Work holding and a threading question

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bosephus

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Ok i have two questions.. the first one is on work holding
A friend wants me to make spindle . My problem is the spindle is about 20 inches long and 3inches in dia .

To big to fit in my steady rest .. so how do i support it to get it center drilled ..the slowest speed i can spin is 120 rpm and having that much hanging out of my chuck un supported just doesnt seem like a good idea .

My second question may just be realy dumb .. but i never have been scared to ask dumb questions .

I also need to do some inside threading to a shoulder .
Now pay attn this is where things may get realy dumb .

Instead of threading to the shoulder blind .. can i just throw my machine in reverse set the tool to the back side of the part and thread it from the shoulder out .

My brain says this makes sense .. i wouldnt need nearly as much relief cut and no crashing and as when reversed both the lead screw and spindle reverse i would still get a right hand thread . .

Feel free to make snide comments ... i have a great sense of humor
 
Not a dumb question, this is a common problem. What we do is carefully center punch the stock chuck it, not tight yet, then stick a small center drill in there then tighten the chuck
good idea to hand turn the chuck lightly until the drill starts, then a larger center drill. That will get you real close doesn't matter if you are to turn it anyways.
Internal threading to a shoulder mostly a problem with seeing and quick reflexes unless the lathe has an automatic half nut kick off most don't. So I cant see why you don't
make a relief cut thats a big help. Or just flip the tool and reverse it and thread out. Most fear the chuck will come off, no so, with that kind of weight of the stock and the
tail stock center bearing on it, it will stay your only threading light cuts. I advise center drilling both ends of the stock and turn or do whatever between centers with a dog and
always mark the dog and chuck jaw or drive plate with a sharpie if threading. Best I can explain or thats the way we do it. forgot, back to the threading thing, get yourself
or make a thread stop "can't live without it" One more thing less to worry about.

sam


Edit whoops I just realized you answered your own threading question; just like left hand threading except the tool
 
A really dumb question would be " Hey guys a threaded to a stop and crashed, what gears do I need to buy?" ahahaha
 
Your answer was way better then anything I could have said on the subject. So I just addressed the scraps with in my pay scale. And I do love sarcasm.
GK1918 said:
????why didnt I think of that good one chuck
Click to expand...
 
Replacing those pesky broken gears is something i do wish to avoid .

And to be honest ... it did sound like a dumb question ... for the life of me i could not figure out why it wouldnt work .

I should have mentioned it is two seperate projects .. the inside threading project is going to have a very short threaded section and i want to keep the relief cut small to have as much thread as possible .
 
IMO that speaks to your ability to use logic and reason. But I assure you, for many, that would not have such a blessing. I have been in a shop full of grown men who want to be machinist.... I assure you, reverse threading nor threading to a blind stop being bad, would not crose many guys minds till it was to late.
 
When i was younger and more prone to doing and not thinking i had a supervisor ask me if i could possibly get any dumber after setting a d11 bulldozer on its side ... the only answer i could come up with was ... wait untill tomarow .

After collecting unemployment for a few weeks i learned that it pays to think before you act .
 
Instead of center drilling can you just buy stock that already has a center hole? Maybe close undersized hole so just need to dress the surface and not bore the entire hole? Assuming you need the shaft with a center bored out and not just the end.
 
bosephus said:
Ok i have two questions.. the first one is on work holding
A friend wants me to make spindle . My problem is the spindle is about 20 inches long and 3inches in dia .

To big to fit in my steady rest .. so how do i support it to get it center drilled ..the slowest speed i can spin is 120 rpm and having that much hanging out of my chuck un supported just doesnt seem like a good idea .

My second question may just be realy dumb .. but i never have been scared to ask dumb questions .

I also need to do some inside threading to a shoulder .
Now pay attn this is where things may get realy dumb .

Instead of threading to the shoulder blind .. can i just throw my machine in reverse set the tool to the back side of the part and thread it from the shoulder out .

My brain says this makes sense .. i wouldnt need nearly as much relief cut and no crashing and as when reversed both the lead screw and spindle reverse i would still get a right hand thread . .

Feel free to make snide comments ... i have a great sense of humor
Click to expand...

Just what size lathe are you using?

You can always locate the center using layout dye and center finding head on a 6 inch ruler. Move it around the diameter a few times to find the exact center and scribe several lines. Use a center punch to mark the center. Then use a center drill in a drill motor to drill out the center. Hope I didn't confuse you.

Good luck with your project.
 
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