[TheForge] Band saw (Was: Vise squad)

[Mike Spencer]

Ralph quoth:

> ...you've gone from a chevy cavelier friction wheel to a line shaft
> and flat belt...

Did the lineshaft years ago for the 100# Palmer hammer and later
hooked up a 25# Jardine. Worked okay but there were numerous
um... flaws, especially noise.

In the new shop, I did it more or less right.  Motor overhead, proper
kind of switch, no noisy transmission.  And closer (very close) to the
recommended speed for a 25# LG.  The previous owner ran it straight
from the 4" pulley on the motor to the hammer -- wayyy to fast --
and it's a wonder he didn't tear the hammer to pieces.  The line shaft
gets me the right speed.

The Cavalier Revolutionary Alldays Powerplant was later and
umm... experimental. :-)

> Is your whole place run off a line shaft?

No, it's just for the 25# hammer.

 I always kinda wanted that, though.  I fell in love with that stuff
when I was a kid, the first time I was in a big shop all on lineshaft.
But I have another piece of shaft, a set of bearings, some pulleys and
a neighbor with more pulleys.  So I may yet get more stuff hooked up.
There's the band saw, and I have my eye on a huge pedestal grinder
that the present owner isn't quite ready to part with.

> Or was the band saw that vintage...

That vintage: Big old cast iron thing, 24" wheels, Babbitt bearings,
two flat pulleys (one drive, one clutch idler), 24"x24" tilting table.
Weighs maybe 800#.

> ...so you were test firing her for blade testing?

I finally wanted to actually *saw* something.  Our house has a
(so-called) breakneck stair in the front hall built about 1880.  Nice
turned newel post but the handrail and balusters have been missing
since forever.  I finally decided I wanted to make a replacement
handrail from the 8' piece of red oak I saved out of the woodpile 4
years ago.  Since I'll do any amount of work to avoid work, I'm
setting up the band saw to saw that piece of oak instead of setting up
to do it with chainsaw and adze.

> My question to you on the brazed blade repairs is the slight bevel
> your mentioning is square to the blade? or did you bevel them like
> you'd weld a truck frame and angle that slight bevel with the length
> of the blade to get more surface area for the braze?

The former.

   Cut the blade with a Beverley.

   Got a good smooth or 2nd cut file.

   Filed the end square to the length to the blade.

   Filed the cut end to almost but not quite a chisel edge. That
   "almost" allows you to see that the bevel is even.  It also means
   there's not an edge so thin that it'll burn up during brazing.

    ----------------   --------------------
                    \  \                        Edge view
    -----------------   -------------------

   

    ----------------+  +----------------------
                    |  |
                    |  |
                    |  |                           Flat view
                    |  |
                    |  |
                    |  |
     | /| /| /| /| /   | /| /| /| /| /| /| /| /| 
     |/ |/ |/ |/ |/    |/ |/ |/ |/ |/ |/ |/ |/ |


This is a fairly coarse, ca. 1-1/4" or 1-1/2" wood cutting blade that
I think was new old-stock from a bargain bin.  Right width but way too
long so I had to cut it down.

> The jig I'm guessing is just a way to hold the blade flat and
> straight while brazing? are you leaving the center open for flow?

Exactly.  Just a cutaway in one side of a piece of 1-1/2 x 1-1/2 x 1/8
angle.  The inside corner of the angle iron is radiused as it comes
from the mill.  Aligning the blade against the radiused corner is
unreliable, so there are shims to raise the blade enough so that its
back edge aligns on the inner face of the angle iron and not on the
radiused inner corner.  Very crude.  If my braze lasts long enough to
do some real work, I'll refine the jig a bit.

> ...there are five "repairable" blades for when I'm real bored and
> want to try my hand at electric annealing - or Mike gives me the true
> secret to success in brazing blades.  :-)

It's an awful thing for a guy with a background in physical science to
say, but:

       "I got back as soon as I could", says Coyote.  "I was busy
       being a hero."

       "That's unlikely," I says.

       "No, no," says Coyote.  "It's the truth."

       "There are no truths, Coyote," I says.  "Only stories."  [1]

So here's a story: I haven't seen an electric blade welder in
operation.  But I *have* seen and used a butt welder for ca. 6mm wire
at a Michelin wire mill.  You ground the ends nice and square first.
Then the gadget clamped the two pieces co-axial and with only a little
stock unsupported between the clamps.

The clamps are attached to the power cables and one is on a slider.  A
spring presses it toward the other clamp but it's held back by a latch
while you set up for a weld.

Now release the latch and the spring presses the two butt ends
firmly together.  When you hit the power switch, the joint glowed dull
red, then bright red and the two ends mushroomed a bit under the force
of the spring.  The small amount of movement in the clamp (that
occurred when the mushrooming happened) tripped a microswitch and
turned off the current.

The you ground the joint smooth and it was strong enough to go through
a rolling mill train without snapping.

I forget now whether you could adjust the spring tension, the current
or both.  But obviously, getting those two variables just right for the
size and composition of the wire would be the trick.

I don't know if that would work with something as thin as a saw blade
or not.  Be interesting to try.  Or maybe only worth it if you had a
dozen blades to do every day.  (I have a Foley Saw Filer that is just a
whiz.  You can file a hand saw perfectly in maybe 5 minutes.  But it
takes so long to set up for a particular pitch, rake etc. that it's
easier to just file a saw by hand in a vise.)


Also, you're talking about bi-metal metal-cutting blades (right?).
That might be a whole 'nother story. 

- Mike


[1] Thomas King, "Green Grass, Running Water".

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

--