Mill: Z-Axis Handwheel Handle

The fine feed knob on the mini mill makes it difficult to smoothly lower the head, which is important when performing operations like boring. Since I had a handle left over from installing the leadscrew  handwheel on the lathe ( http://benchtopmachineshop.blogspot.com/2015/01/lathe-z-axis-fine-adjustment.html) I drilled and tapped a hole in the existing knob and installed the handle. Now it's much easier to consistently feed with the fine feed knob.

Handle installed. Um...just ignore that other hole...

Lathe: Way Wiper

Since I installed a way cover on the left side of my carriage, it's done a great job keeping the ways clean, especially since most of the swarf falls to the left between the chuck and carriage. I wanted to protect the right side of the carriage as well, but there is a lot more stuff in the way and not nearly as much swarf falls there, so it was never a big priority. However, when I found the Phenom Engineering way wiper it seemed like a cheap and easy solution.

The wiper holders are 3D printed with pressed in magnets to attach it to the carriage. I ended up gluing the magnets to keep them in place.

The wipers tend to ride up on the side of the carriage which affects their effectiveness, so some more modifications are still planned. They're not a perfect product, but have given me something I can easily modify for my use.

http://www.phenomengineering.com/store/p12/Mini_Lathe_Way_Wiper_Kit.html

Mill: Y-Axis Bearing Upgrade

While the X axis on the mini mill has ball thrust bearings, the Y axis doesn't, with the leadscrew and hand wheel riding directly on the housing. This really increases the friction in the system and makes the hand wheel harder and less smooth to turn. Unfortunately, there isn't a lot of space to install a bearing. However, Phenom Engineering made custom low profile bearings which work in the restricted space, and a custom Teflon washer for the shoulder of the leadscrew itself to ride on. Installation was very easy and straight forward, and the difference is very noticeable. I highly recommend this kit.

http://www.phenomengineering.com/store/p11/Mini_Mill_Y-Axis_Bearing_Upgrade_Kit.html

Mill: Z-Axis Way Cover

I had some extra way cover bellows left over, so I took a piece of aluminum L channel, cut it to size, notched it, and mounted four neodymium magnets on one side. On the other side I mounted the extra bellows. The magnets secure it in place under the mill head and the notches keep it from sliding from side to side. The bellows only cover the Z axis directly below the head, but since that's generally the part in line with the milling it should protect it fairly well.

The aluminum channel showing the notched portion and the magnets.

The bellows in place on the mill head. You can also see the shim used to align the two portions of the head.

Mill: Adjusting Gibs

Please read the complete article:
http://benchtopmachineshop.blogspot.com/2017/04/mill-gibs.html


To adjust the table gibs on my mini mill I move the table to the middle of the X axis and set a dial indicator measuring horizontal play at the end of the table. I then lock Y and loosen all the X set screws. I adjust the two outside set screws until I have about 0.0015"-0.002" of measured play in the table. I then adjust the two inside set screws individually by tightening them just until I feel resistance in the hand wheel, then easing them off just slightly.

For the Y axis I lock the X and loosen on the Y set screws. If you have only two Y set screws then adjust them until you have about 0.0015"-0.002" play in the table. If you have four set screws then adjust the two outside ones until you have about 0.0015"-0.002" play, and then individually adjust the two inside ones same as on the X axis.

When you're machining, be sure to lock all the axis except the one you'll be moving.

Mill: Spindle Runout

Per Sieg the maximum acceptable runout at the end of spindle 0.0008"/0.02mm and 2"/50mm below the spindle is 0.0016"/0.04mm. 

The runout 2" below the spindle is difficult to accurately measure because the runout of the toolholding system and the tool itself needs to be taken into account. Instead, to check the parallelness of the spindle bore to the spindle axis I think it's easier to measure the runout just inside the bore and then again an inch up inside the bore. If the bore is parallel to the axis then the runout will be the same. 

Having the spindle not be exactly concentric with the spindle axis is almost unavoidable in these machines since the bore is not ground with the spindle already mounted. This is why it's important to correctly stack your tolerances: http://benchtopmachineshop.blogspot.com/2015/04/mill-stacking-tolerances.html.