Have you contacted Don Doyle at Rubber Chucky?
It seems you may have gotten on that was not machined properly.
I have a few of his morse taper mandrels. They have fit every lathe I have tried them in.
It has been my experience that the Rubber chuckle products work.
Also Don is Good guy and a friend.
Be interested to hear what Don Says.
Al
Oh yes, I called Don. I thought anyone would really like to know in case he was unknowingly sending out a bad run of parts.
However, he seemed quite defensive. He was insistent that all his parts are perfectly machined on a CNC machine and I must be confused about the nature of Morse tapers. But he lost me when he said I must not know much about machining if I didn't know that all Morse tapers from all manufacturers must be seated with a mallet to make them hold. Say what??
(At first he said to whack them with a wooden mallet. He changed this to a rubber mallet after he read his own printed instructions. Which yes, say you have to "seat" them with a mallet.)
Sorry, but this is not the way tapers work, either Morse, JT, or R8. Tapers rely on complete and perfect contact over the entire surface. The tapers on his mandrels only touch at the spindle opening.
OK, so I tried his suggestion and whacked one of the mandrels into the headstock with a mallet. This did take out the slop. However, after removing the mandrel and reinserting by hand, the play is still there. To use this method the mandrel would have to be pounded into the headstock for every use. No. A taper should seat every time when inserted with the fingers.
After inserting one a time or two and twisting to test, look at the horrible galling in the aluminum on the single band of contact. There is zero contact down the rest of the 1-3/8" that fits into the spindle. Again, this is not the way a taper is supposed to work:
As a sanity check, I checked my lathe spindles by inserting several other drive centers, live centers, precision ground and hardened MT2-MT1 adapter, taper drills, and Jacobs chucks. ALL worked perfectly and as expected in four different lathes, seating with the fingers. I applied Dykem blue to his tapers and others - this is a standard way to test tapers. His tapers show NO contact except at the point of galling shown above. An expert machinist confirmed my findings.
I checked the Rubber Chucky aluminum mandrels on three wood lathes and one metal-cutting lathe. I also tried inserting them into a precision hardened and ground MT3-MT2 adapter. His mandrels are absolutely wobbly in all cases. Measuring with my surface plate and good Starrett instruments revealed the taper is 0.058" per inch, way off specification of 0.04995" per inch, way too small at the small end. What is worse, the sides of each taper are not even flat - holding them against a (Starrett) straight edge revealed a slight bulge in the middle of the taper. I can actually feel the bulge with my calibrated fingers. Sorry, Don, ain't no way these are going to seat as delivered!
When I told him that I saw 0.006" play at 2.2" from the headstock spindle he said that is nothing when working in wood. However, this translates in to a LOT of play at the end of the long mandrel! Of course, under compression of the tailstock the run-out might be high but there might not be any wobble. I gave up trying to explain what I found. It is easier to just fix them myself and get back to playing with the lathe.
Here's what I think - his parts may have been fine for run after run. Now there is a small error in the machining, perhaps from some setup error or wear in the machine or who knows. Since the previous runs have been perfect, he is so sure that these are perfect that he sees no need to check them. He said I could send them back but since they are all the same I would get back the same thing. (Maybe I shouldn't expect all that much for a mere $300.) I'm not about to tell this guy how to run his business but I hope after my call that he at least checks the machining on his latest batch.
JKJ