Yet another iteration of nothing
Random header image... Refresh for more!

Category — Machining

LMS 39xx Riser Block

Well!

Couple years after I used:

to make mine (Cold Rolled C1018), Little Machine Shop finally has a riser block for their mills. Riser, 2 inch solid column. Given how much trouble it is going to be to scrape steel (I have been shimming), I`m sorely tempted to change.

Here is someone else doing a variant of this Mini- Mill Riser block (YouTube); Warning. slight language vulgarity).

April 3, 2016   Comments Off on LMS 39xx Riser Block

Rigging (suspension and moving of machine tools)

Rigging (in this context) is the act of safely supporting and transporting machine tools.

Some pointers:

  • Twisted rope has a much higher sliding coefficient (ropes are rougher). It can take a lot more static tension to overcome sticktion.
  • This makes it harder to “synch” up the rigging before hoisting the load
  • Twisted rope frays more easily; more rapidly loses ultimate tensile strength when it frays
  • Harder to spot damage on twisted rope
  • Requires a much larger bending radius
  • Unwinds when a load in placed on it, unless it is anti-rotational rope; automatically gets longer when it unwinds
  • Knots can reduce the ultimate tensile strength by a huge margin
  • Nylon or other man-made fiber webbing is much stronger
  • Nylon can degrade with exposure to UV light, oxygen, some acids, solvents with long exposure

November 30, 2015   Comments Off on Rigging (suspension and moving of machine tools)

When CNC is overkill

A great example of what can be accomplished without CNC.

Youtube Link – Paoson Luthier and Woodwork – 3D Router

direct links: PlansInstructable.

 

November 4, 2015   Comments Off on When CNC is overkill

MIT TechTV Machine Shop Videos

From the MachinistBlog.com

 

Machine Shop 1 – Machining Skills for Prototype Development (Length: 40:32)

  • Basic tour of the machine shop
  • Layout techniques (including transferring hole locations)
  • Basic tools: drill press, band saw, belt sander and grinder
  • Locating and drilling holes (includes using a center finder and deburring)
  • Tapping holes (including using a tap guide)

Machine Shop 2 – Machining Skills for Prototype Development (57:33)

  • Drilling holes
  • Special drills for plastics and hard or abrasive materials
  • Drill press limitations
  • Bandsaw
  • Suitable speeds, feeds and materials
  • Bandsaw setup
  • Using the drill press vise

Machine Shop 3 – Machining Skills for Prototype Development (30:02)

  • Good practice – clean up
  • Small belt sander configurations
  • Grinder operations and materials
  • Deburring and buffing
  • Finishing techniques

Machine Shop 4 – Milling Machine 1 (50:33)

  • Parts and controls of a Bridgeport Mill
  • Quill feed
  • Axis handfeeds (11:20) backlash explanation (12:15)
  • Gib locks (14:40)
  • Power feed (18:33)
  • Digital readouts (21:07)
  • Milling machine set-up – squaring/tramming  the head square (22:37)
  • Squaring the vise – adjusting the vise so the stationary jaw is parallel to the bed (32:33)
  • Milling machine accessories and workholding techniques  (41:15)

Machine Shop 5 – Milling Machine 2 (1:03:33)

  • Square and hex collet blocks – used to hold/clamp parts to machine features on 4 and 6 sides of a part respectively (1:02)
  • V-blocks  (2:10)
  • Hold-down clamps – used to hold large or irregularly shaped parts (3:40)
  • Using angle blocks – used to hold materials to machine features not perpendicular on a part (6:15)
  • Drill press vise – using a vise within a vise (8:29)
  • Lathe chuck with vise  – can be used to hold parts in the milling machine (11:11)
  • Double sided tape – can be used to securely hold a part without distortion (12:00)
  • Squaring high aspect ratio parts  (16:02)
  • Right angle attachment (23:04)
  • Slitting saws – used to cut slots/slits/features in a part (33:21)
  • Rotary table – used to machine circular parts, grooves, circles, and segments (41:16).  A dial indicator (43:20) or Coaxial indicator (47:25) can be used to square/center the table to the X & Y axes
  • 5C collet indexer – used to hold collets and to position parts in up to 24 positions  (52:42)

Machine Shop 6 – Milling Machine 3 (42:36)

  • Squaring a part  – machining a piece of metal so all of the surfaces are flat, perpendicular and milled to the nominal size (1:00). Also covers using a fly-cutter (4:50) and deburring (8:40)
  • Squaring a plate (17:52)
  • Using the edgefinder (32:00)
  • Drilling holes with a mill (35:32)

Machine Shop 7 – Milling Machine 4 (23:07)

  • Reaming holes  (1:00)
  • Boring holes with a boring Head (3:04) – also covers using Plug Gages to measure hole sizes (8:54)
  • Milling a slot (10:45)
  • Milling a shoulder, conventional and climb milling (17:11)
  • Cleaning the machine (21:05)

