PDA

View Full Version : Ratchet or friction micrometer ?



mototed
08-07-2011, 03:00 PM
I have a ratchet Mitutoyo, vernier scales, works great. Click,click,click, lock it and read it. My darn eyesight just sucks now days trying to discriminate the lines. Been thinking of buying a LCD display Mitutoyo. Or should I say my wife will be giving this to me for our 31th anniversary. My boy will have some use for my old one.
Never have used a friction mic. Does the thimble just stop turning when the target is reached?
Would this just be a personal preference between the two?
I would imagine they are the same accuracy one way or the other depending on the user.
What's the difference?
Thanks
Ted

topct
08-07-2011, 03:36 PM
Can we vote for neither? The ones I've used did not agree with what I was feeling.

DATo
08-07-2011, 03:43 PM
As you probably already know, with the ratchet type you hold the frame of the micrometer with your little finger wrapped around it so the thumb and first finger can reach out to the ratchet knob. The friction type is a bit more forgiving as the entire barrel of the friction micrometer is available, and yes, the barrel just floats (keeps spinning) when you bottom out at just the right pressure.

When I was a wee nipper I was taught to close the mic at what I thought would be a perfect zero reading but without looking at it as I closed it. By doing this I would not be able to know when I had zeroed out and unintentionally allow my eyes to subconsciously influence my "feel". I would do this over and over until I could nail the zero every time to the tenth (not easy). Then I'd repeat this at different thicknesses and then over telescope gages. Once you develop a "feel" to a high pitch of accuracy you no longer need to use either the ratchet or friction barrel stops. If I have an important dimension to nail today (within a half thou) I pre-test the accuracy of the mic I am using with a jo-block or standard first and test my feel to it before I begin to take measurements.

Mark Hockett
08-07-2011, 03:48 PM
I prefer the ratchet type because you don't have to use it if you don't want as it is out of the way and the thimble is solid. The friction thimble type you don't have much choice because the whole thimble moves. I have a bunch of Mitutoyo digital mics and they are great. I bought a new Starrett digital and it was so bad I sent it back. The Starrett was only available with the friction thimble which had a terrible feel and the digital display was very slow responding.

goose
08-07-2011, 04:02 PM
I don't believe in "Zen and the Art of the Micrometer"

To me, it either works, (ie., works consistently) or doesn't work.

To wit; position micrometer, advance the barrel to close to but not touching the diameter of the workpiece, then in a consistent and smooth motion contact the workpiece while letting the ratchet or friction thimble do its work.

If you're getting inconsistent results, it's either the mic is position incorrectly along the diameter or skewed, or there's a small piece of contaminent in the way, but it shouldn't be an issue of "the feel" or "the magic touch is lacking".

Anyways, to the original question, I have both and like them both. I don't think you'll go wrong with whatever you choose.

PeteM
08-07-2011, 04:21 PM
For home shop use you probably don't need either. As long as you develop a consistent "feel" you should be able to repeat to a couple tenths.

The main use of ratchet/friction devices is in industry where multiple users are expected to get the same measurement. One may have a light touch and the other may think it's a c-clamp. So, one of the two torque/pressure limiting devices is needed to cut down on user to user variation.

Research a couple decades back said that using a ratchet could lead to a sort of impact wrench effect -- it got a tiny bit tighter the more it turned. So, a company should have a standard practice along the lines of three clicks and you're done. Friction types are just a bit more forgiving.

What most folks want is both a speeder at the end -- to get the micrometer quickly to adjustment -- and a comfortable means of controlling pressure when it's needed. It's a bummer to have either a ratchet of friction thimble start spinning as you speed a mic to size.

The old Millers Falls mics had a good approach to this, with a speeder on the end and a ratchet built right into the end of the thimble. Brown & Sharpe had their convertible friction/fixed thimble. Mitutoyo made a number of well designed mics (speeder plus friction thimble) and even Scherr-Tumico made one. Lufkin had a model with the friction thimble well placed. One of my favorites is the Etalon MicroRapid; sadly only sold in metric models now.

