HOMEMADE BENCH TOP MILLING MACHINE

Practical homemade micro miller for low carbon steels, cast iron, wood, plastics and non-ferrous metals. Built from common materials and simple hand tools. This machine can be scaled up as desired and offers a noteworthy return on investment.

[A] Overview:

1. Minimum of 1 meter Aluminium T-Slot Extrusion
2. Fasteners and hardware to suit Extrusion Type
3. 1 x 90 Degree Bracket to suit Extrusion Type
4. Steel / Masonite Plate
5. ~0.2 mm Plastic / Brass / UHMW-PE / POM PTFE Composite Sheet
6. Stainless Steel Threaded Rods to suit Extrusion Type
7. Brass / plastic / wood / aluminium nut to suit spindle / feed screw choice
8. Paint
9. Way / Hydraulic / Heavy Motor Oil
10. 160, 220 Grit Sand Paper
11. Glass Sheet / Mirror / Window Pane / Granite Tile, etc
12. Mild Steel Flat Bar to Suit
13. Steel / Hardwood Base Plate
14. Rubber Feet and or Mounting Bolts

[1] Basic Tools Required

[1.1.1] Hand Tools:

1. Hack Saw with a 24 TPI bi-metal Blade
2. File (Optional)
3. Paint Brush - 19 mm

[1.1.2] Power Tools and Accessories:

1. Corded Drilling Machine
2. Selection of Drill Bits to suit (⌀3.5, 4.8, 5, 7, 8, 12)
3. Step Drill ⌀4-32 mm
4. Hole Saws to suit i.e. ⌀43 mm, ⌀48 mm, etc.

[1.2] Optional Tools

1. 115 mm Angle Grinder
2. Bench Grinder
3. Small Carbide Round Burr, 3 mm Shank
4. Belt Sander
5. Metric Thread Taps
6. Pedestal Drill Press

[2] Spindle Suggestions

1. Mini Die Grinder / Rotary Tool
2. Drill / Power Tool with ⌀43 mm EU collar
3. 6 mm Die Grinder
4. Air Die Grinder
5. ER11 Spindle (STEP 9)
6. 3/4"-20 TPI Drill/Mill Spindle (STEP 9)

Terms:

Threaded Rod = All Thread

TPI = Teeth Per Inch (Hacksaw Blades)

Pedestal Drill = Column Drill Press

Masonite = press-board / Quart-board

UHMW-PE = Ultra High Molecular Weight Polyethylene

POM PTFE Composite = polyoxymethylene resins and polytetrafluoroethylene

Materials Selection Notes:

1. See the MaterialGuide_v1 attached or
2. Download the Project Guide attached below for the best building experience. Includes:
3. 3D CAD Models
4. A4 Print Ready Templates
5. Material Selection Guide [ UDM200b_MaterialGuide_v1_25-01-29 ]
6. NOTE ON CAD FILES - the files are of an early prototype and are currently being updated. However dimensions and 90% of bolt holes are the same.
7. A complete bill of materials will be made available once a popular design emerges
8. A builder is encouraged to deviate from these plans as needed; to suite different materials on hand, budget, methods of construction, etc.

Where to Buy:

1. Aluminum Profiles: mcmaster.com
2. Other Materials: any decent hardware store

Disclaimer:

This document and all attachments are provided 'as is' and with no guarantees of any kind whatsoever. This publication is intended for use by suitably competent persons; designs are replicated at your own risk. WARNING: Wear eye protection. Remove jewelry and loose clothing. Tie up long hair. Exposure to harmful substances may occur. Risk of physical injury. Not recommended for Children under the age of 13. Adult supervision is strongly advised. Follow standard safety precautions as with any power tool.

Design Features:

1. Machining accuracy of 0.049 mm or better*
2. Axis locks on all axis'
3. Sufficient weight and rigidity to tackle most materials
4. Absolutely no specialized tooling or materials are required for construction
5. Expands your workshop / making capabilities by a large margin
6. A full maker's experience.

Cost Reducing:

1. Build using only 1 linear meter of T-Slot Profile, 1 x 300x300x5 mm plate, a few off cuts of 12x12mm square bar and standard fasteners - as an option. (The mini mill covered in this instructable uses a few more materials)

Dimensions and Specifications (mm):

MACHINE HEIGHT: 300

TOTAL HEIGHT (WITH ROTARY TOOL): 500

MACHINE LxWxH: 450 x 350 x 500

X TRAVEL: 200

Y TRAVEL: 90

Z TRAVEL: ~ 65+

TABLE DIMENSIONS: 300 x 35

T-SLOT SIZE: 6 mm

WEIGHT: ~ 6 KG, EXCLUDING SPINDLE and SPINDLE BRACKET

ROTARY TOOL: 130W, 220VAC, 8000-30000 RPM

Comparing Assembly Methods:

1. Bolt Only - No Threading
2. Relies on threaded rods passing through components
3. when threads are a must, threaded nuts are held captive in oversize holes
4. More components are required overall
5. Shims may also be used to substitute captive nuts and bolts as desired
6. Higher assembly tolerances (more forgiving during assembly)
7. Bolt and Studs - Hand Threading
8. Fewer overall components are required
9. Fewer assembly steps
10. Can result in significant time savings
11. Tapping set required
12. Less room for error

*Relies on accuracy of aluminum profile used. Using ME16 Extrusions typically results in ± 0.03 mm level of precision.