Machine Shop 8 – Lathe 1 (42:37)

  • The Lathe components
  • Turning tools  (6:40)
  • Turning and facing (11:04)
  • Cutting off a part (22:45)
  • Drilling (32:20)

Machine Shop 9 – Lathe 2 (46:15)

  • Tapping
  • Boring (7:31)
  • Knurling with a bump knurler (15:30)
  • Cutting tapers with the vompound (22:21)
  • Turning shafts – using a live center (26:18)
  • Single point thread turning (31:03)

Machine Shop 10 – Lathe 3 (29:00)

  • Lathe chuck
  • Lathe arbors (6:42)
  • Turning between centers (15:40)
  • Face plate irregular shapes (19:00)
  • Face plate thin materials (21:13)

January 30, 2015   Comments Off on MIT TechTV Machine Shop Videos

Dan Gelbart : How to Build Stuff

Dan Gelbart has an excellent and well-presented series on YouTube on machines and prototyping. It`s a short course on how to build stuff aimed at students, researchers and others who are not machinists by trade. It`s applicable to prototyping and limited production with enabling technology in 18 parts, which I’ve listed links to below. Note: the chapters were obviously shot out of sequence, as there is referral to `as we`ve seen before` when we have not. It`s not that bothersome.

Running Length of all 18 videos are approximately 5 hours, 20 minutes

1 – Introduction (wide range of items)         10:29 min

  1. Prototype Enclosure discussions, best practices, mostly on waterjet works
  2. What Waterjet manufacturing can produce

2- Safety       19:15 min

  1. Workshop Rules
  2. Unexpected Safety Hazards
  3. Woodworking Tool Hazards (focuses on Table Saw)
  4. Grinder Hazards (don’t use the same wheel for Aluminum and Steel; can you say Thermite?)
  5. Hand Tools – Hammering Hardened Surfaces, how to identify
  6. Lathe Hazards (you’ll look at your fingers afterward), discussion of “grabby” materials (Brass as an example)
  7. Drill Press Hazards (demonstrated on a vertical milling machine)
  8. Machine Press Hazards
  9. Machine Metal Brake Hazards

3- Waterjet  10:15 min

  1. Drool-worthy Waterjet unit (alas, not shown working)
  2. Plasma Cutter Operation, Practices and Demonstration

4- Bending Sheet Metal        11:47 min

  1. Discussion of Press Brake Setup, Best Practices, Operation, Limitations
  2. Work Hardening, Annealing
  3. Gooseneck vs Regular Profile Dies
  4. Rib and Bend Rigidity

5- Spot Welding      30:51 min

  1. Machines, Construction, Features, Safety
  2. Time and Current Settings
  3. Determine Proper Weld Strength
  4. Theory of Operation, Laser Vs Current Welding
  5. Adjustable Current vs steady state
  6. Power Level Sizing (his is 2.5V at 5000A)
  7. Weld Capacity vs Power
  8. Range vs TIG Welding
  9. Welding Captive Hardware
  10. Waterproof Welding
  11. Hardware Welding (Studs, Threaded, Ball Bearing)
  12. DIY Electrode Material Selection (Copper Tungsten or Copper Chrome)
  13. Spot Welding Pivots
  14. Preventing Weld Divots
  15. Welding Unweldable Metals (Phosphor Bronze, Beryllium Copper, et. al.)
  16. Work Holding Welding

6- Coatings      21:52 min

  1. Sandblaster Operation, Upgrades (Diamond Coated Windows, Vacuums)
  2. Coating Theory of Application (Mechanical, Chemical Surface Energy Effect)
  3. Surface Preparation (Sand Blasting, Bluing or Oxidization, Cleaning Agents, Wetting, Volatile Evaporation)
  4. Time Limitations on Surface Preparation, Discussion of Gumming Solution
  5. Electrostatic Painting and Powder Coating: Costs, Practices
  6. Go-No Go Testing

7- Presswork     16:23 min

  1. Machine Press Safety and Operation
  2. Ductile vs Hardened Material Safety
  3. Minimum Sample Size to Prevent Damage to the Press
  4. Excellent discussion about formulation of lightweight strong structures, closed structures
  5. Press vs Shear

8 – Enclosures     33:36 min

  1. Complete Enclosure Build
  2. Error Repair (Spot Weld)
  3. Metal Brake Order
  4. Symmetric vs Mirror
  5. Build Techniques
  6. Layout Processes
  7. Registration Across Bend Lines
  8. Powdercoating Best Practices

