Bandsaw blade welding

[wawoodman]

The US and the UK: two countries divided by a common language.

[TomG]

I'm pretty sure we are in agreement here, despite our language barrier, but life is too short to beat this dead horse any longer. Merry Christmas Rob.

Tom

[RobWilson]

Just engineering banter Tom   

And a merry Christmas to you and your family  


Rob

[awemawson]

Tom sorry to hark on but, it is rather important to get it right. Especially for you as I know that many people follow your instructional videos. Tempering and annealing may both involve heating, but they have very different objectives in mind. Too many terms are used in a loose or woolly way that can only lead to future misunderstandings. Inexperienced people will follow your lead.

Meanwhile Happy Christmas to you all - I know Christmas has begun as I've just come home from "A Service of Nine Lessons and Carols" - more sloppy terminology - there were eleven carols !!!!!

[DaveH]

Anyone reading the above will be utterly confused.  

Normalizing, annealing and hardening of steels the temperature has to go above the Upper Critical Point.
Tempering, the temperature has to be below the Lower Critical Point.

One cannot temper annealed steel, there has to be some hardness to be able to temper it.

Any cutting of some steels can and does harden it, includes grinding - just smaller chips. So it can be tempered to remove some of the hardness and some stress.

I think to fully understand it all one has to look at the different structures of steels and how temperatures can affect it.

 
DaveH

[RobWilson]

Lol if you say so Dave


Those who know, know the difference .

So one inch is the same as 1mm an apple is the same as a banana, they both grow on trees .

Rob

[DaveH]

(12-20-2015, 07:39 PM)RobWilson. Wrote: Lol if you say so Dave

Rob

Rob,
It is not me saying so, all the bits I read on the 'Heat Treatment of Steels' say the same.

DaveH

[awemawson]

I presume that Dave is referring to 'work hardening' :

https://en.wikipedia.org/wiki/Work_hardening

[Highpower]

I've been trying to read up on heat treatment as of late and have come across a few tidbits that I never would have believed before. (Heat Treatment, Selection, and Application of Tool Steels ~ Wm. E. Bryson)

Things like the heat from grinding can produce 2000 - 3000° F in steels. Granted mind you - that is in reference to surface grinding larger pieces of steel than a band saw blade. I've never welded a saw blade in my life, so how that translates I don't know.

I have learned that one size does not fit all. Needed temperatures vary depending on the amount of carbon in a particular alloy. Higher carbon content requires a higher critical temperature range to make the transition. And tempering temperatures can be WAY different between alloys. But so far my understanding is the same as Dave's that tempering stabilizes freshly formed martensite. (hardened steel) If the steel is annealed it is returned to a pearlite structure (unhardened) and therefore there is no "martensite" grain structure present to "temper".

Which begs the question - what steel alloy(s) are bandsaw blades made from?

Ugh. Still so much to learn...

[RobWilson]

Hi Dave 

I am agreeing with you it was late when I replied and I had had a few   ,  what you wrote agrees with what I have been saying , Tempering and Annealing are to different processes with different aims and are NOT interchangeable , odd that some with a lifetime in the trade would think they are  .  

I am just going from what's written in the engineering text books I have . Personally I don't think the blade undergoes any hardening during the short grind time .Maybe I will do some tests with the old Scleroscope ,brush the dust off it . Funny how Starrett feel there is no need for the second heat . 


So is milling still milling or is it turning  


All the best    Rob