The premier source of tooling, parts, and accessories for bench top machinists. Mini Mill User’s Guide from LittleMachineShop.
© Copyright 2006, LittleMachineShop.com All rights reserved. Photos © Copyright 2006, PhotoBoost.com All rights reserved. Written by Chris Wood of LittleMachineShop.com. LittleMachineShop.com http://www.littlemachineshop.com 396 W. Washington Blvd.
Contents Introduction ................................................................................. 5 Specifications ............................................................................... 5 Safety Considerations ..................................................................... 5 Features ..................................................................................... 6 Basic Accessories ........................................................................... 7 Cleaning .............
Common Accessories......................................................................25 End Mills .................................................................................25 Work Holding ............................................................................26 Vises ......................................................................................26 Clamping Kits and Accessories .......................................................27 Setup Tools ........................................
Introduction This user’s guide covers the mini mills that are sold by Grizzly Industrial, Harbor Freight Tools, Homier Mobile Merchants, Micro-Mark, Cummins Tools, and Wholesale Tool. These mills are made in China, in several different factories, but to a similar set of plans. The general operating principles covered in this document are common to all of them. Specifications The following specifications are common to these mills.
Features 1 11 2 3 12 4 13 5 6 14 7 15 16 8 9 17 10 18 1. Motor 2. Drawbar (under cap) 3. High/low speed shifter 4. Motor controls 5. Spindle 6. Drill chuck 7. Table 8. Saddle 9. X-axis lock lever 10. Y-axis hand wheel 11. Z-axis fine feed knob 12. Z-axis coarse feed handle 6 13. Z-axis lock lever 14. Column 15. Z-axis travel stop 16. X-axis hand wheel 17. Y-axis lock lever 18.
Basic Accessories The following accessories come with most mini mills. Some mini mills come with additional accessories. 13 mm (1/2”) drill chuck and appropriate arbor Drawbar Spindle locking pin Two T-slot nuts Oil can Spanner wrench for spindle nut Hex wrenches 3, 4, 5, and 6 mm Open end wrenches 8 x 10 mm, 14 x 17 mm, 17 x 19 mm, and 36 mm. Cleaning Your mill will arrive coated with grease to protect it from corrosion during shipment. Follow this procedure to remove the grease: 1.
axis hand wheel hangs over the edge of the bench, or mount the mini mill on a riser about 1.5” thick to provide room to turn the Y-axis hand wheel. The mounting bolts must extend through the riser and bolt the mill to the bench to keep it from tipping. Be sure that you have room on both sides of the mill for the X-axis travel. The table will move to the right so that the left end of the table is almost flush with the saddle.
Motor Controls 1 2 1. Power switch 2. Speed control The power switch latches in the off position when you press the big red button. To turn the switch on, slide the big red button in the direction of the arrow. The big red button will swing up to the on position. The power switch interrupts the input power to the speed control circuit board. You control the motor speed by adjusting a potentiometer that provides the speed setting value to the speed control circuit board.
To start the mill: 1. Ensure that the speed control is set to the minimum speed position. 2. Advance the speed control to the desired speed. To stop the mill: • Turn the speed control to the minimum speed position. High/Low Speed Shifter The high/low speed shifter is on the left side of the spindle housing. It selects the spindle speed range. Low speed range 0-1100 RPM High speed range 0-2500 RPM Never move this lever when the mill is turning.
X-Axis Lock Lever The X-axis lock lever is on the front of the saddle behind the Y-axis hand wheel. Use this lever to lock the X-axis so it does not move inadvertently. Pulling out on the lever and simultaneously turning it can change the locked position of this lever. Pulling out disengages the lever from the locking screw and allows it to move to a different position. You might need to adjust the screw in the base of the lever before you can disengage the lever.
To disengage the Z-axis fine feed: • Move the hub and coarse feed handles out to disengage the dog clutch. You might need to turn the Z-axis fine feed knob to relieve pressure from the dogs. Fine feed disengaged Fine feed engaged Z-Axis Lock Lever The Z-axis lock lever is on the right side of the head assembly behind the Z-axis coarse feed hub. Use this lever to lock the Z-axis so it does not move inadvertently.
4. Loosen each setscrew 1/8 turn to allow the table to move. 5. While holding the setscrews from turning, tighten the lock nuts. 6. Test by turning the hand wheel. Loosen or tighten all the setscrews the same amount until the table moves freely, but without play in the dovetail. X-axis gib adjusting screws Y-Axis Gib The Y-axis gib provides adjustment for the mating dovetails on the base and the saddle that provide the Y-axis (in and out) motion. To adjust the Y-axis gib: 1. 2. 3. 4. 5. 6.
Tramming the Mill Tramming is the process of squaring the spindle with the table on a mill. This is important on the mini mill because the angle of the head is adjustable from side to side. Because the column is held in position by a clamping mechanism, the angle of the spindle can change without you being aware. Tramming the mill requires the use of a dial indicator, or better, a dial test indicator.
4. Take readings on the left front and right front corners of the table. Calculate the difference to see how much and which way to move the top of the column. 5. Move the column and take additional readings. Repeat until the readings are the same to within 0.001”. 6. Tighten the large nut at the back of the base of the column. Motor to Intermediate Gear Adjustment A metal gear on the motor drives a plastic gear on the top of the intermediate shaft.
