Crabtree isolator switch/Myford MG12

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Crabtree isolator switch/Myford MG12

This topic has 12 replies, 2 voices, and was last updated 29 April 2020 at 14:08 by Ian Armstrong.

Viewing 13 posts - 1 through 13 (of 13 total)

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27 April 2020 at 18:07 #467461
Ian Armstrong
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@ianarmstrong78579
Hi all

I hope you are safe and well

Can anyone help with pictures of the fitment of the bias spring on a Crabtree machine isolation switch? Mine is fitted to a Myford MG12 cylindrical grinder and is situated at the bottom of the door, with the function of precluding you having a mostly live machine with the door open.

The spring should return the lever to the 'off' position with the door open, so it engages with the switch when the door is closed.

Thanks

Ian
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27 April 2020 at 18:07 #13855
Ian Armstrong
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@ianarmstrong78579
27 April 2020 at 19:06 #467469
Anonymous
Posted by Ian Armstrong on 27/04/2020 18:07:04:

Can anyone help with pictures of the fitment of the bias spring on a Crabtree machine isolation switch? Mine is fitted to a Myford MG12 cylindrical grinder and is situated at the bottom of the door…………

Yes, but not right now as I'm going to do a bit more gardening before it honks it down over the next couple of days. I'll give mine (also on a MG12) a clean and take some pictures tomorrow morning.

Just a thought, is the spring you mention on the handle on the door, or on the isolator proper inside the cabinet?

Andrew
27 April 2020 at 21:47 #467496
Ian Armstrong
Participant
@ianarmstrong78579
Andrew

It is the mechanism on the door. One end of the spring is tethered to the through door fastening screw, the second is somehow connected to the barrel in the centre- that is what I'm looking to understand.

I'd mail a picture, but haven't worked out how to append one here yet. Not sure if the forum software likes Firefox

Rgds

Ian
28 April 2020 at 09:55 #467564
Anonymous
Pictures of the lever and spring, in the OFF position:

And the ON position:

The spring is pretty weak, wouldn't pull the skin of a rice pudding. The geometry is such that the spring tends to move the lever to whichever setting is selected. It certainly won't return a lever in the ON position to the OFF position. Given that you can't open the door with the lever ON I can't see why you'd want the spring to return the lever to OFF?

Andrew
28 April 2020 at 10:36 #467580
Ian Armstrong
Participant
@ianarmstrong78579
Andrew

That is perfect!

My set up has been abused prior to me opening the door. It is missing the lug that the spring locates in.

That lug, whilst logical, is new news to me

I think my logic is with the door open the main switch is 'Off' biasing the knob/lever on the front door to 'Off' also means when you shut the door, the pin on the switch and the mating groove in the barrel line up.

Can you point an infrequent user to how you attach photos? I have to icons for image and insert image, that don't appear to allow easy navigation to files on my PC.

Many thanks

Ian
28 April 2020 at 11:05 #467589
Anonymous
Pictures need to be uploaded to an album before inserting in a post. Here's a link to a "how to post pictures" thread:

**LINK**

Andrew
28 April 2020 at 11:10 #467592
Ian Armstrong
Participant
@ianarmstrong78579
Thanks for your help Andrew
28 April 2020 at 11:11 #467593
Anonymous
Posted by Ian Armstrong on 28/04/2020 10:36:07

I think my logic is with the door open the main switch is 'Off' biasing the knob/lever on the front door to 'Off' also means when you shut the door, the pin on the switch and the mating groove in the barrel line up.

Logic is good as far as it goes. But you can't open the door with the lever in the ON position. The only way to open the door is with the lever in the OFF position, which is where you wanted it in the first place.

Andfrew
28 April 2020 at 11:32 #467601
Ian Armstrong
Participant
@ianarmstrong78579
We might be strongly agreeing.

No expectation of the door opening with the switch set to 'On'

Two stable spring positions makes sense. What wouldn't, would be a door that need an intervention to get it to close ie if the spring caused the knob to default to the 'On' position with the door open.
28 April 2020 at 12:04 #467609
Ian Armstrong
Participant
@ianarmstrong78579
Andrew

At first thought, I imagined that the item I call the barrel was missing a lug, and that had been snapped off. On inspection there is no sign of damage on mine. I suspect the part that looks like a lug is also where I have a drive recess.

Do your photographs actually depict a headed pin with a hole in it?

Ian
29 April 2020 at 11:04 #467805
Anonymous
The lug is part of a serrated pin that holds the shaft on the lever to a collar with slots in it to drive the contactor. If that's not clear I can take pictures, or create a sketch.

Andrew
29 April 2020 at 14:08 #467862
Ian Armstrong
Participant
@ianarmstrong78579
Andrew

Again, thanks. I removed (what was left of ) the pin to see a crystalline fracture point where the head shown in your picture should have been.

All clear to me know. Next a small turning job.

Rgds

Ian
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