On Thursday 30 March 2017 07:02:14 andy pugh wrote: > If you have a part with a large bore through the middle, how do you > set up to machine a hole exactly perpendicular to the axis of that > bore? > Similar problem with this taperlock hub I've made, it could tip enough that the shaft it rides on, could not go thru. I wound up leaving it loose from the pulley, and with the shaft in place, drove it with a hammer until it was both aligned with the shaft, and tightly enough held by the taper wedge, that I have now bored the 3 jacking it apart holes without it moving. The shaft is a drop all the way thru fit now.
So if the shaft is available, mounting a dial indicator and scanning the shaft would show any leaning. I don't quickly visualize another way although the hole could be scanned with a dial. That would also check head tram, but I like to do that with a longer baseline. What I did find was that the G0704's head was out of tram so a drill, shorter than my find center probe, was drilling left of the "target circle". I have adjusted that a wee bit. The largest force it will need to stay wedged is probably the rigid tapping of those holes with a 5mm.8 tap. So I'll probably do that last. Humm, sitting here, visualizing this, I just realized that its sitting on a table slot, and I could put a third bolt down thru the 7/8" central hole, with the right sized washer, pull in firmly into the taper. That should prevent any slippage while doing the rest of the machining, What I need next is an electrical pad to serve as a touchoff point since there will be at least 4 tool changes in this to finish it. 6 operations with the tap drill, 3 with the clearance drill, 3 with a 1/8" mill to counterbore for much of the cap screws head, and 6 with the tap. > I imagine that this is quite a common problem, so must have a common > solution? > Each of us probably has his own method of checking that, so the rest of the list should describe their methods of dealing with a similar problem. > My particular setup puzzle is analagous to this, except that I will be > using the horizontal spindle. > > Machining this casting: https://goo.gl/photos/6QhNnqjzRuSJJpva7 > > The order of operations will be, starting with the raw casting: > 1) with the large flat face clamped down to the table machine the base > flat. > 2) Now clamp the base to the table, face off the large flat face > and machine the large bore. > 3) Return to the original setup and machine a key-slot in the base > _exactly_ on the axis of the large bore. > > 3) is the problem. I can indicate the base to make sure that is > perpendicular to the spindle axis, but how do I make sure that the > bore axis and the spindle axis intersect? OIC, you want to key this into the table so the axis is aligned with the table slots and dead level. And the error source is the faceing of the base with the raw front face as the first operation. I wouldn't face the base or the face clean in one pass, just enough to sit flat w/o rocking. Do both faces, the do again since its now square to itself, this time faceing clean. Whatever you clean off the base can be compensated by the holes center height, making sure it is exactly the same as the other end. That takes care of the up-down aiming errors. What remains would be the holes center height differences from end to end. Measuring and zeroing for the hole center by using the base as reference, should get the correct height. The problem then is reduced to machining the key slot exactly on axis with the table, locating that bore axis exactly (left/right) on the table axis I would mount the shaft in the hole, or make something that fits snugly, and could serve as something to indicate for verticality. Or if your dial will fit in the hole, indicate the hole. Then indicate and shim with a feeler gage leaf under one edge or the other until that error is gone, then cut the bases key slot. The alignment should be pretty good. But note Key word "should" Andy. And I'd make that key "press fit" fat, as that should, by eliminating the usual easy fit slop, pretty well fix the lateral alignment. Good luck Andy. I find makeing my own such tools much more satisfying than finding something that might work and dropping card numbers to make it mine. Too often it doesn't fit exactly, but its still yours, and your balance is still lowered at the bank. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
