference as long as the mic was set with the ratchet. And adressing "feel" try using feel on a .00005 micrometer
Its meant to be used, so use it

one of our employees just bought a mitutoyo quantumike. .00005 resoloution. the whole thimble is a ratchet. No questionn as how to use it. this is a very nice micrometer. and when i set it , everyone who uses it WILL get the same results.

Originally Posted by hotbluechips

one of our employees just bought a mitutoyo quantumike. .00005 resoloution. the whole thimble is a ratchet. No questionn as how to use it. this is a very nice micrometer. and when i set it , everyone who uses it WILL get the same results.

I agree. If it's to be properly used, the ratchet should fall naturally to hand. The usual dinky little thing, stuck too far out on the end for comfortable one-hand use, does not.

Shaggy

gawd there are alot of posts in this thread i didnt read them all, just wanted to say one thing its not a C-CLAMP just looks like one

Originally Posted by shaggy

For those advocating the general use of the micrometer ratchet... to take it a logical step forward - surely your in-house micrometer ratchet mechanisms should themselves be checked, cleaned, and calibrated, i.e. all to be precisely equal to each other in applied torque for a given reading??

Shaggy

In all (and I've seen many) brochures that have micrometers in them then, when ratchet force is specified, it's always specified as 5 - 10N which is as per the manufacturing standard for micrometers.

The only exception to this is for special micrometers intended for use with "softish" materials.

If the ratchet is used to calibrate the micrometer then it'll also give a conforming result when used to measure.

Having said that I will admit that I've never heard of anyone ever checking/calibrating ratchet force. It seems to be taken for granted.

I suppose the best test method would be for one person (and using the same micrometer) to calibrate and measure without the ratchet and another person to calibrate and measure with the ratchet. I wonder if there would be a difference and if so how much?

This refers to calibration force (re parallelism and deformation) without any reference to a ratchet. http://www.f-m-s.dk/DIN862+863.pdf

Gordon

Let me get a big snowball rolling down hill,... my thoughts and the thoughts of many of the machinists I have worked with over the years are. Ratchets and friction thimbles are for people who do not know how to use a micrometer.


Standing back ready to duck all the things being thrown in my direction.

Originally Posted by racen857

Let me get a big snowball rolling down hill,... my thoughts and the thoughts of many of the machinists I have worked with over the years are. Ratchets and friction thimbles are for people who do not know how to use a micrometer.


Standing back ready to duck all the things being thrown in my direction.

Keep fishing. This fish isn't biting. It's been discussed often enough to let most know that the for and againsts don't agree. If you're happy with the way you do things then keep on doing them.

Very true Gordon, basiclly the orginal poster asking the question just needs to practice using his micrometers like a previous poster noted about the gage block set. Then determine witch method works best his INDIVIDUAL preference.

It's Friday, the days half over PM'ers

Originally Posted by hotbluechips

one of our employees just bought a mitutoyo quantumike. .00005 resoloution. the whole thimble is a ratchet. No questionn as how to use it. this is a very nice micrometer. and when i set it , everyone who uses it WILL get the same results.

5-6 years prior to that Quantumike this mic came out from B&S/Tesa. The entire thimble is also the friction device but the big difference is it does not move away from your fingertips as you open it as in every other type of mic I've seen, digital or not. The darker knob on top is for speedier opening and closing being it is a smaller diameter.
The person with the tiniest hands in the shop will find it comfortable to use and hold in the traditional way a mic is held throughout its entire range of 0-1.2" (at .00005" resolution)
It might not look it at first blush but it is the most ergonomic mic we've found.

This is insane how passionate people get about the use of a micrometer...

You guys understand you can BOTH be right, or no?

The thimbles should be calibrated along with the micrometer's geometric properties. If you are not calibrating your tools, you probably dont have allot of business working to the fourth decimal place.

A typical calibration house will calibrate the following or atleast emasure it
-Thimble stiffness and force
-Zero
-Deviations form zero in different division schemes
-Linearity fo the range
-Flatness of the faces
-parallels of the faces
-Check the standards
-Constantly measure temperature and humidity

Has anyone ever tried using a micrometer as a go/no go gauge, especially for measuring a cylinder. I find that measuring in the fourth digit on something big and flat is one thing, but cylinders are particularly hard to measure. Also I would think thew ay a person holds the mic might have nearly as much difference as the pressure.

