# Adding a 4th axis



## Holescreek (Jan 19, 2009)

Everybody here has probably already done their CNC conversions so there isn't any point in beating that horse, but I added a 4th axis to mine that I've found as useful as anything I've done before. There was a seller on the Bay that had a stash of servo driven 5" turntables and I was able to get one for $50 or so. I traded out the servo motor with an extra stepper after modifying the shaft of the stepper for the gear and making an adapter to mount it on back of the turntable. I used 4 pieces of scrap aluminum bolted together to hold it up and made an adapter to mount a 5" 3-jaw chuckon the front. I use it mostly for turning bronze rounds into gears. -Mike


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## Brass_Machine (Jan 19, 2009)

That's pretty slick!

Eric


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## Julian (Jan 20, 2009)

Very nice work. My next cnc progression is the fourth axis. I was going to convert my RT to stepper but may go your way instead.

Julian.


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## Maryak (Jan 20, 2009)

Holescreek,

That is one very smart piece of kit. :bow:

Best Regards
Bob


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## Bernd (Jan 20, 2009)

Mike,

Couple a questions. Is that a belt drive or gear driven? Is the table left loose or is there someway of clamping it to keep it from moving while you are cutting?

I was just wondering. I would be concerned about back lash for one and the other is rigidity while cutting a part.

Bernd


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## Holescreek (Jan 20, 2009)

Bernd,

The unit is gear driven. The unit coming from 'Bay was made by TRW Globe. There is no discrenable backlash based on holding a t-bar in the chuck and indexing each way. The photo of the back shows the 1/2-13 cap screws holding it to the table. It also fits on my 6" sine plate with 1/4-20s and some washers (then clamp the sine plate). After bolting the frame together I mounted it against my 6" grinding cube and ground the face square to the bottom.


> I would be concerned about back lash for one and the other is rigidity while cutting a part.


 The largest gear I've cut so far was a 20 degree bevel out of 3.5" diameter brass. The aluminum one in the photo was just a test part. There was no issue with the 4th axis rigidity. If there is a concern about back lash you just treat it like you would any other manual operation and back it up past zero and index it forward again. 
I use this on a Rong Fu 30 mill/drill I inherited. I didn't have a use for the mill as a manual machine since I already have a BP so I converted it to CNC. -Mike


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## Bernd (Jan 20, 2009)

I was just wondering. You've answerd my question. Thanks.

Bernd


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