The Shop > Tools
Bench Grinders & Lathe Tools.
Pete W.:
As promised, I've taken a close-up photo of the shaft of the grinding machine, see below.
If this is the current professional standard for surface finish, does this mean that my efforts to emulate the surface finish achieved by the YouTube machinists community have been a misguided waste of time?
:bang: :scratch: :bang: :scratch: :bang: :scratch:
Fergus OMore:
Read John Ruskin on 'Price'. Not much of a model engineer but they did name a Cambridge University after him.
mattinker:
Looks like a suitable case for turn undersize and sleeve!
Regards, Matthew
Pete.:
That's normal for a cheap grinder. The plates rely on that little step but it's inadequate. This is why I turned my own side plates. I actually turned the plates as a 'plate and hub' so that the bit that sits on the shaft is longer. I then use wheels which have a larger hole, and it works very well, they run nice and true.
Pete W.:
Coincidentally, I was called in by Simon (a neighbour) whose polishing machine had blown up!! :zap: :zap: :zap:
It's an elderly Wolf double-ended grinder fitted with two shaft extensions to take the polishing mops.
He'd been busy polishing when there was a loud bang, a bright flash and all the lights went out!!! :zap: :zap: :zap:
We took the base-plate off the machine and found that the contents of the capacitor had exited the can in a spectacular manner. Sorry, no photo! Fortunately, the inscription on the outside of the capacitor can was complete and readable. I did a bit of resistance checking and found a 9.5 Ω run winding but, at first, couldn't find any conductivity through the start winding. Oh, I thought, either the start winding has blown or the centrifugal switch is defective. We'll have to take the bell off. That was as much as we achieved at the first session - other pressing matters shut that session down.
Two evenings later, off came the RH shaft extension and the bell to reveal NO centrifugal switch and nice honey-coloured windings showing no signs of over-heating. Just to check we took off the other bell, complete with rotor, and found NO centrifugal switch that end either. Things were looking up!! This time, I must have been less fumble-fingered with the Fluke probes because I found approx 20 Ω between the wires to the start winding. I also 'meggered' both windings to frame and got an infinity reading. A replacement capacitor is on order.
The reason I've recounted all this simple stuff is that I am inspired to hope that my own grinder (depicted in my earlier photos) is also a capacitor start & run type. I'll have to listen carefully for a 'click' during its start-up and run-down. If it, like Simon's, has no centrifugal switch, the complete removal of the rotor will be that much simpler and I'd be able to mount the whole rotor in my lathe to re-machine and sleeve the shaft extensions. The squirrel cage rotor will clear the bed and I'd support the outer bearing in the fixed steady.
Harold Hall's method of mounting the entire grinder on the lathe bed and turning its shafts using its own power is do-able but means inverting the tool when machining one end because the rotor is turning clockwise.
Has anyone else trod this path before me?
Watch this space!
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