[TowerTalk] Mast slippage

[Grant Saviers]

Generally, carbide tipped drills use a grade of carbide and tip geometry 
for cast iron, formulated for cutting abrasive materials.  They aren't 
intended for steel but might work for a few holes.

For drilling harder steels, there are solid carbide twist drills ($$$) 
but carbide is very brittle and very easy to break in a hand drill.  A 
straight flute die drill will drill very hard materials because of its 
carbide and geometry. The swarf is more like shavings than chips or 
spirals.  It has a much larger cross section area so is harder to break.

Another problem in drilling alloy steels and stainless is most work 
harden.  It's like the local heating hardens the steel.  Continuous 
heavy thrust and good coolant is needed to keep the drill edge cutting 
below the hard layer left from the prior flute's cutting.  Back off on 
the thrust and then even more is needed to break thru it.  Very hard on 
drills.  Junk steel like fence posts usually have carbide and other hard 
inclusions embedded waiting for a drill tip.

McMaster, Travers Tool, MSC supply, KBC Tool carry almost all drill 
varieties.

Save your Chinese made drills for woodworking.

Grant KZ1W

On 7/28/2020 22:32, K9MA wrote:
> After recently ruining several drill bits trying to drill through a cast 
> iron fence post, I discovered there are carbide tipped bits for drilling 
> metal. I haven't tried them on anything, let alone cro-moly, but they 
> might work.
> 
> 73,
> 
> Scott K9MA
>