2. 3. 4. 5. Shift the mill into high gear. Turn on the mill to approximately half speed. Move the motor until the gear noise is minimized. Tighten the four socket head cap screws that attach the motor mount. Lubrication We recommend the use of two lubricants on your mill. Where oil is required, we recommend Mobil 1 synthetic motor oil. Mobil 1 far exceeds the lubrication needs of the mini mill, and maintains a good surface film between applications. Any of the available viscosities work fine.
2. Remove the cap screw and plastic bushing that limits the upward travel of the Z-axis. 3. Raise the head assembly up the column until the rack disengages from the gear. 4. Manually raise the head assembly until the top of the head assembly is about 1.5" above the top of the column. 5. Use the Z-axis locking lever to lock the head assembly in this position. 6. Insert the lithium grease can’s spray tube into the opening that has been exposed in the back of the head assembly. 7.
3. Use a wrench to loosen the drawbar about ½ turn. 4. Tap the top of the drawbar with a soft-faced hammer to disengage the taper. 5. Hold the tool with one hand to prevent it from dropping, and unscrew the drawbar. Remove the tool. To install a tool into the spindle: 1. Put the drawbar down through the spindle from the top. 2. Put the tool up into the spindle and thread the drawbar into it. 3. If you have an R8 spindle, rotate the tool until the locking pin engages the slot in the side of the tool. 4.
6. Move the X-axis so the dial test indicator’s point is about 1/16” inside of one end of the vise jaws. 7. Move the Y-axis so that the dial test indicator’s point contacts the fixed jaw of the vise. Continue moving the Y-axis to zero the dial test indicator. 8. Move the X-axis so that the dial test indicator’s point wipes across the width of the fixed jaw of the vise. 9. Take a reading when the point of the dial test indicator reaches the far end of the vise jaw. 10.
Clamping with a Clamping Kit The clamping kit is the “Erector set” of the milling machine. Use it to clamp large workpieces, fixtures, and even vises to the mill table. Use 1-2-3 blocks as part of your “Erector set”. They can be used to hold workpieces up off the table so you won’t drill into the table. They can be used to mount workpieces, and they can be used to set work up perpendicular to the mill table.
Most engineering drawings show dimensions from two perpendicular edges of the workpiece. These are the two edges that you should “find,” or locate, as you zero the X- and Y-axis dials. The goal is to set the X- and Y-axis dials to zero with the centerline of the spindle directly over the respective edge of the workpiece. Then all movements of the workpiece relative to the spindle are referenced to these two edges. To find the left edge of a workpiece: 1.
6. Slowly turn the X-axis hand wheel clockwise to move the table to the left. As the workpiece approaches the edge finder it first forces the movable end to become more concentric with the body. 7. When the movable end of the edge finder is almost perfectly concentric with the body it will all of a sudden jump to one side and stay there. The point at which the movable end of the edge finder jumps to one side is the point you are looking for. Stop turning the X-axis hand wheel at this point. 8.
Milling You can use collets or end mill holders to hold end mills. The world is split about 50/50 on which is better. We will give you the arguments for both sides and let you decide. Collets End Mill Holders Collets are shorter than end mill holders and so give you more vertical work area. End mill holders are longer than collets and so let you reach nearer the mini mill's table. Collets grip the end mill all the way around and so provide a better grip.
Conventional Milling Versus Climb Milling Climb Milling Conventional Milling Depending on the direction in which you move the workpiece against the end mill you are either climb milling or conventional milling. As shown in the illustration above, you are climb milling when the end mill turns as to climb the slope made by cutting. Climb milling has several advantages, and is often recommended for modern milling machines.
Milling Slots Milling slots is the signature operation for a vertical milling machine. For example, to make a belt-adjustment slot, you plunge mill through the workpiece at one end of the slot, mill the length of the slot and raise the end mill at the other end. But of course, life is not as simple as this. You may or may not be able to remove all the material in one pass. If the workpiece is thick you might need to make multiple passes along the length of the slot, lowering the end mill between passes.
Two flute end mills Four flute end mills Two-flute end mills are used on aluminum because aluminum is easy to machine and you can take big cuts. Two-flute end mills provide a lot of room between the flutes for the big chips produced when making heavy cuts. But on a mini mill, you are probably not as concerned about maximizing production, and thus you are not taking the same big cuts that a production shop might.
Choose a vise that will handle the work you do. You don't need a 3" vise if the parts you make are a half inch long. While you can usually put small parts in a large vise, it is more convenient to use an appropriate-size vise. Vise jaws are often too deep for the work. In general, you want the top of the workpiece to extend above the top of the vise jaws. To fill the gap from the bottom of the workpiece to the "ways" of the vise, you use parallels.
Setup Tools Once you have your workpiece mounted on the mini mill, you are ready to start cutting metal. Except for one thing: You don't know where the cutting tool is in relation to the workpiece. Edge finders and center finders help you determine the relationship between the cutting tool and the workpiece. Edge finders locate the edge of the workpiece. Center finders locate the center of existing holes. Wigglers locate the intersection of scribed lines on the workpiece.
