Methods for parting off larger diameters

Ignore the following, but I can't igure out how to delete it. I hadn't noticed the relief in the drawing or the whole 2nd page of the thread.

Could you machine the larger pulley into the part and face it off. Then make the smaller pulley from a piece of plate. It looks like there should be enough metal to bolt the smaller pulley to the larger one. The through shaft should ensure centering when you drill the holes. Drill, tap and bolt the 1st hole before drilling the rest. Red LockTite between the mating faces.
 
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A 6" vise is overkill for a RF45 style mill. A 4" is more appropiate for that size mill & IMO 5" max. I have a 5" GMT vise on my PM45 & it's slightly too big. Not enough Y axis travel to make use of the 5" full capacity. Better to save your money rather than getting something too big & most importantly the weight. I take my vise of the table quite often, a 6" is still light enough for me to be carried by hand but I'm glad I have a 5". I also have a 4" vise as well. I prefer the 5" though.

But those GMT 6" Premium vises are pretty nice. I'd love to have one but don't need one on my current mill. But if you plan on upgrading to a full size knee mill in the future than the 6" will be perfect.


Here's what the 5" looks like on my mill.
Img_1921.jpg


I couldn't even complete this cut without my bellows & DRO scale getting in the way. Not enough Y travel & the 5" vise is not even maxed out.
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Here's what a 6" vise looks like on another PM45 (gt40's)
View attachment 253544
 
Actually, I don't think it ever needs to be a left hand thread... someone correct me if I'm wrong.... if I do a male thread on the pulley and a female thread on the body, and the mill turning clockwise, a right hand will suffice... I do not have a reverse on this mill.
 
I have cut 3" Al with a parting blade. It CAN be done but it IS a giant pain in the ass. Everything said above helps - perfect parting blade height, sharp blade, extend it as you go, start with very low RPM, keep a good flow of a good lube (WD40 works well on Al, "Tap Magic Aluminum" is the best.) But I finally bit the bullet and bought an el-cheapo (Harbor Freight) metal cutting band saw. It does the job, yes it wanders a little - and a single cut can take 10 minutes - but I can do something else while it is happening! That saw has earned it keep many times over. One of the best lessons from this experience is that "a way" isn't always the best way, next time plan for the parting operation so you CAN saw and face after, and "measure twice, cut once.". I doubt there's anyone here that hasn't cut off a part too short. The most common cause for that is referencing the wrong side of the parting blade for your measurement.
 
I'd do the bore first. It's much easier deep parting to a hollow than a solid center. Also chapter from spindle brings shows up more on larger diameter.
 
I should never try to do this from my phone------- 2nd sentence should read "chatter from spindle bearings.."
 
That's an option for sure. I had done that before and didn't pay attention and the band saw made a horrible mess..
That would significantly reduce the cutting time as I can't get blades less than 20 tpi in that (Chinese) size saw.

Have you asked a local blade maker, I think you'll find most cities have them, some of them usually only make blades for wood working machines, but you could get an oversize metal blade of the profile and teeth configuration you want and get the blade guy to cut and rejoin it for you. That's how I get mine.
 
Threaded the body. I'll cut a chunk for the pulleys and thread that on then turn the whole thing as a whole again. That's a 24tpi, maybe too fine..? Am I complicating it with such a fine thread? I was concerned with it having good holding power... don't need the threads to be a weak point.


IMAG0899.jpg
 
Since no-one mentioned this I hesitate to post because it might be unsafe?
On edit: removed unsafe practice,


Mike
 
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Since no-one mentioned this I hesitate to post because it might be unsafe? Before I bought my Enco Band Saw I would chuck the work up in the lathe, have it set on a real slow RPM and use a handheld hack saw to cut the work. This worked for me, using plenty of cutting oil. I cleaned the cut of chips and the hack saw blade often and went slow. Hasn't anyone else done this or is it just me? Is this something really stupid that I got away with or acceptable with precautions?


Mike

You are correct, it's not safe. :eek 2:

What I have done it to put a good groove where I want to make the saw cut, and then use the hacksaw with the lathe turned off. Lathes make a pretty good vice for doing that.:)
 
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