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/diy/ - Do It Yourself

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>> No.2584070 [View]
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2584070

>>2582746
>high heat will ruin drill bits
>high heat "work hardens" higher carbon steels, further hardens steel, is tougher to drill, creates more heat which further damages drill
>drilling is high friction, heat must be dissipated somewhere

Heat is only dissipated away from your drill and work piece by the chips you make.
The thicker the chips, the more heat is soaked up, the less work hardening, the less the drill heats up.
If the chip isnt soaking and removing the heat, that heat is soaking right your drill bit and work piece.

Simple as that. You go at a slow RPM, you feed the drill bit hard/deep and take much thicker bites. If there is minor work hardening, you try to bite under it and get material moving before it continues work hardening.
Thats the proper way of drilling hard material.
If you are using a mill, there are formulas on what your feeds and speeds should be. If going by hand, you gauge by your chipload.

As for pilot holes, they are just that. Small holes to pilot the drill.
Your pilot hole should diameter only be SLIGHTLY larger than your chisel point (yes the tip is called the chisel, not the web).
The sole reason for a pilot hole is to engage the work piece with the beginning of your cutting edges, instead of the chisel.
It helps keep the drill from walking, thats it.

If you incrementally drill holes going up in sizes, its really bad on tool life and hole accuracy.
The center of your chisel point is obviously the center of your drills bores.
The further out you go down the cutting edges, the more there is a levering effect.
When you start your cut way out away from the chisel, it levers bad.
There is more movement, you are less accurate, you put immense pressure on the tips of the drill bit, you are taking smaller chips focusing a lot of friction there.
It basically trashes your drill bit far faster than if you were engaged with the whole cutting edge.
You really should never do it unless its a last resort.

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