That is my understanding of the normcore as well. When you bottom out there is the spring applying force between the shaft you are pushing on and the coffee. The spring then limits the overall force to "25lbs". I put the weight in quotes as springs all follow Hooke's law so if have a higher dose than expected it will be more force and a lower then less force but should be consistent for the same height of coffee in the portafilter .

That being said I have done no testing on mine, haven't taken it apart and looked at it to verify, but any other design makes zero sense....

I've been ruminating on this some more and I think people are right - you are supposed to bottom out the Normcore, which gets you consistency by passing any force greater than that needed to bottom out through the portafilter via the sliding collar. You still have the problem that depending on the length of compressed spring you need to reach the "bottom out" point (which depends on how much coffee you have in the PF) the bottoming out pressure will vary, but hey it's a cheapish tamper.

Now the Barista Hustle article quoted earlier has this chart in it:


Is this an accepted view of the world? It seems theoretically very simple - perhaps a bit too simple for my liking. But in any event, I was curious as to whether at "bottoming out" pressure I'm getting to the horizontal part of the chart or not. So I did this:

1. Using bathroom scales and the weakest Normcore spring (I still can't bring myself to call it the 15lb spring) I saw that just before I bottom out I get to around 25lb of pressure. With my 14g of Sumatran Mandheling I got 28g of coffee in 28s with an extraction which looked good on my naked portafilter (and after having sacrificed some beans to the grinder retention gods). I made a cappuccino so you'll forgive the lack of precise tasting notes, but past experience tells me this is a well extracted shot.

2. I then repeated with the middle spring (25lb sic) keeping everything the same (to the best of my ability!). It was just before bottoming out somewhere around 47lb of pressure. The shot extracted in 30s, which is a level of variation I would not describe as statistically significant for my set-up/skill level. However, the following shot extracted in 37s with the medium spring. I still don't know whether that's because of the heavier spring/tamp pressure or because of my inconsistent technique.

So on the face of it, that chart is probably how things work. But it's still unclear whether the 25lb spring gets to the horizontal section or not.

Happy tamping!

Is this an accepted view of the world?

Yes. Or at least it should be.

Once the puck has been fully compressed, tamping any harder doesn't do anything. Voids between grounds have been eliminated. There is nothing left to do. It doesn't take much force to compress it fully.

If you are not compressing the puck fully you are needlessly adding another variable that is hard to control.

I suspect the origin of the guideline to use a certain amount of force when tamping was to make sure baristas in training compressed the puck fully every time. Unfortunately this lead to home baristas turning it into another specific variable that now needed to be obsessed over. Which then leads to all kinds of gadgets.

If you want to know how much force you need to compress the puck fully, measure the depth of the puck in the basket as you increase the force. You'll see it eventually reaches a maximum. For the normcore, try with the lighter spring, then the medium. If the medium doesn't compress the puck any more then the lighter one then you are have reached maximum compression and don't need to worry about it.

Hi all,

I've used a cheap calibrated tamper from Amazon that actually works, and I've also used the Normcore (which doesn't work). The point of this post is to explain how a calibrated tamper SHOULD work if you're looking for consistency, and why the Normcore doesn't. This is not about the "right" tamping force.

1. The cheap Amazon calibrated tamper I used (Dailyart) functions similar to a torque wrench. The 30lb spring is stiff and does not start compressing ("break") until you've applied 30lb of force to it. Therefore, it directly transfers the energy of your downforce onto the puck, until you reach 30lb of force---at which point the spring breaks, letting you know to stop pushing.

2. The Normcore on the other hand does not do anything to indicate when you've reached the "specified" force of its tamping spring. Independent of its leveling spring, the tamping spring (using its "30lb" spring as an example here) will begin compressing almost immediately when you start pushing down---somewhere around 5-10lbs of force. It will continue compressing until it bottoms out, right around 45lb, and after bottoming out it will directly transfer any additional downforce onto the puck.

