7x10 Lathe Switch Panel Upgrade
Replace worn and loose switch panel with an improved and graphically sensible one.
-Allen Keehall-
Goal:  Repair and upgrade a worn switch panel on a 7x10 to 7x14 mini lathe.  It's an easy and durable  method that improves the utility and simplifies future replacements or changes.

Background: I was replacing the On-Off switch since it was acting intermittently.  I also prefer a O/1 power designation and grew tired of snagging my sleeve on the corner of the lifted panel.  The graphics were severely worn from cutting fluids and typical use. The aluminum panel and control box holes did not align as constrained by the perimeters; thus creating an overhang when keyed to the instrumentation.  Cutting fluids eventually permeated under the panel and dissolved the adhesive and the all too frequent snagging eventually peeled and lifted the panel.

As a product developer, I  had several other issues that a factory replacement wouldn't improve. An enlarged 23/64" (9.1mm) potentiometer hole should also be considered while disassembled. This will accommodate a standard 2 Million cycle sealed industrial 5K-Ohm potentiometer the BI Technologies P232-SFC35BR5K.  You'll need a new knob and perhaps shorten the shaft.

Three things I disliked about the panel: unintuitive indication for forward and reverse spindle rotation, the antiquated High-Low speed dial designation, and a missing fuse rating.  A fuse's amperage and type should be clearly marked; how did that slip UL?  Spindle rotation should be designated with arrows.  And the Hi-Low markings are not perceptively "instant".


Construction: I carefully removed and cleaned the panel, trued and deburred the edges, slightly reduced the overall size and re-tapered to properly fit the control box with more clearance.  I scanned the panel at 1200 dpi, overlapped the holes and outlines with vector layers, plotted on bond paper, measured, and re-aligned the outline and holes to the correct orientation on the control box housing.  After aligning all the holes, the speed scale was redrawn and text layers overlayed.  I verified that the panel, new overlay and control box holes meshed properly, providing proper edge alignment and clearance.

Before assembly place the panel face down on a thick phone book.  Roll a large round glass jar or similar object over it, carefully smoothing out any kinks, bends or imperfections.  You'll create a slight bow-out.  Clean and degrease the control box and remove all trace adhesive.

I plotted the new overlay, laminated with mylar, and cut the holes.  I used clear postal tape to wrap the new overlay over the panel twice.  This secures the overlay, triples the resistance to abrasion, and makes it easier to disassemble.  Done properly, the tape seals the edges and prevents permeation of fluids into the paper.  The use of tape on the back of the aluminum panel also eases future disassembly, since I was going to use silicone rubber adhesive.  Silicone is fairly resistant to cutting oils, seals, and is simpler to remove for repair.

After applying a  thin layer of silicone adhesive to the back of the panel I aligned and secured the panel with small clamps and wooden block.   Unless you seal the back of the panel, the aluminum corrodes with the acetic acid byproduct of standard silicone, unless a specialized alcohol curing electronic grade silicone is used (conformal silicone).  Let cure over night and reassemble the instruments.  I was satisfied with the outcome.  It's not going in a showroom or to a customer and it will soon exhibit typical shop wear, but easily replaceable.

Conclusion:  Check the hole alignment carefully and move the datum to suit your control box/panel.  My lathe uses a 5A fast blow 5mm x 20mm fuse and that's what I put on the panel graphics.  So check your manual.  You can modify/plot/print/laminate in many ways.  For fancy prototypes I typically use a white polycarbonate professional grade material, but the adhesives are not very compatible with machine oils.  I also didn't want to adhere the overlay to the aluminum panel and create more work later.  A laser printer is recommended.

Special Considerations:   I would be most appreciative if you would keep the Alkeehall-Labs logo and copyright on the "improved" overlay.  It's free for personal use only.  Commercial use or representations will require permission.    -7/24/2011-
 "Do not curse the crocodile until you've finished crossing the river" -African proverb-
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