9 – Materials     35:02 min

  1. Minimal supply of materials he thinks useful:
    1. Bearing Bronze:
      1. Make anything sliding on steel is bronze and steel, not brass
      2. Plates and rods
      3. Lubricated against hardened steel, lasts forever
    2. Sheet metal:
      1. Cold rolled mild steel; strong, cheap, readily available, spot welding, bending, waterjet. Stock gauge 18 and gauge 10 if nothing else; 10 for brackets, bases assemblies
      2. Stainless: 300 series cheaper, gauge 18 to gauge 12.
    3. Spring Steel:
      1. Buy spring stock from sidecuts.com; send ends of rolls very economically
      2. Type 301 full hard. Series 300 in spring temper can be bent and shorn. 400 series cannot be bent or shorn. full hard or 3/4 300 series recommended
      3. 17-7 Stainless spring comes annealed; heat treat much harder and springy than the 300 series. Heat 750 and cool, heat to 580 or so, cool down again.
    4. Spring Wire:
      1. Needs one heating cycle, not two
      2. 480C for one hour typically; temper and annealing determines heating cycle
      3. Stock 3-4 sizes of wire, and make your own springs, both compression and tension.
      4. Handmade mandrels with power drill
      5. Heat in oven or torch for hardening
      6. Examples of construction and finishing springs (tension, compression)
      7. Faster to make it than buy it
      8. Two types of wire
        1. Piano or Music Wire (carbon steel and no corrosion resistance) cheaper
        2. 17-7 for corrosion resistance
    5. Plates and bar stock
      1. Free Machining. Both steel and stainless have alloying elements to make it a little more expensive, but saves dramatically in surface finish and machining time
    6. Aluminum:
      1. Large structures and heat sinks;
        1. copper better for heat sinks but very expensive. Aluminum good alternative
        2. If had to stock one size, gauge 10 or 12 in 5052 Alloy
          1. 5052 does not crack, unlike 6061 (heat sinks are bent for surface area)
    7. Plastics
      1. Polycarbonate (Lexan)
        1. Completely shatterproof
        2. Bendable
        3. High temperature
      2. Acetal (Delrin)
        1. White and Black
        2. Machines bet of all plastics
        3. Fairly inexpensive, available in many shapes
      3. Phenolic Laminate (Garolite)
        1. The original plastic (Phenolic Resin) and cotton layered together
        2. Does not easily deform with heat and no creep (composite material)
        3. Does not break, threads well
        4. Self-Lubricating. Make moving parts and impregnate with oil, used heavily in gears and bearings
        5. Combination of steel gear against phenolic gear; lasts forever
      4. Teflon
        1. High temperature
        2. Good lubricity
        3. Cold flows, weak, does not hold threads
        4. Excellent Electrical insulative
      5. PVC and ABS
        1. Glue-able
        2. Structural
        3. Piping
        4. Low temperature material
        5. Weak
        6. Cheap and readily available
        7. Does not hold threads
      6. Polyamide (Dupont Vespel or Kapton)
        1. Tape, Rods, Plate
        2. 300C tape, electrical isolation
        3. Excellent pierce resistance
        4. Virgin brown or carbon filled for color or bearing material
        5. Very Expensive
    8. Threadlocking Material
      1. Locktite
      2. Can cause cracking in plastics
    9. Wax
      1. For cutting lubrication
      2. Can be used to machine Aluminum with woodworking tools (not generally recommended due to higher speeds of woodworking blades)
      3. Does prevent Aluminum from welding to tools
  2. Steels, Hardenable
    1. A2 Air Hardening
      1. No quenching needed, which puts distortion in steel
      2. Optimized for very low dimensional change after hardening, unlike oversizing and grinding the others
      3. Practically net shape
      4. Outer layer may decarburize (lose hardness) without inert atmosphere oven
        1. Wrap it in paper and stainless foil; the small amount of air inside will be used up when the paper decarburizes, long before the steel does, leaving no oxygen for surface change
    2. 4-40 Hardenable Stainless
      1. Medical devices
      2. Not as corrosion resistant as 300 series
      3. Hardens sames as A2
    3. High Speed Steel (HSS)
      1. Cutting tools
    4. Regular Carbon Steel
      1. Requires Quenching, other issues
    5. How to tell Steel apart by Spark Test
      1. Regular Mild Steel: sparks appear as few sparks and no star at end
      2. Carbon Steel: Many sparks, end of spark there is a star
      3. A2: Different spark, dimmer, no star
      4. HSS: Almost no sparks, darker, red
      5. 4-40: No sparks at all
    6. How to Harden Steels
      1. Best to use Kiln or Oven
      2. Can use Torch
        1. Use thermal insulator to trap heat
      3. Case Hardening vs Total Hardening
      4. A2
        1. White Hot, let it cool down 950C, not so critical
    7. Tempering
      1. Hard as a file but very brittle
      2. Tempering is a trade off between hardness and toughness
      3.  Narrow temperature range: 220C to 300C
        1. Every 10C makes a huge difference
        2. 250C Rockwell RC60, common
        3. 300C Rockwell RC56C, impact resistance toughness
      4. Judging heat by color in steel (Straw to Light Blue)
        1. Straw: 220C Rockwell Hardness RC 60
        2. Dark Blue: 270C
        3. Light Blue: 300C RC 56C
        4. Grey: Overheated
      5. Small flame, rapid movements, do not overheat
      6. If the part has an asymmetric shape, direct most of the heat to the thick part; more mass, longer application
      7. Hear by the sound the file does not bite; do not overdo it.
    8. Braze discarded carbide to Steel for homemade cutting tool
  3. There is about six minutes of blank space after the credits, which has some titles and audio from Chapter 11; obviously errors in edit.

