I have what i would call a hobby grade bt30 spindle and cheap toolholders. I would say comparable to tormach stuff. My spindle has probably about 5 tenths runout at 4 inches from nose. My toolholders range from a couple tenths to over a thou runout. Some of my tools ive been able to get down to a few tenths by clocking things around but i would like to do better. Im considering sending out my spindle for a regrind as assembly and maybe invest in at least a few good quality holders for the tools that matter.
If i decide thats too much money, im thinking there might be another option. I can buy some centerless ground stock that is larger than the tool, lets say for example i do this with a 3/8 tool. I will load a chunk of 1/2 inch ground stock into the toolholder with a half inch collet, maybe inch and a half long, sitting about flush with nose of collet. Then fixture an undersized drill and small boring bar in milling vise, spin up the spindle and drill, then bore a 3/8 hole in the chunk of ground stock that is loaded in toolholder. At this point the bored hole should be perfectly concentric to the spindle bearings. Then i will put clocking marks on toolholder, collet, and sleeve. The sleeve can then be removed and have a slot milled into it lengthwise. Reload the sleeve into the holder with a 3/8 tool and align the clocking marks. I should now have a tool loaded with zero runout no matter how much runout there is in the spindle taper, toolholder, and collet.
Is this a known method for getting excellent tool runout with not so great gear? I cant think of any reason why this wouldnt work great. One thing i can say about my spindle and holders is that they seem to have good taper contact. With a gauge pin loaded in in holder, i can load and unload holder from spindle many times and the direction and amount of runout is exactly the same every time down to about half a tenth. Any reason why this may not work out so well?

Similar Threads: