Millers Falls Mic Find - WW uses?

[Randy Klein]

I got this at a garage sale for free. Are there any uses for it in Woodworking?

It's a 1-inch micrometer, by Millers Falls No. 701R.

I'm not really sure how to read the scale. The tube is graduated from 0 to 10, with 4 smaller ticks between each integer. So I assume that it is decimal inches.

But the thumb dial has 32 graduations. 1 full turn takes it between 1 small tick to another.

So each tick on the tube is then 1/4 of 1/10 of an inch? Than each tick on the thumb dial is 1/32 of 1/4 of 1/10 of an inch?

Does anyone know how to interpret these readings?

[Mike Cutler]

Randy

I'm sure Bruce Page or one of the other machinists will chime in, but if I'm correct you have an outside mic.
The 0-24 graduations represent Thousandths of an inch. One turn of the knob from is 25 thousandths, or 1/40th of an inch. The pitch of the thread of the tool is a 40 tpi (40 threads per inch) hence the 25 thousandths value for each single rotation of the dial.
There should be 3 minor divisions in between the major divisions, and one in the middle above the minor divisions at the 50 thou' value. The minor divisions are multiples of 25 thousandths, and the major division are 100,200,300 thousandths etc.
Realize that 100 thousandths is .1 inch, or 1/10th of an inch. Keeping track of the rotations in between each major division will resolve the measured value down to 1/1000th of an inch.
Add up the major, minor and numerical scales and you get the reading.

It is very valuable for high accuracy readings of any nature, especially machine setups

[Alan DuBoff]

Not much use for working wood, IMO. That looks like a 0-1" mic, and woodworking doesn't require accuracy to the thou of an inch.

I have a GP that is very similar, but yours looks like it has the ratchet, that helps adjust on the piece being measured.

They are excellent for working metal!

There is one thing that it is excellent for that you might find it useful for...measuring the thickness of handsaw blades. A deep throat is better to allow one to check if there is taper and measure in increments to the depth of the throat, this will only to be able to measure around the edge, but still this is a useful mic to determine the thickness of the plate.

[Randy Klein]

Mike, you're right. I don't know where I got the 32 from. That all makes sense now.

Alan, I like the idea of measuring handsaw thickness. I'll do that just with it. But what do you mean by a ratchet?

Also, what does this thing do?
Slide1.JPG

It just spins freely.

[Alan DuBoff]

But what do you mean by a ratchet?

On the very end there is a smaller circular portion to the adjustment knob, and typically you would snug that up against the metal being measured, and it will kinda ratchet and allow you to keep spinning it and adjust the metal so you can get an accurate reading with proper tension. That proper tension is a by feel kinda thing in some cases, as you can crank down on the knob and tighten up the mic anywhere from .001"-.003", in my experience, depends on what is being measured.

If you turn the larger piece, it shouldn't ratchet, but if you turn the smaller one, it should. That is if it has a ratchet built into it, which is typically what that setup is for, but without turning it, I can't tell.

Even with it closed, if you can turn the smaller piece clockwise and it ratchets, that's what it is.

Most saw plates are between .015"-.035". Common thicknesses on modern saws is .018", .020", .025", and .032". Some folks are using .015" and .016" but that is only good on very small saws. Older ones will vary. I have a Patterson made in approx. 1860 I use often and it's about .023".

The part that spins freely might be what separates the non-ratchet from the ratchet mechanism, if it has a ratchet.

HTH,

[Mike Cutler]

Mike, you're right. I don't know where I got the 32 from. That all makes sense now.

Alan, I like the idea of measuring handsaw thickness. I'll do that just with it. But what do you mean by a ratchet?

Also, what does this thing do?
Slide1.JPG

It just spins freely.

Randy

Without actually having it in hand there are two possibilities. If the smaller knurled knob part behind your arrow moves and breaks away when the mic is at "0" then that is the "Ratchet" function Alan is referring to. On my mic, that is where the mechanical break away is located.
If you had bought the mic brand new. there would have been a funny looking little wrench/screwdriver with it. This would be the tool used to set the "zero" at "0" on the dial. On my mic there is a free moving section of the handle that moves freely until the tool is inserted into a slot. Then the entire mechanism rotates, without moving the mic so that the zero can be set.

