Best Digital Caliper For Engine Building
Article by Mark Trotta
Although you can buy a caliper really cheap, that's not a good idea for engine building purposes. If you're needing to measure parts for woodworking, or crafts like jewelry making, any caliper will fit the bill. But for engine work, measurements often need to be as precise as five-thousands of an inch (0.005).
Rebuilding an engine requires accurate measuring of precision machined parts. One example is bottom end roller bearings, which in a running motor spin several thousand times a minute. This is where 0.005" means the difference between a short-life or long-life engine.
Types Of Calipers
The vernier caliper is the least expensive style. It works on a rack and pinion and requires no power source. The downside is they are slow reading, and it takes a few steps to get the measurement result.
Like the vernier style, a dial caliper works on a rack and pinion and does not require a power source. They are easier to read than a vernier caliper, but not as easy to read as a digital. One drawback is the clock display is usually set for either metric or inches, not both.
Before I bought my digital caliper, I had an inexpensive dial caliper. I never used it for engine building though, it was more for measuring things like bolts and bolt holes, etc.
To measure internal engine parts effectively, a caliper needs to be accurate and consistent. Stay away from plastic body calipers. Look for an metal body and hardened tips, which prevent flexing.
The quickest and easiest caliper to read is the digital style, which operate from a tiny electronic circuit board. They can convert inches to millimeters and back with the touch of a button. Their main drawback is initial price. They are also sensitive to water, oil, dirt, and shock (being dropped).
Before I bought my Mitutoyo caliper, I looked at several cheaper Chinese calipers, including the Vinca and Neiko brands.
For the home workshop, the Vinca DCLA-0605 is a good inexpensive digital caliper. Features include a stainless steel body plus a wide screen for easy reading. It has an inch/metric/fraction conversion, and a resolution of 0.0005"/0.01mm. Measure range is 0-6 inches.
Shop: Vinca Digital Caliper
No need to push a button to turn on the Vinca - sensors do that automatically when the jaws are opened. An automatic on-off feature shuts off the caliper after 5-7 minutes of non-use.
There is an advertised accuracy of plus/minus .001" (0.03mm) but no calibration certificate is included. It's Chinese-made, but has a good reputation and positive customer reviews.
The Neiko 01407A digital caliper also features a stainless steel body with a large LCD Screen. It also has inch/metric/fraction conversion, and a resolution of 0.0005"/0.01mm. Measure range is 0-6 inches.
Shop: Neiko Digital Caliper
The tips on the Neiko 01407A are hardened to reduce flexing. There is an on-off switch with auto-off. Like the Vinca, it's Chinese-made and not certified - you won't get certified calibration in this price range.
Mitutoyo instruments are made in Japan - not China. They started producing precision instruments in 1934, and have headquarters in the U.S. since 1963. Their calipers are heavy and well built.
Shop: Mitutoyo Digital Caliper
All Mitutoyo calipers include a certificate of calibration. This means it meets standards set by the International Organization for Standardization/International Electrotechnical Commission (ISO/IEC).
Mitutoyo - Positives
- Certificate of calibration
- Name brand recognition
- Long battery life
- Low-voltage alert
- Lifetime precision tool
Mitutoyo - Negatives
Aside from the initial price, my only critique is that there is no automatic shut-off. After leaving it on a few too many times, I came up with this clever reminder.
Beware Of Fakes
Unfortunately, there are fake Mitutoyo calipers being sold on the internet. The obvious giveaway is the cheap price, but there are several ways to check authenticity.
Genuine Mitutoyo's come with an uninstalled SR44 battery and the word "Japan" printed right on the battery. The calipers and packaging should not mention China anywhere, especially on the box in which it was shipped. The serial number on the caliper should match the serial number listed on the calibration certificate.
Digital Caliper Maintenance
As mentioned, digital calipers are susceptible to water, oil, dirt, and being dropped. When not in use, I keep mine in the back of a tool drawer on top of the case, out of the way of other tools.
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There are 51 roller bearings in the lower end of an early Ironhead Sportster. After purchasing a new connecting rod set, I did not assume that all the bearings were correct, so I checked each one of them. Twice.
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Engine bearing clearances are crucial, and learning to correctly read a micrometer takes some time. First-time builders should practice-measure 10 or 20 times before trusting their readings.
When your new digital caliper arrives, try it out on your spark plug gap tool. Set it to .040" and lock it in place, then measure the gap tool.
You may be surprised at the difference.