![]() ![]() If the material allows, what about using larger pins, for starters? And make sure the bracket is securely fastened and not moving around. ![]() If there is movement in the bracket, or too much load on it, it could be simply hammering the pins loose due to vibration. I have been machining aluminum and pressing in pins for about 35 years, and I see a red herring in the last response about what the dowel pins do. Reaming to tenths in aluminum can be treaturous. 1245 there should be no loose pins at 400 *F with a. Steel dowel pins are +.0002 over nominal. The differential expansion of the aluminum away from the steel pin is. ![]() 0000065 is a good number for this first cut look at the problem. Steel alloys vary also in coefficient of linear expansion. 00054 inchÄon't forget the steel pin is also expanding so what matters is the differential expansion between the steel pin and aluminum hole. The calculation of the change in diameter of the hole is simple: 332 X. The change in temperature is 400 - 68 = 332. Let's use 68 *F, a standard, for your shop. The change in temperature from your shop temperature to 400 *F isn't 400 *F. The expansion of your hole would be the change in temperature times the diameter of the hole times the coefficient of linear expansion. Lets say it's 6061 for example and use 0.000013. I doubt if your part is pure aluminum, common aluminum engineering alloys coefficients of linear expansion vary from. A one inch piece of material would expand or contract its coefficient dimension if it underwent a one degree change in temperature. The coefficient of linear expansion is expressed as linear change per unit length per degree of temperature change. 0000126 per degree, assuming 400 degrees means the part would change. "The expansion rate of Aluminum is supposed to be. ![]()
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