As said by others the thimble adds consistency weather its right or wrong, if that mic is calibrated to the thimble it should operate consistently and calibrated for that consistency it will be just as good as feel.
Variables with a micrometer when measuring to 0.0001

-Temperature
1. Parts and mikes must be the same temperature
2. You can't be injecting temperature into that measuring tool, you should nto eb handling it more than 30-40 seconds, or you are probably going to be over heating the instrument.
3. Temperature fluctuations should be minimized, and measuring on a surface plate and keeping instruments ont hat surface plate can go a long way to keeping temps steady.

-Force
1. The thimble gives you the same torque every time, it has been designed to do that, and it should eb calibrated when the micrometer is calibrated.
2. Feel can work well too, but you need to be experienced and you need to get some quantitative measurements on your feel
3. (From: Pete M): Thimble stiffness most especially for soft materials can cause a significant force lading to material deformation (Polymers) and at times a micrometer suited for these materials with the addition of a +/- Gage(Indicator) should be used.
4. (From: Pete M): Thimble force is dependent on the friction of the screw itself, and the thimbles torque generating capacity, an oiled mike with lower friction at the threads will give different results than a non oiled mike.
-Cleanliness
1. The mic should be cleaned wit something non abrasive every time it is used
2. The surface you are measuring must be perfectly clean
3. beware of raised surfaces, the mic is taking an effective average over a small area.

-Feel (Not the pressure)
1. Especially on cylinders, if you are not at a diameter, you are not measuring right, be sure you are at a diameter and not a chord
2. the mike must be perpendicular to a surface, you might be across a diameter on a cylinder, but the mike can be cocked.

Can anyone add some more tot his?

Originally Posted by vettedude

This is insane how passionate people get about the use of a micrometer...

Isn't that the truth.

- Leigh

Originally Posted by vettedude

. . .
-Force
1. The thimble gives you the same torque every time, it has been designed to do that, and it should eb calibrated when the micrometer is calibrated. . . . Can anyone add some more tot his?

FWIW, a slight amendment to an otherwise excellent list. Few ordinary mics provide a means of changing the the torque/force/feel. Rather, most ratchet and friction type spindles operate with a fixed and reasonably firm torque. As long as it (the torque, and hopefully the pressure) stays the same from measure to measure, it should conform to its calibration.

In those cases where torque (or even better pressure on the anvils) must be controlled, usually to a lower level, a special micrometer must be used. There are, for example, mics with a graduated spring loaded anvil (usually with a non-rotating spindle) for softer and low pressure items. Mics with a +/- indicator at the anvil end may also have a means of altering spindle pressure.

One of the slight problems with both ratchets and friction thimbles is that oiling the spindle or tightening the adjustment nut will change the force.

Originally Posted by PeteM

In those cases where torque (or even better pressure on the anvils) must be controlled, usually to a lower level, a special micrometer must be used. There are, for example, mics with a graduated spring loaded anvil (usually with a non-rotating spindle) for softer and low pressure items. Mics with a +/- indicator at the anvil end may also have a means of altering spindle pressure.

Correct, I should have included this, when measuring polymers especially, the materials are much softer, due to the significantly low modulus.

Originally Posted by PeteM

One of the slight problems with both ratchets and friction thimbles is that oiling the spindle or tightening the adjustment nut will change the force.

I don't get that. If the ratchet/friction thimble is used to calibrate and measure how can it be even a "slight" problem?

Gordon

Originally Posted by Gordon B. Clarke

I don't get that. If the ratchet/friction thimble is used to calibrate and measure how can it be even a "slight" problem?

Gordon

I will try to explain,

-The friction thimble delivers torque, and not force
-Torque is not constantly delivered as force within a screw, and is very dependent on screw friction.
-There is a calibration of this torquing mechanism that should keep the equipment properly working for a while, however if lubricant is added, the above will come into effect.
-For a metal part this is not an issue, and the part can be inspected with a stiff or loose thimble making no discernible difference of the micrometer due to high part stiffness.
-For a polymer or soft part (thin metallic ring is an example), the friction thimble has the ability to deliver force such that the part will deform

So for certain cases developing a feel for torque could be an advantage.
The goal of tightening the mike is only to get the mike perpendicular and parallel wit surfaces you are measuring, not to deform the part. If you were to develop a feel you could probably determine by that feel if you were deforming the material or actually "feeling" for parallel and perpendicular. Also, I disagree with what was said earlier about not ringing the mike, the mike surfaces might need some amount of ringing to remove trapped gas.

Also on very clean metal surfaces there should be an amount of friction that you can hear with the mike, in the form of squelching. I would need to do some research to know if the screeching is at a point of adequate pressure, or over pressure. These ratchets are on the mikes for good reason, to eliminate error, not to dumb the tool down. you can calibrate the tools to read correctly based on a given pressure, its harder to calibrate for different people on the same mike.

Does that help?