X2 Mill

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All DROs Mounted.jpg

This page documents the setup and modification of the Harbor Freight Mini Mill (Sieg X2 Clone).

General Information

The Harbor Freight Mini Mill (SKU 44991) is a clone of the Sieg X2 Mini Mill. It is one of various clones of the Sieg X2 on the market, including others by Grizzly, Little Machine Shop, Micro Mark, etc. The Harbor Freight variant has a variable speed 350W DC motor with 2 gear ranges for 0-1100 or 0-2500 RPM, and an R8 taper spindle. The mill has a tilting column with -45 to +45 degree range, and has a tension spring supported mill head. The main table is 3-5/8″ x 15-3/4″, and has a total X travel of 9″, Y travel of 4", and Z travel of 8-1/2". The X and Y dials have 62.5 mils per turn with 1 mil graduations. The Z dial has 60 mils per turn with 1 mil graduations.

3D Model

A 3D CAD model of the Sieg X2 along with CNC additions is available at GrabCAD here: https://grabcad.com/library/sx2-mini-mill-cnc


11/12/2015 - Harbor Freight Mini Mill arrives; damaged in shipment, both hold-down bolts came loose and the unit was dropped on the Y axis jamming the notch into the bearing/sleeve thus preventing any movement of the Y axis. Contacted customer service who made a note to return the mill to a local store and get a receipt to place a replacement order.

Damage to Y axis on original mill.

11/13/2015 - Damaged mill returned to Harbor Freight.

11/16/2015 - Replacement mill ordered by phone, shipping charge was waived since it was not refunded by the store with the damaged unit return.

11/20/2015 - Replacement mill arrives, was only held down with one bolt (which was loose), but undamaged. Stripped down unit, cleaned, and lubricated Y and X axes and adjusted gibs.

Cleaned/lubricated/adjusted X/Y base on bench.

11/22/2015 - Stripped and cleaned Z axis/mill head, lubricated and adjusted gibs, and partially mounted unit to bench. Removed power supply box from back as it interfered with the shelf on the bench.

Assembled/mounted mill on bench.

11/30/2015 - Fully mounted unit to bench, re-adjusted gibs.

12/4/2015 - Mounted and squared vise, adjusted motor gear meshing, re-attached baffles, removed drill chuck and attached 3/8" R8 collet. Made first cuts in aluminum (shown below).

Assembled/mounted mill on bench.
Surfacing operation removing 1.5mm from aluminum bracket.

12/7/2015 - Milled holes in 2 aluminum pieces to be used as spacers for mounting the Z-axis DRO. Drilled and tapped 2 M6 holes in mill column, mounted Z-axis DRO fixed portion. Mounted vise properly using step blocks.

CAD drawing for Z-axis DRO spacer blocks.
Spacer blocks with 6.35mm holes milled in center per drawing above.
Mill with Z-axis DRO mounted to column.

12/14/2015 - Purchased a bandsaw to help with rough-cutting parts. Finalized Z-axis DRO bracket design and cut + milled the two brackets, as well as a small spacer to go between them. Waiting on a 3.3mm drill bit to use with the M4 tap to drill/tap/install the brackets to the mill. Still need to drill and counterbore the holes for the DRO body and mill side mounts.

Top: Rough-cut Z-axis DRO bracket, Bottom: Finished Z-axis DRO bracket.
Finished Z-axis DRO brackets.
Z-axis DRO bracket mocked up in final position.
Newly acquired bandsaw.

12/16/2015 - Finished Z-axis DRO bracket milling/drilling with countersunk holes for mounting to the mill head, to the DRO slide, and between the 3 parts of the bracket.

CAD drawing of the Z-axis DRO bracket (top).
Finished and fully drilled Z-axis DRO brackets.
Bottom view of the finished/drilled brackets.

12/17/2015 - Drilled and tapped the M4 holes in the mill head to mount the DRO bracket, and mounted Z-axis DRO.

Z-axis DRO bracket mounted to DRO slide before drilling/tapping holes.
Fully mounted and functional Z-axis DRO.

12/29/2015 - Designed PCB for interfacing the DROs to a Bluetooth module (per instructions and software here). Only work left to do is verify the tachometer circuit on breadboard.

1/4/2016 - Milled 6.35mm hole in 2 aluminum blocks (same as Z-axis DRO spacers). Bent metal bracket slightly to accomodate mill base angle.

1/5/2016 - Drilled and tapped M6 holes in mill base to mount DRO slide, and M4 hole in Y-axis slide to attach moving part of DRO. Started machining 45 degree brackets to hold a length of aluminum angle stock over the DRO slide to prevent chips from getting in.

