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I am attempting to refurbish the drum switch on my 1939 Southbend Lathe. On these old machines the drum switch was used as the power switch and being a manually actuated switch, the contacts suffered over the years. The spring leaf contacts I can clean up pretty well using a small rotary sanding flap wheel at low speed. The rotary contacts however are a different story. One in particular is very eroded and corroded (see pics).My approach will be build up material by brazing then reshaping to the original curvature. The rotary contacts appear to be made from a bronze material and I suspect it is phosphorous bronze. Would using a phosphorus bronze filler rod work to build this back up ? My understanding is that phos/bronze is better suited for electrical contacts.Is there any special type of flux that would be required? I plan on using the smallest tip I have to try and keep too much heat from spreading to the hub area, maybe even clamping a heatsink in between the damaged area and the hub.Any input is appreciated.
Reply:You can buy new drum switches for South Bend lathes. Dave
Originally Posted by DivingDoug
I am attempting to refurbish the drum switch on my 1939 Southbend Lathe. On these old machines the drum switch was used as the power switch and being a manually actuated switch, the contacts suffered over the years. The spring leaf contacts I can clean up pretty well using a small rotary sanding flap wheel at low speed. The rotary contacts however are a different story. One in particular is very eroded and corroded (see pics).My approach will be build up material by brazing then reshaping to the original curvature. The rotary contacts appear to be made from a bronze material and I suspect it is phosphorous bronze. Would using a phosphorus bronze filler rod work to build this back up ? My understanding is that phos/bronze is better suited for electrical contacts.Is there any special type of flux that would be required? I plan on using the smallest tip I have to try and keep too much heat from spreading to the hub area, maybe even clamping a heatsink in between the damaged area and the hub.Any input is appreciated.
Reply:If you need a manual on lathe let me know.What size is the South Bend?Dave
Originally Posted by DivingDoug
I am attempting to refurbish the drum switch on my 1939 Southbend Lathe. On these old machines the drum switch was used as the power switch and being a manually actuated switch, the contacts suffered over the years. The spring leaf contacts I can clean up pretty well using a small rotary sanding flap wheel at low speed. The rotary contacts however are a different story. One in particular is very eroded and corroded (see pics).My approach will be build up material by brazing then reshaping to the original curvature. The rotary contacts appear to be made from a bronze material and I suspect it is phosphorous bronze. Would using a phosphorus bronze filler rod work to build this back up ? My understanding is that phos/bronze is better suited for electrical contacts.Is there any special type of flux that would be required? I plan on using the smallest tip I have to try and keep too much heat from spreading to the hub area, maybe even clamping a heatsink in between the damaged area and the hub.Any input is appreciated.
Reply:That looks as if the switch has been used to control a DC motor. If that's the case (and it may not be) you might consider some sort of arc snubbing diodes to keep that from happening again.
Reply:Dave - New drum switches are all kinds of expensive. My plan once I get the lathe going is to use a good 220v power switch and use the drum for direction control only. This is a 1939 11" model. I have downloaded several pieces of nomenclature from the goto southbend sites and have purchased a full wick kit plus the rebuild manual for the overhaul. The manual doesn't specifically cover this model but most of the mechanics are the same or very close. Not a full job as I am not going to strip and paint, just make it reliably functional.Doberman - These drum switches are known for degrading over time as the speed of making contact is not a snap action so there is always plenty of arcing. Once the surface starts degrading, it accelerates the damage.So still needing some input on the brazing and filler material.Thanks...Doug
Reply:Most drum switches used a silver oxide alloy. I never tried to repair I only replace the drum switch. Here one will work on your lathe under $20.00.https://www.amazon.com/dp/B08176N6GS...N97ERATD9DAP_0The one I have past is Dayton but price is $118.00 today. If you need help with wire the new switch I help with that part too. Dave PS:The switch South Bend used then was Furnas witch is very costly today
Originally Posted by DivingDoug
Dave - New drum switches are all kinds of expensive. My plan once I get the lathe going is to use a good 220v power switch and use the drum for direction control only. This is a 1939 11" model. I have downloaded several pieces of nomenclature from the goto southbend sites and have purchased a full wick kit plus the rebuild manual for the overhaul. The manual doesn't specifically cover this model but most of the mechanics are the same or very close. Not a full job as I am not going to strip and paint, just make it reliably functional.Doberman - These drum switches are known for degrading over time as the speed of making contact is not a snap action so there is always plenty of arcing. Once the surface starts degrading, it accelerates the damage.So still needing some input on the brazing and filler material.Thanks...Doug
Reply:Posted by DivingDoug: My approach will be build up material by brazing then reshaping to the original curvature. The rotary contacts appear to be made from a bronze material and I suspect it is phosphorous bronze. Would using a phosphorus bronze filler rod work to build this back up ? My understanding is that phos/bronze is better suited for electrical contacts. |
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发表于 2022-7-16 15:51:36