I think I have a new favourite. <3 thanks guys.
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Oh hi there @woodtechs . That looks familiar. 
Iāve already mentioned this to @joeatkin2, but the centrifugal switch in that thing is gone, so the starter cap is never switched in. You can spin start it manually but that goes against your rules so please donāt do that. 
We did open it up and looked insideāsomeone had taken a needle file to the switch contacts, so thereās no coming back from that. Furthermore even if the contacts were fine, the switch isnāt staying in the location/position it needs to be inside the motor housing, and I suspect this is the current status of the sander. I think itās fairly obvious whatās wrong once you look inside.
TL;DR: youāll need to order a new centrifugal switch. Hereās a link (to a link) to the/a manual (different brand but identical), along with some tips on opening the thing up: https://wiki.london.hackspace.org.uk/view/Equipment/Axminster_Belt_%26_Disc_Sander
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Cool thanks for the info!
This thing huhā¦
https://www.mmtoolparts.com/jet-centrifugal-switch-jsg-6dc-990019
Can someone take a look see inside the machine? Thanks!!
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That link stopped workingā¦ try this one:
https://www.ereplacementparts.com/centrifugal-switch-p-939903.html
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Ok Iām not an expert but Iāve done basic google search and looked at the magnetic switch. I assume the first thing is to change the switch contact (we have a spare one in the space but maybe it belongs to @joeatkin2 or someone else). We can then test the motor without the belt paper that Iāve removed (less torque required). If it works changing or cleaning the centrifugal switch is the next step. @liyang did you already access the motor to clean the centrifugal switch? Thank you
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There was no mention of a magnetic switch previously! (Did you mean the on/off & e-stop?)
Yes I (together with two others) figured out how to access the centrifugal switch, and have cleaned the contacts as best as we could around July. But itās equally (or more) likely that itās just currently dislodged, and not functioning. See my above link to the LHS wiki for some details.
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Yes.
Iām certain that part is working perfectly fine. The caps also measured fine on our LCR meter.
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Amazing i incorrectly thought you mentioned and issue with the start/stop switch tooā¦ no point in me guessing if you have have already opened and cleaned the centrifugal switch.
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Itās on my list of things to fix but until Iāve got the belt sander running Iām not going to take it to bits I donāt like having two machines in pieces at once I think itās the centrifugal switch that fails but Iām going to have to take the motor bits to figure out what the problem is
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So yesterday @joeatkin2 and me disassembled the thing. Its tool page cannot be edited like other wiki posts there for some reason, so Iāll leave instructions here alongside findings.
Instructions
Hereās a wiring diagram:
Multimeter test points available:
1, 2, 3, 4 - on the power switch
5, 6 - on the starting capacitor connector
7, 8 - on the running capacitor connector
9, 10 - on the centrifugal switch (inside motor housing after disassembly)
In order to access the centrifugal switch:
- Tooling: bolt heads are 10mm, allen key holes are 10mm except motor shaft, screws can be undone with flat screwdriver
- Centrifugal switch as well as winding wires are located inside the motor housing on the right side of the unit - next to disk sander.
- Start with removing the disk part. The disk is connected to the motor shaft with three small hex head set screws (one is missing) which could be accessed through the single hole from the top one by one when the shaft is rotated.
- Remove the casing on the belt end. It is impossible to remove the lower belt drum without removing the motor shaft, so only undo the nut on it.
- Unscrew motor and belt assembly from the stand.
- Remove four bolts on the right side of the motor only. Pay attention to three scratch marks made by someone on the paint of the right cap which are used for alignment when assembling.
- Use a wooden mallet on the shaft (belt drum side) and wooden wedges to move the shaft and undo the right cap of the motor gaining access to the centrifugal switch. Be careful not to damage the wiring, you cannot undo the cap without disconnecting the switch first.
What the final result looks like.
Findings
The problem is, as was mentioned earlier, the centrifugal switch should be normally closed when the motor case is closed and now it is not. As seen on the picture below, It consists of two separate parts - centrifuge and switch. When the centrifuge rotates, its black plastic cap should stop pressing switch contacts, disconnecting the start capacitor and start winding. Currently, black plastic cap doesnāt reach the switch in any position/state leaving it permanently disconnected. Switch is working fine when pressed, wiring is ok, so it is safe to assume it is bad positioning of the centrifuge relative to the switch. And thatās when things stop making sense.
The current distance separating the centrifuge and the switch on a shaft is around 22mm. The shaft is stepped, so the switch cannot move at all in its final position. Switch/bearing step diameter on the shaft is 30mm. We didnāt undo the centrifuge so we donāt know if the shaft beneath it has another step, but visually it seems likely. Centrifuge is also bound to the shaft by the set screw. Hereās how it looks like:
So now we have two possibilities.
- Centrifuge is positioned only by the set screw with no kind of recess or shaft step (or screw moved out of recess) which allows it to slide along the shaft.
Pro: easy explanation. Can be fixed by threadlocker and drilling a recess for the set screw.
Con: seems to be a really bad case of engineering, where looking at the other parts it is unlikely. - Centrifuge is now positioned properly using a step. The assembly is missing some sliding part between it and the switch.
Pro: Redeems engineering.
Con: Spare parts linked above donāt have anything like that.
Current status
@joeatkin2 proposed to contact Jet and ask for a motor exploded view which is missing from the manual.
Sander is partially reassembled. Need to decide further actions.
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Thanks @scythian and @joeatkin2 for the diagnosis!
As we know it has been apart before, it is very possible that it was just not put back together properly.
From some research it looks like the set screw indeed keeps the position of the switch and it needs to be properly adjusted to workā¦ from another vendor, but very similar setup:
I would have to take a look, but as it is adjustable I would guess it is by design that it has no recess or step to hold the set screw. So I think it is possibility 1 not 2. Does the set screw not hold it? Is the whole assembly rotated in the wrong orientation?
This video may help as well, seems that screw is what holds it to the shaftā¦ obviously loctite may help if it is loosening for some reason:
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Let me contact the manufacturer and get the proper clearances and setup.
Trying to avoid guesstimating and stuff
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Go for itā¦ thx
So five months after this is fixed.
Centrifuge is positioned inside using a 6mm thick custom washer and is threadlocked so it shouldnāt slide anymore. Switch part was broken in the process and redone on CNC from tufnol whale. Contacts on the switch are in questionable state.
Previous disassembly instruction should be updated - thereās no necessity to remove belt part and motor from the stand. Remove disk side (cap, two grub screws on the shaft, guard), undo disk side motor bolts, tap belt drum shaft nut with wooden mallet - motor lid on disk side will undo, detach it further using two screwdrivers as levers.
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Thanks Roman it works really well! It would only need a side extraction, i think next to the belt sander (judging by this evening test)
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Awesome! Thanks Roman!!!
Nicely done! Incredible persistence!
