cad wrote:
JoeD,
I used PM-C1018ON Marshallcrat (C1018) Low Carbon Onsize Ground
Flat Stock to make my scraper bits.
This is the low end quality. But, in scraping,I never make pressure
cuts. They are light barely discernable when I do it other than
watching the obvious fluff that comes off of the bit. So I rarely get
the bit hot.
On my scraper bits I gring one end with a radius point, probably about
a 1/8th radius. The opposite end ground to a 1/2" radius for the
actual finish scraping. I have a hole in the middle of the bit. When I
need to remove heavy cut lines I use the 1/8" end. Then when I am
ready to impart a smooth wall I reverse the bit 180 degrees and take
light passes. A two in one bit.
You can get better steel, A2, that will hold an edge longer, but with
the proper releif angle on the scraper bit it does a fine job for a
long time.
I'm a very frugal person, by necessity. I dont have a nifty retirement
plan and oodles of time to figure out what I will do each day. I am
still trying to figure out how to pay two mortgages and a car payment
on unemployment.
cad
cad,
I'm offering this information from ancient memory so you might want to
double check every syllable.
If you can bump your steel up to just 1020 (a tiny bit more carbon), you
can harden it without any special treatment. ISTR you'll want a water
bath for that one. This is a through-hardening. You can also case harden
the 1018 buy cooking it in a bed of charcoal briquets. Build a good
fire, heat the steel in a torch flame and insert into the charcoal, well
buried. Allow the charcoal fire to die naturally. ISTR that this adds
enough carbon to the skin to harden it when you re-do the heat / cooling
cycle normally.
If not, try this: get your steel to a bright cherry and plunge it into a
box of high-nitrogen fertilizer. Let it cool completely there ...
overnight at least. This is a case-hardening which leaves a hardened
skin on a softer middle.
When case hardening, grind to near-net size before hardening as only a
thin layer will be hardened and major re-shaping will remove that layer.
Chemically speaking, this is how some of the fabled swords were
hardened. Although, they used living slaves and convicts as the source
of nitrogen. We have other, re-useable, sources. Urea fertilizer will
set you back only 2-3 GBP for a lifetime supply. Or, use it for a few
pieces and spread it on your lawn (well watered) or your neighbors lawn
(without water). };-)
--
http://nmwoodworks.com/cube
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