Process Planning

Host  Gene Nieghoff

September 24th 2005

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The meeting was held at Gene's shop.  The meeting was a discussion of planning your process. Gene shared several nuggets of good practice.

1. Remember the 3-2-1 rule. 3 points make a plane. 2 points make a line, and 1 point is a point

2. Establish a 3-point plane using a plate and 3 pins in a triangular pattern to locate the primary reference surface. Tool plate is a good candidate for the plate to mount the pins.  Capital Metals in Phoenix has scrap pieces of various thickness by the pound. This material is ground both sides and is suitable for this purpose without further grinding. Gene uses a brass pin he buys. Good quality round head rivets will work fine.

3. Always put the same surface in the reference position with the same face against the fixed vise jaw

4. Maintain a consistent zero point for locating measurements. For manual machining the upper left hand corner is the normal zero point

5. Always mark the reference surface

6. Always start the process at the most critical dimension point. This saves wasted effort if this part of the work is compromised.

7. When machining a precision hole, the best way to get a straight and true hole is:

        Step 1 center drill the hole

        Step 2 drill the hole .015" undersize

        Step 3 bore the final dimension of the hole Boring is the most accurate way to finish cut the hole

Ream the final hole for finish if needed. Remember a reamer will follow any inaccuracy in a drilled hole and increase the error

8. If drilling a depth of greater than 1 diameter of the cutting tool, use the pecking technique. This is going in & out of the hole several times. This produces a straighter hole.

9. If drilling thru thin material, clamp it to a backer board or sandwich it between boards to mitigate the tendency of the bit to grab as it goes through the back of the work piece.

10. Plan your feeds and speeds before you start the work.

11. In steel, watch the color of the chips. When using HSS cutting bits, do not allow the chip color in steel to go darker then light blue. This allows the fastest stock removal  without ruining the cutter

12. If aluminum galls on your cutter, increase the cutter speed and cut down the feed.

13. When using a mill with a vise, indicate the vise at the start of each day to insure proper alignment.

14. When using hot rolled material for your project, plan the stock size to allow removal of the surface material to reach virgin metal. This can be as much as .093" of  contaminated stock in the surface layer.

15. When using cold rolled steel, stress relieve the material before starting the work. The recommended method is to heat the work piece to 900 degrees (red heat) and bury it in sand to cool naturally. Do not rush the cooling by quenching. Do not use wet sand.

16. When using a mill, the cutters tend to cut oversize.  A 2 flute cutter will cut .004" oversize if the feed is wrong. A 4 flute cutter will cut .002" oversize.

17. Use coolant to get the chips out. Chip load hurts surface finish. Mist coolant is good but you risk breathing the fluid. Flood coolant is good. Watch for rancid coolant if kept too long.  Brush on coolant is a good home shop solution. Vortex coolers are a great solution, but take a lot of air, and are expensive. Check the Reid catalog for air coolers and a host of other set up fixture supplies. Use black sulfur oil as coolant on manual machines when cutting steel

18. Use the side of the end mill to do as much of the cutting as possible

19. When choosing cast iron for your project, G3 0r Mehanite cast iron material is the best choice for machineability.

After the meeting another BBQ event was held.

10/04/05