- Joined
- Oct 17, 2018
- Messages
- 1,024
I wondered the same thing until I tried one. It cuts just fine, but the adjustment is not consistent at all. One turn of the adjuster knob would result in different distances each time, rather than being exactly the same. I'm not sure if there's too much slop in the adjuster screw or something else. I even accounted for backlash by screwing it one direction only and not backing it out.
I was thinking of getting a Precision Matthews or LMS boring head (they are about $100), as they have better quality control, but everyone has recommended Criterion.
That's probably the varying production tolerance you get with "no name" tooling. My ebay special cuts fine and the adjustments on the tool itself are also accurate. At least accurate enough for the work I do. I can easily work my impost boring head to .001. But as I said, it's probably more luck than anything else that my unbranded one works as good as it does.
I checked the new (used) Criterion head I received today and the cheap import with a dial indicator. The Criterion was spot on. The import is graduated in metric, .01mm per mark, BUT, when I checked it with the DI, it moved exactly .020" each revolution. It was at exactly .100" after 5 turns, when it should have been at .098". That would explain why the last hole I bored was off just a bit. It's 0.0004" per mark, which is really close to the 0.0003937" it theoretically should be.