A highly versatile and accurate tool

  • Advertise with us
Review by Mark Colan posted 08-16-2010 07:34 PM 4551 views 3 times favorited 2 comments Add to Favorites Watch
A highly versatile and accurate tool No-picture-s No-picture-s Click the pictures to enlarge them

[This is a repost of a review I wrote and posted on Amazon in June. If you find it useful, I would appreciate a visit to the Amazon review and click “Yes” for useful.]


A house framer once told me “there’s no such thing as an eighth of an inch.” A friend who has a metal shop told me that accuracy of 1/100 inch is useless for his work. So what accuracy do YOU need? It depends on the kind of work you are doing.

Wood expands and contracts with changes in humidity, and can sometimes be crushed, squeezed, scraped, or sanded to fit. Still, high accuracy is essential for fine cabinetry where you don’t want to see seams; making joints fit well; miniatures and other small scale work; templates and jigs; measuring or maintaining your tools; using other materials (plastic, metal, hardware)... and it’s good for people who just can’t live with “off by a hair” (which, by the way, can vary from .00168 to 00255 inch or more, depending on whose hair it is).

Many woodworking tools are not designed for precision beyond 1/32 inch. My table saw fence, for example, has no fine adjustments beyond bumping it with my hand or a mallet, though part of the scale does read in 1/32’s. With patience, it is possible to achieve a great deal of accuracy in woodworking, but accuracy is limited more by your measuring tools than by your cutting tools: you can’t achieve 1/32 accuracy if your tools measure only to 1/16.

My own range is 1/8” (for framing) to as close as I can get in fine woodworking, maybe 1/64, or on a good day, 1/128 inch. What matters most is what I can see and feel. I am a hobbyist woodworker, not a professional, and I find satisfaction in high accuracy.


There are three essential parts to this tool, which can be used together or separately for a variety of purposes. A “1-2-3 Setup Block” is a highly accurate 1×2x3” steel block with some holes drilled in it. It is common in metal shops. I measured the 1” edge of the block at my friend’s metal shop, and it came out to 1.00005 (this was a 4 1/2 digit scale, so last digit is rounded to 0 or 5). The block can be used as a highly accurate square, but unlike typical squares, it checks for square in three dimensions at once. It can be used as a highly accurate reference for 1, 2, or 3 inches, or as a platform to elevate another part to 1, 2, or 3 inches.

There is a vernier dial gauge with markings to 0.001” (but a lot of space between that allow interpolation), with a round tip (for measuring flat things) and a flat tip (for measuring things that have a round end or point, like a bit or blade tip).

The third piece is the real value-add: a clever assembly of two aluminum pieces, two tiny but powerful magnets, a set screw that holds in the dial gauge, and a nylon thumb screw. Its purpose is to hold the block and the gauge together, and allow it to slide along the block. It is beautifully and precisely made, with just the right amount of play to snap onto the setup block. It makes it easy to position the gauge along any of the 1-inch wide edges, where it stays because of the magnet, but then keep it there by tightening the thumb screw.


The included 4-page manual tells you many of the common things you can do with the device, and shows several possible positions of use. It can be used as a depth gauge for table saw blades and router bits, which is how it is most valuable to me. It can also check the depth of a hole or groove that you have made, which is very helpful. It can accurately measure runout (how much off-center is the motor shaft, because error there affects the width of your router groove, depth of your saw groove, actual width of your drilled hole) for tools with a motor and room to measure the axle. It can be used to check fence and table alignment.

I have used this with my table saw, my router, and my drill press. I don’t have radial arm saw, chop saw, band saw, jointer, or planer, but the instructions discuss uses for these tools too.

There are other uses, limited mainly by your imagination. It can be used to measure thickness of materials or a drill bit, for example, although a caliper may be a better design for those. The setup block can be used as a precise reference for 1”, 2”, or 3,” or for 90 degrees for squaring in three dimensions at once. The gauge can be removed and used in other jigs.


(Definitions: precision is the smallest digit or unit on a scale, but accuracy is how close the measurement is compared to the actual size.)

Digital devices have very precise displays, but are not necessarily as accurate as they appear to be. Measurements are rounded to the nearest digit (or fraction). The excellent Wixey digital caliper, for example, has precision of .001”, though the specifications say it is accurate only to within .002” (which probably means + or -). Fractions are the nearest fraction, not exactly the fraction.

The gauge included with 123 MicroGage has markings of 0.001”, but the markings have a lot of space between them. It is possible to interpolate for more precision. Also, in measuring depth, for example, you can creep up to the marking line, which is something you cannot do with a digital device. Once it is properly zeroed, it should be very accurate.

The down side of an analog gauge, vs a digital one, is that it does not show you digits (and the nearest fraction); instead, you have to read where pointers are pointing, and if you think in fractions, you may have to convert.

An analog gauge needs to be kept clean to run smoothly. Digital gauges do not usually have gears to get dirty and jam. Assuming this gauge is kept dry, it seems sealed well enough to stay clean in a woodshop.

I like the advantages of both digital and analog, which is why I have both in my shop.


I bought one of the first digital depth gauges to come to market. It was mainly plastic, and had a small magnet to hold it into place. It took some pressure to move the sensor. Consequently, if I placed it over the blade and then cranked up the blade, it pushed the gauge out of position rather than giving me a reading. I could hold it while cranking, but not conveniently. I returned it the next day. I have seen better ones since, but I’ll use the 123 Microgage instead.

The 123 block is metal, and heavy enough to stay in place. The dial gauge is sensitive: it does not require very much pressure to change. Consequently, I can place it over the blade, then go to the front of the saw and crank until I get the right height. The gauge stays in place, and it is easy enough to read the dial.

BOTTOM LINE: I’m delighted to have a great measuring tool with different capabilities than my others for shop use, hence 5 stars.

DISCLOSURE: Mastergage provided the 1-2-3 MicroGage for this review. All of my reviews are written honestly – exactly as I see them.

UPDATE: Another good use for the tool is to get the router plate perfectly level, or down a tiny amount evenly, for adjustable router plates like Woodpecker’s. Same for adjusting the table saw throat plate to get it perfectly flush.

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

View Mark Colan's profile

Mark Colan

211 posts in 3698 days

2 comments so far

View jim C's profile

jim C

1472 posts in 3951 days

#1 posted 08-17-2010 12:44 AM

Right on in your great explanation of the tools. I was a Tool & Die maker and as an apprentice, the first order of business was making your own 1-2-3 blocks. It certainly taught you how to square and make parallel steel parts.
I am partial to mechanical measuring instruments vs. digital readouts. You have a better “feel” for what you’re measuring.
Another set of tools for setup to compliment your above instruments would be a set of gage blocks. The set allows you to combine the different blocks to any given size so you can use your indicator to “compare” and set your other tolls within “tenths of a thousandth” if you appreciate precision.
The gage block sets are available on Amazon for as low as $50.00 (chinese) or higher.
You won’t be able to live without them.
I have all my toolmakers tools and I use them constantly for setups, measuring etc. even though I’m working with wood. It’s the extra advantage.
Guys like Charles Neil can guesstimate a cut and end up with beautiful pieces. I need all the advantages I can muster. LOL

View Mark Colan's profile

Mark Colan

211 posts in 3698 days

#2 posted 08-17-2010 04:13 AM

I have a set of brass gage blocks, 4” long, in fractional increments. The gage block set from Victor Machinery does not describe the sizes. Do they tend to be in fractions or decimal? Aside from the precision width, how long are they?

-- Mark, hack amateur woodworker, Medford (greater Boston) MA

Have your say...

You must be signed in to post the comments.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics