Three Mod Night, or "Taming a Titan" (Macap M7K)

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#1: Post by Anvan »

After reading the Titan Grinder Project, Beat the Robur and other threads on this site a couple times through, I settled on the Macap M7K (68mm) as the large-bore conical grinder most likely to provide Titan-quality performance while being tame-able for practical use in our (patently non-commercial) kitchen.

Taming the M7K involved three modifications which I was able to finish in one evening. All three were fairly easy, and I'm documenting them here as one take-off point for anyone considering a similar project. The overall purpose is to optimize the M7K's usability and consistency in a single-dosing (grind-per-shot) routine, weighing the beans for one shot, grinding those beans, then dosing them out completely prior to grinding the next shot.

The general requirements for usability and success within this schema that required changes were (1) ease of grinder on-off control, (2) ease of access for cleanly sweeping the chute and (3) a usable bean hopper with consistent weight and pop-corning suppression at the grinder throat.

Some believe that any bean hopper weight, regardless of its construction, cannot perform as well as a mass of beans in the hopper. This may well be correct, but if you wish to single-dose or enable cycling through multiple blends within a session, that discussion is moot, at least short of (to me) unreasonable waste, fuss and/or time. So the objective of this project was to use the M7K's innate capabilities to optimize its handling and performance in repeated shot-by-shot weigh/ grind/ dose/ tamp cycles, replicating a partially full bean hopper within that context to the greatest extent possible, using reasonably common tools and materials you can find around your own home town (or for most, within a reasonable drive...)

Fair warning: I don't possess the crafting skills - never mind the tools - of some other H-B members, so the accompanying photos will not be exhibiting results that rise to, say, a Cannonfodder or RayJohns standard!

A Few Notes on the Stock M7K Grinder
It is not my intention to review the Macap M7K - instead I recommend the reviews extant in the TGP thread, which are especially helpful, but I will add a few comments here for those contemplating this grinder:
  • * I bought the M7K from 1st-line, who proved great to do business with, as well as the only practical domestic source for a Macap M7K. The single available model (M7KC83) is finished in chrome, has a doser and includes Macap's "dynamometric tamper" attachment which, if you like that sort of thing, can be attached to the grinder front - just press the lever down and it tamps your basket to 30 pounds, dead flat and even. (Just for fun I used it when running off a long series or two of 20-30 of practice shots. Frankly, it worked very well, although the tamper piston supplied is a lowest-denominator 57mm diameter which proves a little small for optimal extractions in my current baskets.)

    * Yes, the M7K is quite tall with the stock bean hopper attached. But cutting back this hopper is easy, and it's also easy to run the M7K with no hopper at all since (unlike the Robur for instance) there's no interlock you'll need to defeat.

    * It's not loud: the M7K runs with a relatively slow 400 RPM action, so you get a lower, powerful sound that's kind of reassuring. As mentioned in some reviews, during the first second or so there's an extra growl as the motor starts up, but this isn't loud either. Best of all, however, the M7K takes only about five seconds to grind a shot, then you're quickly back to dead silence.

    * The M7KC83 has stepped adjustments instead of the worm-gear I'd liked so much on the Macap M4. I considered buying the parts to convert the M7K to a similar stepless setup, but decided to try it out first. So far, the step gradation - given the conical burrs - has been sufficiently fine that I've left it as is: I've yet to need an adjustment where the steps provided aren't fine enough. (Still, it's nice to know that if someday I really want to change it, the mod is straightforward: replace the adjustment ring, drill two holes, attach the worm gear assembly, done.)

    * +1 to reviewers who remarked that this doser sweeps clean. There are almost no remnants on the dosing hopper floor - so little in fact that I haven't bothered with the usual add-some-tape-to-the-sweeper-vanes modification.

Ok - on to the Three Mod Night!

Anvan (original poster)

#2: Post by Anvan (original poster) »

First Modification: New Grinder Controls

The M7K comes equipped with an automatic doser filler function, which grinds additional coffee whenever the doser fill drops below about 2/3. This is accomplished with a pivoting vane which senses the doser's fill level and tips a micro-switch to grind more when needed. This mechanism blocks access to the grinds chute and is anathema to grind-per-dose anyway, is simple to detach (two screws). But its most useful feature is leaving behind a convenient controller wire pair - with handy spade connections - in a neat little built-in enclosure behind the dosing hopper, from which you can connect any kind of switch you like.

