Servo - November 2009

(middle, feather, hobby, hockey pro, Sumo 3 kg auto) and one silver (Sumo 3 kg R/C). Here are the combat results:

Middleweight:

• 1st — Touro (Team RioBotz), drumbot

• 2nd — Johnny Bravo (Team Savuca), drumbot/rear wedge

• 3rd — A Besta (Team Uairrior); vertical disk spinner

Featherweight:

• 1st — Touro Feather (Team RioBotz), drumbot

• 2nd — Drakon Feather (Team Triton), wedge

• 3rd — Cascudo (Team Muqueca), thwackbot/full body spinner

Hobbyweight:

• 1st — Puminha (Team RioBotz), wedge

• 2nd — Butcher (Team Uairrior), shell spinner

• 3rd — Fenilciclidina (Team The Killers), wedge SV

Action photos by Leandro Bergamo. Bot photos courtesy of www.buildersdb.com.

PARTS IS PARTS:

H le Drilling How-To

In this short fact sheet, we’ll cover the most important terms and techniques for trouble-free hole drilling. Hang this up by your drill press for a quick go-to guide.

Drill Geometry

Point angle

Drills come in several standard point angles. The important thing to remember is that larger angles like 135 degrees are better in hard materials such as alloy steel and titanium. Smaller angles (giving a sharper point) will cut very well in soft materials like aluminum or plastic. If you have a range of materials to cut with one drill, go with the larger angle.

Point style

There are two common point styles: standard and split. Standard points are fine for lower accuracy and softer materials, while split points are less likely to wander off location and will start drilling with less pressure. If you use a mix of hard and soft materials, then split point drills will cope with more tasks than standard points. Split point drills often have a thicker web (the core between the flutes) and smaller flutes; this makes them

● by Nick Martin

stiffer but less able to clear stringy material.

Standard points are harder to get started on target and need more force to cut. Their advantages are ease of re-sharpening and lower cost.

Lengths

Drills come in a number of standard lengths. The type you get in hardware stores are ‘jobber’ length drills and are fine for most applications. Difficult drilling tasks call for special drill lengths:

• Short length drills are very stiff and are great for starting off holes accurately as they will not wander off center like longer drills can. Their short flute length means they are only useful for shallower holes, however, I find they cover 80% of drilling operations in my workshop. They are often cheaper than jobber drills, so give them serious consideration.

• Maintenance length drills fit between short and jobber lengths. Unless the size drill you need is only available in this length, go shorter for accuracy or longer for reach.

• Extension length drills are used

for extra deep holes or hard to reach places. Their extra length allows them to flex more and they are likely to produce a hole that is not straight or properly sized. If possible, start the hole off with a shorter drill and swap to the longer drill only when the regular drill is at maximum depth. Also remember to clear the chips out of deep holes more frequently.

Drill Composition

Drills have to be harder than the material they are cutting – the harder the drill, the less often you have to re-sharpen it. The three most common types of drill material are:

High speed steel (HSS)

These are the drills available at bargain prices from places like Harbor Freight and Home Depot. They are suitable for non-abrasive plastics, softer metals, and mild steel. HSS fails dismally in hardened steel parts or titanium – you may have to re-sharpen between every hole!