Nuts & Volts - July 2004

Personal Robotics

• For soldering wires together, make the wires into two hooks, then twist the wires together. Follow up with solder and heat shrink. (Heat shrink is infinitely preferred, unless you intend to remove the joint in short order.)

tedious, but larger cuts are a breeze.

Soldering gun: What goes for the iron goes for the gun. I use my gun in place of brazing. It is easier, but the joints are not as strong. It is also a must if you get into soldering your own tabbed battery packs or use heavy gauge wire. (Never solder non-tabbed batteries.)

Needle Applicator

• Once there is an appropriate amount of solder, remove the iron and hold the component still for a few seconds. Components in a board should be soldered in such a way that the solder flows across the whole pad, through the hole (if plated through), and across the opposite side.

Needle applicator for Plastruct Bondene: This allows you to apply very precise amounts of adhesive. I like the 20 gauge, 1” long needle. Remember to keep your adhesive stored with the thin wire in the tube to keep it from evaporating. Larger gauges can handle more viscous adhesives, like carpenter’s glue.

• Frosty-looking joints are called “cold.” A proper joint should be clean and shiny. If you are not getting proper joints, your temperature may be off.

Machinist’s scribe: This is useful for marking cut lines on metal or plastic. You can also scribe multiple times and bend on the scribe line to cut many plastics.

Digital Caliper

Tap and Drill Set

Calipers: Calipers allow you to precisely measure external and internal dimensions to a high degree of precision.

A set of really cheap digital calipers can be had for about $20.00 these days, but, personally, I prefer not to skimp on measuring tools. I have had my Mitutoyo digital calipers for 10 years now and they were well worth the investment.

Small through taps: If you want to tap into brass or other metals, these are a must. You will have poor results with small screws in plastic, however. Taps require a drill of a certain size to “pave the way” before you cut threads. Taps can be bought in sets with the drills.

There are three types of taps: taper, plug, and bottoming. If you intend on tapping “blind holes” where the hole does not go all the way through the material, then progress through the three types, being extra careful with the bottoming. Otherwise, simply use the taper all the way through.

To tap a hole, first drill with the tapping drill, clear the hole of debris, then screw the tap into the hole, changing directions frequently to clear the tap. This is sort of like two steps forward, one back, as it were. The harder the material, the deeper you go; the smaller the tap, the more critical this is. Also, it is recommended that you should use tapping fluid on metals. When tapping blind holes, clean out the hole frequently.

Keeping the tap perpendicular to your work is important. If you have a drill press, you can remove the belt, chuck up larger taps, and manually drive the tap, but you must be careful. You must have a steady hand to do this with a small tap. You can also make a tapping guide by drilling a piece of material with the clearance tap.

Screw 1-72 2-56 4-40

Clearance #48 #43 #32

Tap #54 #51 #44

F o r

E l e c t r o n i c s

NUTS & VOLTS E v e r y t h i n g

Bow compass with two points: This allows you to make cut-curved sections in styrene by gently and repeatedly scribing the cut you want. Remember to do the outermost diameters first on multiple cuts. Smaller diameter cuts may be

Those of you across the pond who are accustomed to the highly complicated, decimal-based metric system must now screw on your thinking caps, but I’ll walk you through this. Take the pitch of your screw, subtract that from the diameter, and that is your tap drill size.