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The Range
Gunsmithing & Repairs
Looking for caliper recommendations.
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<blockquote data-quote="Ahall" data-source="post: 4206210" data-attributes="member: 49426"><p>Calipers - There are a lot of choices and price ranges.</p><p>So what are you buying</p><p></p><p>A digital caliper is little more than a magnetic film stretched flat and glued to a steel bar and a pulse counter in the head. If the film has a flaw or is stretched too tight, the precision drops. That means quality checks and lots of rejects. The easy way to avoid scrap on the low margin end of the market is to sell a variety of grades of calipers with different precisions and avoid scrap by putting different labels on the same physical product.</p><p></p><p>ITs no uncommon for the precision displayed to be less than the accuracy they are capable of, especally for larger ones on the budget end of the market.</p><p> </p><p>Dial calipers were popular in the last century, replacing Verners, and are being replaced by digital devices. They are easy to read and have no batteries to die. The internals are complex and can be affected by dirt and grime. The inexpensive ones from Wholesale Tool, Harbor Freight, Travelers, etc. will hold up to home use and seem to work in the sense that if you measure the same part half a dozen times you get the same measurement. So they have acceptable precision out of the box, but accuracy of the number displayed depends on the care and craftsmanship of the maker. Also, with years of use the budget end of the spectrum may not stand up as well as professional grade ones. </p><p></p><p>Verners - the simplest form and not so hard to use once you get used to them. Not great for old eyes and not the easiest to use, but they don't have much that can go wrong either. Accuracy and precision are all about the craftsmanship. The lowest end of the market should be left in the store to rust. The top end are good tools.</p><p></p><p>Used </p><p>Caliper jaws ware. Close the jaws and hold them up to a bright light - any light comes through, and the jaws are not parallel and you won't get the same measurement at the tips as in the middle.</p><p>Repair is usually not cost effective. </p><p>Ball and roller bearing races are made to tight tolerances. If you want a reference to carry when checking a garage sale caliper, they do in a pinch, provided you have looked up and know what the dimension is. Its also useful to see if the caliper repeats. </p><p></p><p></p><p>The rule of thumb is use an instrument with 10 times the resolution you need if you want accurate measurements.</p><p>Also read the manufacturers literature - especially with digital ones. It will tell you what the guaranteed precision and accuracy is. </p><p></p><p>For most of my needs the inexpensive dials do just fine. </p><p>I used them for most of my checks in the reloading room and basic gunsmithing.</p><p>If I need to work tighter than I am comfortable the caliper will do, I reach for a micrometer.</p><p></p><p>Understand the limits of your tool and what effect precision has on the system your working with.</p><p>If you want everything the same, almost any can do that. If you want the actual dimension to match the reference material, you need an accurate instrument capable of resolving the tolerance.</p></blockquote><p></p>
[QUOTE="Ahall, post: 4206210, member: 49426"] Calipers - There are a lot of choices and price ranges. So what are you buying A digital caliper is little more than a magnetic film stretched flat and glued to a steel bar and a pulse counter in the head. If the film has a flaw or is stretched too tight, the precision drops. That means quality checks and lots of rejects. The easy way to avoid scrap on the low margin end of the market is to sell a variety of grades of calipers with different precisions and avoid scrap by putting different labels on the same physical product. ITs no uncommon for the precision displayed to be less than the accuracy they are capable of, especally for larger ones on the budget end of the market. Dial calipers were popular in the last century, replacing Verners, and are being replaced by digital devices. They are easy to read and have no batteries to die. The internals are complex and can be affected by dirt and grime. The inexpensive ones from Wholesale Tool, Harbor Freight, Travelers, etc. will hold up to home use and seem to work in the sense that if you measure the same part half a dozen times you get the same measurement. So they have acceptable precision out of the box, but accuracy of the number displayed depends on the care and craftsmanship of the maker. Also, with years of use the budget end of the spectrum may not stand up as well as professional grade ones. Verners - the simplest form and not so hard to use once you get used to them. Not great for old eyes and not the easiest to use, but they don't have much that can go wrong either. Accuracy and precision are all about the craftsmanship. The lowest end of the market should be left in the store to rust. The top end are good tools. Used Caliper jaws ware. Close the jaws and hold them up to a bright light - any light comes through, and the jaws are not parallel and you won't get the same measurement at the tips as in the middle. Repair is usually not cost effective. Ball and roller bearing races are made to tight tolerances. If you want a reference to carry when checking a garage sale caliper, they do in a pinch, provided you have looked up and know what the dimension is. Its also useful to see if the caliper repeats. The rule of thumb is use an instrument with 10 times the resolution you need if you want accurate measurements. Also read the manufacturers literature - especially with digital ones. It will tell you what the guaranteed precision and accuracy is. For most of my needs the inexpensive dials do just fine. I used them for most of my checks in the reloading room and basic gunsmithing. If I need to work tighter than I am comfortable the caliper will do, I reach for a micrometer. Understand the limits of your tool and what effect precision has on the system your working with. If you want everything the same, almost any can do that. If you want the actual dimension to match the reference material, you need an accurate instrument capable of resolving the tolerance. [/QUOTE]
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