Aluminum press-fit

Any advice on achieving a good press-fit / slip-fit for a steel dowel pin into aluminum part? Anyone have experience? Dowel size is ~1/8". I would guess that you mill the hole pattern with each hole undersized and then ream on a drill press?



You are saying two different things. Press fit is within a thousandth would not be able to push in by hand or really remove. Slip fit is closer to 3 or 4 thousandths larger, the dowel could be easily removed or even drop out or slip through if hole through the part. Reaming may be necessary, but all depends on your application. 1/8" mill won’t do press fit, may not even get good slip fit…


Once you know your exact size, try a 3/32 tool and bore a hole. Sneak up on the final diameter and the best way to easily measure and test hole sizes is using a pin gage set. Keep in mind you need to feed adjust if side milling, contour ect.

Should be able to get good enough results to not use a drill press. Plus the run out on the chuck isn’t going to help.

Thanks. To be clear, it would be a press fit on one side into an aluminum part and a slip-fit on the other. The slip fit is plausible with the SO3 XL given that I can live with some tolerance. I guess I’ll have to test to see if I can achieve a reasonable press fit. No contour required, just pecking the holes. Good point on the chuck run-out.


Can the Shapeoko 3 hold tolerances that well to reliably make holes within 1 thou of what you specified, using an endmill? I’m used to using boring bars and reamers on my machines when I need to hit those sort of dimensions.

McMaster does sell over and under sized reamers which should get you to the exact size you need to be. I have seen them sell stubby reamers to fit into tighter spaces. I do not know if they make a stubby reamer short enough to fit in the shapeoko and leave enough room for your workpiece.

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