Last night I went over to "Open Shop" at Kent's. He has been having problems with his Lagun mill for the last year or so, it wasn't cutting square. He had tried a bunch of things, cleaning the ways, adjusting the gibs, but still had a problem, and he couldn't afford to take the mill out of service completely and try a rebuild. What made things so hard to diagnose was that the mill seemed to be true in the x-axis, but when cutting along the y axis the cut wasn't square, out by about .001"/1" which is not precise enough for his work (or most work).
So last night we tried a bunch of measurements. Checking a cylindrical sqare butted against the z-ways showed that there was no error in either x or y. What could it be? I figured it was either the vise or the head. Checking the back jaw of the Kurt vise showed it was parallel to the x axis travel. Clamping a square down in the jaws of the Kurt also showed no error. But then we put the square up on some parallels so that it was gripped by the top 1/8" of the jaws (which is how he holds most work in the vise). The error then showed up. It was the vise all along, not the machine. Seems it was twisting the work, and while when unclamped it was true, under the pressure of clamping it was out.Kent put a different vise on and the machine cut perfectly square. What was odd is that the vise was one he bought when he got the mill, new, about 20 years ago. All the Kurt vises he has have a key retaining the back jaw, but this one didn't. Maybe they added one later just because of this sort of problem, or maybe it has nothing to do with it at all. But he's happy now.
George was there to keep us on the straight and narrow, he was a machinist at GE and knows just about everything, when he pronounced our different test setups correct we knew they were, and when he saw problems we eliminated them.
George related a tale about how for one job he had to put a slot in the face of a bar, with the slot centerline through the center of the face. About half of them would come out with the slot slightly off of center, and he couldn't figure out why. Each bar had the same diameter and the setup wasn't shifting, but on some of the pieces the slot would be above or below the center of the face. he then realised that the bars were actually pentagonally lobed, and although when measured they would show consistent diameter, when put in the vise some would be on a flat and some not, causing the height to be different.
As you can see from the picture at the top, Max is now able to pull himself up and "cruise", even though he is only 7 months (not even yet) old. Yikes. Henry can now catapult himself over the baby gates, and I am loath to top them with razor wire. Henry has an annoying tendency to crank the volume on his computer. I asked on the Make "Talk" forum, but the only reply I got suggested that I should break him of the habit, rather than suggesting a technical fix. Like a boy can resist twisting a potentiometer all the way to "11"...Anyone know how to limit computer volume, besides operator adjustment?
It's cold and rainy and Felice is probably going to play hooky from the market tomorrow. My dad sent a 4 volume DVD set of Warner Bros. cartoons, so I hope to watch some Bugs Bunny while supine. I have no idea why he sent it, but it's great.