[skmetal7]

i was wondering how i could get a surface finish like the one on this part. on the right is the finish i get with my lathe (i dont mind it) and on the left side is the original finish (shinier and i like the way it looks). i have no idea what type of aluminum this is. what type of cutter do they use, really pointy (no radius)? im guessing a high speed and feed since it is a mass produced part (hdd spindle)

[Hursty]

To finish the selection of tool will determine the depth of cut; finishing cuts less than 0.5mm (0.02inch) tend to produce poor surface finish unless the speed is increased. The attachment is a copy of a page from my book, it lists the surface finish against tool radius.

[Runner4404spd]

also make sure you are using a very sharp tool. i can buy tools with a 1/128 radius on the tip although i find the 1/64 radius on the tip gives the best finish for what i'm doing.

[skmetal7]

ok so i guess the next question would be, what type of surface finish is that in the attached pic? .06um or 6.3um? what is RA and CLA stand for?

[Hursty]

A machined surface is made up of valleys and peaks, Ra is the arithmetic average deviation of the surface valleys and peaks, ISO uses CLA (Centre Line Average). Ra 6,3 (CLA250) = Rough Machine, Ra 1,6 (CLA64) = Normal Finish Turn / Mill. Less than Ra 1,6 (CLA64) = Fine Finish but difficult to maintain over a batch of parts (tool wear).

[Paulo E.]

Assuming the material is 6061 I would use a tool with a positive rake of 7deg and a radius of .004 with an rpm of about 2000 to 2500 and an ipr of .002 to .004 and a depth of cut of .01 to .02 thou.

With those setting you can do parts with the finish you see on the pic all day long d-_-b

[Mr.Chips]

ok so i guess the next question would be, what type of surface finish is that in the attached pic? .06um or 6.3um? what is RA and CLA stand for?

Couls it be a ground finish?

[M-man]

I would use max rmp that the machine could give me,(IT would prob be much below correct speed) and as low feed as needed to maintain surface roughness..... Do not use cuttingdepth smaller then the toolnose radius..