There is no way to know when you're at 30lbs. The only reliable indicators of force are when the spring first breaks (at 5-10lb) and when it has reached full compression (around 45lb). Anything between those points is a complete guess.

Furthermore, using the bottoming out method is not ideal because (besides the fact that you end up with a force far higher than the specification) once you bottom out, any additional downforce goes directly to the puck with no limit. And, unless you use the exact same beans and grind for every shot, you can't use tamping depth for consistency---and why would you want to? Your tamping spring should do what it claims and remove beans and grind as factors.

In closing, Normcore doesn't seem to understand the concept of what they claim to make. If you want to be accurate to a specification, you need (1) a consistent way to get there, and (2) a reliable indicator once you're there. It should be as simple as the concept of a clicking torque wrench---a stiff spring that doesn't break until you reach specified force.

FYI I no longer use the Dailyart because at 58mm it doesn't fill the basket, and it doesn't have a leveling plate. I switched to the MiiCoffee which has a 58.5mm diameter and a leveling plate. It doesn't have any tamping calibration.

All of your post makes sense apart from one bit. When the Normcore bottoms out, the additional force does not go via the puck - instead it passes through the collar via the portafilter. So you do get a known max force though it does depend on where the level of the beans is so it does vary a bit and it's a fair amount higher than the spring "rating".

Interesting there is a "torque-wrench" like tamper for $30 - I imagine it's only a matter of time before more of these are available with fewer flaws.

Good point on the additional force going to the portafilter, although like you mentioned I would think it depends on the volume of the puck. Hard to know for sure without a Normcore in front of me to test.

And yeah hopefully soon we'll see a tamper that functions like the Dailyart but adds a leveling plate with a separate spring, is 58.5mm diameter, and stays relatively cheap.

Ugh. Once it bottoms out, it rests on the part that sits on the edge of the basket, so no matter how hard you push it's not giving any more force to the plunger inside the basket because it's not moving any further.

Imagine you had a pogo stick and set it up over a 5 gallon bucket with a some towels bunched in filling 3/4 of the bucket, and say the spring post below the foot pads would normally extend half way down the bucket without the towels but no further due to the foot pads sitting on the rim. Now, with the towels in the bucket the pogo stick will compress them but once the foot pads hit the edge of the bucket the towels can be compressed no more no matter how much more weight you put on the top of the pogo stick. The towels will always be compressed the same amount as long as you push the pogo stick down far enough to hit the edge of the bucket. If you add another towel they will be compressed harder, but always the same amount for that dose of towels. If you use the neighbor's super fluffy towels, they will be compressed slightly differently, but always the same for those type of towels.

The Normcore works like this except it has a an additional disc that sits on the edge of the bucket and an inner collar that slides up into the pogo stick with an easily compressed spring that initially holds it away from the foot pads. That spring is so easy to compress that it doesn't impact the compression of the towels, it only keeps the pogo stick level in relation to the bucket. It also makes contact between the footpads and the rim of the bucket when the pogo stick is fully compressed.

Why ugh?

Anyway yes OP and I agreed that when it bottoms out the extra force goes to the PF. You still have the problem of the tamper being misleading in that it's not really calibrated though.

If you're going for consistency based on depth, then the calibrated spring isn't what you should be shopping for. If you're constantly trying new beans then you can't rely on depth for consistency, and that's where a calibrated spring would be useful.

natew545 wrote:Why ugh?

Frustration at myself for not being able to explain it clearly for everyone in my earlier posts in the thread.

Calibrated isn't necessary, repeatable is. The normcore is very repeatable if you keep everything else the same. In coffee where you are looking for reproducibility so that you can control variables this is all that is needed. In particular when you take the 'simple view' from above. Then one could say as long as you use a strong enough spring it is "calibrated" to make sure you stay in the flat area of the curve.

The variation of the $30 unit without auto levelling will create way more reproducibility concerns than any variation in force the normcore applies.