Blacksmithing question - Used oil for quenching, OK?

[chainsaw_louie]

Hi ,

I am making some  scrapers  for my wood lathe  and have gotten to the part in the instructions where it says to quench the orange  hot steel in oil.  Well I have a 5 gallon pail of USED crankcase oil ... is there any problem with using used , dirty oil vs new oil  for  hardening quench?

Thanks.

Tim

[Sprucegum]

Most blacksmiths I know would save the new oil for the crankcase and use the old stuff for quenching.  ;D

For the type of quenching you are doing the rate of cooling is more important than the additives you might get from the oil. Oil is used because it cools the steel slower than water would but much faster than air cooling. So the steel ends up harder and tougher.

Good luck

[fstedy]

You can get away with using old oil be sure to check the alloy you're using to be sure the oil doesn't have to be heated some alloys require that. Also be very careful to do your quench outside and make sure you imerese the whole part in the oil if the red hot metal is exposed to both air and oil you'll have one heck of a fire (been there done that it gets your attention fast). After quenching it you'll have to temper it to the proper hardness for your application. If you need temps I'll look and see if I can find my book on hardening but I will need the alloy you use.

[bitternut]

Louie I assume that the lathe scrapers are sort of file shaped ( long, narrow, and thin ) so be sure to immerse the heated scraper straight into the oil on its long axis or it will warp the scraper. Then again I suppose if they are file shaped you are probably just hardening the first couple inches of the working end and will not need to drop the whole piece into the oil. Then after cooling you can shine the hardened end up till it is shiny and reheat slowly till it is straw colored. Immediately quench again and your scraper is ready to be sharpened.

[chainsaw_louie]

Hi,

Thanks for the advice.  I went ahead and used the crankcase oil for the first scraper and it worked fine.  I did it outside and it flared up but my face was off to the side so no problems happened. 

At some point, one has to stop reading about it and start doing it.

  After I successfully did the heat-to-orange-red-then-quench-in-oil operation .  I continued to read on the net .   One bit of sage advice made me pause and think - apparently its important to use a METAL container and not a Plastic Drywall bucket (me) to hold the quench liquid.  If the red hot steel were to drop into the bucket, it would melt the plastic and burning oil would be all over the place.  Wow !  "Big fires start with small ones " 

Well I guess I learned that lesson the easy way.  I have spilled some oil in the driveway before but 5 gal of burning oil on a sloping driveway (towards the road) would attract way too much attention, next time its a metal bucket, for sure !

CSL

[wassaw]

have used used oil myself for many things. just keep in mind that used oil is carcinogenic and keep it off your skin and do not breathe the vapors

[sawmill_john]

I thought I'd mention an old shop teacher once told me that old worn out files, make great lathe tools they're already hard all you have to do is grind the profile into them.  I have done it and it "really works"!