Harbor Freight 47158 Micro Mill friction reduction?

[CactusChip]

Hi all,
I've been asking in a few places about this little mill/drill machine (with some very good responses), and thought I'd check here, too.

I bought my machine when it was on sale for around $260, so I thought it would work out well for my first CNC. After polishing the dovetails and counterweighting the head via a pulley and weight, I can move the x,y, and z screws fairly easily. I ordered some timing pulleys to provide a 3:1 reduction of my 150 oz-in steppers (5V, 1.4A). I'm now pumping in 24V with current limiting power resistors. However, I'm still worried that I might miss some steps when working with hardened aluminum or somewhat "sticky" delrin.

Has anyone upgraded this little machine to ballscrews? I priced some 5/8 screws and nuts at Mcmaster, and think I can upgrade for less than $150 (of course I'd have to buy another $90 set of pulleys to clamp to the large diameter screws). I have not worked with ballscrews before, but have seen them mentioned in many places. Do they make that big of a difference in backlash and the torque required to push the beds?

Does anyone have any other friction reducing hints? Is there a way to mount a row of bearings on the contacting surfaces of the dovetail slides? I've seen linear bearing type things designed to roll over rods, but I don't think there is enough room to replace the dovetails with rods and the bearings.

Thanks for any tips. I'd love to make this a nice little machine for my desktop, especially at the low prices I've paid for the machine and motors.

Billy Byler

[CNCadmin]

I'm in the process look here
http://www.cnczone.com/showthread.php?threadid=237

[sanddrag]

I know this is an old thread but for anyone who happens to stumble upon it in the future, I'll reply with my findings.

The XY screws on my new X1 were totally dry when I got them, so I pulled them out and dunked them in oil and reinstalled. Also, the tightness of the nut on the handwheels hasa big effect. From the factory, it was set up for no backlash but if you can live with a little backlash (.006" or so) then it'll get a lot looser. Adjusting the handwheel nut even just a little bit has a big effect on backlash and ease of moving.

Also, make sure you grease the thrust surfaces of the bearing block. Mine were dry.

Last, adjusting the gibs can be quite tricky, I could not get the table to move really freely yet have no play. There is a very fine line between a bound up table, and a table so wobbly your accuracy has gone out the window. Take your time adjusting the gib screws until there is no play but it can still move.

[Rob T]

Adding thrust bearings to the screw bearing blocks makes a huge difference to the friction without increasing the backlash. You can bore the standard bearing blocks, but I made new ones from some 6061 bar.

[phantomcow2]

I think somebody on the yahoo group HF47158toCNC made some new brass gibs for his X1, he said it made a big difference.