DoAll DBW-1 Bandsaw-Blade Welder
Revision as of 21:22, 16 September 2012 by Djscholl (Updates for work progress)
This highly specialized welder is really only useful for one thing: repairing broken bandsaw blades. It is also called a buttwelder, because the technical name for the type of weld it makes in the blade is a butt weld.
- Don't try to repair bandsaw blades yet, and please don't plug in the power cord.
- Please don't adjust the heat switch (slotted screw head). This is not a user adjustment. It should always be set to the third detent, counting from the lowest heat (etching pencil) toward higher heats.
- Only one user adjustment (force) is required to accomodate different blade widths.
- 1/8 in. blade: on the "N" in "NARROW"
- 1/4 in. blade: between "NARROW" and "SAWS"
- 3/8 in. blade: on "SAWS" (between "NARROW" and "MEDIUM")
- 1/2 in. blade: on second "M" in "MEDIUM"
- Other widths are TBD
- The optimal force settings may change if the jaws are realigned. This is because the friction in the moving jaw mechanism is extremely sensitive to the clearance of the alignment gibs.
- Vise-grip pliers are recommended for holding blades during pre-weld grinding.
- The back corners of the jaws are worn, so simply pushing the blade back into those corners is not enough to guarantee that the blade ends are parallel. It is necessary to examine the blade ends from above to manually align the back edge of the blade before tightening the knurled screws.
- The welder only has one blade thickness gauge: for 0.025 in. thick blades.
- Be gentle when checking the thickness of an unannealed weld; it is surprisingly easy to break the weld (especially with narrower blades).
- Has anyone else ever repaired one of these old welders? Yes, someone rebuilt an entire 63-year-old DoAll Bandsaw, and rebuilt the welder as part of the project. Photos and written discussion are available on this thread in The Garage Journal. The URL is to page 5 of 26 pages, which is in the middle of the section that discusses the welder. The same author has made over a dozen videos of this project. They are available in the YouTube channel for APmachinist. Blade Welder Parts Repair is #14 in the Bandsaw Rebuild video series, and is one of several videos that discuss the welder. Note that the author's welder is model 1A, which is more recent than our model 1, and features different electrical adjustments, among other differences.
- Can bandsaw blades made with newer technologies (1950 or later) be repaired with this welder? Yes, if the annealing instructions from the manual for a newer model, e.g., the DBW-15, are followed.
- Continue evaluation and repairs
- Disassembly and cleaning is finished.
- Status of electrical testing/repairs
- New light socket (local lamp store) and bulb (Mouser) are installed and work at 220V.
- An electrical schematic diagram has been drawn and most of the wiring has been replaced.
- New insulators have been cut from 0.016 DMD sheet (Dacron-Mylar-Dacron from a motor shop, to replace the original waxed cardboard)
- Transformer wiring completed. Weld switch, heat switch, anneal switch, all transformer taps, appear to function OK. With 243VAC on the primary, the open secondary voltages are as follows:
- Anneal: 0.93 VAC
- Etching: 1.65 VAC
- Less: 3.00 VAC
- LessLess: 3.27 VAC
- More: 3.52 VAC
- MoreMore: 3.80 VAC
- These open-secondary voltages are higher than the nominal values listed in the manual, apparently because the nominal primary is 220VAC and our primary is 243VAC. For this reason, it is likely that the Less and LessLess heat switch settings will make the best welds in our shop.
- Replacement grinding wheel (Production Tool) is installed. It needed more clearance inside the housing, and we were able to use the wheel to grind its own clearance.
- Steve H. has made new Delrin tips for two of the adjustment screws, and both have been installed.
- Reassembly and rewiring have been completed.
- The movable jaw travel limits have been set.
- Welding trials continue.
- Box is needed to cover the parts behind the front panel
- Long-term location with 220V 1PH 30A power is needed