Hi all. Does anyone know if single dosing would be bad for a grinder? At the end of the dose when the grinder is spitting out the last bits, it's essentially running with no resistance from beans.

Is that an issue, not an issue?

I can't figure out an efficient way to not single dose since I make espresso only 3 days a week (not in a row).

I've never seen anything that suggests not to do it and that includes the grinder user manuals. So many people do it, I find it very unlikely. There are duty cycles for the grinder motors, but even then I think those are under load while grinding. Thus you can probably run the without coffee for longer than the duty cycle rating.

The amount of current a motor draws and therefore the amount of heat it generates is smallest when the rotor is turning freely. So I would say that running the grinder without resistence is essentially free.

What you want to avoid is stalling the grinder. If the rotor stops turning the motor will pull its maximum current and the wire coils will get extremely hot. You can easily burn it out unless there's an over temperature cutoff or you lunge for the off switch.

Back EMF of the motor is highest at a high speed which means current is lowest and losses are lowest (both copper and steel losses).

See measurement at Automating the Versalab M3

Under no load current was less than 400mA RMS. At load almost 1.4A RMS. So 3-4 fold.

So you are safe.

As for burrs touching? No way. Don't let that happen.

I can't imagine single dosing to be bad for a grinder (the hardware) in any way.

It might have impact on grinds, or not.
BTW Single dosing can also be done with a weight on the beans right up to the point where the beans are being fed to the burrs as to prevent popcorning etc..

Burrs touching - that's something else entirely. That would be bad, but it has nothing to do with single dosing as such.

I do find that strict single dosing in some grinders just doesn't work well. My B Vario did it beautifully. My K30 doesn't really like it. While retention is nearly zero if I run the burrs longer to expel grinds, the consistency changes. I need a full number finer on the dial to not get a gusher and even then there is variation throughout the 18-20g ground into the PF.

Grinding finer all the time would wear your burrs more quickly.

One thing I believe you have to worry about with single dosing that you don't normally think of when loading a hopper full of beans is popcorning. Without the weight of beans above them to hold them down, the burrs can pinch beans and push them away rather than smoothly feeding them in to be ground. There's no extra wear and tear on the grinder, but it does affect the evenness of the grind. You just need to put something on top of the smaller amount of beans to hold them down. Preferably it should move down to keep pressure on the remaining beans as the grind progresses. Depending on the dimensions of the grinder you might be able to set your tamper on top of the beans while grinding. Of course, you don't want to use anything that might get caught in the burrs....

i think single dosing is fine, not sure why a lot of people are against it