How to Modify Twist Drills to Make Them Safe for Use in Plastics and Brass

[Tom Griffin]

One of the most hazardous operations in the shop is drilling holes in plastic or brass, especially in the drill press. Here is a simple technique to prevent drills from grabbing when drilling soft materials.

Tom

[video=youtube_share;8Ri6poVpQM8]http://youtu.be/8Ri6poVpQM8[/video]

 

[Charley Davidson]

Thanks for the great tip, Keep it up and your gonna be famous on the internet:man:

 

[Tom Griffin]

Lol, I thought everyone was famous on the internet.

Thanks Charley.

 

[KMoffett]

Makes me a bit..no really uncomfortable when you reach in and stop the spindle with your hand (1:34) by grabbing the chuck, especially while that piece of Plexiglas is spinning on the bit. That's just the kind of thing that you were referring to (0.34)...when people start taking seemingly simple machines for granted.

Ken

 

[Tom Griffin]

Sorry that made you uncomfortable Ken, but I didn't stop the spindle with my hand. What you can't see in the video is my other hand on the spindle brake. Hopefully that little distraction didn't take away from the real message in the video.

Tom

 

[george wilson]

I was in a shop that sold audio equipment years ago. One of the things on display was a clear plastic speaker cabinet they had made. It was high priced. The guy said it wouldn't be so expensive except for all the plastic they had broken while drilling the holes. I made him a drawing of how to grind his drill bits for drilling plastic. I'm sure he found it useful if he made another plastic speaker cabinet. I grind a vertical edge on the cutting edges of the drill bit,similar to what you are doing,but I don't put a negative cutting edge on the drill.

The cutting ability of the drill doesn't seem to be affected when using it in a machine. Might really be noticed when using it in a hand drill.

I have several old brass drills. Their flutes are ground just like regular drills,except they go straight up the drill's body,not spiraled like a normal drill bit. I'm not sure if these are made any more. They look sort of like those old straight fluted drill bits you used to get inside the wooden handles of egg beater drills,but more carefully made,and of HSS.

I really don't see why anyone would want a transparent speaker cabinet ! You could see the speaker,and all the messy wiring,too!

 

[Tom Griffin]

I've used that style as well George and they work just as well as these. I just thought these might be a bit easier to make.

Clear Plexiglass speakers sound so 1970ish.

Tom

 

[jamie76x]

There is a big difference between making the drill " Dull " and removing some of the rake.

A "dull" drill will not drill. A drill than you have removed some of the rake will not grab but will still cut.

 

[Tom Griffin]

Both are common ways to prevent drills from screwing into plastic and both accomplish that goal equally well. I opted for the stoned cutting edge approach because it's the easiest for a novice to do. The idea here is to make sure the novice is aware of the hazard and to make it as easy as possible to prevent. Perhaps you should produce a video of your own showing the other method, we'd love to see it.

Tom

 

[schor]

Thanks for the tip. I do drill plastic and it's always the same thing, it runs up the bit.

So I guess I should be starting a set of plastic drilling bits and use them only for that?