7x mini lathe capabilities???

[Dan S]

I have been tossing around the idea of getting a mini lathe to help in the construction of my router. After looking at what it would cost to have ball-screws turned down, and collets made, I think it justifies buying the tools and doing the job myself.

Does a 7 X 12 from homier or Cummins have the ability to turn down rolled ball screws?? I know people turn down drill rod, but I don’t know how that compares to the hardness of ball screws.

Anyone have any experience with this?

[Moondog]

Hello Dan...

I am in the same situation as you. I went and bought a Lathe/Mill Comination machine about 1 month ago. Whatever you spend on the machine allow the same again for tooling.

I bought my lead screws (too hard to make) and am in the process of completing all of the Bearing Support Blocks for the Y & Z axis. For the block design I just copied the specs from an NSK specs catalogue. I also made my own lead nut from Delrin.

Next I will use the lathe to bore the pulleys to size etc..

Metal Machining was all new to me and I have thoroughly enjoyed learning new skills and having the satisfaction of making it myself.

At the end of the day you won't save money overall, but the machine will pay for itself with the savings in parts.

cheers

Frans

[CNCadmin]

I believe that http://www.industrialhobbies.com/ is providing a ball screw turning service so he maybe able to do the machining for you.

[JFettig]

Im sure its capable of turning the screws, I am also sure that it wouldnt be fun and you would need some decent carbide. If you ran it at about 400rpm and a little coolant from time to time and turned right next to the chuck, you might be able to get through them, I have personally never turned rolled ballscrews or drill rod on my lathe, but I have done some stainless and regular cold roll steel, If you do it right next to the chuck(seems dangerously close) and low rpm and light cuts you can probably do it.

One thing that I wish I could do is knurl stuff, so far I havent been able to, Its probably a user error but the lathe doesnt seem to be ridgid enough for what I have.


Jon

[Chagrin]

It gets clumsy spinning long rods (ballscrew) and I believe the largest diameter rod you can put through the headstock is 1/2". With proper homebuilt steady rests it can be done, but it's a heckuva lot easier letting someone else do it

[Moondog]

Dan.. don't even consider the Ball Screws.. cheap enough to buy.. its the Ball nuts and Bearing blocks where you can save money. Plus lots of other things.

[Dan S]

It sounds like my post might have confused some people. I’m not going to try any make balls-crews, right now I’m planning on buying precision ball screws and nuts from industrial hobbies as well as angular contact bearings.

1. http://www.industrialhobbies.com/Mer...t_Code=5-8_PBS
2. http://www.industrialhobbies.com/Mer...t_Code=5-8_PBN
3. http://www.industrialhobbies.com/Mer...egory_Code=odd

I drew this up in AC real quick. The ball-screw is white, angular contact bearing red, “thrust nut” green, and locking nut blue. The pulley would mount on the end. At most I would be looking at turning down the last 2 inches of each end like this.





All the mini lathes I have looked at have spindle bores of between .75” and .8” so I won’t have a problem getting the ball screw through. I think with regard to the free end whipping, I could take care of that with an oversized bearing or two, and some kind of simple wood jig.

So it sounds to me like I can do it I just need to go slow and take small cuts?

[Moondog]

Dan...

If you use an Angular Contact bearing you will need a housing for the bearing. If you use a Double Angular Contact Bearing (mostly used) you do not need a Thrust Bearing. Also you need to use a spacer between the bearing and the nut. Have a look at the NSK site at the bearing block arrangements.

Isel have an excellent Rolled Lead Screw 16mm that is ideal for a Z Axis and they sell for less than $100 with the ends already machined.


cheers

[Moondog]

here is the detail for an Isel Lead Screw 16mm that sells for $68.29 machined both ends.

They also have Ball Nuts at very good prices. This is what I bought and it is very good quality.

https://sdp-si.com/eStore/ part number Hl5136M20458

[Dan S]

Moondog I’m planning to use two angular contact bearings one on each end apposing each other, and then putting the ball screw under tension to zero out mechanical backlash.
It’s not really a thrust bearing, but a special nut that will grip the ball screw so that it can be placed under tension.

[Moondog]

Dan.. you don't need angular bearings both ends. If you do you'll need to use a nut on both ends as well.

Normally you only need to support 1 end. Often the other end is not supported, ie. left floating.

Using a double angular on the support end will eliminate movement. Backlash comes from the Ball Nut and not from the support bearings.

[Dan S]

My x axis will be 36" long and my y 24”. The servos will be able to drive them at 150 ipm, so I will need to support both ends or it will whip like crazy.