Touch Probe problem with Makita (and other) endmills

(Dieter Stoll) #1

Right. So the Probe finally arrived. Tried it and was flabbergasted to see that it worked flawlessly on X and Z but not on Y, it would just keep on pushing the Probe north. Turns out that the particular Makita endmill has got two cutting blades 180 degrees apart. Measured 0 ohms between blades and shaft, but no continuity between shaft and the black (obviously coated or laquered) part that holds the blades. The endmill blades happened to be pointing east-west when I did the probing, see attached sketch.
Turning them to point northeast-southwest makes probing work, but obviously then it introduces an (albeit small) error because it gets the endmill diameter wrong.
I guess I will have to revert to manual zeroing when using one of those endmills. Sadly, there are many like those on the market, so I will have to be extra careful next time. What do you think?

(Neil Ferreri) #2

Zero your X & Y with a different endmill or a piece of 1/4" aluminum rod. Probe Z with the tool being used.

(Dieter Stoll) #3

A bit inconvenient but doable. Maybe wrap a layer or two of aluminum foil around the tool? Too redneck maybe :smile:

(Nathan Woodruff) #4

Does the paint serve any purpose? If not, take a razor and expose the sides. I think I would be more worried that I was not getting an accurate read on the Y axis.

(Bryan Haring) #5

So my first thought was to file off a little bit of paint. The second thought was the diameter of the cutter would not be correct at that location either and would cause the math not to work correctly.

Good luck and great illustration.

(Phil Thien) #6

Can’t you just turn the bit 90-degrees during the probing?

(Luke) #7

Good advice!

This is good practice.

(Dieter Stoll) #8

Turning the bit during the probing is probably what I’ll resort to eventually - seems a bit clumsy but what the heck :slight_smile:

(mikep) #9

Good observation, thanks for sharing that, it brings up another point. That’s not an spiral flute endmill, which is what the probe was intended for A spiral flute endmill doesn’t have this problem, and that’s what’s generally used in a mill because an endcutting (almost all of them in the sizes we use) endmill can be plunged straight down. A router bit like this cannot (you plunge them at an angle…which the mill can’t do, and the ones that are end cutting don’t have the right geometry for most of the things we do)

(Dieter Stoll) #10

Yup, that’s the lesson I learned here. While the non-spiral bit did plunge straight down OK, getting spiral flute endmills seems to make so much more sense. They are quite a bit more expensive, though. Maybe this is a European thing? Whatever, I know how to proceed now. Thanks, everyone, for your advice.

(Craig) #11

With an endmill you will not experience this challenge. With this type of router bit, the cutting edgehas a different diameter than the coated portion on your bit. The back bevel of the cutter has a different diameter than the cutting edge, You will need to make sure you are touching off largest cutting diameter - also called top dead center - in both X and Y axis. If you are familiar with setting jointer knives or planet knives,it is the same concept.

Depending on the accuracy you are looking for, this may or may not be good enough.

(Luke) #12

I’ll jump in again. Whilst I can’t comment on why this bit isn’t making proper contact it is important to rotate your end mill.

Typically even spiral end mills are not completely round. A single flute end mill (which I recent’y found to be great on cheap aluminium) is almost off set- if your doing anything that requires precision you should mark the side of the end mill and have that side face the x probe side. During the probe rotate it by 90 degrees so the same side it makes contact with Y.

I’ve been doing allot of precision milling on small aluminium parts recently and this can make the difference of say 1mm even when using multi flute cutters. The other workaround which is not supported by CM is to set the height after Z probe to be greater than the CM -5mm to -10 or -15mm allowing for more of the bit to make contact.