[TheForge] Re: scraper

[Mike Spencer]

I have a couple of sets of bearing scrapers.  Three of them look like
triangular taper files that have had the file teeth ground away, with
the added detail that the flat surfaces are *hollow* ground.  You
would get that result by turning a triangular file at right angles to
the plane of a (very fine) grinding wheel and running it back and
forth.  You'd have to use a jig to get very straight 60deg-sharp
edges.

Another looks like a 10" or 12" half-round files but smooth -- no
teeth -- and also very slightly hollow ground on the flat side.  The
edge here is quite a bit less than  60deg. This one is curved toward
the half-round side over the distal 2 inches or so but perfectly
straight from the tag to that curve.

I've done okay scraping bearings but when trying to scrape steel, I
found it hard to avoid gashes and, harder yet, ripples in the
resulting surface.  I've usually resorted to draw-filing with a
single-cut file (mill smooth or mill second cut, IIRC) for flat or
convex surfaces.  Doesn't work very well for concave ones.

When I applied for a job as a millwright at Michelin (that's a whole
'nother yarn) in '74, they gave me a hands-on shop test.  One of the
tasks included filing a small piece of 1/2" steel plate just so.  A
former cow orker in sports car mechanicing trade said in the Canadian
Navy, his journeyman's test for (machinist's mate? fitter? I forget
the rank) required doing most of the shaping and finishing on a
ratchet wrench with files.  Filing is getting to be a lost art and
specialized files hard to find.

- Mike

-- 
Michael Spencer                  Nova Scotia, Canada       .~. 
                                                           /V\ 
mspencer at tallships.ca                                     /( )\
http://home.tallships.ca/mspencer/                        ^^-^^