D-bits

[Maryak]

Hi Guys,

Don't forget when quenching to quench end on otherwise the bit will distort.

Ask me how I know :-[

Best Regards
Bob

 

[tel]

Yes Bob, that is a very important point - plunge it in end first and swish it about a bit.

 

[lampy]

I made my first D-bit, seems to be a success ;D I used a piece of 3/8 w-1, chucked it up in the lathe to put a 90 degree tip on it. I milled the D then honed the milling marks off. I decided to harden but not temper this one. I'll mess with tempering later when the need arises.

Spotted a hole location first, Then bored a hole, put a 45 deg. chamfer on the edge of my test block.

 

[Sshire]

Since I'm about to do this hardening thing, a question occurred. If I'm grinding the d bit to shape and dip in water to cool it WHILE grinding, won't the piece harden?
Noing nothing at all, I got some oil hardening drill rod because I thought the cooling water dip would harden it before I finished grinding. Am I missing some key point about hardening oil vs water rod?
Best
Stan

 

[Swede]

Since I'm about to do this hardening thing, a question occurred. If I'm grinding the d bit to shape and dip in water to cool it WHILE grinding, won't the piece harden?
Noing nothing at all, I got some oil hardening drill rod because I thought the cooling water dip would harden it before I finished grinding. Am I missing some key point about hardening oil vs water rod?
Best
Stan

Not really, except for the possible exception of an immensely thin/small layer of steel at the edge. Remember, the transformation temperature is a dull cherry red, and no one I know grinds bits that heavily. Now, grinding temperatures can easily affect the hardness of a piece after it has been hardened, since the temperature of the grind is well into tempering temps, several hundred degrees f.

So grind away on already annealed stock, but use caution after it has been heat treated.

 

[Sshire]

Swede
Thanks much. I had not taken into account the grinding temp.
Best
Stan

 

[Dunc]

Some info from Google's Popular Mechanics & Popular Science archives.

http://books.google.com/books?id=RdMDAAAAMBAJ Popular Mechanics back issues
http://books.google.com/books?id=iigDAAAAMBAJ&source=gbs_summary_r&cad=0_0#all_issues_anchor Popular Science back issues

Go to the webpage and navigate to the required year, then the issue.

Pop Mech: Sept 1951, Feb 1955
Pop Sci: Oct 54, Oct 67