Bridgeport M head spindle run out

[techymechy]

I imagine that you folks are getting tired of my M head questions.

I placed my 1/10th indicator on inside spindle of my M head. I measured .0002" TIR last night and .0004" TIR tonight. The TIR didn't change if I was measuring on the top'ish of the taper or on the bottom'ish of the taper. I have no idea what caused the change. I installed my collets and use pin gages to measure the TIR about 1" from the spindle. I was measuring .0002" to .0008" TIR for a 3/16"(.0007"), 1/4" (.0002"), 3/8"(.0008") and 1/2"(.0006") collet.

I haven't powered the head yet---I need to get the VFD set up. I haven't made one chip yet.

I'm mostly concerned with the smaller end mills and the amount of run out I have on my head. What is, practically, the limit of TIR? What is the value when I should expect to have issues?

My ultimate goal is to make small steam engines and to make more tools.

I'm just wondering if I will have to rebuild this head in the future. I'm certainly not going to do this unless I determine if it needs to be done. But, one never knows how much better this head can perform if the TIR is better until they rebuild the head. I don't have any other mill for comparison.

Thanks for your input.

Dave

 

[techymechy]

Thanks for the thoughts. I'll be sure to do rotate the endmill. The B3 collets are keyed to go in one way so I can't rotate the collet. I never realized that the endmill would have significant TIR as well. I'm mostly concerned with a 1/8" endmill - probably the smallest I'll commonly use.

Do you have any suggestion for the TIR for a 1/8" endmill. According to the feed/speed charts, the chip load per tooth should be around .0006". I'm thinking if I had a TIR greater than .0006", one tooth wouldn't do any cutting and one would be overloaded (if it is a 2 tooth endmill) which will cause broken endmills, etc.

Of course, I'll run the head before I tear into it.