Hello !

I've recently built a CNC machine which is somewhere between hobby and semi-pro level. It uses the ER25 chuck system so I can grab up to f16 mm(0.63'') tools.

I've tested the machine and it works very good, good positioning and made a hole for a bearing with the ISO tolerances for H7 for f47 hole. I needed to make three different holes by gradually increasing the offset with 0.01 mm(0.0003'') before my bearing fits properly into the hole with slight use of a hammer.

I wondered what the reason is and by using a micrometer, I measured the tool diameter. For my surprise, it was not f16 but rather 15.96 mm. I found out where my mistake was.

Now, to the question, what is the best endmill tool(material, coating, number of flutes etc.) to use for making precise holes for a series of parts(5/10 or 20 items) so that the tool doesn't wear quickly off if the speeds and feeds are not too aggressive? The above miller is low-cost, costs about $10 and is from China. After several hour use without going to aggressively, it wears off.

I am currently asking about aluminium which is the material I mostly use.

I don't mind spending much more money on a single tool if I am certain it will not wear off too quickly and I will be able to do my parts with a single or with 2-3 such tools.