Harbor Freight 44991 Mill Y Axis Slight Binding When moving towards me

AugustOriginals

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Hey Everyone,

Just purchased a Harbor Frieght Mini Mill and it seems that the Y Axis is a bit tighter than the X axis. I have not taken it apart yet but i did my best to clean it and try lubing it up a bit and it definitely is much better.

Seems like it could just need a little use to break itself in but wanted some feedback from more experienced users as to whether there is something I should look into regarding this and any way to improve it. Thanks for any info and look forward to getting to know you all!


Sean
 
First, welcome to H-M!

Second, I own a mini-mill as well, a Micro-Mark with the R8 spindle. The Y axis on these machines doesn't have any thrust bearings, as opposed to the X axis. Backlash on the Y axis depends on how tight the nut on the handwheel is (tighter is better), but if it's too tight the handwheel becomes difficult to turn. So you have to find the right balance between backlash and a relatively easy-to-turn handwheel. Since the feed screws and nuts are standard threaded types (not ballscrews) you always will have some backlash.

BTW it is a relatively easy project to make a new bearing block that incorporates thrust bearings and it makes a big difference. You will need a boring bar and boring head to make the bearing pockets, but you likely will want to get a boring head anyway.

Also, when advancing the table toward you on the Y axis, the nut gets closer and closer to the bearing block, so any misalignment between the nut and block will cause more and more binding problems as the table moves forward. To address this, you need to slightly loosen the bearing block bolts, advance the table as far forward as possible, then tighten the bolts back up. There also is a fixing screw to hold the nut in place (IIRC, it is underneath the front bellows). You may find it helpful to do the same thing with the fixing screw.

Good Luck!
 
The ultimate answer to binding is alignment. Identifying the issue creating the alignment problem isn't easy, especially on a chinese mini mill with pretty minimal QC. Flat ways on base aren't parallel /co-planer to each other. Flat ways on compound aren't parallel / co-planer to each other. Guide / Gib ways on each aren't perpendicular to lead screw axis and parallel to each other. The Gib itself isn't flat and parallel front side to back side. Lead screw nut isn't perpendicular to axis of lead screw....... Start simple and fiddle with the nut and try and get it centered as best as possible. If that doesn't work and it is a big enough problem then it can be everything else.
 
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