View Full Version : Just what do you check
02-07-2008, 01:14 PM
I have been reading several threads on here that have giving me cause for some concern.
If you suspect that your drill chuck is a bit suspect as to run out and several posts regarding morse tapers of dubious quality, just what would one start to check.
My tail stock is 2mt and the chuck end is 3mt so I would have to use a morse adaptor so is this going to compound the errors not that I suspect it would make much difference to my level of machining anyway but I am very interested in just how to go about testing the stuff anyway.
Clean the taper socket and the morse taper with a paper towel and color the taper portion all over with a black Sharpie. Insert and give it a light tap or two. Eject and see where the ink has rubbed off. That is the contact area.
02-07-2008, 02:16 PM
The easiest method is to drill a hole and measure it. If it is close to size and straight, you are probably OK. If it is radically oversize or bellmouthed, the chuck, tailstock, taper or all three could be off. If you are using an increasing sleeve, you are adding potential error to potential error.
If you want to measure runout of the assembly, a test indicator in the lathe chuck indicating the drill or a ground rod in the chuck will show runout. An indicator in the toolpost will show parallelism.
Drilling is not a particularly precise operation, but more of a means of rapid metal removal. If precision is needed, boring is the answer.
02-08-2008, 12:02 AM
It's not hard to find smooth, round, and straight rods- every old printer has them. Chuck up a piece of something like that and if there's runout, you'll see it. A drill bit is not a particularly good thing to gauge by, since they're often not completely straight.
You do have to pay some attention to the length of the piece held by the jaws. It would be best to ensure that the entire length of the jaw is bearing down on the 'test rod'. Basically, insert the rod most of the way, don't just tighten down on say, a half inch of it.
As far as the morse taper fits, I'm no stranger to adapters, etc, that don't quite fit right. I've turned tapers myself that fit better than some of the store bought ones, and I'm no professional machinist either. I've learned to check these things carefully before drawing them up snug in the spindle or tailstock. It's pretty easy to see if the big end is too small, not so easy to see if the small end is too small.