Bottom line is to try a bunch of quality mics and find one you like. FWIW, I've set my hands on a couple hundred mics and would have to say that while the Starrett models have maybe a bit better than average accuracy (certainly not the best), their ergonomics are just average IMO.

Forrest Addy
08-07-2011, 04:42 PM
Paaper or plastic. Peanut butter or chocolate. After one there's too many choices.

I've used all three (plain thimble is one of the choices) but I prefer my own sense of touch un-influenced by looking at the thimble as DATo illustrates. Soon as you look at the thimble you start "wishing on" or "wishing off" whatever shouldn't be there.

That and heat from your hands, a sunny day with light streaming through the clerestory windows, the blast from the space heaters, coolant chill, heat build-up from machining. Sometimes taking a reliable reading in an open shop is like working a shift in a coal mine in a white shirt - not even the best of intensions results in complete success.

topct
08-07-2011, 04:45 PM
When I was a wee nipper I was taught to close the mic at what I thought would be a perfect zero reading but without looking at it as I closed it. By doing this I would not be able to know when I had zeroed out and unintentionally allow my eyes to subconsciously influence my "feel". I would do this over and over until I could nail the zero every time to the tenth (not easy). Then I'd repeat this at different thicknesses and then over telescope gages. Once you develop a "feel" to a high pitch of accuracy you no longer need to use either the ratchet or friction barrel stops. If I have an important dimension to nail today (within a half thou) I pre-test the accuracy of the mic I am using with a jo-block or standard first and test my feel to it before I begin to take measurements.

I count about 10 yes's. :D

mototed
08-07-2011, 05:11 PM
So, with the ratchet types you have a choice of the ratchet handle on the end, or old school by feel on the main thimble ?
Do the friction mics only have one thimble?
Sorry for the stupid questions.
Never had an opportunity to use a friction mic before.

TGTool
08-07-2011, 05:33 PM
I've got mics with friction thimbles (Tesa) but that's just the outer sleeve and you can still hold the upper end for feel. So, like the ratchet you can use either way.

Dr Stan
08-07-2011, 05:36 PM
I too have both friction & ratchet thimble mics, but rely on feel as this is the way I was taught.

PixMan
08-07-2011, 06:23 PM
Can I vote for both...in one?

The newest version of the MItutoyo Absolute IP65-rated digital electronic, (which also happens to have the most exquisite manual feel) has a beautiful execution of a ratchet thimble within the friction thimble. It's model number 293-344 for the switchable 0-25mm/0-1" model, and it is easily the nicest micrometer I've ever handled.

It's classified by Mitutoyo to be "ratchet thimble", but does not have the traditional ratcheted "speeder" at the end of the thimble. The ratchet "lumps" are built into the friction thimble, and it's just impossible to describe in words how nice it is. The mechanical thimble still has the inch scale with Vernier for "tenths', but the huge LCD readout is so nice and easy to read that you may never look at the analog scale.

Mind you I own a lot of Starrett and Mitutoyo, and Starrett's HQ is just 40 minutes from my door by backroads. I have the slick little Mituoyo 101-117, Starrett No.734 and No.230RL in 0-1" mics, and the Mitutoyo 293-340 1-2" that has the ratchet stop (speeder) thimble, but now lust for the 293-344 I'd used at my employer's shop. I referred a friend to this particular one, and he got it for $129.95 from General Tool & Supply of Attleboro MA.

Here's a link to the PDF describing them. I'd need to sell off one of my other perfectly serviceable micrometers to make room, but I just might do it. It's that good.

http://www.mitutoyo.com/pdf/ABS1813-293.pdf

DATo
08-07-2011, 06:31 PM
One other thing to mention, though I know I am preaching to the choir where experienced machinists are concerned, is to close the mic from time to time fairly snugly but not tight over some clean paper and pull the paper out from between the anvil and piston of the mic. Almost always you will see some dirt there on the paper and that dirt has thickness. So clean the mic before you use it to determine an important dimension.

topct
08-07-2011, 06:42 PM
One other thing to mention, though I know I am preaching to the choir where experienced machinists are concerned, is to close the mic from time to time fairly snugly but not tight over some clean paper and pull the paper out from between the anvil and piston of the mic. Almost always you will see some dirt there on the paper and that dirt has thickness. So clean the mic before you use it to determine an important dimension.

