Dial Indicator Score Card
The scores we give in the following chart are highly subjective, based on our observations of current models. We have repaired thousands of these and are quite familiar with the pros and cons. Each column is described below.
Information applies to the majority of each manufacturer's current model dial indicators only. It does not reflect our opinion of test indicators which are discussed on page 37.
Notes to above chart:
† B&S is not a manfacturer. Their dial indicators are made by Kafer, for the most part.
Vacant areas have yet to be rated.
(1) Spare parts availability
Whether you plan on fixing these yourself, or sending them for professional repair, the work can only be done if the manufacturer makes parts available. A reference to "easy availability" is made when Long Island Indicator stocks the parts or the manufacturer is willing to sell them without minimums.
(2) Bezel and crystal replacement
This should be the easiest do-it-yourself repair. The crystals get scratched, cloudy, or break and you want to know whether you can install a new one. This hinges on availability of parts, of course (see #1)
You can send your indicators to any of numerous repair shops and some indicators just won't be worth repairing. Either they're poorly built or just not economically worthwhile.
Some items are designed to be thrown away, others will last a life-time. The price is usually a reflection of this. You have to decide what it's worth to you.
(5) Functional design
We've seen the insides of all of these and are willing to laud some manufacturers and curse others. Every chain has a weak link and every indicator has something that can use improvement. Understand that this is a highly personal opinion.
(6) Accuracy and precision
All indicators are accurate when new (at least, we'd like to think so). But many indicators are made with inferior quality components which will not last: bearings wear down, spindles become worn, teeth get bent, play develops and repeatability and accuracy eventually suffers.
The days of all-metal construction are almost over. It all has to do with making an indicator which will be cheaper than the competition from China. Quality often suffers in the process. Plastic bezels, while easy to replace, will break just as easily. Plastic gears, it is our experience, are damaged more often than metal gears.
(8) Long Range
Indicators with more than one inch of travel are often referred to as "travel indicators." These are challenging to build for the manufacturer because of price considerations. The best ones cost the most. Less expensive models often have flimsy bodies which are easily damaged. Starrett models have spindles of soft steel which wear down quickly. Mitutoyo models have been redesigned and are probably the best of these. Kafer models are very sturdy but rack teeth can become damaged. Compac are the best but rarely available, only in metric, and they are outlandishly expensive.
(9) Bezel Rotation
A bezel clamp is used to keep the bezel stationary but most of the time you'll need to rotate the bezel for one reason or another. Different manufacturers have come up with different methods to hold the bezel in place yet still allow it to rotate. The newest technique seems to be the o-ring which, when functioning correctly has a smooth movement, allows for easy bezel removal and also acts as a moisture seal. Unfortunately the rubber doesn't age well. Solvents may cause it to stretch out of shape and turning the bezel can become difficult or impossible. A little bit of vaseline on the o-ring can help. A more reliable method uses metal springs to hold the bezel. These can be bent to produce the desired amount of resistance and they won't give out or change with time. Some manufacturers use 2 or three clips, or little screws, or pieces of wire, etc. We can't decide which method is really best. When the indicators are new, the bezels all turn well. The real test comes with time. Our chart above refers only to the manufacturers' newest models.
(10) Where are they made?
Where they're made can influence purchasing decisions because we might be interested in adding fuel to a certain economy, or we may have preconceived notions of product superiority based on origin. This information reflects our own prejudices and should probably not be used as a sole determining factor in choosing a particular instrument. In recent years, there have been changes in origing, sometimes carefully obscured by the manufacturer. If there is no clear country of origin printed on the dial face of the indicator then you should assume they are made in China.
(11) Serial numbers
Serial numbers are an important element for ISO qualification, for calibration certificates, and general record keeping. Even in a less formal setting, the serial number can identify who owns which gage. We should be leery of a gage which has had its serial number scratched out or obliterated. Stolen goods, perhaps?
For more general information on dial indicators take a look at Dial Indicators: For what it's worth on page 139.