Intro: Ohaus Harvard Trip Balance Repair Calibration With US Mint Calibration Weights
Repair Broken Pointer Indicator & Calibrate your Scale or Balance With US Coins accurately.
For Ohaus Harvard Trip Two Beam Balance Model 1550
For a $1.25 plus glue we repaired this OHAUS balance. A new balance would have cost more than $200 USD.
This balance came to us from the thrift store for $6.00 with a broken pointer assembly and a cracked pointer indicator combination bearing dust cover. We were able to glue (using Loctite Extra Time Control Super Glue) back together the indicator though a chip from one corner was missing. We let gel super glues like this set overnight with pressure applied to the joint.
The more difficult replacement was the pointer indicator which was sheared off at the base of the mechanism. It is held in place with a set screw. What was left was a piece of brass rod which originally had a plastic piece at the base formed to a point.
3mm was the measurement of the brass round left in the mounting hole. We could have gone to the trouble of buying some brass 3mm stock and shaping a piece. We found an easier solution, a thin bamboo skewer (ours are from Walmart under a $1.00 for a bag of 100) Almost the right size. Cutting the pointed end off at the correct length and slightly trimming the bottom with a razor knife and slightly flattening just below the beginning of the taper of the point, voila a very pointy indicator that weighs very little. Plug into the hole, tighten the screw and you are back in business.
The US Mint by the “weigh” has inexpensive calibration weights so you can check the accuracy of your balance or scale. Find five uncirculated (or nearly so) US nickels. The US mint conveniently and accurately manufactures these at 5 ¢ each to a high degree of precision. Take 5 of them as a sample and know your calibration weight is 25 grams, 5 grams for each coin. No nickels? Use 10 new copper clad pennies each of them weighs 2.5 grams. The consistency of the nickels is proven qualitatively, even OHAUS in their maintenance manuals has recommended the “nickel” calibration for this type of balance. Having multiple item sample helps to work out any small variance among coins. If you have a more accurate scale you can weigh your nickels and add or subtract weight by various methods (tape on the balance platform is effective) if you want high accuracy, however with this type of balance any error in the nickels is far under the ability of the balance to resolve.
So we turned this $6.00 find into a viable and useful object again for a $1.00, glue, and some change! If you need to lubricate do it sparingly, we have standardized on molecular lubricants such as Liquid Bearings over any oil or even Teflon. Often this type of balance needs a though cleaning including the magnetic dampers in the bottom of the unit.If you are looking for repair maintenance manuals for some items, the US Government is a good go to. There is one website that provides PDF manuals free for download, type in your search engine: liberated manuals. The US Government does not own any copyrights and often rewrites maintenance, instruction, and repair manuals for commercial items they purchase, worth a look.