Presentation on theme: "1- Pipsqueak Engine Millwork on uprights and base."— Presentation transcript:
1- Pipsqueak Engine Millwork on uprights and base.
The base and uprights must be carefully machined so they will both support and align the moving parts of the engine correctly. Base and upright function
It is more economical and convenient to use aluminum bar stock rather than aluminum plate for these parts. Both bar and plate come in a variety of thicknesses, however, aluminum bar stock is formed by extrusion, and is available in a variety of widths as well, (up to about 12 inches) including the widths we need for these parts. It comes in 12 foot lengths. Plate stock is rolled and is only available to us 4 feet wide and 8 feet long. (We can pay our supplier extra to cut it into smaller sizes) Plate aluminum is significantly more expensive by the pound (even before extra cut charges) and requires more sawing and milling to make these parts. It’s only advantage is better flatness and it comes in wider sizes.
Cutting speed chart Locate surface feet per minute cutting speed for your material. Speeds are for high speed steel tools. Example: low carbon steel shows a roughing speed of 75 SFPM
Selecting RPMs Select RPM based on cutting speed (SFPM) and tool diameter. Example: 75 SFPM with a ½” HSS end mill would give a RPM of about 575
Feed rate in inches per minute is: feed per tooth X number of cutting edges X RPM. Determining a feed rate
Cutting speeds are established to give maximum productivity without compromising tool life. Cutting speed charts generally give speeds that can be used in ideal conditions. Ideal conditions would include essential cooling and lubrication of the cutting tool, adequate machine horsepower and rigidity, sharp rigid quality cutting tools and adequate means of rigidly holding the work piece. Adjusting the cutting parameters such as speed, feed and depth of cut to compensate for the lack of ideal conditions is necessary. Using lower cutting speeds generally do not adversely affect part quality. Due to lack of ideal conditions (cooling and lubricating elements), reduce RPM and feed by aprox. 50%
Notice the difference in the surface finish Climb milling gives a better surface finish and also extends cutting tool life. Use two flute end mills when milling aluminum. Climb milling Conventional milling Tool path Tool rotation is Clockwise Tool path Tool rotation is Clockwise
Rough cut bar stock for uprights about 1/8” longer than finish size. Use parallels under stock. Extend stock out the side of the vise. Mill the first end only to clean up. Mill the other end to finish size. Remove sharp edges and burrs on ends as you finish them. Mill ends of bar stock used for the pipsqueak base in this same manner. Facing upright to length
Edge finder setup Use an edge finder, locate position of upright holes in X and Y axis. Run edge finder about 1000 RPM. Edge finder radius is.100 inches. Approach datum surface until edge finder runs true. Slowly proceed until edge finder moves off to the left. Set readout to reflect current position in appropriate axis (X or Y) and direction. (positive or negative)
Center drilling To create a hole in a precise location, first use accurate means to get to the desired location, then use an appropriately sized center drill to establish the hole location.
Next, drill the hole with a drill that is.010 to.015 inches smaller than the finish size. Note: Drills are not precision hole making tools. They generally cut oversize. If you need a precision sized hole, reaming or boring are good options. Drilling for reaming
Finally, use a reamer that is the same size as your finish hole size. The reamer needs to run about half the speed of the drill and must be lubricated with a cutting fluid as it cuts. Reaming
Because a reamer has at least 4 flutes, it is stable as it cuts. Reamers produce a better surface finish than drills and are slightly tapered so that they cut only on the starting end.. Reamers
Drill bits Notice that one cutting edge can be longer than the other. When a drill bit is not enlarging an existing hole, but is drilling solid material, the center of its rotation is the point of the drill, or where the two cutting edges meet. If one edge is longer than the other, it will produce an oversized hole. No drill is sharpened perfectly.
The margin of the drill is a narrow spiral surface that contacts the walls of the hole to stabilize the drill. This stabilizing effect can only work when a sufficient length of the margin is engaged in the hole. The margin is not a cutting edge. Drill bit margin Margin
Place finished end of upright on smooth portion of vice bottom or square upright in vise using a precision square as shown. You may need a third hand to tighten the vise while you hold the square firmly to the vise and your part firmly to the square. Using a machinist’s square
Use edge finder as before to locate upright mounting holes.
Drill holes deep enough to accommodate starting threads on tap and chip accumulation ahead of tap. Be sure to use cutting fluid when drilling deeper holes to avoid twisting drills off or spinning the drill shank in the chuck. Tap drilling the upright
Tap holes using tap handle and guide. Be sure to use cutting fluid.
Fixture for milling both large and small uprights Small upright requires step in fixture for alignment.
Contour is milled in three steps Standard end mill depth of cut is about ½ the diameter. End mills lose their cutting capabilities dramatically as their length in diameters increases. Specify larger radii in deep pockets and contours when possible.
Contour is finished Uprights with other contour shapes can be milled using this fixture. Additional holes are needed for air ports. It may be necessary to cut them prior to machining contour.
Mill the Pipsqueak base to size. Locate, center drill, and drill it’s holes using the same techniques as used on the uprights. Use an 82 degree countersink for flat head screw holes. Use this same tool for the countersink in the spring cover. Baseplate