Winter Project (milling machine)

[jim rozen]

Recently purchased a pratt and whitney no. 3 horizontal milling machine
from a member here. It's now in the process of coming apart and
some refurbishing's going on.

It's a small machine, portable by one or two folks - the column by itself
looks like this:



The knee came off with a couple of bolts, and is resting on the bench:



There's also a large assortment of various bits/pieces strewn about:



Along with the machine itself, I received a box of extras, including the
coveted pratt and whitney PN collets:



The machine's been used, but not really abused. It has substantial
amounts of the original scraping present, and was nicely manufactured
from the start. The lead screws in particular are hardened and
ground, and run on double-row internally preloaded ball bearings.

My first task was to dismantle and clean the leadscrews and make some
repairs. I havent't gotten to the knee yet but that's next!

Jim

[SteveM]

Jim,

If you make it look TOO good, I'm going to have to retroactively charge you more

Actually, I need to get going on mine. Maybe this will provide inspiration.

Steve Brooks wrote up how to remove the spindle. I can post it here is you want.

Steve

[jim rozen]

Thanks Steve. I've got plenty to do before getting to the spindle.

Here's some before/after shots of the X axis feedscrew - I am really
amazed at the quality they put into this machine:





Really this is only some cosmetic polishing, aside from dismantling the
bearings and whatnot, so the parts could be cleaned agressively.

The Y axis screw is fine as well, but one former owner must have had a
boo-boo with the handle, and then did a halfway passable job of reparing
it, with braze:



I figure the 'ol gal deserves to have the handle repaired nice, so I'm
in the middle of that task. More photos to come. Did you know this
machine was probably originally delivered to the US navy? It has
two of the standard anchor marks on the face of the knee casting:



Pretty cool that.

Jim

[SteveM]

Definitely cool!

Keep taking lots of pictures. I'll probably need them when I get to mine.

Steve

[jim rozen]

Goal: fix the handle on the infeed screw. First off, sketch up what
the part *should* look like, from the other, crossfeed, screw:



Next, how to hold the darn thing? A brass bushing, with the OD
equal to the largest diameter ball, and the ID equal to the middle
size ball:



Thought I was going to need a split on the side, so it would clamp down - but
this turned out to be not needed. The six jaw chuck compressed the
bushing enough to grab the handle solidly, without:





At this point I have to make apologies, to harold, if he ever sees this.
The last word indicator, does a passable job in cases like this. The
combination of the bend in the handle, and the fixturing, meant the
runout was about two thou, TIR. Even the last word indicator can see
that!

Kind of fuzzy here, but the cutoff operation:



and then, centerdrill, drill, and ream 0.251 diameter:



The final result, ready for installation of the yet-to-be-made part:



More later.

Jim

[Harold_V]

At this point I have to make apologies, to harold, if he ever sees this.
The last word indicator, does a passable job in cases like this. The
combination of the bend in the handle, and the fixturing, meant the
runout was about two thou, TIR. Even the last word indicator can see
that!

I'll pretend I didn't see that, Jim.

Very nice setup you made there. Good stuff you're posting.

Harold

[jim rozen]

The saga continues - the replacement handle end is turned up from
some cold rolled steel. After roughing it out using a corner-rounding
end mill as a lathe tool, I set my over-the-top ball turning tool up
on the toolpost, and roughed the ball down to 0.6 inch diameter:



A closer view of that operation - it's important to get the centerline
of the tool shaft in line with the spindle centerline, using the vertical
adjustment on the QC toolpost, and to get the tool shaft at the
correct location along the length of the bed, once the first is
accomplished. Then the carriage is locked down, and all adjustments
from then on, are done with the boring head screw:



After roughing it out, I transferred the part to my smaller bench lathe,
and used a parting tool to generate the taper between the two ends
of the shaft. After that, a quick filing to clean things up, a bit of
400, and a bit of 600 grit paper. Then simichrome polish to finish
off. The smaller lathe has a VFD drive, and a spindle that runs a good
deal faster than the southbend:



Now it's all ready for silver soldering. There's about one thou of clearance
on the diameter, between the reamed hole and the shank that will be
soldered in there:



Jim

[jim rozen]

Well I did clean up the braze joint, but the ring of silver braze is still
visible at the joint between the shank and the center ball. The joint
came out nicely, the ring of braze showed at the inside, all around.



Obviously after brazing, I polished, and then set the part up in the
milling machine and drilled the hole for the handle, and pressed in
the handle.

Here's the pair of leadscrews, all in one shot:



That pretty much finishes up this task for the pratt and whitney miller.

Jim

[Harold_V]

Beautiful job on the handle, Jim.

Harold

[Rich B.]

Wow, just gorgeous thank's for the pics!

Rich

[dly31]

Really nice results on a rather tricky job!

Don Young

[jim rozen]

Thanks folks. I know it's silly to spend so much time on an item I
could just buy off the shelf. But handles like that, no two are really
the same. Plus, the other end was fine. I wanted to keep as much
original metal in this as possible.

Besides, aside from shovelling and snowblowing the driveway and
sidewalks, there's not that much to do. Keeps me out of trouble!

My rule is, "if I can draw it, I can make it." So every project like this
starts with a sketch of what I want. Then it becomes a task of thinking
through the steps before I start cutting. The only mildly tough part
on this job, was figuring out how to cut the shank of the ball, down to
size, and put the step on it, so it would be truly concentric with the
axis of the ball as it was first formed.

Jim