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