Tapping - The Guide

• Tools Needed
• Drill Press
• Centre punch
• Drills (see chart for sizes)

What to do

• Centre-punch material to mark where to drill. This is very important as it ensure the drill doesn't skate and drill exactly where you want! I strongly suggest using pilot drill bits such as these:

• Drill hole
• Attach tap to chuck and lightly lubricate (I use Rocol cutting compound)
• Lower into drilled hole and manually turn chuck to tap hole. I hold the drill press lever in one hand and turn the chuck with the other. You don't need to apply any force to the lever once you get going
• You'll know when you've reached as far you can because you can't turn it any more easily. Then simply reverse the chuck manually out of the hole and you should have a perfectly tapped hole. Voila.

Should take you about 20-30 seconds max to tap a hole.

looks great in acrylic too:

I drill a thin hole first as well most of the time. But the Pilot points are designed to reduce skating when starting the hole off as well. They really come into their own when following that predrilled pilot for getting perfect finish like in the attached. To get those socket head screws to sit dead centre requires first a thin pilot (preferably the size of the next pilot point to be used) then opened up to max size for the head of the bolt, then open up the remaining bit to the thread diameter and then tap.

If you're using any method which applies power (cordless drill etc) then you've increased the chances of snapping the tap several fold. If it has a clutch then you can put it on the lightest torque setting and that should be ok (i.e you should be able to stop it turning easily with your hand). The other other problem with a hand held device is holding it dead straight. This again increased the chance of it snapping.

Drill presses can be picked up quite cheap these days, say £20

Peter Daniel has a good explanation of how he uses a cordless drill with clutch to great effect. And he's the master fabricator: http://www.diyaudio.com/forums/showthread.php?postid=69413#post69413

Feed rate is important and needs to be adjusted depending on material. I use the same bits for acrylic but need to adjust the drill speed and rate at which you feed (for alu you should also be using a slow drill speed Shin - it's tempting when first working with metal to think it's stronger so therefore need to go top speed with the drill). Also the lube makes a big difference too. I've heard some people say it's best to drill in water for plastics. I certainly got improvements (read: more transparent cut/finish) from trying different lubes (I've tried thinners, WD40, water and cutting compound) - but I can't remember which was best OTTOMH.

Info taken from SKA Forum Thread by Vikash