Knee Mill Z axis question

[chrisken]

I have been lurking for quite a while and have decided now that I have time I want to CNC this old thing. I have had it for 31 years and its done everything I wanted. I thought it would make a nice restoration project.I cuts true so instead of assigning it to the scrapie I am going to CNC it. I have read a lot of the threads about Knee mill conversions and only query I have is about Z axis. As you can see I have removed the vernier from quill feed and was thinking of machining mount for ballscrew and fitting it in area marked and driving z axis from existing mount .Any thoughts appreciated ( I have X3 with 3 axis DRO and lathe to produce bits )
Regards
Chris

[79TigerPilot]

Chris,
I CNC'd my J head BP and drive both the knee and Quill. Normally I only cut with the Quill drive as it's a little faster but if I have a deep hole to drill the 4" Quill travel sometimes in not enough.

Hint: That rusty looking plate below the pulley and belt and above the quill window can be duplicated but with a longer front section. Make a ballscrew thrust bearing mount and attach it the the bottom of that longer plate. Above or below that put a timing pulley.

Then remove the block that attached to the quill through the slot and replace it with a new larger block that captures the ball screw nut. Add a lower lateral support bearing and a stepper and you are done.

Craig

[chrisken]

Thanks Craig ,those were the lines I was thinking along. What about the spring that returns the quill when you manually drill,how will I work out how big s stepper motor I need act against it.
Regards
Chris

[SCzEngrgGroup]

Thanks Craig ,those were the lines I was thinking along. What about the spring that returns the quill when you manually drill,how will I work out how big s stepper motor I need act against it.
Regards
Chris

You don't - you disconnect the spring, or remove the whole quill feed pinion assembly.

Regards,
Ray L.

[chrisken]

You don't - you disconnect the spring, or remove the whole quill feed pinion assembly.

Regards,
Ray L.

Thanks Ray
I disconnected the spring last night and because there is no tension quill extends under its own weight. Will this not happen when you power down the machine ?.
Regards
Chris

[judleroy]

Your screw should hold the quill up when powered down.
Judleroy

[chrisken]

I have made the ballscrew mount and fitted it to the quill.I machined a dummy ballscrew from delrin for setup.Measured force required to raise quill with spring balance and worked out at 13kg . I have also decided as part of the build to replace motor and fit variable speed control.

[chrisken]

Lots of progress on build. I have test fitted all ballscrews and run them their full travel using a bit of delrin fitted over the end and turned to fit cordless drill. All function fine so now will build motor mounts and bearing housings and turn down ballscrew ends. Have removed 240 volt motor and fitted 3HP 180v DC Motor and Penta Drive . I have turned out original bearing housings to use for bearings and motor mounts. I have all components and expect to be ready to test by end of January. Weight of motor is supported by sides of casting the screws just hold plates in position. just need to attach top plate and belt adjuster.

[Deano7/11]

looking good mate well done. will be watching this thread

[chrisken]

Almost finished conversion.x,y,z axis drives finished and working. Controller working,Mach3 demo loaded and steppers calibrated. I got Gigabyte GA-D525TUD Intel Atom Board and Small Case to Run the machine.Just fitting up the DC motor control and waiting for a Tacho kit. I have dry run a couple of the wizards and all seems fine.Real cutting after I refit the motor.

[Deano7/11]

you make it look so easy. well done.

where abouts you based mate?

[chrisken]

Thanks Deano7/11 I live in Ipswich Qld. The conversion was not what I originally planned . I purchased a Sieg X3 new to convert as there are a lot out there and I was going to get rid of the old knee mill. The more I looked at the knee mill the easier it looked to convert.