10 – Flexures      12:54 min

  1.  Classic Flexture: big block with linear stages and reduction levers
  2. 5:1 reduction lever with pivot, wiggle bars to eliminate rotational forces (decouple the rotational force), connects to 3:1 lever with micrometer screw, connected to a classic linear deflection stage
  3. Pre-drill the holes, since how well it moves depends on exacting duplication of pivot points.
  4. 2mm travel following a straight line to 1 micron
  5. Capacitance meter at 10 nanometers per division shows movement without any backlash
  6. Tutorial unit is made of Aluminum to show thermal instability, shows 100 nanometer drift just from radiated body heat
  7. Real Life examples should be Glass, Quartz, Invar
  8. Smallest you can make on a waterjet example 0.3-0.4 mm wide; narrowest parallel you can reliably make (example of Beryllium Copper)
  9. Limited by elastic range of the material: steel is 1%. Make the flexture parts of Nitinol (Nickle Titanium, `memory metal`), which has an elastic range about 10x that of steel.
  10. Too expensive to do the entire unit of Nitinol, so composite design of Stainless Steel and Nitinol.
  11. Talks about build design methods of the above (design, measurement of parts, welding, spacing, adjustments afterwards)
  12. Talks about measuring deviation in linearity with a laser, autocollimator.
  13. Flex Pivots: used when you don`t need a full circular movement
    1. Center of Rotation is fixed for small angular movements, large angles it does
  14. General advantages of flexures: nearly free cost (if using waterjet) No lubrication, No wear, no backlash, if designed right, unlimited flexing (generally do not exceed 2/3 elastic range)

11 – Non-Metals     17:10 Min

  1. Plastics in general:
    1. Are unstable unless heavily filled
    2. They can absorb water via humidity
    3. Soften with temperature
    4. Much larger thermal expansion co-efficient than metals (range of 10-23 for metals, 50-150 for plastics)
    5. An example: a plastic sheet bolted to a metal sheet and placed in the sun will generally show the plastic sheet buckling; 100ppm over a meter is .1mm per degree; 10 degree will be 1mm movement, causing a buckling.
    6. Best design is mount one side with fixed points, other with slot and washers to account for this movement.
  2. Polycarbonate (GE Trade Name Lexan)
    1. Shatterproof and ductile, can bend like sheetmetal
    2. Does not hold threads; inserts or helicoil are needed
  3. Ceramic Materials: High temperature and electrical insulator
    1. Machinable Ceramics (comparable to Alumimum), call can be cut, tapped,
      1. Micalex (Glass Powder and Mica): works up to 1000C, can file it like metal, good finish, becoming rare and expensive
      2. Micor
      3. Machinable Alumina (can be fired to increase hardness; example shown, needs diamond tooling), not a thermal insulator
      4. Boron Nitrite/White Graphite; self-lubricating and take high temperature, low thermal expansion, not expensive. Unfortunately not that strong
      5. `poor man`s ceramic`: Slate. Machinable like Micalex and Boron Nitrate. Will delaminate with high temperatures; design with this in mind (example given, use in compression).
      6. Zirconia: one of the highest strengths, melting points, hardness, excellent thermal insulator. Can buy it in blocks in `green form` and further harden (fired). Very similar to Tungsten Carbide in properties. Cutting tools can be made of it. Expensive, however. Large Shrinkage factor. Approx. 17%, omnidirectional. Finished with Diamond tooling.
    2. Glass
      1. Unusual property: Make a prismatic shape and draw the glass, it will maintain the shape (providing proper temperature maintained). The accuracy is 1 micron in maintaining the shape.
      2. Shows example in plasticine made by original and drawn profiles; they match in profile.
      3. Main use of the property is to make cylindrical lenses.

