[WOTDesigns]

just a thought: jog the z without a tool down as far as it was when you made that cut. Put an indicator off the table touching the nose. pull down on the head and see if you can get a thou or three of movement. These aren't insanely rigid machines. There is bow, flex and movement in the ball screws, gibs, base, and some thermal growth over time/temp. Add it all up and it can easily be 0.004" when indicating vs a 1" deep side cut. Your helix is pulling UP on the plate. Newtons law says it's pulling down on the head/ball screws/gibs as well. you likely lifted the table .001 and pulled the head down .002 and the spindle grew 0.001 = .004 (as an example). Even LIGHT cuts are not light cuts when there is a 1" DOC and a high helix EM pulling down on the head/up on the table. Just pointing out there are a million things that want to move. If you put the indicator on the head and touching the table and lift up on the table you will see 0.001+ movement. Mind you... I see movement when I do any of these on my Haas and Brother as well, less, but flex is ALWAYS there. Thermal growth is as well unless the entire machine is made of granite.

In the end there is a reason all controls usually have such easy offset adjustments... Program 0.005 HIGH and measure/inspect, adjust offset after seeing real world conditions applied to the cut and repeat the finish cut or program for a final finish cut. I do very tight tolerance work (+/-0.0005) all. day. every. day. There is only one way to hit those numbers and it's raking rough/finish/measure/finish again/measure/finish again. Even if I get it right at 8am it's wrong by 845 and needs the same process repeated over and over. 300+ parts a day and the same process on them all.

[mountaindew]

I see movement when I do any of these on my Haas and Brother as well, less, but flex is ALWAYS there. Thermal growth is as well unless the entire machine is made of granite.

In the end there is a reason all controls usually have such easy offset adjustments... Program 0.005 HIGH and measure/inspect, adjust offset after seeing real world conditions applied to the cut and repeat the finish cut or program for a final finish cut. I do very tight tolerance work (+/-0.0005) all. day. every. day. There is only one way to hit those numbers and it's raking rough/finish/measure/finish again/measure/finish again. Even if I get it right at 8am it's wrong by 845 and needs the same process repeated over and over. 300+ parts a day and the same process on them all.

Your setting up tool height offsets with electronic probes and touch plates on those machines Right? My experience with the Tormach system, measuring tool lengths on the bench with a plate and a height gauge does not always translate into real world precision when placed in the spindle and used. I mostly chase precision on the z axis. As long as I watch tool stick out / feeds speeds I rarely have x,y precision issues that I can measure anyway btw I get best results out of my Tormach when the shop is about 75 deg. Metal parts even fit and assemble better at that temp.

Anyway I was thinking after reading this post it might help to use a electronic tool height setter on the machine bed itself.
Thoughts?

[WOTDesigns]

Your setting up tool height offsets with electronic probes and touch plates on those machines Right? My experience with the Tormach system, measuring tool lengths on the bench with a plate and a height gauge does not always translate into real world precision when placed in the spindle and used. I mostly chase precision on the z axis. As long as I watch tool stick out / feeds speeds I rarely have x,y precision issues that I can measure anyway btw I get best results out of my Tormach when the shop is about 75 deg. Metal parts even fit and assemble better at that temp.

Anyway I was thinking after reading this post it might help to use a electronic tool height setter on the machine bed itself.
Thoughts?

I never bought into the offline measuring on my X3 nor Tormach. It takes seconds to measure on the machine and of all the places to save seconds, that's just not where I want to save them.

On my tormach I used an edge technologies 3" setter. On the Big Haas I got the probe and setter but it still didn't work well for my micro tools. I switched to using a cheap touch sensor that completes a circuit. More accurate that the Renishaw setter for those and takes me the same amount of time to touch off.

For the OM2A I had to add a wire to an alligator clip clamped to a small magnet. It has ceramic bearings so I have to throw the magnet on the tool holder body as I jog it down. I used the rolling pin method for months on the OM but this cheap Chinese sensor is more accurate after all. It did not fit on the fixture that I was using when I first started running this machine so I had to use the rolling pin.

The brother I bought with a Blum Pico setter for micro tooling "down to 0.005". So far that seems good but I won't start production on the Brother until tomorrow so time will tell. No probe on that one either since fixtures will sit for weeks at a time. Haimer was overkill honestly, but I love them and they are cheap.

I can touch off 7 tools in 2 minutes with those Chinese 'coolet circuit' probes and they are DAMN accurate. I'm talking 0.0001-0.0002 every single time. Those 2 minutes won't make or break my day.... But inaccurate tool LENGTHS would. I like measuring on the machine.