[GrizHFMinimill] Re: $50 mini-mill power feed

I started out anealing a 12 point 9/16" 3/8" drive socket by heating it cherry red and letting it cool slowly. I bored it out to fit snug on the slotted end of the X axis leads screw and used a small bolt cross drilled and tapped to engage in the slot. The gearmotor shaft has a flat side, so I turned a piece of round stock, milled the hex on the end using a rotary table on the mill. I installed a countersunk set screw that was length adjusted to allow it to slide on the shaft flat. I turned the .080" groove in it for the cam to engage in. The cam itself is a 6mm socket head cap screw I offset in the lathe by about 6mm and turned down the head leaving a .060" pin sticking out of a .030" head base, like a tiny crank shaft on a disk. I drilled and tapped a hole in the X axis bed and threaded the cam bolt from the bottom, adusting so the pin rides in the slot on the sliding half.
I case hardened the hex, socket, and the pin so it won't wear too much. It was a trial and error process to get it adjusted but it works great. It has no springs or latches to keep the clutch engaged, and it does not disengage itself under load. Sometimes it may take a slight turn of the hand wheel to get the hex to engage on the socket, and I can actually hand crank against the gearmotor for minor adjustments without disengaging.

I'm sure some will say the clutch handle blocks off the end of the t-bolt slot and eventually I'd like to figure out a different way to engage the clutch but the clearances under the bed are pretty restrictive when the carriage runs to the full right position. I'm open to suggestions....

--- In GrizHFMinimill@yahoogroups.com, Gary Liming <g_liming@...> wrote:
>
> Very cool, Rick - it has an elegant simplicity to it.  Could you describe the sliding mechanism and cam lever arrangement?  I'm not sure I understand what is going on under that lever. 
>
>
> Does the controller  or power supply get very warm?
>
>
> From your video, I think I may need to use a gear motor - I was thinking of using an electric drill motor, but a gear motor should have better torque at the low speeds, which is where I might want to be for many operations.
>
> Thanks for posting this!
>
>
>
> ________________________________
> From: Rick Grimm <grimmrlg@...>
> To: GrizHFMinimill@yahoogroups.com
> Sent: Wednesday, December 7, 2011 5:13 PM
> Subject: [GrizHFMinimill] $50 mini-mill power feed
>
>
>  
> I completed the powerfeed I mentioned a few days ago, you can see the photos in this album:
>
> http://groups.yahoo.com/group/GrizHFMinimill/photos/album/2130350934/pic/list
>
> or view a video at:
>
> http://www.youtube.com/user/grimmrlg?feature=mhee#p/a/u/0/_Cy-zF6R6cI
>
> I found a 24 volt at 2 amps gearmotor with 144 RPM and 6 in/lbs of torque. I checked for more of the same motor but it appears this was a one time only item.
>
> I'm sure a similar motor combo can be found, but I'd be wary of any 24v motor that isn't drawing at least 1 amp or it probably won't have enough power, its sometimes hard to find torque specs on ebay listings, luckily the one I got had a link to the spec sheets. I also would not recommend torque less than about 4 in/lb or RPM under 120.
>
> http://www.ebay.com/itm/130556417718?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 This is the motor speed controller
>
> http://www.ebay.com/itm/200674705469?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 This is the 24v gearmotor
>
> http://www.ebay.com/itm/370524958531?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 This is the 24v power supply
>

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