12 – Plastics Vacuum Forming and Casting     12:00 min

  1. Vacuum Forming: Heater above the plastic, or heat the plastic in oven
    1. Lexan doesn`t soften easily, difficult to do. Example shown
    2. Needed: Bottom mold, top frame, heated sheet of plastic, any source of vacuum (vacuum cleaner).
  2. Replication of parts in plastic
    1. Methods
      1. Desktop Printers (poor finish)
      2. Molding
        1. Filled plastics need molding
        2. Silicone rubber moldmaking material used
        3. Can mold undercuts and pins
        4. Ability to copy goes down to molecular resolution (LP record had a 50 micron groove depth with 100dB dynamic range; faithfully reproduced)
        5. Not so good dimensionally, need screening to make it stronger
        6. Mixing viscous materials need degassing in a vacuum chamber, or pressure chamber (pulls out all air or squashes all air)
        7. Example of resin use: degass the resin, insert feed tube into resin, other end into mold, pulls resin into the mold. cure it
        8. Examples of molding design, pigmentation, resin impregnation, can melt some molten metals in silicon molds (red silicon and Zinc-Aluminum diecast)

 13 – Adhesives and Large Structures (with focus on waterjet production)      25:54 min

  1. Two adhesive bonded metal joints shown: sheer and peel test joints
  2. If you need longer working time on 5 minute epoxy, mix it on a chilled piece of metal with good specific heat
  3. How to build large structures with waterjet (generally temporary)
  4. Cheapest way is still welding
    1. Hard to learn to be a good welder
    2. Causes very large distortions, which then needs machining.
    3. Only way for strength; if only stiffness needed, adhesives
  5. Make end plates from Aluminum plates, columns from pipes, assemble with adhesive bonding
  6. Take advantage of waterjet`s small taper (50 microns), temporary assembly made easy
  7. Heat up the whole structure and knock it apart when the experiment is over (150c will disassemble epoxy)
  8. Why not use T-Slot members. Those types of structures are not rigid compared to adhesive bonded (screw will stretch since there is a huge lever). Great for enclosures without any accuracy.
  9. The above is an excellent reason NOT to build a CNC machine out of such
  10. Example of waterjet wedge locking edges
  11. Assemble the entire thing on a granite Surface Plate for registration for co-planar
  12. Flexture Clamps: Machine slot with room for a plug (tap with tapered pipe thread), turning the plug will lock sliding parts in. No localized load (gives example about setscrew deforms and puts all the load on one point, cracking)
  13. Flexture clamps are superior to setscrews; many tons of force generated through one turn (leverage of threads and lever of wedge.
  14. Adhesive Joints:
    1. should be designed to work in:
    2. Shear mode best (puts stress on entire joint at once, lowest stress concentration per area). Shows his model breaking at 2 tons (scale model), talks about scaling increasing with area)
    3. Tension second best, but much weaker
    4. Never in peel mode (shows example and it has no strength). Puts all the load in one line, geometrically zero area, maximizing stress
    5. Take care to verify modes won`t convert to peel mode (shows examples)
  15. Adhesives: 4 types needed in a lab
    1. Outgassing from Adhesives; accelerate via baking. When building lasers, none of the below applicable
    2. Epoxy
      1. Zero strength in peel. Epoxy is inflexible, so stress nearly infinite
    3. Silicone RTV
      1. Only one that can take high temperature among common adhesives
      2. stays elastic forever
      3. tenacious bond to glass and ceramics. Does not need surface preparation for those
      4. Peel strength is better since stress in over larger area
    4. Polyurethane (example Gorilla Glue)
      1. Bit flexible
      2. Bonds tenaciously to rubber and flexible materials, unlike the rest
      3. Certain types designed to form up by themselves
      4. Excellent for bonding sheets together, good peel strength, has to cure overnight
      5. Same as silicone for peel
    5. Contact Cement
    6. Acrylic Adhesive: has properties in-between Polyurethane and Epoxy
    7. Cyanoacrylics (superglue)
      1. Not very good because they are very rigid, can break on shock load
      2. Are very good for rubber due to instant bonding
      3. Emit gas slowly, so optics will fog and cover with white film
      4. Gas will craze some plastics, causing cracking
  16.  Temperature Expansion and Adhesives
    1. Glass and metal have different expansion
    2. Thermal expansion of the adhesive can distort optical measurements
    3. Bond a parallel surface, the slight expansion doesn`t generally matter, but a wedged adhesive surface will cause angular errors, increasing with distance

14 – Brazing:  14:05 min     Three dimensional structures needing rigidity, solid, heavy, machinable need to be made from solid. Methods used to produce three dimensional solids

