7 replies to this topic

[Tex]

I need to drill a hole through a Scale Auto chassis... steel. I broke a drill bit, went and bought a "cobalt" drill bit, but it doesn't seem to make any headway either. What kind of drill bit do I need(1/16")? Thanks in advance.

[Pablo]

Bunky says make sure the drill is twisting right and the bit has a right hand twist

 

Don't laugh, I've done it.

 

[havlicek]

Hi Tex.  There's "steel" and then there's "STEEL".  The effort required to drill (and cut and otherwise machine/fabricate) steel can go from "no big thing" to the equivalent of painting the ceiling of the Sistine Chapel.  I've done some chassis making using old saw blades (definitely on the tougher end of the spectrum, but still not the toughest) and a couple of things became clear when drilling:

1)  The straightness of drill bits used when drilling steel becomes more and more important as the hardness of the steel increases.  Use good straight bits to avoid walking and to keep the cutting action centered and efficient.

2) Avoid both too much pressure and too high drill speeds.  Both will burn up a good bit, making it pretty much useless.

3) A cutting lubricant can help, along with stopping along the way every so often to let both the workpiece and the bit cool down.

4) Both "cobalt" and "titanium coated" bits work substantially better on harder steels than "high speed" bits, but you can ruin them easily too.

5) Drilling in "steps" isn't a bad idea.  Working up to the final diameter hole can sometimes (*not always) save you some grief.

6) If you DO have a good bit and it wants to "walk", do whatever you can to at least start a pilot hole.  That doesn't always mean using a smaller "starter" bit.  On curved surfaces like an armature for example, a larger diameter bit will often tend to walk far less than a smaller one.  Just "nick the surface so you have a starter hole smaller than the hole you want to wind up with.

 

7) If you manage to get a small starter hole  all the way through, but your larger bits won't cooperate, you can always use a small diamond burr in your rotary tool to get just a hair under the final hole size and then only use the drill bit to "clean things up"...but be careful that larger bit doesn't grab and spin the workpiece which can lead to all kinds of mangled digits, ruined work and the hollering of every conceivable profanity, plus a few new ones you ad lib on the spot.  You can still damage or even ruin the diamond burr, but they cost very little nowadays.

 

...that's all I got.

 

-john

[Booger]

Take a small single mill file and see if you can nick the frame some place that's not important....If you CAN nick it,you can drill it.If you CAN'T nick it,if the file seems to glide over the surface....Good luck!

 

In order to drill tempered steel,slow the drill bit WAY down,use cutting fluid,sulfer based is best (Tap Magic,CRC,Mobil 1...WD-40 or ATF is better than nothing.....sort of) use a drill press if you have one.If you can sharpen drill bits,make the angle real shallow with a shallow relief to give the cutting tip more strenght and not take as big of a bite.

 

Last resort,use a carbide drill bit (about $10 for a 1/16) but you will need a green wheel and diamond lap to sharpen it again.You will HAVE to use a drill press with this or it will break....It won't take sideways motion.

 

If it's really hard,your not going to drill a hole through it, period......EDM is your friend!

[Jay Guard]

A solid carbide but is the only way to go on tempered steel.  I've drilled 1095 blue spring steel many times but mostly with small 1/8" holes.  Be prepared to break a few bits until you get speeds/feeds just right.

[Phil Hackett]

Good advice about the file test.

 

Even if it''s a fully hardened steel you can drill it with a carbide drill. However, you need, at a minimum, a drill press to keep the drill from breaking and a decent drill press at that.

 

I'd still try the steel drills you're using but like the post above, SLOW DOWN THE SPINDLE SPEED and give steady pressure. Once the drill "bites" and starts drilling DON'T STOP.

 

Otherwise, Gary's post above says it all.

[MSwiss]

Tex,
I used to drill 1/16" holes in 1095 steel all the time, to pin guide tongues on.

All the above info is great.

Yes, a drill press at a slow/right speed.

But, IMO, and as Gary mentioned, the most important thing is to modify the bit.

Use a regular gold bit and soften the cutting angle with a Dremel and a 409 cutting disc.

If it doesn't bite right away, stop.

No need to dull/heat up the bit or snap it.

With the same bit, keep experimenting, trying slightly different angles.

Eventually, like magic, it will go through.

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[Phil Hackett]

While we're talking about modifying drills…. there is a type of drill call a "crankshaft" drill and instead of the normal 118° angle they're made with a 135° angle. Even better these drills have a split-point center which means the center doesn't have the web/non-cutting center. Even better for making shallow holes are Screw Machine length drills. They're stiffer and don't wobble around as much as the longer Jobber-Length drills which you find in hardware stores.

 

An example is linked below. Your local industrial hardware store should have these.

 

1/16 Screw Machine Length 135° cutting angle Drill