Specialty Shop Training

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Hex Broach

This tool is used on the mill or lathe, and cuts a hexagonal shaped hole with sharp corners. The team has a 1/2" hex broach, which is kept in the bottom drawer of Jerry the Tool Chest. Note that our broach is a Slater brand broach (not pictured in these videos), but it works the same way.

5 steps to using the hex broach

Step 1: Pre-drill a hole at least as large as the minimum distance across the broach tool (but no more than 5% larger). For 1/2" hex, use the 17/32" = 0.532" drill bit we bought and keep with the broach tool. The generic formula is 3%-4% larger than the width of the finished hex across the flats.
Step 2: Add a chamfer to your pre-drilled hole that's at least as large as the maximum distance across the broach tool. For 1/2" hex, make the chamfer at least 0.600" (but larger is OK too - it doesn't need to be precise).
Step 3: Install the tool in the mill (or lathe).
Step 4: Set the machine speed to 1800 RPM (this can be approximate, but 1800 is recommended by Slater).
Step 5: Turn the machine on and gradually engage the broach in the work piece. The broach is supposed to wobble, and it spins freely until it engages the chamfer (then it stops spinning but wobbles side to side). The wobble does the cutting.

References

5-minute overview video
1-minute refresher video
Super-detailed 8-steps to broaching

Drill Doctor

This tool sharpens drill bits. It's kept in the shop between the mini-lathe and the yellow metal cabinet along the back wall.

10 steps to using the Drill Doctor

Step 1: Look at the dull drill bit and figure out which angle it is: the more common 118°, or less common (flatter) 135°. Drill angles.png
Step 2: Check the adjustment of the grinding port (the one with the cam and the steel pin at the top) to make sure it's set to the right angle. To change angles, loosen the knob on the side, move it to 118 or 135°, then tighten the knob.
Step 3: Put the drill in the 6-fingered chuck. Make sure it's loose enough that it can slide in or out, and at least 1/2" sticks out the end. Find the white mark for on the chuck.
Step 4: With one hand, push the alignment button that opens the clamp arms (two small steel spring fingers), and hold it open.
Step 5: With the other hand, insert the drill with the chuck, matching the alignment guide (white mark on the chuck) with the 118° mark on the alignment port. The bit will hit the stop and slide in the chuck to reach the proper depth.
Step 6: Release the button pressed in step 4. Make sure the fingers clamp on the narrow part of the drill bit (i.e. make sure they stick between the flutes), and aren't holding the outside of the bit. This orients the bit so the grinding wheel cuts the edge.
Step 7: Tighten the chuck on the drill bit to secure it.
Step 8: Remove the chuck from the alignment port and insert it into the grinding port.
Step 9: Turn the unit on (button is in back) and rotate the chuck in the grinding port while keeping the cam pushed up against the ~1/4" diameter steel pin. Rotate again and again until you no longer hear it grinding.
Step 10: Return the sharpened drill bit to the correct hole in the drill index.

References

Using the Drill Doctor. Skip to 2:55 to see them name the key parts, or 4:14 for a detailed demonstration.