  • Milling from Billet: Expensive in material and machine time, better to produce a `near-net` shape and machine from there.
  • Casting: non-trivial in home or lab environment. Requires patterns, pattern sand, ovens or kilns. Most of the large world machinery is made from castings
  • Weldments: Requires welding skills, heavy distortion dimensionally due to weld bead shrinkage, cannot weld very dissimilar metals
    • There are exceptions: A Laser welder ($20 000) Can weld in hard to reach places, and can weld dissimilar metals due to high energy concentration, short time frame, no need for inert environment
    • Not generally suitable for large scale use
  1. Building segments up by Brazing:
    1. Brazing can join dissimilar metals by choosing compatible filler materials to the two metals with flux (silver copper typically)
    2. Flux wets metals and protects metals from oxidization. Two general types: White Flux (borax), common for non-ferrous and iron, and Black Flux (likely Fluorite salt), used for stainless and harder to braze since it is more aggressive
    3. Discusses proper Brazing methods (making fillets, applying wire, flux), vertical joins, brazing on two planes, gap limitations, wire forms (wire, foil)
    4. Brazing via oven (too high temperature causes excessive oxidization, too low and poor liquidity). About one hour per kilo for temperature soak
    5. Claims bit stronger than casting (compares to cast iron)

 15 – Mill and Lathe     9:29 min

  1. General Purpose Mill/Drill
    1. Drilling Vise: quick acting, but not stiff enough for milling
    2. Milling Vise: precise, rigid
    3. Belt Drive units (good for quiet, reliability)
    4. Variable Frequency Drives (VFD): excellent for speed adjustments
    5. Talks about home made laser centre finder (according to my invesigations, they`re not precise enough for a lot of work, which is why they`re not sold in place of wigglers, edge finders, co-axial finders and such). Claims 50 micron accuracy (0.002 inches), which matches my own investigations.
    6. Desirable to standardize on one collet size (amen!). buy tooling with the same shank
    7. DO NOT use milling cutters in a drill chuck; NOT rigid enough, they will vibrate out and cause damage
    8. Key Chuck units have disadvantages: Key can fly out if forgotten, get lost, do not tighten the same on each segment.
    9. Keyless chucks open when run in reverse unless very tight.
  2. General Lathe
    1. 3 Jaw Chuck is quick to put a part in, but has no ability to handle adjustments for out of round stock, runout, cannot register the part exactly the same if it was removed. Cannot grip square items
    2. Best to buy a 4 Jaw Chuck, can handle out of round, square, hex, adjust for zero run out, can remove parts and re-register, does take longer.
    3. Recommends video camera for tooltip. Uses backup cameras and cheap screen. 100x magnification. Buy rear view kit. Change lens distance for magnification

 

 16 – Machining (will only cover some basics)     16:30 min

  1. Locating A Hole:
    1. Centre punching: Scribe Lines (carbide scriber, hardened caliper jaws) don`t locate by looking at the lines, locate by feel: where the scribed lines grip the punch
    2. Use a contrast medium to highlight the lines (dry erase, Sharpie, Dykem layout fluid)
  2. Drilling a Hole
    1. Talks about a centre drill for starting; while acceptable, they are fragile; should really use a spot drill. The centre drill is meant for making holes for lathe live and dead CENTRES, which have a 60 degree angle. A spot drill is stiffer, can be run at one correct speed. Most centre drills are run either at a speed too low for the tip diameter or too fast for the countersink portion
    2. Talks about the usefulness of a Digital Read out (DRO)
    3. Start with smaller diameter hole, enlarge. The web of the drill bit will walk on the centre punch mark if there isn`t a guide hole.
    4. Use a deburring tool to remove the burr from the hole; talks about burr size vs tool sharpness. Deburring interior surfaces: describes a reworked wood chisel to shear off the burr
  3.  Reaming
    1. A ream is a tool with cutting flutes (runs one direction) precise in dimension. it is a tapered tool (to allow ease of start), and unsuitable for blind holes (those that stop in a material and do not protrude through both surfaces)
    2. Use a calibrated ream to precisely enlarge the hole, or a boring head (drilling is for clearance generally). Boring has similar accuracy as reaming, but variable in size. Useful for bearing surfaces
    3. .1 or .2 mm undersize the drill to accurately enlarge the hole
    4. Use lubricant to leave a good surface, especially on aluminum, which is a `gummy` material and can tear/stick to tooling surfaces
    5. Runout isn`t important as the reamer will match the hole
    6. To avoid precision interlocking condition of parts, machine a groove in the shaft since a ring can always tilt in precise bore; machine a resess 1mm back of full diameter, machine a lesser diameter a few mm back, and then leave the rest. The groove allows some axial shift to start, and then allows self alignment with shaft advancement.
  4. Boring
    1. Enlarges an already existing hole
    2. Suitable for blind holes
    3. Special sized holes that are difficult to get
    4. Rigidity of the machine is very important when boring, due to the single point cutting. The tool will deflect, unlike a drill which would bear cutting forces equally on two points
    5. Final passes needs to be done without re-adjustment to allow for tool spring/flexure.
  5. Milling a Housing From Solid
    1. Talks about Labyrinth seals
    2. Ball Nose Endmills vs Normal Endmills
      1. Ballnose removes metal much faster than normal, and doesn`t have a sharp edge to break. Specify ballnose if you don`t need square corners
      2. Tool deflection has to do with stiffness. Formula for stiffness Diameter power 4 to Length power 3. A mill that is 2x the diameter and .5x the length of another, the stiffness will be 128 times higher (a 7 power factor). How to use the biggest diameter and shortest mill.
      3. Split the housing in the middle if possible, to keep the the above in mind. Thin and thick will mean much less rigidity in one endmill, slower feeds, more chatter.
      4. Thought process for clamping to maximize time. Some good thoughts here. Everytime you re-clamp, you lose all registration

