So one day some people in the design engineering department decided to increase the diameter of the bearing bores so as to allow a very close slip fit (.0005. This type of aluminum would have sand inclusions that would greatly wear away the cutting surfaces of bearing bore reamers quickly. This type of tight tolerance on a bearing bore on sandcast aluminum was difficult to maintain on a constant run of parts. This was designed to be a press fit situation with an interference between. There were three bearing bores that had to be cut into the internal bottom of the casting. The gear housings were T-356 sandcast aluminum. We were manufacturing linear and rotary actuators for Boeing 737 aircraft. And basically ask the question "will it hold up?" Let me offer a practical example that happened at an aerospace company I was working at. The joinery may open up and possibly become loose.Īlso, you have to consider the conditions under which loctite or any other adhesive will be exposed. However, if this joinery will be submitted to environments of great swings in temperature - either extremely cold or extremely warm - the two materials, steel and aluminum, expanding and contracting different amounts and at different rates. If the pin and aluminum will not be exposed to Great increases or decreases in temperature, then the coefficient of expansion of each of the two metals may not be of great significance and in that case use of an adhesive with a slip fit may work well. Personally, I think an interference press fit is always better than adhesion with glue in a slip fit situation. I think the use of loctite or any other adhesion substance in securing a steel dowel pin in aluminum is totally conditional upon the environment under which this joinery will be exposed.
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