Starrett EC799B-6/150, Starrett 6 12 Micrometer Set, and Multimeter/Megger Basics: A Shop FAQ

Here's the list I wish someone had handed me in 2017, when I started maintaining precision measurement tools and test equipment in a small manufacturing shop. It answers the questions we get asked most: Is the Starrett EC799B-6/150 electronic caliper worth the premium? When should you consider a Starrett 6 12 micrometer set? How do you use a multimeter to test voltage without blowing a fuse? Is the Extech EX330 autoranging mini multimeter enough? And how do you use a megger insulation tester without damaging the equipment you're testing?

In eight years I have personally made—and documented—19 significant measurement mistakes. Collectively they cost me roughly $9,600 in rework, replacement fuses, and one very embarrassing calibration rejection. This FAQ is the checklist I train new technicians with.

Starrett Precision Tools

1. Should We Standardize on Starrett or Mitutoyo?

Not the answer anyone wants, but both are excellent. The internet arguments are much louder than the actual measurement differences we have seen in our shop.

When I finally put a Starrett micrometer and a Mitutoyo micrometer through the same checks—same gage blocks, same operator, same afternoon—I realized the difference wasn't accuracy. Both measured within spec. The difference was feel and support. Starrett's thimble action felt more natural over a long day, and the local Starrett service rep made calibration turnarounds faster. Mitutoyo had better availability on some dial indicators from our supplier.

My practical take: choose one primary brand and build your standards around it. If you value long-term durability and local support, I usually recommend Starrett. If you already own quality Mitutoyo tools and your repair shop knows them well, switching would just create new problems—calibration logistics, spare parts, and operator retraining. Neither choice is wrong, but a mixed bag of cheap no-name tools is.

2. Is the Starrett EC799B-6/150 Electronic Caliper Worth Buying?

For a caliper that gets used every day in a machine shop? Yes. For something that sits in a drawer? Probably not—a good mechanical caliper or a simpler electronic model will do fine.

The Starrett EC799B-6/150 electronic caliper is the one I keep in my apron. Big digital display, inch/metric conversion, zero at any position, and a sealed housing that handles cutting fluid much better than cheap calipers. It resolves to 0.0005 in. / 0.01 mm, which is enough for most inspection work.

Here's the thing: a zero on the screen doesn't mean accurate at every opening. In March 2023, I watched an operator measure 40 finished parts with a caliper that zeroed perfectly but was off by 0.003 in. at the 3-inch position—a tiny nick in the beam. That batch cost about $900 in rework and re-inspection. Now our rule is simple: zero the caliper, then check it against a gage block or pin at a second size before trusting it.

So yes, the EC799B-6/150 is worth it if you use it professionally. But buy it as part of a measurement system, not as a magic accuracy tool.

3. When Does a Starrett 6 12 Micrometer Set Actually Make Sense?

Searching for a Starrett 6 12 micrometer set usually means you need to measure something over 6 inches. A set like that gives you matched micrometer frames in one case, typically covering 6 to 12 inches in one-inch steps: 6-7, 7-8, 8-9, 9-10, 10-11, and 11-12.

Before you buy, look at your part-size history. I made a classic mistake in September 2022: one order required measuring 8.5-inch diameters, so I pushed for a full 6-to-12-inch Starrett set. That order didn't come back. The large mics sat in the calibration cabinet, used maybe four times over the next year. That wasn't a tool failure; it was a buying mistake. The budget would have been better spent on a good 0-to-6-inch set plus regular calibration.

My guideline now: if parts over 6 inches show up weekly, buy the set—it's the right tool and the readings are repeatable. If large diameters are rare, send them to a measurement vendor or rent a large micrometer for the job. Most shops overestimate how often they will need a 6-to-12-inch range. Don't be me.

Multimeters and Insulation Testers

4. How to Use a Multimeter to Test Voltage (Without Blowing a Fuse)

This one brings a lot of people to our blog: how to use a multimeter to test voltage. So here is the process we train on.

1. Stop and look at the jacks. Black lead into COM. Red lead into the voltage/resistance jack (usually labeled V-ohm), not the current jack. In March 2019, I measured a 24V DC supply with the red lead still in the 10A current jack from a morning current check. The meter made a sad click, and I spent an hour replacing a blown fuse.
2. Choose AC or DC. Wall outlets and most industrial power are AC. Batteries, sensors, and control circuits are usually DC. The most common error here is assuming a 24V control circuit is the same as a wall outlet—it isn't.
3. Set a range above what you expect. An autoranging meter does this for you. With a manual meter, start high and step down. And remember: OL on the display means over-limit, not necessarily a dead circuit.
4. Touch the probes in parallel. Red on the live or positive side, black on neutral or negative. Read the display.

That's it. The expensive part is skipping step one.

5. Is the Extech EX330 Autoranging Mini Multimeter Good Enough for Shop Work?

Real talk: I like the Extech EX330 autoranging mini multimeter for everyday troubleshooting, but it isn't a heavy industrial meter. It's the one we hand to someone checking sensors or tracing a 24-volt control fault—not the one we grab for high-energy distribution panels.

What makes it useful: autoranging removes the which-range pick; it's compact enough to carry; and it handles basic AC/DC voltage, resistance, and continuity checks, which covers most of what we do daily. Is it the last meter you'll ever need? Probably not. Is it a sensible first meter for a maintenance bag or apprentice toolbox? I think so.

One caution I give everyone: check the meter's category rating in the manual before connecting it near mains. A mini meter is convenient, but the rating—not the size—tells you where it is safe to use.

6. How to Use a Megger Insulation Tester Without Damaging Equipment

A megger insulation tester does something different from a multimeter: it applies a controlled high voltage (often 500 V or 1000 V) between test points, then measures how much current leaks through the insulation. Healthy insulation reads very high—commonly tens or hundreds of megohms. A low reading means the insulation is breaking down.

Three mistakes I have seen, and one I almost made:

1. Testing a live circuit. Never. Lock out the equipment and verify it is dead first. The whole point is to stress the insulation safely, which requires the circuit to be off.
2. Testing components still connected to electronics. In September 2022, my teammate was about to megger a motor with the variable-frequency drive leads still attached. The megger's high voltage can damage drives, PLCs, and soft starters. Disconnect the motor leads and test the motor and its cable separately.
3. Skipping the discharge step. A megger test can leave a capacitive charge on the equipment. Discharge it after testing, before you touch the leads.

Choose the test voltage from the tester manual and equipment specs. The old rule of thumb is about 1 megohm per 1,000 volts of operating voltage, but the manufacturer's spec wins over any rule of thumb.

The Calibration Habit Both Tool Types Share

7. If a Tool Reads Zero, Does That Mean It's Accurate?

Good question to ask before you trust any reading. A digital caliper can read zero perfectly and still be off at other positions. The same is true for a micrometer whose anvils touch and show zero. Zero only confirms the starting point.

Zeros drift with wear, dirt, and temperature. After the third rejected batch in Q1 2024, I created a pre-check list for our team. It's not complicated: every morning, zero the caliper, then check it against a gage block at one or two positions. Check micrometers with a standard too. Record the result. If the check fails, pull the tool from service immediately.

In my experience, Starrett tools hold accuracy and calibration well when treated properly. They're still precision instruments, not magic. A simple verification routine will catch 90-plus percent of measurement problems before they become expensive ones.