torqueman2002
Well-known member
CM grinders with Block style motors use various power switches (PSW), determined by horse power and date of manufacture.
I have read of at least 1 switch with a plastic body and toggle like the ones below, where one of the terminals pulled loose from the rivet.
Yesterday, while I documented replacements for the plastic PSWs, a terminal connected to the lamp conductor, pulled loose from the back of a black/red OEM PSW.
I have seen 2 different colored plastic PSWs - black/red & white/black. I believe the color is the major difference.
To my eye, the failure is due to insufficient rivet material above the terminal.
With a thin blade screw driver, I gently teased apart the 2 halves. I'm surprised this 30+ year old plastic didn't break.
The off-white goo, in the top (left of picture) and bottom, must be old grease that has thickened to almost-dry putty. The greenish color maybe from the oxidation of the conductor strip(?).
All the bits 'n pieces were cleaned with electrical contact cleaner. The contacts and terminals were burnished and then cleaned with Iso. Alcohol, as were all the other parts.
With everything clean, the next task is to place the terminal on the rivet. This step required a bit of fiddling with part of the rivet that extends through the terminals.
The 'head' of the rivet inside the switch, is the contact-point and care needs to be taken to not damage it during repair.
The rivet 'tail' was worked 'straight' with small needle nose pliers, to allow the terminal to be re-fitted over the 'tail' of the rivet.
An oval-head wood screw was used to back-up the rivet head. The PSW body was positioned over the screw, with the head of rivet resting on the screw head.
A small socket and screw driver handle, were used to seat the terminal over the rivet tail.
The rivet was 'set' using a small flat drift, small BP hammer, and the screw head.
The internals were coated with dielectric grease and reassembled into their respective PSW body half.
After the 2 halves were gently put together, the re-furbished PSW was tested.
I prefer a voltage drop test. I did not take the time to do this.
http://www.fluke.com/fluke/uses/com...articlecategories/electrical/diagnosevoltdrop
As an alternate, I used a static resistance (Ohms) check.
http://en-us.fluke.com/training/tra...al-multimeters/how-to-measure-resistance.html
With the meter set to resistance, I hook the leads together, to measure the meter/test lead resistance (000.2 Ohms).
The Fluke 87 has a relative (small triangle) resistance feature; this sets the reading to 000.0 Ohms with leads connected together.
Open circuit (OL.).
000.2 Ohms between the terminals on the rivet.
Open circuit (OL.), with PSW in the OFF position.
000.2 Ohms with PSW in the ON position.
After cycling the PSW ON/OFF for 25+ times, the above readings remained unchanged.
As I write this, I have decided as an extra measure I will apply metal epoxy to the terminal and rivet.
Thanks for looking.
I welcome your comments and suggestions.
Link to thread "CM Block Grinder power switch - replacements" --> http://www.garagejournal.com/forum/showthread.php?t=310418
I have read of at least 1 switch with a plastic body and toggle like the ones below, where one of the terminals pulled loose from the rivet.
Yesterday, while I documented replacements for the plastic PSWs, a terminal connected to the lamp conductor, pulled loose from the back of a black/red OEM PSW.
I have seen 2 different colored plastic PSWs - black/red & white/black. I believe the color is the major difference.
To my eye, the failure is due to insufficient rivet material above the terminal.
With a thin blade screw driver, I gently teased apart the 2 halves. I'm surprised this 30+ year old plastic didn't break.
The off-white goo, in the top (left of picture) and bottom, must be old grease that has thickened to almost-dry putty. The greenish color maybe from the oxidation of the conductor strip(?).
All the bits 'n pieces were cleaned with electrical contact cleaner. The contacts and terminals were burnished and then cleaned with Iso. Alcohol, as were all the other parts.
With everything clean, the next task is to place the terminal on the rivet. This step required a bit of fiddling with part of the rivet that extends through the terminals.
The 'head' of the rivet inside the switch, is the contact-point and care needs to be taken to not damage it during repair.
The rivet 'tail' was worked 'straight' with small needle nose pliers, to allow the terminal to be re-fitted over the 'tail' of the rivet.
An oval-head wood screw was used to back-up the rivet head. The PSW body was positioned over the screw, with the head of rivet resting on the screw head.
A small socket and screw driver handle, were used to seat the terminal over the rivet tail.
The rivet was 'set' using a small flat drift, small BP hammer, and the screw head.
The internals were coated with dielectric grease and reassembled into their respective PSW body half.
After the 2 halves were gently put together, the re-furbished PSW was tested.
I prefer a voltage drop test. I did not take the time to do this.
http://www.fluke.com/fluke/uses/com...articlecategories/electrical/diagnosevoltdrop
As an alternate, I used a static resistance (Ohms) check.
http://en-us.fluke.com/training/tra...al-multimeters/how-to-measure-resistance.html
With the meter set to resistance, I hook the leads together, to measure the meter/test lead resistance (000.2 Ohms).
The Fluke 87 has a relative (small triangle) resistance feature; this sets the reading to 000.0 Ohms with leads connected together.
Open circuit (OL.).
000.2 Ohms between the terminals on the rivet.
Open circuit (OL.), with PSW in the OFF position.
000.2 Ohms with PSW in the ON position.
After cycling the PSW ON/OFF for 25+ times, the above readings remained unchanged.
As I write this, I have decided as an extra measure I will apply metal epoxy to the terminal and rivet.
Thanks for looking.
I welcome your comments and suggestions.
Link to thread "CM Block Grinder power switch - replacements" --> http://www.garagejournal.com/forum/showthread.php?t=310418
Have to wonder why they did a nice job on the center contact ? Looks like a different type of "rivet"