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View Full Version : Still laughing! (parting off)



torker
05-14-2006, 12:51 PM
I finally said to heck with all the automotive crap I've been working on the last few months and decided to take a couple of hours off this morning.
I've been dreaming up this fancy swinging, all adjustable,lockable, blah,blah, arm to mount my DRO readout on.
Finally got around to making some of the swiveling parts this morning.
From a 2" piece of mild steel I needed to make 3 -1 1/4" and 1- 1" long pieces.
Started to part them most of the way through as this is held between centers.
Massive chatter...ooops...had the cheap live center in the tail.
Swapped that out for the ol' dead center and continued on.
Parted them all down to around 5/8" dia on the cut line @ 400rpm with one of those cheap brazed cutoff tools that I have sharpened just the way I like it now.
When it was done and I was packing the piece over to the saw to do the final parting it dawned on me....
A couple of years ago I would have done everything in my power to avoid parting off on the lathe.
Had my little SB9 and just couldn't get it figured out.
Even this newer 14X40 drove me nuts til I got all the problems solved.
Now I just part things off without even thinking of it.
Funny how things change when you hang around places like this for long enough.
Just a little thing but when it happens I just have to thing about all I've learned here...thanks guy! :D
Well I better "part" my butt back down to the shop :D
Russ

beckley23
05-14-2006, 05:16 PM
Mass and rigidity mean everything in cutting off, you've learned the lesson.
Your next challenge is to get rid of the tailstock and complete the job on the lathe.
Make sure you get the cut off tool as close to the spindle bearings as possible, it really helps, as does coolant.
Harry

torker
05-14-2006, 06:10 PM
Harry, guess I didn't explain, thie 2" piece is (was) 14" long and won't fit through the headstock.
Had to use the center.
I do lots of parting off just with the chuck. You're right though, you do have to keep it close to the chuck.

IOWOLF
05-14-2006, 07:02 PM
Use a center rest.

beckley23
05-14-2006, 08:01 PM
Russ, now I understand the problem.
I would have done the job differently by cutting the pieces long on the bandsaw then finishing on the lathe.
Harry

wierdscience
05-14-2006, 08:04 PM
Russ,I find myself parting off more stuff since we got a lathe with a 4" spindle bore:p:D


Ever try way oil for parting lube?

Mcostello
05-14-2006, 10:55 PM
screw machine shop experience talking---- 10% more overhang = 33% more deflection.:)

CCWKen
05-15-2006, 12:13 AM
You're building a DRO readout swing arm out of 2" stock? :eek: That must be some monster readout! :D I've got an old swing arm off a Quad Router. It's made to hold a CRT and keyboard and it's made from 1 1/2 x 3/4 stock, IIRC.

torker
05-15-2006, 12:55 AM
Darin, is the spindle bore EVER big enough? I went from 3/4" to 1 9/16" and would sure like to have that 4" bore.
Funny, that big ol' McDougal we are rebuilding only has a 2 1/4" bore.
Mark, Thanks for the tip! I'll have to remember that!
Ken...No, the 2" stock is for the locking swivel parts only. The actual arms are 1" square tubing/.125 wall. The whole thing will accordian so it'll lay flat on the wall when it's not in use. I have my lathe set at 45* to the mill and need to get in behind it sometimes. The readout would be in the way.

torker
05-15-2006, 01:09 AM
Russ, now I understand the problem.
I would have done the job differently by cutting the pieces long on the bandsaw then finishing on the lathe.
Harry
Harry, guess we all do thing different.
I thought I was being cagey.
Turn and finish OD between centers,
Measure parts to length with compound and part deep enough so shaft is still strong enough not to induce chatter.
Saw the pieces off.
The matching swivel parts where to have depressed centers, so a couple of passes on the inner part depresses the center. The length was already done when parting off.
Drill center holes, chamfer holes...done!
Russ

Evan
05-15-2006, 12:24 PM
I have good success parting on my SB9. Something that I think most people forget about on that lathe is to lock the rear carriage gibs under the back carriage way.