Precision Manufacturing with Mini Mill

[RoboChair]

Originally Posted by asid61

Why wouldn't your DRO be perfectly (or very close to perfectly) installed!? That's probably one of the most important things you'll need to get perfectly square with the table. Take pains to get that within 0.003" on a 12" travel; even my cheapo Ebay DROs are within that.
As a side note, you probably won't benefit much from a DRO Pros on a mill that small IMO. I've had good results even with just the 0.0005" resolution things off Ebay. It seems like a waste to spend $800 on a DRO for a $900 mill, when you could probably get a CNC upgrade for less.

I like these cheap DRO scales

Originally Posted by aldaeron

I can't afford to buy a set of plug gauges so will a measurement with a caliper be close enough?

If the DRO is perfectly installed (unlikely), the 4" wide vice is perfectly square to the table (hard to measure with a 4 inch vice), the screws have some backlash (even when locked) and the head has much more flexure than a large knee mill (to the point that its .001 or more), what error am I adding with such a cheap mill that the DRO cannot measure?-

Yes, calipers are just fine.

Backlash doesn't matter when you have a DRO so long as you lock your axes when it matters. If it's moving you need to either lock harder of adjust your gibs tighter. If you are worried about getting your vise really square just put a straight bar in it and tram off of that. You can also just clamp a plate to the bed with a piece of sacrifice material under it and go entirely off of coordinates for making gearbox plates.