All materials are cut to size according to the cut list, holes drilled, chamfered, deburred and sharp edges broken.

All faces making contact with an aluminum surface should be 'trued up' by sanding (or scraping) the surface to an acceptable level of flatness.

Remember: the accuracy of the machine stems entirely from how well each component is made to interact with the Profile Extrusions. And so, it is helpful to ensure that all parts are prepared as carefully as possible and that high quality aluminum extrusions are used.

Purpose of Column Design

The column forms the main structure of the milling machine and all other assemblies are fitted to it. Every force acting on and through the mill will almost certainly pass through this assembly and so the design should reflect that. There are a few main challenges to consider. Firstly, the two sliding planes must meet at 90 degrees. The extrusion's faces which are exposed outwards must be flat relative to the same vertical plane - there can be no twists or bends in either piece relative to one other. And, lastly, the structure must overcome forces that would otherwise cause bending or separation of the two perpendicular extrusions.

In keeping with the original design principles of affordability and accessibility, this approach has been conservative. For added performance the width of the column side panels and be increased and larger aluminum sections used.

Reducing Friction and Wear

Avoiding metal on metal contact - whenever two metal surfaces are to slide or rotate about each other, steps are take to keep the respective parts from touching. The main method employed to do this in this build is by adding a layer op plastic and effectively two oil films - one on either side of the plastic divider. This method has two main drawbacks, there is increased deflection in all axis' due to there being two individual oil film layers and the plastics used are not hard wearing nor self lubricating. One solution will be to use engineering plastics like those mentioned in the materials break down.

SUMMARY OF PARTS USED

M8 SS Threaded Rod / Bolt 150 mm AND 400 mm in length

M8 Brass Nuts

Plated Steel washers

Fibre Washers

4.3 mm Unhardened Nickle Plated BBs

Mild Steel Cutouts left over from drilling

Mild steel handle fashioned from 5 mm thick flat bar

M5x25 mm SS Grub Screws

DIY THRUST BEARINGS

Here, a method of easily producing your own thrust ball bearings is demonstrated. There are several disadvantages the biggest of which is producing an evenly deformed washer. If the set up is not perfectly centered and square to the force applied, the washer warps and is not suitable for use. A better approach is using flat washers only and holding the rolling elements captive in a ring or cage.

The fiber-washers tend to deform over time but offer smoother operation and have performed well in testing, better options may be stainless steel or brass. The rolling elements are 4.3 mm unhardened steel BB's. As shown, tape is wrapped around the assembly to retain the rolling elements and oil (grease is used in the open type). A further improvement would be a layer of PTFE plumbers tape between the rolling elements and outside layer of tape. These designs are experimental and don't outperform standard thrust bearings of course.

BRASS NUT AND SS THREADS

The brass nut and stainless steel threaded rod paring offers almost zero backlash in this case. Traditionally a faster wearing material like brass or bronze is used with hardened spindles to significantly reduce wear in the expensive part, rendering the nut as a wear item instead. In this scenario the nut is a similar cost to the spindle and so focus can be shifted to other benefits such as helping to maintain reliable accuracy over time, less backlash out of the box and smooth, quite operation. Decent lubrication is still required.

Forming Internal Threads Without a Tap

Internal threads may be achieved by embedding a nut having the desired thread type into an appropriately sized hole.

There are two basic methods of retaining the nut without gluing or brazing. First, by means of a slightly undersized hole (Selecting a drill size the same diameter as the across the flats dimension i.e. spanner size will usually be a good starting point) into which the nut is carefully pressed. Or by drilling a slightly too shallow hole to the same diameter as the nut and clamping it in place. Each method has a distinct advantage over the other. The pressed in method maintains a low profile and the clamping method is better for strong, reliable threads.

Each of the 3 Axis' is locked by means of a bolt passing through a clamped nut, in these instances a nylon locking nut is used. The nylon ring is first drilled out and a hole drilled to match the profile of the nut, taking care to drill slightly shallow so that a portion of the nut is raised above the clamping face. The nut is placed in the hole with the thin walled rim left over from removing the nylon facing inward. This will allow the wall to crumple as force is applied making for a seamless fit between parts when bolted together.

Short Length Gib on Knee Assembly for Clamping Down the Back of the Table:

Before installing the table assembly, thread one of the stud nuts all the way to the upper limit, raise the plate and fix it in the raised position using the second nut from below. Now you are ready to slot in the table. Once in, the full range of thread is available for clamping pressure adjustment. Leveling of this plate is achieved by clamping the plate between the 4 nuts once the correct level and sufficient pre-load is set.

In this example, the plate has had a number of spot holes drilled and one through hole for oil to pass through from the top and lubricate the back sliding surfaces of the table.

Ruler Scales:

Steel rulers are held in place by magnets - leaving them adjustable. Alternatively, one can fix them to the feed screw brackets for a more permanent solution.

