On 2019-03-04, John B Slocomb wrote:
On Sun, 3 Mar 2019 21:16:51 -0600, Terry Coombs
wrote:
* I've read about it somewhere , but don't recall the details ... Broke
the last (nearly new) band for my horizontal , figured I have nothing to
lose but a little time , a bit of shield gas and some 'lectrons - oh ,
and I'll need to make a clamp block to keep the blade aligned as I weld
on it . Got a new blade on the way , but just got a bug to try this . I
know low amps DCEN , what filler ? Got ER70S2 ,ER70S6 (MIG wire) , ER
308/309/312 and some Invar 42 nickel/iron . The blade is an Irwin (IIRC)
bimetal 10/14 pitch . Am I going to need to anneal the weld ? O/A torch
OK for the task if it's needed ? I know I want to minimize the HAZ .
For whatever it is worth, I seem to remember a band saw with an
attached blade welder that clamped the blade in a holder with two
sections, a fixed clamp and a movable clamp. When you hit the switch
the current was applied and the spring loaded clamp moved that end of
the blade toward the fixed end of the blade, sort of like a spot
welder. There was no filler material. When the weld was finished there
was some "bead" on both sides of the blade and the welder had a small
grinding wheel attachment so that the weld "beads" could be ground
smooth. No annealing or filler metal
These are made both to build into the bandsaw, and for benchtop
use. They also include a lever-operated shear to cut the blade cleanly.
One reason for them being mounted on the bandsaw is so you can
drill a hole in the workpiece, thread the cut blade through the hole,
weld the blade, and then cut along a line which never intersects the
outside edge of the workpiece, to cut out an inner piece.
An example of the benchtop version (similar to what I have) is
this one on eBay:
Auction # 273699228238
Note the semi-repaired "Anneal" switch. After the welding, you are
supposed to loosen the clamps, slide them back, center the welded spot
between the clamps, and then start out with long pulses of the anneal
switch, moveing slowly to very short ones to let it cool slowly. After
this, you grind off the flash.
The rotary switch sets the current for the width of the blade.
And you need more current for a bi-metal blade than for a carbon-steel
one.
Earlier on we used to grind each end of the blade to a knife edge, and
then overlap the ends and silver solder them together.
Given that most band saws have large enough wheels that the blade is
not bent sharply I suspect that the joining is not a really critical
thing.
You do want to anneal it properly -- especially if you have
something like my 4x6 Horizontal/Vertical bandsaw.
Enjoy,
DoN.
--
Remove oil spill source from e-mail
Email: | (KV4PH) Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---