I tried the electric pepper mill Michael.

Should I have replaced the pepper with coffee, cause this tastes like liquid pepper

matadero210 wrote:I bought the 71mm, because they were cheap(er) and available. The bigger diameter works against a hand grinder, which is already free of over-heating problems. Increased diameter would increase the torque needed--and its a fairly firm crank at 71. It would be a lot easier if my hand was larger or the mill smaller (71 for the burrs, 74mm is my OD for the mill).

Thanks!

How much force do you think you use and how long is the Zass crank you use?

matadero210 wrote:In other news: I'm thinking about a grinder that uses differential screws. This would be two plates, with flat burrs mounted on each, and an axle and crank.

Raj,

Don't you think that conical burrs more completely expel all the ground coffee better than the flat burrs would? You could probably rig some sort of cam lock to open up the gap between the conical burrs to thoroughly clean them, as well.

- Steve

Mathias - its about 4"--from the Zass Turkish mill. I'm not good a guessing force, but I'm a dedicated couch potato/nerd, so it can't be that hard.

Steve - Maybe some kind of augur would help keep the space in the mill clear, but you are probably right about conicals generally expelling better. They have gravity working for them. I'll try to post a drawing of my current design ideas--there is screw that allows dissassembly and cleaning without messing with the grind settings (as there is on my conical design).

raj

Perhaps a crank like this one on ebay - 190131506249 - would make it easier.

That's fantastic! Another place for handles might be at Grizzly.com


I'd love to take a shot at a project like this. I've got a machine shop that I am learning how to use and this and the marriage threads are looking very intriguing as useful projects. I'd love to see a disassembly of your grinder too someday.

arri

Okeedokee, I've acquired a set of 71mm robur conical burrs. Well, actually, they're on their way. I am dreaming up designs to play with and really appreciate what has been done here. I agree that differential screw maybe a fantastic way to adjust. The versalab is a nice starting point... build a simple container to hold the fixed burr, and suspend the cone from the top with two bearings. I imagine there should be a thrust bearing of some sort to take the grinding force trying to separate the burrs?

In hindsight, did you end up being content without having bearings or support on both sides of the burr? I realize versalab does it without as well.

arri

Hi Arri,

Yes, I think bearings at the top only are the way to go with conical burrs. I'm thinking about a simple differential screw system based on 27 and 28tpi threads--you can buy 0.5 and 0.75 taps and dies. Or maybe lathe cut threads, though I don't know how to do interior threads on the lathe (super boring bar?). I'm still too worried about stale coffee remaining in the flat burrs to build the flat burr mill--maybe I'll try to retro-fit the existing one with differential screws.

I have a single plain bearing at the top to hold the cone axle in place, and a thrust bearing on the lever arm to take the axial force. Seems like wobble in the cone doesn't matter.

raj

That's interesting, I was actually moving back towards a lever arm from the differential concept! As far as machining interior threads on a lathe, it's not much different from the outside. Like you said, you'll need a boring bar. Problem is when they get small, and of course it's kinda hard to see what you're doing in there! Since you're thinking differentials, it is probably easier to just use taps and go with readily available standard pitch.
I'm not sure where on the machine you are talking about using the differential. Is it going to be part of the drive axle? (think about inertia affecting your setting) or is it offset (think about linearity) or is it on the static burr?

My concept for the pseudo versa lab is starting to come together, I haven't been in sketchup for a long time though, it killed my keyboard shortcuts so I feel like I'm starting from scratch there. I envy your solid works skilz.

arri

Here's a first shot at starting a model. I'll probably try to drive these big burrs with a hand crank to start off, then figure out motive power once I know how hard they turn.

obviously missing is the height adjustment, still working that out. I found a fun bearing search engine here:
http://www.bocabearings.com/

arri