Not strictly car related - but one that LCBers will be able to answer no doubt...

Last weekend I had to drill an 8mm hole in some steel tubing - using my handheld power drill.

I have some brand new drill bits (http://www.screwfix.com/p/titan-hss-drill-bit-set-170pcs/59953) - and used a 4mm for a pilot - and an 8mm afterwards to go out to the width I wanted

The swarf was extremely 'bitty' - basically coming out as chips of metal.

I am under the impression that it's best when the swarf comes out in long threads - presumably indicating a nice even, smooth, cut is taking place.

Am I right - and if so - what did I do wrong?

[Edited on 21/5/15 by jps]

Mond

quote:

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Originally posted by coozer
Mond

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I suspect it was the hand held drill, you cant keep then in the same place like you can with a pillar or similar.

He he...

Drills just need to go at the correct speed for drill size and metal type.

Wouldn't worry as long as the hole is what you wanted, generally the harder the steel the more chipping the swarf is.

Hard to get the right steady speed with a hand drill.

Only time I get long smooth swarf is on the lathe and occasionally getting the right speed on the pillar drill.

Drilling stainless steels usually ends up with red hot chips flying all over cause its much harder than mild steel.

I don't think it would help greatly with the drill bits you was using. I had a set of those and they were terrible. The only good thing about them was you could change to another one once it went blunt or snapped which is quite common. I purchased my self a set of Heller HSS Cobalt drill bits and they are as sharp as the day I got them and not snapped a single one and usually get the spiral swarf even drilling stainless steel. Like coozer said though as long as you have the hole you wanted then its all good.

Matt

On a slightly different front I think that Ø4 to Ø8mm is quite a big jump for the final hole (if you are trying to get a nice finish anyway) I would have gone Pilot Ø4, Ø7 and then finished with a Ø8mm

As above better drill bits will probably make the most difference

Either really good quality HSS drills or decent quality cobalt ones will be good enough for most things, but bare in mind that different materials have different recommended point angles and styles too...


making sure you use the correct speed and feed to suit the drill bit and material is always important - if you were doing it with a CNC drilling machine this would be easy to control, but with a hand drill you just have get a feel for what's right...
Any decent workshop data book will give you drilling speeds and feed rates if you want to look them up.

Also don't forget about cutting fluid (depending on what your drilling) it acts as both a coolant and lubricant - even WD40 is better than nothing if you overheating the drill bits

[Edited on 22/5/2015 by mcerd1]