As for whether the tool should be routinely used to measure wood, I tend to agree with Alan. If you measured the thickness of a piece of wood coming out of a drum sander with the mic. It's an odds on bet that the measurement would be different the next day.
It still has a place for very fine small work, or matching small pieces. If we break down the fractional equivalents to thousandths they would look like this'

1/2" = .500 or 500 thousandths
1/4" = .250 or 250 " "
1/8" = .125 or 125 " "
1/16" = .0625 0r 62.5 " "
1/32" = .03124 or 31.24 " "
1/64" = .015625 or 15.625" "

Resolution of scale isn't really practical to less that 1/2 of a minor division, so the 1/16th and smaller values are kinda academic. I can still see that some woodworkers,possibly model makers, luthiers, lathe worker, could require the type of accuracy and readability that your mic would provide.

It's a good tool, keep it around. It's great for determining drill bit sizes on the tiny drills.

[Randy Klein]

Well here's a close up of the end. All I can figure out is that the little piece locks the 1/25 tube to the 1/40 tube. I don't think there is any ratcheting mechanism in there.

Still don't know what the free spinning knurled portion is though...
IMG_4759 (Medium).JPG

[Alan DuBoff]

Randy,

I have not seen this type, but since it doesn't have a ratchet, I suspect the section that spins freely allows you to adjust both barrels independent of each other. You mentioned there is two different increments, and the 25 tics are a thou of an inch for each tic, so one full revolution takes you 25 thou of an inch, or 10 revolutions for 1/4". This is common on these small mics. I'm not clear how that relates to the other tic marks, and/or barrel, but you can easily calculate by turning the other one and see how they related to the thou tics.

To give you an idea, your mic has a .001" grad, but there are .0001" grad, or .00005" grad on some mics. This is good for metal, but for wood you just don't even need .001", IMO, although we see folks fussing over it on their woodworking equipment. It is perfect for measuring the thickness of a handsaw plate, as I mentioned, but you can test it on some other stuff...like a drill bit, or a router bit shank, if you have either of those. You might be surprised how accurate they really are! Check it out on a few drill bits.

[Johnny Kleso]

Its the best thing for measuring drills..

You can use to to match boards from a planer,
Its more accurate than a caliper but not as fast..

To put it back together close the spindel down all the way and match the thimble to zero on the main line and tighten the end screw..

The free spining knurled barrel is use when you check a part to use that to tighten the spindle down on to the part..

The free spinng is alway the same presure, if you used you fingers you could add a little more or less..
I am talking about the verneer scale on the back that measures .0000 ten thousands of an inch

Wait I think yours is a ratchet style not a free spinning knurled thimble.. You need to tighten the ratchet screw down tight when set at zero..

[Bruce Page]

Randy, Mike nailed it on how to read the micrometer. You have to think decimal, not fractional. As for uses in the wood shop, there’s not many. As mentioned, they’re good for checking drill diameters, blade thickness, and things like that. I have a set of mic’s up to 6” that I use all the time in the metal working half of my shop but for WW, I usually reach for my dial calipers.
Mic’s typically come with either a ratchet or friction knob on the barrel end. Their purpose is to give consistency to the measurement and prevent you from clamping down too hard. For example, when measuring a shim thickness you would lightly bring the mic anvils into contact with the shim and then turn the ratchet 3 clicks before reading the measurement. Friction knobs work the same way but IMO aren’t as good because they will wear out and get loose over time.
Probably more info that you really wanted to know…

[Eddie Darby]

I got this at a garage sale for free. Are there any uses for it in Woodworking?

Does anyone know how to interpret these readings?

http://www.linnbenton.edu/auto/day/mike/read.html

The wrench is used to hook into tiny holes so you can zero the unit, should it be out.

The ratchet mechanism is so that you get the same pressure when you check thickness, as somethings will deform, giving a faulty reading.