- Joined
- Apr 21, 2015
- Messages
- 690
I'm late to the thread, but I also built a spindle square a while back on a whim. While it was never that much of an ordeal single-point sweeping to tram, simultaneously seeing two points is sufficiently better that I'll never go back. It's especially helpful when tramming in the "nod" axis where adjustments are particularly non-linear (and in my case requires shims to adjust).
With two points you adjust until both dials read the same. With single point tramming you can't just zero and halve the error because of cosine effects. With a DTI on a bar, you have to iteratively zero/sweep/bump back and forth, incrementally approaching tram. With two points there is no sweeping or thinking involved: just loosen the nuts and bump the head until both dials read the same.
It's possible that I'm more incompetent than most (some days more than others) but I'll admit that I tend to bump the head in the wrong direction about half the time. No big deal with two-point tramming — you knock the head around in both directions until the dials read the same.
With single point tramming this caused a lot more mental friction since the indicator moves differently on each side of the spindle due to "bilateral ambiguity." The real mental gymnastics were when I swept to the back side and was reading the dial through a mirror. Which side of the head do I bump to move the needle toward zero? Whoops, wrong way, bump it back. Far enough? Too far? Dunno, sweep to the other side and check. Whoops, too far, now which way do I bump? I got better with practice, but even after I got pretty good at it I didn't exactly relish the task.
Anyone who thinks that a spindle square is a foolish extravagance has simply never used one. I built mine out of scrap and a couple cheap indicators rather than buying a commercial unit, but I certainly don't begrudge anyone who spent the money. Great tool.
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Rex
With two points you adjust until both dials read the same. With single point tramming you can't just zero and halve the error because of cosine effects. With a DTI on a bar, you have to iteratively zero/sweep/bump back and forth, incrementally approaching tram. With two points there is no sweeping or thinking involved: just loosen the nuts and bump the head until both dials read the same.
It's possible that I'm more incompetent than most (some days more than others) but I'll admit that I tend to bump the head in the wrong direction about half the time. No big deal with two-point tramming — you knock the head around in both directions until the dials read the same.
With single point tramming this caused a lot more mental friction since the indicator moves differently on each side of the spindle due to "bilateral ambiguity." The real mental gymnastics were when I swept to the back side and was reading the dial through a mirror. Which side of the head do I bump to move the needle toward zero? Whoops, wrong way, bump it back. Far enough? Too far? Dunno, sweep to the other side and check. Whoops, too far, now which way do I bump? I got better with practice, but even after I got pretty good at it I didn't exactly relish the task.
Anyone who thinks that a spindle square is a foolish extravagance has simply never used one. I built mine out of scrap and a couple cheap indicators rather than buying a commercial unit, but I certainly don't begrudge anyone who spent the money. Great tool.
--
Rex