Number one.

SGW
08-07-2011, 06:49 PM
I've got both friction and ratchet...and like a lot of others, I never use the friction or ratchet feature.

Of the two though, I tend to prefer the ratchet type. It still has some sense of "feel" about it. I find the friction thimble has no "feel" to it at all.

Whatever you have, take Forrest's advice and practice. Ball bearing races and ball bearings are good to practice on because they're accurately to size and easy to get. Just don't look at the thimble while you measure something that you know the correct size of.

PixMan
08-07-2011, 07:13 PM
I've got both friction and ratchet...and like a lot of others, I never use the friction or ratchet feature.

Of the two though, I tend to prefer the ratchet type. It still has some sense of "feel" about it. I find the friction thimble has no "feel" to it at all.

Whatever you have, take Forrest's advice and practice. Ball bearing races and ball bearings are good to practice on because they're accurately to size and easy to get. Just don't look at the thimble while you measure something that you know the correct size of.

Ever tried the friction thimble of a Starrett No.733/734 or the "analog" predecessor the No.221? It's a friction thimble for sure, but has the nicest little "spring loaded" action that you feel just before the friction grip of the thimble breaks. In that little 1/64th of a turn zone there is a very sensitive feel for how the anvil and thimble are contacting the workpiece to be measured. As friction thimbles go, I find that one to be better than the Mitutoyo 101-117 I have.

toolznthings
08-07-2011, 08:08 PM
Hello,

Plus on the paper and learning to feel. Never used either device and personally
like a no frills mike.

Brian

Carld
08-07-2011, 08:45 PM
When I was machining for a living I would ask different machinists to come and check my work with my mic. It was interesting that most of them could get the same dimension over and over but different from my dimention using just feel, no ratchet or friction. ;)

No matter what you may think, no two people can or will have the same feel and reading with the same mic. It just doesn't happen if your talking tenths.

Feel is a personal thing but the main thing is are YOU constant in your feel. I doubt it. Your feel can vary from day to day and even through the day.

I like the ratchet mic because when it clicks once or twice that's it. The friction type doesn't give me that confidence even though it may be just as accurate.

PixMan
08-08-2011, 12:13 AM
While some of the members here may choose to use a plain micrometer, the OP is like me in that his eyes are now needing aid to discern the lines. A digital electronic micrometer makes the most sense IMO.

With that in mind, there are cheap Chinese ones that may work OK for varying numbers of weeks or maybe years, but since his wife is gifting, might as well get an "heirloom quality" tool. For that, I very highly recommend he go back to my original recommendation of a Mitutoyo 293-344.

No regrets, I promise.

Carld
08-08-2011, 01:14 AM
I prefer a standard mic using a magnifying glass to anything digital, electronic or analog.

PixMan
08-08-2011, 01:24 AM
I prefer a standard mic using a magnifying glass to anything digital, electronic or analog.


Uh...isn't a standard ordinary plain micrometer.....analog? :p

Have you ever owned or used (to any extent) a good Mitutoyo digital electronic? They really are quite nice, and require no magnifying glass to get the reading.

Carld
08-08-2011, 09:38 AM
I was referring to the mic's with a dial reading rather than a digital readout. I guess I needed to type out another sentence to explain what I meant.

I have not owned a dial or electronic digital but have used them others owned. I just do not like them or trust them.

There are three types of mic's I referred to. One, the standard thimble mic with or without friction or ratchet ends. Second the mic's that had a dial that showed the alleged same reading the thimble did but was not always the same. Third, the newer electronic digital readout mic's that display the mic reading over the work.

