I have been trying to get this grinder (M4 black stepless with doser and on/off button) but think there may be a manufacturers defect in the newer crop:

I already got one from a very reputable vendor and it shut itself off when running EMPTY at various intervals from 1 1/2 mins to 8 mins while adjusting the dial. It gets hot when it shuts off and stays hot (all on the upper back of the body).

Now: my friend got the same model (from a different vendor!) and his is having similar problems. I witnessed this: He set the zero point, backed off, and ran it for under 10 mins (to try to adjust from coarse to fine--a long stretch and motor must be running when doing so) . and it shut off. It wouldn't go back on again for 2-3 mins, even after unplugging. Then he got it to go on again and it shut off after 3 1/2 mins and the same area (upper back of body) was hot. It stayed hot for 2 hours unplugged. There is a bit of a smell of warm rubber or petroleum product on his too, from the start.

What can be going on with these?
Thanks.

Why would anyone want to run their grinder for hours without beans in it?

Most grinders are not designed for long duty cycles, especially the smaller ones. Some are quite short, as shown below for the Mazzer Mini E:



Why you would want to run it for minutes at a time?

Bluecold wrote:Why would anyone want to run their grinder for hours without beans in it?

Not for hours. A few minutes. Adjusting, etc.

A few minutes is way, way too long. Even commercial grinders like the Compak K10 WBC has a limit of 3 minutes on, 5 minutes off. You're overheating the motor.

Well--if you actually try to adjust from fine to large grind it can take several minutes of turning the knob and the machine must be running when doing so, per the manufacturer's instructions and the vendors too.

Anyway, the vendors claim they don't know any specific time limit and that nothing is provided by the manufacturers. That is where one usually tries to get specific information.

Even the Tech at the vendor I used told me to run it for at least 4 mins and see if it turned off. You see the situation this is for a consumer?

If this is correct information now, it is really terrible that even vendors who supply warranty service don't know any specifics about this issue and that they will even tell you to run it for what people are saying is too long here.

I'm aware of the vendor/manufacturer advice about always running the grinder during an adjustment. Their concern is binding the motor by forcing the burrs together when the grinding chamber is full. Rather than explain the reasons behind their recommendations, they offer blanket statements, with the caveat that they'll void your warranty if you don't do as prescribed. I appreciate their predicament with a public that unknowingly does damage to new equipment and blames the reseller. However, to be clear:

• Grinder motors generate a lot of heat; they'll all overheat eventually, even if run empty
• Running the motor to the point that the thermal protector cuts off power is a bad thing
• How long it will take to overheat depends on the grinder. The owners manual may state the max on/min off time, it may not. I advise no more than 30 seconds on and a minimum of one minute off
• There is no risk of binding the burrs if the adjustment is coarser
• There is no risk of binding the burrs if the grind chamber is truly empty.

Finally, you may want to invest in one of these:


From Handy accessory for Macap stepless

Alternatively, consider this easy mod for Macap M4 stepless to adjust from espresso to drip.

Fine to large can be done OFF. Not so the other way.

Why on earth anyone would buy a stepless espresso grinder if they intend to grind press coffee boggles the mind.

In 2.5 years, my MC4 has varied ±2 turns and the motor can handle that minor a change with the power off.

I would like to feel like this is a friendly site that is here for people of all levels of experience and buying experience and that posting should be to offer help or advice (or ask for it) or have other friendly and respectful discussions.

While one person did offer what seems to be real and useful information in response to my request for help, a couple of people made very erroneous assumptions about what I use the grinder for or how long and then posted condescendingly based on their erroneous assumptions.

The reality is: it is not easy for many consumers to buy and understand what is at least quasi-commercial machinery and everyone has a learning curve, obviously, if they have never done this before. If we can't even get any straight information from the manufacturer or the vendors about the machine specs for certain behaviors--and I mentioned I was actually given information to let the machine run at least 4 mins from a vendor's tech guy who stated he did not know how long the machine should be able to run--we are not in a very good position to decide what is happening. People at that vendor also enclose a very strong written statement with the machine about not ever adjusting the machine without it running, as well. So all I have done is all that could be done for a person in my position and who is cooperative with the vendor.

So I would like to specifically thank Dan for posting useful, non-judgmental information in the spirit of helping people who want to make good espresso ultimately.

Sarah, you make good points. Much of this is confusing for someone new and inexperienced with this stuff. It actually doesn't make real sense to me that an expensive grinder cannot run for minutes at a time. It is an electric motor...we have cars driven by them!

As for forums, you will see different personalities all the time. This forum is pretty good when it comes top that. Stick with it. We definitely need an Espressogirl!