One complaint about Macap grinders is the on-off switch, which takes the form of a big rocker switch located low and on the right side of the main housing. It's under a waterproof flexible shield, but because of that shield, operating this switch can feel kludge-y - you have to press against a resistant ridge of the rubbery cover. This is fine if it's just used to turn the machine on or off for a session, but if you're going to use this switch to start/stop a single-dose grind (or especially "bump") multiple grinds, it's a little unfriendly.

So the first modification adds a second switch in an ideal position at the upper left of the doser hopper. I selected a SPDT ON/Off/(ON) toggle switch (Philmore 30-10010). It's mounted so that when you click the switch upwards the grinder will stay on until switched off; pressing down on the toggle triggers the spring-loaded momentary connection, making it easy to bump the grinder motor for fractions of a second to sweep and clear the chute.

The new switch is mounted by simply drilling hole in the doser's acrylic hopper. Feed the three wires (soldered to the switch's rear lugs and terminated with spades) joining the two "ON" poles and re-using the two contact wires remaining from the now-removed vane switch. You can attach them and stow the connectors inside the housing chamber provided. The back part of the switch and wiring are then sealed in shrink tubing for protection and cosmetics.

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Anvan (original poster)

#3: Post by Anvan (original poster) »

Second Modification: Improved Chute Access

The M7K features a generously sized wide chute that feeds the doser hopper. This makes it particularly easy to sweep it out for grinding single shots, a primary objective of this project.

To provide easier and more complete access to the chute, I cut away a section of the doser hopper. Since the natural direction of the exiting grinds is to the left in the hopper (and I'm right-handed for holding the sweeping brush) the section removed was biased to the right side, and cut just low enough to provide level access to the chute.

To cut the hopper, I traced the shape onto the acrylic cylinder, using masking tape to approximate the line to protect the remaining surface, then free-handed the curved cut with a Roto-Zip. Wet-or-dry sandpaper (200-600-1200) followed to smooth the cut edge, which was finalized with fine steel wool and polished with the small buffing wheel of a Dremel.

Since I had the Dremel out for polishing anyway, I used it to polish interior of the chute too, in order to ease the grinds' escape. Actually, the chute was very smooth to begin with - the Macap factory had done a nice job - but now it feels even a little slicker (although my take is that I'm well shy of claiming any measurable advantage).

I've had no problems at all with grinds escaping through the new, wider gap, and sweeping the chute is now much easier and more thorough. My routine has settled on (1) grind and sweep once, not too carefully this time; (2) "bump" the momentary grinder switch and sweep - again not too carefully, (3) repeat the bump/sweep twice more, thoroughly only after the final bump. Almost no additional grinds appear in the chute after the third and final bump/sweep so I regard further actions as being past the point of worthwhile returns.

It likely took you more time to read the above paragraph than it takes to complete the entire process it describes. Timed with a stopwatch, the three bump/sweeps after the initial grind add only 8-9 seconds to the grinding routine. The weight delta between the in-going beans and out-coming grinds is often zero, usually within 0.1g and almost always within 0.2g.

For sweeping, I've been using a long-handled pastry brush (Ateco model 60200) which fits the chute nicely. Ian Eales (cafeIKE) recently suggested brushes from - their 6005 Highlighting Wands, which I am going to try next, and may well work better still.

Anvan (original poster)

#4: Post by Anvan (original poster) »

Third Modification - Bean Hopper and Plunger/Weight

The dual objectives of this third and last modification are to (1) fit the grinder within the available cabinet clearance above the kitchen counter and (2) enable the best single-dose grinding possible without a hopper-full of beans.

The summarized steps below involve cutting the funnel, creating a cylindrical (straight-sided) insert and creating a matching plunger/weight.

Cutting the funnel was done by tracing a line at the measured height (whatever fits best fit under your particular cabinets). The easiest way is to steady a marker or scribe at the correct height (vise, stack of books, sleeping cat - whatever) and then mark the circle by turning the inverted hopper against the marker through the full 360 degrees. Apply masking tape right up to that line to protect the final product from scratching, hold the hopper steady (vise, clamps, teen-age volunteer) and cut. In a perfect life, one would own a band-saw for this, but a fine-toothed hacksaw works fine.

After cutting, you will have a short funnel for the top, and if you don't care about pop-corning you can stop right there: the Macap hoppers provide a neat sliding barrier at the hopper bottom, about 1¼" from the top of the burrs, preventing unauthorized escape of rogue bean shards. However, if you went so far as to procure a Titan grinder, I'm guessing that you do care about pop-corning, so onward we go.

