Todays Project - What did you do today?

[PixMan]

Well, tired of walking around with a fiberglass splint and my left arm in a sling, I shed it today and headed for the shop.

With the help of my younger son Brian, I mounted the 12" Pratt Burnerd 4-jaw independent chuck that's been on the machine perhaps ONCE and clearly never made chips. I had to clean off old Cosmoline that was in all the jaws, too bad my dad had already wiped it off the larger surfaces because it was coated with a layer of rust that took a lot of work to get (most of it) off.



I then put the long 1-1/4"-5 Acme screw I'd made weeks ago for Darren into it, gripping with copper between the jaws and the Acme threads. To make sure it was running true to the threads, I engaged the lead screw, set to 5TPI and put the spindle in it's highest speed gear to make it easy to turn by hand. With the half nut engaged and an indicator running on the crest of the threads, I dialed it in quickly and brought in the live center.



With the workpiece trued up, I finish turned the 20mm diameter for the bevel gear, and threaded the M12x1.75 for the nut that keeps the thrust bearing and bevel gear in place. It's now ready for the milling of a keyway and a couple of small holes. I ran out of time, so it'll have to wait (probably) until next weekend for that. I don't have a 5mm end mill so I'll be profile milling it with a 3/16" or smaller end mill, using the 2 axis Prototrak control.



Not the best finish, but the 20mm size was verified with the 20mm bores on the spurs gears I had to make to enable metric threading.

[Mayhem]

That looks better than the one it is replacing Ken. I'm so glad that I could be part of your recuperation

[PixMan]

Darren,

Happy to be of help. While I'm thinking of it, do you want to have a small (1/8" or less) through hole to the bottom of the 5mm round hole for a pin at the Acme thread shoulder, and would you want to omit the one beneath the keyway?

[Mayhem]

Thanks Ken - we can omit the hole beneath the keyway, as I cannot see the need for it. A hole beneath the 5mm hole for the pin that engages the bearing carrier would probably be a good Idea, as I am sure I will have to remove it a few times during fitting.

[PixMan]

Agreed, consider it done!

[dallen]

turned the end of this ball screw so it would fit the 1/2 inch ID bearing that I have in the block, and rethreaded it.

   

[arvidj]

(04-10-2014, 08:47 PM)dallen Wrote: turned the end of this ball screw so it would fit the 1/2 inch ID bearing that I have in the block, and rethreaded it.

I have read that the hardening process applied to the threads on ball screws makes them very difficult to machine. Would you care to comment on how you went about machining yours?

Thanks,
Arvid

[dallen]

(04-11-2014, 08:44 AM)arvidj Wrote: I have read that the hardening process applied to the threads on ball screws makes them very difficult to machine. Would you care to comment on how you went about machining yours?

Thanks,
Arvid

used an cnmg insert which was rated for hardened tool steel and took very shallow cuts till I had the ball thread which makes for one heck of an interrupted cut removed then it was pretty easy cutting from there on. The threading was straight up single point threading job using a Kennametal insert that I had a couple of which handled the inner portion of the screw fine, but I still took shallow cuts with .005 being the deepest I went in one pass.


BIGGEST thing is to have it set up ridged as close to the chuck as you can get and have room to work.

The first ball screw I turned I drilled and tapped it, hope I never have to do that again, Ball Screws and Taps don't really mix as far as I'm concerned.

[DaveH]

Good job there David, glad you sorted without too much grief

DaveH

[dallen]

here's a shot of the start of the scratch pass to thread the Z Axis screw, this screw was to short for me to have the nut on the outboard end of the spindle so I had a lot more sticking out of the chuck then I wanted. It turned ok, just that I would of been a lot happier with the setup if I had of only had like 4 inches sticking out. Was going to put the nut inside the chuck behind the jaws but there wasn't enough room to set it up that way

DA

   

came home from hardware store to find this sitting at my back door begging for chips and some paint