FALL 2020

118 THE DISTRIBUTOR’S

118 THE DISTRIBUTOR’S LINK LARRY BOROWSKI INSPECTING SCREW AND BOLT STRAIGHTNESS from page 38 The camber gage illustrated in the ASME standards and shown in this article is an attribute gage. It will only indicate to the user whether or not the part being inspected is within the specified limits for straightness, but will not indicate the exact magnitude of the camber or bow in the part. Indicating Gage For Measuring The Amount Of Screw Or Bolt Camber To determine the extent of the bow in a part used for either gathering statistical process control (SPC) data or for final inspection documentation, an indicating, variable type of gage such as the CamberChek® is needed. The CamberChek® gage is similar to the rail-type gage illustrated in the ASME standards except the nonstationary side rail slides on two precision bearings instead of a fixed position. The gage is designed so that gravity provides a constant closing pressure against the sliding rail. A digital indicator contacts the outside of the sliding rail for indicating the exact amount of bow in the parts being inspected by the gage. To determine the exact amount of camber or bow, the part is placed between the rails so that the sliding rail is at its closet position to the stationary rail. To find this spot, the bolt would be rotated 360º to determine the lowest indicator reading. The indicator is then “zeroed out”. The part is then rotated until the maximum indicator reading is achieved. The reading on the indicator is the exact amount of camber or bow in the measured part. Unlike the fixed jaw style of gage, you do not add the screw diameter to the allowable bow. Using this style of gage and our 1/2-13 x 4” fastener, you cannot exceed the .024” max allowable bow in screw or bolt to determine if it is within the acceptable straightness limits of the standard. Inspect Straightness To Avoid Complaints Bent screws and bolts can cause their users major assembly problems. When supplying screws and bolts that have lengths greater than eight times their body diameter, suppliers should inspect them for straightness to avoid potential customer complaints and/or rejects. LARRY BOROWSKI | GREENSLADE & COMPANY INC