Engineering and fabrication

In machining steel or aluminum, is the tolerance different for a ream and a drill?

An engineering geometric drawing for a machined part with a hole in it has no tolerance on the actual hole size, let's use the hole size as 0.500, but the tolerance block on the print states that a 3-place decimal has the tolerance of ±0.010. If the hole is drilled or if the hole is reamed, is the tolerance the same or is the tolerance different for a drilled hole as opposed to a reamed hole and if so, what is the tolerance on the reamed hole?

Public Comments

1. Im not an engineer but whether you drill it or ream it you will stay within the tolerance it says on the blueprint, controlling the ream tolerance will be harder than a drill, but the end product should be the same if there is no error on the side of the operator.


2. For drilled holes....the tolerance is wider than for a reamed hole.

   If your print made by the designer, says plus/minus .010 then driling should be enough. Reaming is meant for closer tolerance holes....more like plus/minus .0005.

   You have to figure out what it is you need. Can your design tolerate plus/minus .010?? If so...then reaming will just add cost.

   So I think in order to answer your question, reaming will get you a better tolerance on the hole size than drililng. Just remember that reaming is secondary op that adds cost.



3. For a + - tolerance of .010, you can just drill, and be pretty sure you will be in tolerance.

   Reaming results in a hole of much closer tolerance, typically the tolerance used in producing the reamer (solid reamer, not adjustable).

   Your hole tolerance does not suggest any need to ream.

   If internal finish has to be fine and the hole parallel all the way, reaming can be used.