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Author Topic: Ballscrew End Machining  (Read 18078 times)

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Offline RICH

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Re: Ballscrew End Machining
« Reply #10 on: March 15, 2013, 06:08:12 AM »
Russ,
Looks good and one starts to think that the price  the manufacturer's charge  for doing the machining is worth paying.
I would guess that I spent 8 hours doing the three for the mill and ruined 4 three sided carbide inserts.
I even sacrificed a diamond insert cutter. 

Don't t know how they make them but will guess that it's a multi step hot forming process similar  to how they make high strength bolts.

RICH
Re: Ballscrew End Machining
« Reply #11 on: March 25, 2013, 10:28:46 PM »
I would bet you they do the annealing with an induction coil placed over the end.  You can very rapidly heat the end so that the heat won't travel very far down the shaft.

Gary H. Lucas
Re: Ballscrew End Machining
« Reply #12 on: July 12, 2013, 07:34:23 PM »
To anneal just a short part of the shaft. How about standing the shaft on end in water up to the point you want annealed. Then use the torch to heat the part sticking above the water.

Just a thought.

Offline RICH

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Re: Ballscrew End Machining
« Reply #13 on: July 12, 2013, 08:29:18 PM »
Good comment Gary as that is how I anneal shell casings and would work for a ball screw.
One needs to remember that the stress at that point or in the vicinity of the transition will be less and you would need to go beyond some exact point.

RICH
Re: Ballscrew End Machining
« Reply #14 on: July 12, 2013, 09:07:24 PM »
Rich,
I'm sure it would take a little experimenting, but it should be fairly easy to heat a little piece and test machine to see where the annealing stops.

Offline derek

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Re: Ballscrew End Machining
« Reply #15 on: July 13, 2013, 06:12:12 AM »
I tried machining a few ball screws and they were a problem. It's really hard to get the screw true in the chuck. I ended up replacing all 3 72" screws on my router with pre machined screws.

I'm not trying to discourage anyone that has the screws already but if you're trying to save money by machining your own…..don't. Spend the bucks and buy them machined.


Derek

Offline RICH

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Re: Ballscrew End Machining
« Reply #16 on: July 13, 2013, 10:36:16 PM »
I was  building a knife sharpener today and used a ground hardened rod and figured it would be nice to have a threaded end.
So being lazy I didn'd anneal the end and started threading it.
 What the heck....... the good file gave a little scatch on the end.  :D
Well............3 carbide inserts ( they are indexable and have three cutting edges), 2 hours of machining, more crackling and poping of material then  I ever experienced, and finaly had a 3/8"- 40 thread - 1 1/2" long.
Happy i didn't try 16 or 24 tpi.  :P

Guess one just never pays attention to his owne advice!  :D

RICH
 

Offline Hood

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Re: Ballscrew End Machining
« Reply #17 on: July 16, 2013, 03:51:51 PM »
I wonder if the rigidity of the lathe used may have a bearing on how things turn out? I have never had an issue turning the ends of ballscrews and I have done a few. The lathes I have used have either been my Computurn CNC or my manual Triumph. The Computurn is certainly very rigid, the Triumph less so but still relatively sturdy.

Hood
Re: Ballscrew End Machining
« Reply #18 on: July 16, 2013, 04:02:37 PM »
My lathe is not super rigid, not even very rigid.
I chucked the screws up and roughed all ends close to where I wanted them, then with fresh finishing tooling, rechucked, dialed in as true as possible and finished them. They all came out very well .... but it took some time. (and several regrinds of the tools).
Russ
 :)

Offline RICH

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Re: Ballscrew End Machining
« Reply #19 on: July 16, 2013, 06:50:44 PM »
Russ,
When I machine ball screws anymore I make a bushing that is bored or reamer to the OD  of the rolled ball screw and then spit the bushing. I then use the collet chuck to hold the ball screw / bushing. The bushing is about 2" long for a 5//8"
diameter. The setup provides a better hold on the screw and it's centered.

To put flat on the end, ie; where the ball screw will push against a bearing, a piece of stock is bored for the OD of the screw and two set screws push against a ball bearing against the ball screw lands. This allows later removal of the
bushing or stop without damaging the screw.

Threaded a ground .375" hardened rod the other day. Only put a 40 tpi on the end for 2" long.
What a PITA.....Rexroth.........it was. Never again...........out with the torch next time I do one of them!


-----------------------------------------

Don't know how they make a rolled screw but I watched HOW IT's MADE on TV and they showed how big high
strength bolts were made. They are forged and those threads are actualy stamped / formed when hot
and come out very accurately.

RICH