Of the three the most accurate in my opinion is the old standard type mic where you read the measurement right off the mic. I do not trust the mechanical dial type or the electronic digital mic's. You can set the manual mic to "0" and know they are correct through the whole travel of the mic.

bborr01
08-08-2011, 11:08 AM
Think of a ratchet or friction thimble as a torque wrench for your mics.

The ratchet kind is like the clicker type torque wrenches. The friction ones are like the old type torque wrench.

If you clean the anvils with paper or a $100 bill like one of my instructors advised back in school, then close the mic using the ratchet or friction thimble, then adjust the barrel so the lines are on "0" you will be able to measure quite accurately.

Brian

mototed
08-10-2011, 07:15 PM
Played around with my new toy. It worked perfect out of the box. I tried to go with PixMans selection but wound up with a 293-340 for a good price after the Enco 15% off. The 344 is sold out every where.
http://i217.photobucket.com/albums/cc28/mototed/IMG_0066-1.jpg
After a little play time, I found out with this one if I used the ratchet slowly (click....click....click) it was good to .001" But if I went (clickclickclick) it would repeat 98% of the time to its limit of .00005" Way more than I could ever achieve with my old machines and lack of knowledge.

I really don't want to take my new one apart, but how do these things work? I understand glass scales and the other DRO measurement devices. Anybody knows whats inside these things that makes them count?
Thanks
Ted

Carld
08-10-2011, 09:32 PM
How do you know it's accurate to .00005"? Have you tried it on some gauge blocks? Do you have something that breaks down to that small increments?

PixMan
08-10-2011, 10:10 PM
Congrats, mototed. Nice micrometer. I have the 1"-2" version of the same, and love it. They have a nice feel to the thimble and feel right in the hand. Numbers sure are easy to read, aren't they?

Unlike Carld, I trust mine implicitly and like it too. I had used these at screw machine shops I worked in for many years and NEVER had one fail nor give me a misreading. I wish I could say the same for Brown & Sharpe slant line micrometers!

All you have to really be sure of in setting it up is to properly set the "absolute" zero point. After you've done that, just be observant that when making critical measurements that you don't see the "INC" symbol. That means you're in the incremental mode and not in absolute mode and could be working off of a secondary zero point.

I own a Mitutoyo micrometer stand and often use my micrometers held in that. Very nice way to do it for best results.

HWooldridge
08-10-2011, 10:34 PM
Played around with my new toy. It worked perfect out of the box. I tried to go with PixMans selection but wound up with a 293-340 for a good price after the Enco 15% off. The 344 is sold out every where.
http://i217.photobucket.com/albums/cc28/mototed/IMG_0066-1.jpg
After a little play time, I found out with this one if I used the ratchet slowly (click....click....click) it was good to .001" But if I went (clickclickclick) it would repeat 98% of the time to its limit of .00005" Way more than I could ever achieve with my old machines and lack of knowledge.

I really don't want to take my new one apart, but how do these things work? I understand glass scales and the other DRO measurement devices. Anybody knows whats inside these things that makes them count?
Thanks
Ted

There is a little wheel that runs past an electronic pickup. It doesn't have any zero reference point because the Origin button performs that function. In other words, you can take it apart and put it back together without regard for position - but I wouldn't recommend doing it for fun. I've taken apart several after they were dropped in an attempt at repairs and only been successful if the frame isn't sprung and/or the spindle is damaged.

I also believe everyone - even home machinists - should own at least one Class X Jo block kept in a controlled environment, so you can calibrate the micrometer to verify its accuracy and repeatability. Most shops in the machining business have a master set they send out to an NIST certified lab so traceability can be established to the lab's master set. This becomes important when a customer comes to audit but is also good practice.

With regard to the original question, I prefer a friction thimble because it's easier to hold in one hand. OTOH, a ratchet is ideal for a micrometer stand where one hand holds the part to be measured and the other turns the thimble. However, I've seen folks use both interchangeably so it's probably really just a Ford vs Chevy question...