Mini Mill X axis shift

[redvan22]

I own the same Micro-Mark. That much movement seems excessive for a relatively unworn nut and feed screw. It's possible that the feed screw nut wasn't firmly held in place and that's what caused the movement. Other possibilities include loose gibs. The straight gibs on this machine are a bit fussy -- too loose and you get unwanted motion, too tight and the handwheels become difficult to turn.

The X axis is far better than the Y axis, simply because the X axis has thrust bearings on the feed screw so you can tighten down the nut (on the end of the handwheel) much more aggressively than on the Y axis. I have seen an aftermarket replacement bearing block for the Y axis, but IIRC it has just one thrust bearing so you still have one metal-on-metal "bearing" surface to put up with. It is reported to be better, but it can't be as good as the X axis in that regard.

Nice to know I'm not the only one with this machine. The nut was flipping and flopping around. Neither set screw was snug, rather they were both very loose.

 

[homebrewed]

The Phenom Engineering kit has a thrust bearing for the inner surface and a Teflon washer for the outer: not a perfect solution, but other than shortening the key no machining required.

I sent an email to Phenom as their website says they are relocating and not shipping until May - not sure if it’s left over from earlier this year or they mean next year. I suspect the latter as I’m pretty sure I looked at their website a few months ago and didn’t see the notification at that time.

A teflon washer definitely would be better than the OEM metal-on-metal scheme. Good to know!

 

[homebrewed]

Nice to know I'm not the only one with this machine. The nut was flipping and flopping around. Neither set screw was snug, rather they were both very loose.

In my experience the set screws tend to loosen up over time so it's a good idea to periodically check them -- or just keep track of how much backlash you're getting. A loose nut will increase the backlash.

Just to make things a little more complicated, some folks recommend leaving the screws a little loose because otherwise the nut can bind up. The pocket the nut goes in is pretty rough so the nut may not sit perfectly flat. Tightening the set screws down real good may tilt the nut a bit & then you have a different kind of problem. One more machining step and it would be a lot better, but apparently that adds too much cost to the mill!

FWIW the binding-up problem is machine dependent. Mine is pretty good so I can get the nuts pretty solidly locked down but that's just the luck of the draw. I haven't heard of anyone modifying their mill to really fix that problem, but you'd need another mill (or access to one) to do the mod. Or buy another saddle and modify it. LMS currently is asking about $56 for one, but you probably could sell the original saddle on ebay. Modifying it (with your new! improved! mill) would increase its value; or make it easier to sell.

 

[ChazzC]

A teflon washer definitely would be better than the OEM metal-on-metal scheme. Good to know!

I actually had it backwards (hey – I installed mine almost 5 years ago!): the Teflon washer goes between the lead screw and the retainer and the thrust washer stack is on the outside between the retainer & hand wheel. There is a PDF of the instructions available on the Phenom Engineering product page, and a video of the install on YouTube.

No response to my email to them yet.

Could install Teflon washers on both sides: not as good as the washer/thrust bearing combo, but better than stock. If you bored the retainer you could install thrust bearings on both sides, just like there are on the X-Axis. The Phenom kit is an easy improvement that doesn't require machining (you could use a hacksaw to cut the key to length if you didn't want to mill it).

 

[homebrewed]

I actually had it backwards (hey – I installed mine almost 5 years ago!): the Teflon washer goes between the lead screw and the retainer and the thrust washer stack is on the outside between the retainer & hand wheel. There is a PDF of the instructions available on the Phenom Engineering product page, and a video of the install on YouTube.

No response to my email to them yet.

Could install Teflon washers on both sides: not as good as the washer/thrust bearing combo, but better than stock. If you bored the retainer you could install thrust bearings on both sides, just like there are on the X-Axis. The Phenom kit is an easy improvement that doesn't require machining (you could use a hacksaw to cut the key to length if you didn't want to mill it).

Boring the retainer won't work. The thrust washer's OD is too big. I had a similar idea awhile back but it foundered on that rock. It would be necessary to machine a new (taller) retainer. And that, in turn, will slightly reduce the range on the Y axis because the retainer will be proud of the base & foul the saddle. It isn't a lot, but sometimes a little IS a lot.....depending on the task at hand!