Sheldon Xl-56 Spindle Dead Center

Robert,
As a Task Master you remind me somewhat of long ago dif eq and q-physics profs I was fortunate enough to have--they humored me and convinced me to work a little harder. I did a shorter version of what you suggested with the DI on the face of the spindle nose and the TI @0900. Before plunging into the taper I rotated the spindle while in contact with the DI just to see if there were any bobbles. None. The first time I ran into the taper I got a .0258 instead of .02631--quite different from what I got the other day ( .0300) but still disapointing. Did it a couple more times and got different answers. Did it once more and then turned the spindle ever so slightly and got .0262. Repeated @ .0263, .0264 and so on so I thought I was getting reasonable results. Moved the TI to 1200 repeated as above and got very similar results. Apparently my made in China TI is acting very much like it was made in China, but it's the only one I have so far. Anyway with a little nudge on the TI it convinced me that the taper is indeed an MT5--just as other responders said above. Enough exercises like this and I may learn how to measure like a machinist.

As a side note, after after riding fences for the morning in rain showers and on a cranky mule, I needed a crank fix so when I got home I peeled a test bar (without tail stock) and interpolating the mic I got a difference of +/-.0001" for a length of 9". I was just starting 1st grade when this lathe was made and that made my day. Thanks to all.
 
The Sheldon has what is called a Short MT5. The measurements are:
Short MT5 : Large end is 1.625 inches +/- .005” length of taper is 2-5/16” instead of 5-1/4"

I took a standard MT5 dead center, annealed it, then turned it down until I made a nice center.

One thing you could consider is if you have a 5C collet drawbar/adapter for your lathe, you can make a center with a standard diameter drill rod held in a 5C collet. There are dead center 5C collets on eBay that could also be used.

Like this: http://www.ebay.com/itm/HARDINGE-5C...829114?hash=item3600461dba:g:a7MAAOSw9ZdXKPy9 or this: http://www.ebay.com/itm/Hardinge-5C...841957?hash=item28165c5625:g:3FcAAOSwiYFXFuqV

(No affiliation with those eBay sales, just showing them for reference)
 
Dan,

OK. I'm glad that I didn't say before that the 0.300 reading at 0900 could indicate that the headstock is cocked toward the operator. FWIW, that was why I suggested repeating the test at 0300. But the test bar results probably indicate that that isn't the case!

One has to wonder about why several manufacturers created things like Short MT5 and MT 4.5. They have certainly caused problems for people later on.
 
You can guarantee the machine tool builder got the taper right to a tee at the factory!
The Chinese test indicator more than likely has some error in it. Even some USA made indicators have error in them. They just don't tell you about it up front. Plus test indicators were never design for real measurements in general but we are all guilty of using them as so.
 
Ah, the short MT5 taper!! I had an emco super 11 that also had that taper, I believe, but had forgot about it.
 
wa5cab said:
One has to wonder about why several manufacturers created things like Short MT5 and MT 4.5. They have certainly caused problems for people later on.
Click to expand...

The short MT5 was supplied so that the machine spindle would have the 1-3/8" bore and the 2 1/4-8 threaded spindle while supporting 5C collets. A true MT5 would require a larger spindle and yet would not provide any more benefits such as transmission torque for using the complete MT5 taper length.

The cost of the redesigned machine would be much higher for no real additional benefit.
 
Well, you're probably right but there would be one benefit - far less confusion half a century on. :)
 
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