[Public-List] Public-List Digest, Vol 3148, Issue 2

[Kris Coward via Public-List]

I've heard the same thing from machinists, and have likewise heard that
cobalt is an acceptable substitute for carbide when (not if[0]) you
harden your SS by backing off the pressure.

-K

0) unless your downward force is being supplied by a machinist or a
machine

On Mon, Nov 09, 2015 at 04:04:51PM -0500, Anders Bro wrote:
> They (machinists) say that there is no problem with drilling SS with HSS, but... when drilling SS you have to use a lot of down force and do not stop. If you drill slowly, the SS hardens and then you dull the bit and cant get through it. Then you do need carbide. I have certainly found this recommendation to hold true for the stainless steels I have tried to drill.
> Anders 
> 
> Sent from my iPhone
> 
> > On Nov 9, 2015, at 2:29 PM, Kris Coward via Public-List <public-list at lists.alberg30.org> wrote:
> > 
> > 
> > Cobalt bits work too, and aren't as brittle as carbide.
> > 
> > -K
> > 
> >> On Sun, Nov 08, 2015 at 09:24:16PM -0800, Glenn Brooks via Public-List wrote:
> >> Gordon,
> >> 
> >> Ideal would be to use tungsten or carbide tipped bits.  Depending on what grade stainless, you have, you might get by with a high quality high speed steel (HSS) bit, if you drill slowly, say 250 to 400 RPM or thereabouts.  these will dull quickly, but might work for enlarging existing 1/4" holes.    Other wise look for a tungsten or carbide bit.
> >> 
> >> It's Critical that you clamp the chain plate to a drill press table to control the work as you drill through it, particularly the last little bit.  preferably use a drill press so you can turn down the speed (RPM) of the bit.  A hand drill just won't do it.  They turn to fast.  If bit speed is to fast, for example, over 800 -900 RPM, the bit will likely heat   up quickly and loose its hardness. If the tip turns bright red then  it won't cut and will work harden the Stainless by grinding/rubbing against the hole.  Work hardened stainless can almost never be drilled thereafter. So be careful not to work harden your work surface.
> >> 
> >> Also, always use some cutting oil - even 3in 1oil if nothing else is at hand.  The cutting oil will help dissipate heat and make all the difference in the world getting through the chainplate.
> >> 
> >> Regards
> >> Glenn 
> >> 
> >> Sent from my iPad
> >> 
> >>> On Nov 8, 2015, at 3:16 PM, gordon white via Public-List <public-list at lists.alberg30.org> wrote:
> >>> 
> >>> what drill is good for use on the stainless chainplates?
> >>> 
> >>> - Gordon White
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> > -- 
> > Kris Coward                    http://unripe.melon.org/
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-- 
Kris Coward					http://unripe.melon.org/
GPG Fingerprint: 2BF3 957D 310A FEEC 4733  830E 21A4 05C7 1FEB 12B3