So I upgraded my Sharp/YC mill to 30 taper...

[cmjohnson]

...and though this is nominally a part-for-part Bridgeport clone, I found that there were a few differences that I had to deal with.

Just in case this is of any interest to ANYONE, I'll tell you of the pitfalls associated with the conversion.


The machine: 1980 Sharp/YC 1 1/2 VA vertical mill with 2 HP motor, step
pulley head, 9x42 table, and retrofitted with ball screws. Comes with R8
spindle. Very standard type machine, no surprises. But it's a very solid,
rigid machine, with beefy, genuine Meehanite castings. Very little wear,
not enough to justify rescraping any wear surfaces.


I decided that I wanted to change over to Erickson Quick Change 30 taper tooling, primarily because I discovered I could get a complete QC30 spindle
assembly for free, from a Bridgeport Series 1 Boss CNC machine not far
from me.

So I got the spindle and rebuilt it with new matched bearings.

I went to put it into the machine and found out that it wouldn't go through
the splined hub in the bull gear in the top of the machine.

It turns out that the Sharp splined shaft has smaller spline land sizing (OD)
of about .200 inches, while a Bridgeport spindle's splined shaft measures
about .250 across the outer surface of the spline lands. The bridgeport
splines are beefier.

So, I obtained a genuine Bridgeport splined hub, which mates into the
bull gear up in the head.

Now the QC 30 spindle fits into that hub.

But the hub doesn't fit into the bull gear. It's about .002" oversized for
the Sharp bull gear. So I had to get the hub ground down to match the
original Sharp hub.

One other part also changes: The bronze drive gear for the power feed
system. It's driven off the triple lead worm that's part of the splined shaft
hub, on the bull gear. The Taiwanese made Sharp hub's gear tooth profile is
slightly different from the Bridgeport gear tooth profile. So, I get a new
Bridgeport (identical repro part) gear from High Quality Tools, and install it
in place of the original gear.

NOW, everything is falling into place. Though I haven't run the machine yet
as I'm finishing up the electrical system, installing four DRO scales, and
rebuilding the automatic oiler system, all at once, all the parts fit and work
smoothly together and I am highly confident that NOW, the conversion is
complete.

So, if you're contemplating this conversion, you now know what you will
need to do: Get the spindle, get the splined hub, get the bronze drive gear
for the head power feed, get the hub ground to fit your bull gear.
That should do it.

CJ

[skullworks]

Its never just a simple bolt on it seems.

[cmjohnson]

The job is completed. It's running. I'm now in the process of installing a new multi-point lubricator system on it to replace the original one that threw a seven. I went with a larger quart capacity Bijur model with custom brass manifolds, as the original zinc die-cast manifolds were crumbling. I had to rebuild this lubricator, too. I've also got to install four scales for my 4 axis DRO head. I'm putting both knee and quill scales on.

I rebuilt the X axis power feed, too. I rebuilt a lot on this!

And of course I've got to shim out the end play in the ball screws. But the machine
is solid, and judging by the finish I'm getting on test cuts, the new spindle with new angular contact matched pair bearings is running just right. No slop, no drag, fantastic surface finishes.

I found no broken gear teeth anywhere. This makes me happy. The machine has not
been abused.

I'm just days away from being finished with the rebuild, and it's about time!

I'm sure this will serve my needs, and do it in an excellent manner. It's going to be
pretty first rate for a manual mill.

CJ