Felt / Foam Wipers:

Wipers are cut from a relatively thick piece of felt or oil proof foam and to match the profile of the backing plate. By crushing the sheet in position it expands slightly providing an adequate wiper-seal blocking dirt and grit from fowling up the guide ways.

Two sizes are shown here.

Euro spindle neck mount - ø43mm

1. Accepts the standardized 43mm diameter collar.
2. Such as routers motors, geared drills and spindle motors
3. Off the shelf brackets are available

Custom Size - ø48 mm

1. Suits pictured model of Mini Die Grinder

The pair of holder plates are drilled and finish sanded as one (bolted together). It is also important that the two plates are clamed parallel to each other, ideally the holder should be one solid peace of dimensionally stable material. We have used a peace of hardwood that was first dried, planed, 'thicknessed' and sealed. A person can also use a sheet of thick plastic (an old cutting board for example) or aluminium.

Here, a second handle blank was fashioned to match the first one made for the table. Two, M5 Cap Head screws, brass washers, lock nuts and M6 coupling nuts are made up to form the handles.

A GT2-6 x 200 teeth belt is fitted over a 16 and 36 tooth pulley respectively. Bearings used are 624zz flanged type but 625zz also work with the downside of the belt rubbing against the side plates.

Note how the table locking nut was swopped out for a low profile flat head screw.

Whilst it is certainly possible to make each part from CAD models and drawings and then assemble and fit. We found it fairly quick to produce a wooden prototype based on the machine dimensions and once we had a design that worked transferred the holes, dimensions and spacing to steel. This design does not allow for the maximum possible travels unless there is a hole in the base plate and space enough for the threaded rod to pass down under the machine. A new and thicker base plate can be made up or a second plate of suitable thickness and design added below the first.

Used corded hand drills are an inexpensive way to source precision ground shafts suitable for a micro mill spindle. Try asking local steel fabrication shops if they have burned out drills laying around, visit a scrap dealer, pawn shop or yard / garage sale.

Gate wheels are a great way of finding lathe turned bearing block and will generally have a 32 mm inside bore that suits the 6201 or 7201 bearings perfectly. In this case, the wheel came fitted with metal shielded bearings (which were upgraded to better quality ones) but it is more common that the bearings have rubber shields which aren't suitable for high speed use - see the manufactures spec sheet to double check if the bearings will cope with the speeds you end up with.

Once the shaft is placed through both bearings and held in place firmly, a measurement is taken between the nearest inner race and circlip groove top edge and the thickness of the circlip subtracted to get 't'. Now, ideally, a hardened and ground spacer could be made up to approx. 0.01 mm oversize of 't'. Alternatively, the spacer may be made up by stacking washers and shim stock. In this case, a high quality spring washer equal to or slightly below the nominal thickness ('t') was selected and the circlip pressed in place by means of a suitably sized mild steel collar as shown.

The collar is simply the female end of a 20 mm male/female 'bullet hinge' pair.

A fair amount of force is required to compress the circlip and so the inner races of the bearings are pulled together tightly whilst an equal and opposite force pushes on the pair of outer races, this removes all play in the bearing, improves concentricity and limits vibration. (Note that the spacer between outer races as pictured is required for this reason). Care is taken to press the circlip in safely, NEVER USE a second hand circlip as it will not seat correctly under load. In the case of no spring force, bearing pre-load is achieved by the spacer being ~0.01 mm too long.

Damage may occur to the bearing races if the circlip is pressed on with too much force. For best results, use a bench vice or other type of screw clamping method to slowly force the clip into its grove. Keep the bearings in constant rotation throughout clamping and feel for tightness. The wheel should always be able to spin freely with only a slight increase in friction. If the bearings start making an audible squelching noise as the rolling elements roll through their grease, the width of the spacers needs to be reduced.

Spindle pulleys may be made from hardwoods and o-rings used as drive belts. In this example, the rotary tool is mounted upside down, further along the ram and a small pully fitted to it's nose. A second, larger pulley is fitted to the drill shaft and a suitably sized o-ring connected between. (Not yet pictured). If slippage occurs, add a second groove to the pulley set and fit one more o-ring. Tensioning is achieved by moving back the rotary tool holder and driver pulley.

ER11 COLLET CHUCK

A common ER11-8mm collet chuck is fitted onto the small bearing end of the shaft once the excess length is cut off and burs removed. This should be a slight press fit; if there is any side-to-side wobble, then the small end bearing journal may be worn or otherwise undersized.

One of the set screws is aligned with the keyway / indent pictured such that the screw point can slot down and in for a slip-proof grip on the shaft. The spindle assembly is then flipped 180 degrees in its holder and chuck removed. A suitable pulley may be attached using the left hand threaded screw supplied with the drill. (Not yet pictured)

HORIZONTAL MILLING and More Coming Soon. Stay Tuned! This instructable is updated regularly.

The UDM-200 Micro Milling Machine is Open Source. If you'd like to learn more about this project, feel free to visit: https://libreindustrial.cc/

1. LIBRE INDUSTRAL DESIGNS are licensed under CC BY-SA 4.0