Gorton 8D Spindle upgrade & CNC project

[Stuff-Builder]

Hello all,

I've had this project in the works for a while and I'm now getting up enough steam to have something to share. I've written a few posts/questions about this mill in various places but it was suggested that I start something here.

Last summer I picked up a 40's vintage Gorton 8D mill. It had a custom spindle with a 300 DA collet system (ie 1/4" and smaller cutters). Long story short, I broke this spindle and have had to figure out how to repair or replace it. After a lot of pondering and a few false-starts, I've decided on the following: I'm going to cut new bearing bores and a larger center bore into the Gorton quill, and install bearings and spindle for a Super X3. That'll give me an R8 collet and will hold up to the 1 hp motor on the Gorton.

Alright, so I started cutting last night on my old Gorton 8D quill and I need some advice. I've attached a drawing of the quill housing to give you an idea of what I'm planning. The lower drawing is the existing quill, the upper is going to be the finished part.

I also included a drawing of my planned modifications. You can see the original Gorton housing along with the new Super X3 spindle. I don't have the lower tapered-roller-bearing shown, but the upper thrust and ball bearings are there.

In preparation, I chucked up the quill in the 4-jaw on my G0602 and got it running true to about .0005" TIR.

The center bore of the quill cut fairly reasonably - some light squeal, but good surface finish and I was able to take off a decent chip.

However, the old bearing bores appear to at least be case hardened. I did manage to take some material off, but the lathe protested, squealed, grunted, and generally made it's displeasure known. The cut was very rough. I tried a touch of oil and I tried running the lathe at 150 and 300 rpm. All of this is with my twinky little 5/16 boring bar. So, where to go from here:

I do have a new 3/4" x 10" boring bar w. indexable inserts coming in the mail today - that should be worlds better than the twinky one. I'm hoping this will cure a lot of my ills.

I want to open up the steady-rest a skosh, and then use that to help stabilize the quill - the part is about 11" long and most of that is cantilevered off the chuck.

I've got some "real" cutting oil on the way.

What else should I think about when trying to put precise bores in hardened steel? Feed rates? Depth of cut? Any advice would be appreciated.


Thanks, Scott

[Stuff-Builder]

A bit more info on my plans:

If the spindle upgrade goes well, then I'm planning to also add CNC control to the mill.

I have a bunch of CSM servo motors and amps from a former employer that should work well. Two are 3.3 hp (!!!) 4" units that will spin up to 4200 rpm. I'm thinking these will work well for a spindle motor and also a Z-axis knee-drive. I have scads of smaller 2" servos in the 1/2 hp 6000 rpm range that I'm going to implement for the x and y axes. I've got some gearboxes available to up the torque on the small motors. I'm going to leave the quill manual and lock it up during CNC use.

If all my amps work ok (at least one is a little spotty) I'll be controlling everything through Rutex R2040 servo controller and Mach3.

Thanks for looking!

Scott

[Stuff-Builder]

I cut one of the quill bearing races last night using my G0602. It was doing pretty well with the new 3/4" x 10" boring bar and some Anchor cutting fluid. I had the spindle speed set to 560, and took 0.010" off per pass. Made some noise, but the cuts were pretty smooth.

When I started doing my finishing passes to take off the last few thou, the tool started to chatter on me. I got the ID about where I wanted but the surface finish wasn't particularly stellar. What's the typical technique for finish passes on hard steels? Should I have speed up the spindle speed?

Then I tried taking some material off the middle of the quill - it needs a larger through hole. Previously this part of the quill had cut pretty readily, but last night the tool just wanted to push away and not cut. I couldn't get it to cut at all at small depths of cut. Any suggestions? I'm going to make sure something didn't come loose in my setup, then I'll play with spindle speeds.

Thoughts?