Annealing, bending, retempering v-spring

[BrentD]

I need to spread a replacement v-spring to get sufficient travel.  It doesn't need to bend a lot, but I definitely need to spread it a bit.  I know I need to anneal it first, then bend, and then retemper.  Can any one suggest or describe a good tutorial for doing so? 

I have heard of putting the spring in a saucer of burning motor oil to temper it.  I believe I have heard of soaking it in a lead pot, but the latter doesn't seem hot enough for me.  Any suggestions?  I can't seem to find anything in my basement library.

Thanks.

[rich pierce]

The steps are get it orange hot and spread it hot. Re-heat to orange and quench harden while stirring in warm canola oil. Check hardness. A file should skate across it. Safest tempering is the lead pot soak.  For hardening I wrap with black tie wire to hold it.  When quenching and when tempering the long black wire “handle” keeps the spring pushed down into the quench or molten lead.

[BrentD]

Rich,
Thanks very much.  Sounds simple.   How hot do you have the lead pot?  I was looking at a youtube video that suggested fire bluing salts at 600 F.  Would 600 F in the lead be about right?

[rich pierce]

Lead melts at 625. You want 700-750.

I’m no expert. Springs can be made to break several ways. Too much preload is one. So be careful to not bend too wide. What is the v spring for?

[Bob Roller]

Who made the lock and is the spring a casting or a forged one??
I have had no experience with cast mainsprings but on all the
forged ones I made over a long period of time,after I set the preload
I heated it to a bright orange and dropped it in a can of light motor
oil and after it cooled,got it out with a magnet,wiped the oil off and
then polished it.Using a Bernzo-matic torch with an adapter to pin
point the flame it was drawn to a dark blue and that process started
at the upper end of the spring and traveled down to the bend where
I gave it a little dwell time in that thickest area and then continued
down to the claw that is hook to the stirrup or link.The spring is held
with duck bill pliers by the pin on the upper limb that goes thru the
lock plate.I have been told by "experts" that this can't work and my
reply IS,50 years of success says it does,world wide.I have used
only 1075 and am used to it and comfortable in sending locks to
Europe when I was making them.
Bob Roller

[Dphariss]

OK there is no need to anneal most springs unless really heavy bending is needed.
TO increase tension on a tempered V spring: Polish it bright. Clamp firmly at the BEND in smooth jaws vice or padded with brass/copper.  Flex the spring to the point needed with pliers or vice grips and HOLD IT. Carefully heat with a propane torch moving the flame constantly heating the heavy sections a little longer than the thin to give even heat. As the spring starts to turn blue it will lose its tension to some greater or lessor extent. Stop heating and hold in the flexed position un till it cools somewhat. 30 seconds or so. Spring should now be rearched and ready for service.. Works on most springs I have tried it on and I do this routinely to put more life in cast springs.


Dan

[rich pierce]

Dan, never heard this technique till now but am going to use it for sure. Thanks.

[Jim Kibler]

The method Dan suggested works well.  I will add that you can heat up to the original tempering temperature without softening the spring.  Heating to this point will help ensure the spring will take the set you want. 

I will also add once again  , the ideal tempering temperature of a spring is not a fixed temperature, but is dependent on the spring material!  People continually suggest tempering temperatures just because they worked for them before.  This is fine, but only part of the story.  Look up a tempering curve for the material the spring is made of.  Pick a temperature to get a hardness around 45 HRC or a little less.  This will work well for mainsprings.  Other less stressed springs are much more forgiving.

[BrentD]

Thanks one and all for the comments.  Dan, your method is completely new to me.  But I think I will try it, although this is a fairly short spring that may prove difficult to hold onto and heat at the same time.  I might try to make some sort of jig.   

I wish I knew what the spring material is. 

[Craig Wilcox]

Just for info, nitre bluing salts are heated to 570-650.  You would get "some" annealing effect, but I am with a lot of others and use a Bernzomatic or Propane and watch the color carefully.

[Dphariss]

Thanks one and all for the comments.  Dan, your method is completely new to me.  But I think I will try it, although this is a fairly short spring that may prove difficult to hold onto and heat at the same time.  I might try to make some sort of jig.   

I wish I knew what the spring material is.

A metal blocks or a wedge can be used for some springs. But be careful with wedges.

[Dphariss]

Just for info, nitre bluing salts are heated to 570-650.  You would get "some" annealing effect, but I am with a lot of others and use a Bernzomatic or Propane and watch the color carefully.

I often temper springs in a saltpeter bath. Great for mainsprings since the heavy sections can be put in the bath first so that the lighter sections are not over heated. Once the coating from inserting the cold spring melts off watching the color is easy. Small springs I will use a torch unless doing a larger spring at the same time.

Dan

[JCKelly]

Metallurgically speaking, I would suggest just buying a new spring.
These heat treat suggestions are very nice
Nevertheless the very first time one tries to heat treat something - a spring, say - by eye the results are
That he needs a new spring.

Good luck