As the inventor of the Knife Sharpener Coffee Roaster Making Your Own 57 Ounce Roaster Updated Again, I can't help but think that every kitchen needs a small drill press.

In particular, I wonder what the difference between a Robur or a Versalab is and a drill press. (I'm not talking yet about dosing, etc., but the basics). The Robur and other such grinders seem to generally have large heavy motors and a way to accurately bring the burrs into proximity to each other. The large heavy motors are necessary for direct drive machines.



The Versalab seems to be closer to a mini-milling machine or drill press in that it has belt drive and therefore doesn't need a massive motor, and it has a way to bring the burrs together, though not with micrometer repeatability. (I know they have a scale, but I'm talking about machinist's tolerances, not lining up some dots.) I haven't measured run-out on the Versalab, but I suspect it isn't better than a drill press, but I am not at all sure about this.

For me, what Versalab has contributed is the ability via the belt drive arrangement to have an unimpeded exit for the coffee grounds. This seems (as a former Rossi 45 owner) to be a huge improvement for someone who wants to experiment with different coffees and grinds and not be always cleaning out the chute and doser. Roburs and all traditional grinders require that the grounds be swept out through a chute. This is clearly not an elegant design, but required because the motor is under the burr. It also doesn't matter if you are a shop doing volume.

SO:
1. If I made a shaft for a Robur inside burr ($160) and mounted in a small drill press ($120) and

2. Milled the table of said drill press so that it would hold the lower burr still and have a large hole in the bottom for the grinds to exit

Would I have something that grinds coffee as good as a Robur? (I didn't say "as convenient" or "as stylish" or "as sexy", but as "good"?

The input side of the device could range from a paper cup to a nice delrin funnel. The output could range similarly.

Here is what I'm wondering:

a. Do small drill presses have small enough run-out so as to do justice to the expensive burrs, or would there be too much "wiggle" which would negate the whole idea. This is the biggest unknown for me. The quill arrangement on a small drill press seems more or at least as robust as the Versalab. On the Robur, depending on how much play there is in the burr holders, there could be more or less run-out.

b. Drill presses, assuming a., isn't a factor, might have significant advantages over Roburs because they offer variable speeds and the table holding the lower burr can be raised on the rack and pinion for quick cleaning and lowered back again to the exact same position. Similarly, one could use the fact that the top burr is in the drill chuck to raise and lower it by resettable, microscopic amounts. One could even do it on the fly and make layer cakes out of pucks (vary the grind).

Centering the bottom burr relative to the top burr isn't hard.

I guess it is going to boil down to run-out. I wonder what the run-out on a Robur is? and whether we are talking about something similar in spec to a cheap drill press or to a Bridgeport mill.

Any feedback before I make a fool of myself would be appreciated.

Kind of a neat idea...

I would envision a 'table' with legs to hold the bottom burr, so that a funnel or basket could be placed directly under the burr. Shims, or fine-threaded height-adjusters could be used to raise or lower the 'table'.

You may want to pick up the drill press first, and check for run-out. You could always return the press and not be out any cash.

I have drill presses in my shop that I can test it out in a jury rigged fashion. Amazon has a Skill brand press with a rack and pinion table that caught my eye. I'd mill out a hole with an lip a bit bigger than the size of the bottom burr and drill the burr mounting holes oversize to allow for centering.

I kind of suspect (hope) that run out won't be a problem because there is no way that the Versalab with its long free shaft won't have significant wobble caused by the beans during operation, even if the run out is minor without a load of beans.

Hi Dan, that's a brilliant idea.
A combination of Robur,Versalab & Pharos.
As OE Pharos already proved it for manual grinder, this should be success ingredient.
Yours could be come out with a grinder with Robur grind quality, minus the Versalab slippage, with adjustable speed with market friendly prices.

If you already have the drill press, building the prototype should be easy.
My input, a rigid single block unit to hold both burr carrier maybe helping to make the burr center , precise and consistent.
I'm imagining something like Pharos frame on single block. Because motor usually create more forces that a simple plate and bar possibly couldn't stand (at least not in long run). You could mill it to make the prototype and cast it for final product.

Just a brilliant idea!

Wobble is a big deal for consistency (one only needs to look at the grinds of a hario mini mill) and most good hand grinders have a solid lower carrier.

What I meant was the Versalab doesn't have precisely repeatable adjustment. I assume the adjustment can be as precise as you want, but if you change the adjustment, getting back to where you were exactly isn't accomplished by a 'stop', but by eyeballing the dial. That's probably good enough, depending on the time of morning and your eyesight.

I'm aware that hand grinders (other than the Pharos) wobble. See Spong Coffee Mills: A Grinder for the 23rd Century. However, it seems that hand grinders generally operate under slightly different principles. The traditional hand grinders are not precision in any aspect of their construction, from the shaft, handle, burrs and bearings. I made a Spong more precise with the addition of a thrust bearing and it made it worse, not better! They can still do an excellent job. Notwithstanding my admiration for the Spong and more recently the Mimoso, preparing a dozen or even 4 consecutive shots is a challenge to my patience.

What I'm considering is basically duplicating the grinding functionality of the Robur using its burrs but a different framework for holding them, that's all. I'm trying to figure out if I'm missing something obvious (such as will my wife like a drill press in the kitchen). Luckily Mazzer sells its nice MM badges... for less than $10.00

Sounds like a fun idea. Seems to me, though, that a Robur's heavy duty design will hold the burrs in relative alignment a lot better than the $120 drill press. If you replace the drill press with the Bridgeport, that might work real well. What would your wife say about a Bridgeport in the kitchen?

If I would ever want to pursue something like this, I would do so with a set(s) of USED Robur burrs.

Its not the runout of the drill press you need to be concerned with (although that is a factor) - it is the runout of the connected gizmos - chuck, driveshaft, etc. As regards using the rack & pinion table mechanism on an inexpensive drill press to adjust burrs - it is about an order of magnitude less precise than a typical grinder, not to mention the radial play which typically gets simultaneously locked with the height adjustment.

Yes, it is a forward thinking idea and sincere kudos to you for thinking of it but . . . not today.

Eric,

Thanks for your substantive reply. You could be correct; we'll see. My thought on the issue of the chuck run out, if it turns out to be an issue, is to get rid of the chuck and if the drill press has an MT2 shaft (some do), make an adapter that will hold the shaft that holds the inner burr. Or another adapter than MT2, if required. That isn't difficult.

The table, can be made precise with some minor additions which are easier for me to show than to explain. It involves a way to force registration in what are probably not precise parts. Similarly, the rack and pinion can be stopped by a collar that is micro adjustable, (a double collar, one threaded into the other). This would allow the rack and pinion to be used to open the burrs for cleaning and the collar is used as a micrometer/stop. Again, not difficult. Or I could use the moving quill as the way to bring the burrs into the right place, again using finely threaded parts and the quill lock (though that will probably cause some run out).

However, the cheap drill press itself might not be robust enough and I won't be able to tell without testing. So first I'll try with one of my existing drill presses.

I'm a former letterpress printer (who still has his fingers) so I'm used to making massive antique iron do precise things on the order of ink film thickness... While I'm just a novice machinist, maybe that's why the tolerances of a grinder don't seem particularly intimidating. The difference between a satisfactory ink film and not is much less than .002", which isn't itself super impressive, but that's what I used to deal with. Anyhow, more substantive criticism is welcome because it will save me a lot of time. All of the above sounds like a lot, but it is really a couple evenings or three of machining...

Thanks again.

dan

There's really not much difference between a Hobart 100 qt mixer and a Bridgeport Mill and a Robur... They all go round in circles and the Hobart has planetary gears....