[Uman]

I realized the dimensions on a part was out of spec and checked the responsible finish end mill. Sure enough the 1/4" EM diameter was actually .247". Using a caliper and carefully measuring across the cutters on a 2-flt cutter and realized it was somewhat subjective with a +/- .001, depending exactly where I called it. I took a scrap piece of delrin and ran a shallow slot in it and then measured the slot gap to achieve the .247" on the 1/4 EM. This seemed like a more accurate method and the recently cut part error matched the difference. I recall a earlier post about measuring a 3-flt EM but was unable to locate it.
How do you guys measure up?
-uman

[SCzEngrgGroup]

I would be tempted to put the endmill in a 90-degree V-block, then measure using a height gauge. Use a solid bar of the same nominal diameter as the tool to calibrate.

Regards,
Ray L.

[AUSTINMACHINING]

I have the tormach granite block with tool setter. I just lay the tool on the block and measure diameter if needed. I have a 1/4" end mill that is .0005" oversize that I use as a reamer for dowel pins . Works great + I'm too cheap to buy a reamer.

Sent from my SM-G900T using Tapatalk

[pickled]

See Above

[handlewanker]

Hi.....3 flute end mill measuring.....LOL.....try measuring a one flute one or the stick out of a tool in a fly cutter.

I measure the 3 flute type by laying it on a flat surface and rotating one of the flutes against a hard shoulder and a second hard shoulder on the opposite side to give the size/width between them.

A fly cutter is more difficult, but if you mount it in a drill chuck in the mill or just a drill press and rotate the shank with the tool tip against a hard block and with another hard block measuring the gap between the two faces you'll get the swing diam of the single point tool.

BTW.....how many people tolerate a run out on a cutter because they bought cheap collets......a .001" run out is .002" bigger on the cut diam/width than the marked or measured cutter size....don't ask me how I know.
Ian.

[Steve Seebold]

I do it the easy way. I have a micrometer that will measure both 3 and 5 flute end mills.

[handlewanker]

LOL.....good on you Steve.....now try the single flute carbide cutters.....
Ian.

[Uman]

I took a scrap piece of delrin and ran a shallow slot in it and then measured the slot gap

Would not the slot cut method account for the spindle and collet run-out as well as the cutter diameter and give the most accurate cutter dimension?
This may be over kill since the caliper will measure plus or minus .001 for a radius of .0005". But may an option for an odd flute cutter.
-uman

[dertsap]

if the shank is on size , then put it in a holder in the spindle , dial the shank , set to zero , then dial the flutes to find the difference .
Since it's unusual for a decent end mill to be undersized by that much , I'd check the calibration of the calipers first