Machining threaded shaft ends.

[edbo68]

This is a question For those of you that machined thier own threaded shaft ends down to fit couplings and bearings. I have a Sherline lathe and only had it for a few months. I want to turn down the ends of 3/8"-16 tpi threaded rod. The rod fits through the spindle of the lathe but the rod is 20" long.

How do I prevent the threaded rod from whipping around wildly out of the back of the spindle of the lathe or how did you guys do it I should say?.
Even if I were to support the rod between centers there would be alot of the threaded rod sticking out of the end of the spindle unsupported.

Please shead some light, tip, tricks etc..

Thanks

Ed

[JRoque]

Hey Ed,

I was in that same spot a couple of months ago. Here's a link on how I did it: http://www.cnczone.com/forums/showth...2&page=4&pp=10

Basically, I used a couple of flange bearings to stiffen up the material while being cut. The bearings I got had set screws which made it an easy fit. If you can't find bearings that match the OD of the material you want to cut, slip a piece of PVC over the material to take up the slack and then fit the set screws. One of the bearings can be mounted on the steady rest and the other, if necessary, held with a bench press as seen in the link above. The screws I cut were 72" long and they were my first job on a 9x19 lathe. I also used this method later on to cut a spindle. The bearings made it possible to make much more precise cuts than otherwise possible with just the chuck holding the material. It also beats using a steady rest any day.

Regards,
JR

[edbo68]

JR,

Thanks for the info!!!
I was going to use a steady rest too. The bearing and PVC Idea will make life easyer.
Did you have a lot of trouble setting up the rod to run true from the bearing to the spindle of the lathe?

Ed

[JRoque]

Hey Ed,

I didn't have much problem centering the screw on the lathe. I used the live center to locate the screw's center and then mounted the bearing to the steady rest bracket to match that. You might have to cut a small plate to mount the bearing on the steady rest so its centered on your lathe.

With the first screw I cut, I didn't use the bearing and figured the screw was strong enough and sticking out of the chuck short enough that would be rigid for cutting. However, even the 5" sticking out of the chuck would bend a bit and cause problems maintaining good accuracy. This might not be a problem for your application. The second screw was cut using the bearing method and that worked great.

There are tons of sources for the flange bearing and you can probably pick them up locally but if not, here's where I got mine from: http://stores.ebay.com/KML-BEARING-S...eNameZl2QQtZkm

JR

[Hobbiest]

Sounds like way too much spindle speed is being used if excessive shaft whip is present. I am not a machinist, but all of the lathe work that I have done has not given me this problem until higher speeds. The lathe was much larger too, but 200-400 Rpm isn't too fast, will still cut. Just a thought.

[peter@slater]

Would a spring loaded live center help in an application like this?



I've been wondering if anyone has tried them in an application like this.
Peter

[LeeWay]

My little mini lathe is on a rolling tool cabinet with a wooden riser built on top. I just clamped a small piece of plywood with a hole in it to a work bench. The long shaft was supported very well this way.