Y-axis DRO mounted to mill.

3/25/2016 - Modified X-axis DRO bracket (drilled and countersunk holes for mounting the sliding part of DRO). Drilled and tapped 2 M6 holes for mounting the fixed part of the DRO.

X-axis DRO bracket mounted.
X-axis DRO mount on X-table (Left).
X-axis DRO mount on X-table (Right).

3/28/2016 - Finished X-axis DRO bracket (drilled 2 holes for mounting to the Y-axis slide). Removed X/Y table in order to drill and tap 2 M4 holes for mounting the DRO bracket. Re-assembled X/Y table after completing X-axis DRO installation.

X-axis DRO mounted to table.
Current configuration with all DROs mounted.

X2 Mill System Cost

Part Quantity Unit Cost Total Cost Source
Harbor Freight Mill #44991 1 $587.45 $587.45 Harbor Freight Tools
12" Digital Readout 2 $31.54 $63.08 eBay
6" Digital Readout 1 $28.29 $28.29 eBay
3" Screwless Vise 1 $59.95 $59.95 Little Machine Shop
Edge Finder 1 $7.50 $7.50 Little Machine Shop
3/8" R8 Collet 1 $6.95 $6.95 Little Machine Shop
Shipping/Handling/Tax 1 $13.38 $13.38 Little Machine Shop
58 Piece Clamping Kit 7/16" 1 $48.05 $48.05 Amazon
Dial Test Indicator 1 $30.51 $30.51 Amazon
1/2" R8 Collet 1 $7.59 $7.59 Enco
2 Flute HSS End Mills: 1/4", 5/16", 7/16", 3/8", 1/2" 1 $53.41 $53.41 Enco
HSS/Cobalt Screw Machine Drills: 5/32", 1/4", 3/8", 1/2" 1 $20.55 $20.55 eBay
M6x1 HSS Spiral Flute Tap 1 $10.04 $10.04 Amazon
Tap Wrench 1 $8.77 $8.77 Amazon
M6 Washer x50 1 $4.88 $4.88 eBay
M6 Hex Cap Screw x20 1 $9.22 $9.22 eBay
Aluminum Lubricant 1 $13.94 $13.94 Amazon
White Lithium Grease 1 $4.46 $4.46 O'Reilly Auto Parts
Mobil One 10W-30 Synthetic Oil 1 $7.84 $7.84 O'Reilly Auto Parts
Magnetic Base for Test Indicator 1 $18.43 $18.43 Amazon
Wood Spacer for Mill Base (0.75" x 2.5" x 16") 2 $1.05 $2.10 Home Depot
Hardware for Mounting Mill to Bench (Fender Washers, Washers, 3/8" Nuts) 4 $1.46 $5.84 Home Depot
Odorless Mineral Spirits 1 $6.83 $6.83 Home Depot
M6 Hex Nut 8 $0.59 $4.71 Home Depot
M6x30 Socket Cap Screw 6 $0.65 $3.92 Home Depot
Sheet Aluminum 18x6x0.025" 1 $9.78 $9.78 Home Depot
3/4" x 3 1/2" Cariage Bolt 4 $0.66 $2.66 Home Depot
5mm HSS Drill 1 $4.97 $4.97 eBay
10pc 6" Thin Parallel Set 1 $35.83 $35.83 Amazon
Machinist Square 1 $7.95 $7.95 Amazon
Double End Mill 3/8" 2 Flute HSS 2 $5.74 $11.48 Enco
Ball End Mill 1/4" 2 Flute HSS 1 $14.37 $14.37 Enco
End Mill 3/16" 2 Flute HSS 1 $6.52 $6.52 Little Machine Shop
End Mill 1/8" 2 Flute HSS 1 $6.52 $6.52 Little Machine Shop
Dykem Blue Layout Fluid 1 $5.74 $5.74 Enco
M4x0.7 HSS Spiral Flute Tap 1 $9.07 $9.07 Amazon
3.3mm Jobber HSS Drill 1 $4.95 $4.95 eBay
17pc. Metric Feeler Gauge 1 $4.36 $4.36 eBay
M5x0.8 HSS Spiral Flute Tap 1 $8.42 $8.42 eBay
4.2mm HSS Screw Machine Drill Bit 1 $7.52 $7.52 Amazon
Solid Angle Set 1 $43.45 $43.45 Amazon
Total Cost $1200.04 (as of 6/13/17)