17 – High Accuracy     28:25 min

  1. Normal parts machining generally not that accurate
  2. Dry erase marker used to show high spots
  3. Good technique shown
  4. If the tools touches on the whole surface, it won`t wear due to hydrodynamic forces with lubrication, forces are evenly supported, lowering stress points.
    1. Shows this principle with a hard drive and electrical contact and sliding granite surface plates; excellent examples.
  5. Surface Grinding
    1. Clamping distorts work, surface grinding needs less clamp force and grinding tool has less force
  6. Lapping
    1. Small Parts, only parts that can be moved in two directions; Cannot a lap a taper
    2. Honing is similar, but uses a stone
    3. He`s using sandpaper; a traditional lap is a softer metal embedded with harder abrasive material; talks about this. Use a softer material that cannot embed in the material
    4. Lapping compounds discussed
    5. Move the part in figure 8 pattern, no corner pressure unless correcting for parallelism
    6. Wet Sandpaper on Surface plate (180 – 220 typical – 400)
    7. Remove all machining marks
    8. Danger in lapping is rounding; attach two dummy pieces to prevent corner rounding
    9. If parts just need to fit and not slide, remove excess material from centre to speed job
    10. Dry erase too crude for precision; use Dykem, or look for the shiny spots (burnished areas are the high spots)
    11. Lapping holes: split lap
    12. Lapping cylinder: Split external lap
  7. Scraping
    1. Small parts and large
    2. Don`t have to move the part
    3. Touch to reference surface, remove the high spot with a tool (ground 90 degrees or close)
    4. Change directions by 90 degrees
    5. Test
    6. Scraping is an art, and it is easy to cause more damage than you correct
    7. Hand and Power Scraper (Biax) demonstrated
    8. Re-scrape at 90 degrees to original direction
    9. Discusses `fake` scraped surfaces
    10. Discusses and gives examples of making something square, parallelism, roundness vs runout, vs trueness of rotation.
    11. Principle of Reversal Methods: EXCELLENT.
      1. How do you measure without reference
      2. Set a dial gage to scan the surface; write value every cm. Flip the part, scan it from underneath.
      3. The original errors were the sum of the irregularities in the two surfaces (table and surface). Underscanning separates the irregularities.
      4. Powerful concept: Can separate runout from roundness, straightness, determine if a circle is divided accurately

 18 – Design     23:22 min

  1. Strength vs. Stiffness
    1. Classical mechanical engineering mainly concerns with strength
    2. Instruments and machine tools worried of stiffness
    3. Examples of why stiffness matters (microscope and lathe bed)
    4. Stiffness determines dimensions, not strength
    5. Example with pre-loaded metal bar and rubber band bar
      1. Two bars held together with rubber band have only the strength of the rubber band, compared to a solid bar
      2. Same two bars held with rubber band have nearly twice the stiffness of the solid bar, because it acts as a solid
    6. How to mount bearings and pulleys
      1. Pully
        1. Setscrew will damage shafts, which will interfere with sliding surface; File flats or install roll pins
        2. Flexure based clamping: Example is split piece, distribute the load, or use a taper plug idea
      2. Bearing
        1. VXB.com is good house; 8mm ID by 22mmOD ABEC 5 compatible skateboard bearings are very good; huge supply
        2. ABEC 7 is a company supplying bearings, name NOT the rating.
        3. Bearing is designed to have play or lash
        4. Designed to work in preloaded pairs: Excellent examples
          1. Sleeve shaft
          2. Put spring or Wave Washer
        5. Installing bearings in sheet metal
          1. Additional plates to contain the bearings
        6. Talks about Taper Fasteners for low precision alignment
        7. Talks about Line Boring
      3. Snap Rings for retaining bearings
      4. Methods of aligning after assembly
      5. Locktite good for bearing housing gap filling. 150C softens it
  2. Design Philosophy
    1. How do you approach designing the part
    2. Hierarchy of design (ease of production)
      1. Can you make it of wire (wire hinge bottle cap example); zero waste, minimal finishing, CNC bends wire cheaply. Example given
      2. Can you make it of sheet metal (adjustable arm laminated example) total friction multiplied by surfaces; multi disc clutch example. Excellent
      3. Can you make it of solids (start looking at accuracy and precision)
        1. What are you after. Stiffness or strength
        2. Are they adjustable or not
        3. Rely on brute force precision means cost (lapping, scraping)
        4. Can achieve precision feel by having one side accurate; setscrew example with and without ball bearing
        5. Is there a place where precision parts can be inserted vs the entire thing being precise
        6. If only want the feel of precision, insert precision. gives examples
        7. Is this an instrument with no load or machine with loads
          1. Kinematic mount for instrument, resting on small points. Point contact by definition. Cannot carry any load
          2. Machine tool relies on full surface bearing overdesign
        8. Design of a product
          1. Lifetime costs (maintain, replacement parts)
          2. Is there electrical cabling needed, where do they go. Anything electrical lay out everything built in design
          3. Hydraulic and Electrical tubing. Put the electrical above the hydraulics
        9. Atheistic
          1. Something is 100 percent functional it is beautiful
          2. Design a part with no extra metal it is beautiful
          3. Example of a classical bow

