drilling in ss...untill it stopped

R

rsmithsr

Well-known member
I am making some wind flag counter weights, and was in the process of drilling a thru hole
when the drill stopped cutting.
I was at 330 rpm with a .125 coated bit with flooded cutting oil.
so I slowed down to 160 and went to a .063, then a .093
broke the 093 when it hit the spot were the first drill quit cutting.
I am guessing I hardened a spot.
what do I do now ?
(I have solid carbide coming today in 125 and 155)
just never had this happen before
too much speed ?
 
Not enough speed and too little feed pressure. You work hardened the hole bottom. Use the .155 carbide drill at max speed and high feed pressure. Oil is optional. Next time get some 303 or 410 SS and you won't have a problem.


RWO
 
RWO said:
Not enough speed and too little feed pressure. You work hardened the hole bottom. Use the .155 carbide drill at max speed and high feed pressure. Oil is optional. Next time get some 303 or 410 SS and you won't have a problem.


RWO
Click to expand...

Adequate feed pressure creates larger chips that remove more heat.
What lube?
SS can benefit from some of the more sophisticated lubes.
Try Tap Magic.
The correct type is labeled for SS and not all that expensive.

SS is usually not all that hard because most types do not especially work harden, and many grades do not harden at all.
 
sorry , it was asked before
304
dark pipe thread thinned a little
BUT
the good news is, higher speed, and more/firmer feed, and all is well
thanks guys..i just do not do enough with ss on my lathe
 
Believe it or not...

rsmithsr said:
sorry , it was asked before
304
dark pipe thread thinned a little
BUT
the good news is, higher speed, and more/firmer feed, and all is well
thanks guys..i just do not do enough with ss on my lathe
Click to expand...

More than any other steel Stainless seems to be prone to irregularities in mfg. I have used tons of it throughout my working life and hard spots just as your mentioning do occur. More frequently in 304 than any other in my experience. 4140 is close behind.
 
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