 

 

January 14, 2015   Comments Off on Dan Gelbart : How to Build Stuff

Digital Read-Outs (DRO)

While my machine went right to CNC, and I use the integrated program for read out, there is a healthy environment for manual or precision DRO units.

Basic Categories

– Capacitance: lowest cost, lowest resolution, accuracy, and repeatablity

– Magnetic : middle, quadrature to achieve resolution. Can be cut and custom fit

– Optical/Glass: higher, direct reading, bulkier, cannot be shortened, can be affected by dust and coolant

Costs range from mild to extreme.

For this class of mini-mill, with the typical positional accuracy in ACME/transport grade screws, several claim the magnetics are good enough. However, to achieve the stated accuracy, they are quadrature units and interpolated. For true accuracy, Glass Scales are the way to go, but they have their own limtations; cost among them.

 

An excellent source of information on DRO`s in general, and the Android Open Source DRO project: TouchDRO (Wireless DRO)

Yuri`s Toys excellent primer on the differing types of scales : Selecting Scales for DRO

Home Machinist on same

I`m still converting my archives to web, so more to come.

 

January 10, 2015   Comments Off on Digital Read-Outs (DRO)

Machining Blogs and Forums

Various places I have gleaned good information from

Machinist Blog – Aimed at plans, projects and how-to`s for home machinists

Hobby Machinist – Forum for all levels; the `friendly`forum

CNC Zone – The most ungainly collection of forums this side of …anything. But useful

Practical Machinist – Professional Machinist level forums

Home Shop Machinist – Magazine and Forum

 

 

 

 

 

January 9, 2015   Comments Off on Machining Blogs and Forums

Milling Tools: Rake Angles

Random information I thought it a good idea to collate.

From Wikipedia: Rake Angle

Rake angle is a parameter used in various cutting and machining processes, describing the angle of the cutting face relative to the work. There are two rake angles, namely the back rake angle and side rake angle, both of which help to guide chip flow. There are three types of rake angles: positive, negative, and zero.

Generally, positive rake angles:

  • Make the tool more sharp and pointed. This reduces the strength of the tool, as the small included angle in the tip may cause it to chip away.
  • Reduce cutting forces and power requirements.
  • Helps in the formation of continuous chips in ductile materials.
  • Can help avoid the formation of a built-up edge.

Negative rake angles, by contrast:

  • Make the tool more blunt, increasing the strength of the cutting edge.
  • Increase the cutting forces.
  • Can increase friction, resulting in higher temperatures.
  • Can improve surface finish.

A zero rake angle is the easiest to manufacture, but has a larger crater wear when compared to positive rake angle as the chip slides over the rake face.[1]

From The Home Shop Machinist: Carbide Rake

It’s my impression that the positives are recommended for home-shop and relatively small machine use. They take less HP and work better with less-than-rigid machines. The negatives are better for high-production-rate, high-metal-removal applications with heavy machines and rigid automated machines. That’s not a hard-and-fast rule, of course, but that’s generally it, and why people here tend to recommend the positives.

A carbide inserts cutting edge is pretty fragile. By having it at 90° this strengthens the edge as much as possible. The inserts are negative to give the edge more strength – carbide is brittle and the acute angle formed by positive rake doesn’t last well. Negative does require more cutting force meaning more hp and rigidity (hence the common recommendation its not the best choice for light home shop machines), but creates longer lasting tooling when using carbide. Negative or neutral rake inserts are also best on grabby materials.

 

 

January 6, 2015   Comments Off on Milling Tools: Rake Angles

The Virtual Machine Shop – Wikipedia for Machining

Lovely: LINK

November 29, 2014   Comments Off on The Virtual Machine Shop – Wikipedia for Machining

Excellent Post of the Costs of Supporting Hobby Level CNC and A Guide to CNC (from a moldmaking perspective)

April 23, 2014   Comments Off on Excellent Post of the Costs of Supporting Hobby Level CNC and A Guide to CNC (from a moldmaking perspective)