The cast metal grinder throat of the M7K is slightly conical; it does not have straight sides. So the part of the acrylic Macap bean hopper that fits into that throat is also conical - on the outside, but, critically, not on the inside! Macap's acrylic gets progressively thinner toward the bottom, providing essentially straight sides on the inside. This enables construction and installation of an inner cylinder - with a constant inner diameter top to bottom - through which the plunger/weight can travel to control the beans all the way down to the burrs.

I got some clear acrylic tubing from my local plastics supplier with an outside diameter of 2 3/8" with 3/16" walls, leaving an inside diameter (for the beans and plunger/weight) of 2". Regarding these dimensions, only that outside diameter of 2 3/8" inches is critical, since that equals the inside diameter of the Macap funnel throat into which the cylinder must fit.

You will also need to grind some plastic out the top of the funnel base (Dremel again), removing the channels for the aforementioned Macap sliding barrier. This is needed so the funnel will accept the full diameter cylinder, which is otherwise constrained by the presence of these slider channels.

For my own setup, I cut three lengths of the acrylic tube, the first one being 1" long, plus an additional 2" extension tube and finally a longer 6" extension tube (using the same scribing/tape/hacksaw routine used when cutting the funnel above).

The shortest 1" piece fits inside the bottom of the Macap funnel. This piece fits tightly enough without help, but you can keep it even more firmly in place by tightening Macap's original funnel retention set screw through one of the slot-holes in the funnel base and tightening it against the wall of your new inner acrylic cylinder.

This is really all you need, just tossing the beans into the funnel base with this 1" piece installed, and using the plunger/weight. In this configuration, you'll be at the minimum height (for under the cabinets, remember) plus as the picture shows, it's the perfect storage location for an Orphan Espresso 58mm dosing funnel (if you don't already have one of these little genius gems, go order one from the OE Web site right now since it will change your life).

The 2" or 6" (or whatever size you like) extension tubes can be added on top, however, to give you a deeper total cylinder in case you want to grind more beans at a time, or you wish to give the plunger/weight more stability. To hold the extension in place, there's roughly half an inch of the Macap funnel base left above the bottom 1" tube to lock the extension in a nice tight press-fit - but it's easily removed whenever you want to slide the grinder back under your cabinets or use one of the other hopper options. Note that the same plunger/weight is used in all cases to maximize consistency.

This picture shows the 6" extension set into the funnel on top of the the 1" base tube:

You'll also discover that it's easier to pour all the beans into the extension tube's opening if you place or fasten another Orphan Espresso dosing funnel (49mm this time) on the top of the extension tube.

The final step of the project is making the plunger/weight. I used a solid cylinder of UHMW (ultra-high molecular weight) polyethylene rod stock with a 1¾" diameter that fits inside the new acrylic bean cylinders. For a half-pound weight, cut about 6".

Since the inside diameter of these cylinders is 2", that leaves 1/8" of play all around, which is ok but I'd have preferred the UHMW to be 1 7/8" for a slightly tighter fit. My local plastics supplier only carried the 1¾" diameter stock however, and the only place I located 1 7/8" diameter UHMW rod on the Web required a $600 minimum purchase. So: you may have an easier time if you use a slightly thinner wall (1/8") acrylic, which would leave a wider inside diameter of 2 1/8", enabling the more readily-available 2" diameter UHMW rod to be used for the plunger/weight and providing a slightly better fit.

To make the plunger, I started by cutting a 6" length of UHMW bar, then sanded the ends smooth. Advice: use a fine saw blade for the cut, which will make your sanding a lot faster and easier. UHMW is great material to work with and it machines beautifully, but sanding out a coarse cut with deep scratches will take you some time since this stuff is dense-dense-dense. You also need to sand it very smooth since otherwise, grinder fines will lodge in the scratches and the plunger/weight gets dirty-looking at the ends pretty fast - although you can always fix that via dishwasher.

In the top center I drilled a pilot hole for a stainless eye bolt which, while perhaps less than the acme of elegance, proves very easy to hold or pull out of the cylinder with thumb and forefinger. Make sure whatever hardware you choose for this purpose is stainless steel to withstand the aforementioned dishwasher.

On the opposite (bottom) end of the rod, center a relief hole about 1/2" deep and 5/8" wide to accommodate the grinder's top burr retention nut. On my M7K, this takes the form of round hex-key nut with a nice smooth washer underneath (see burr photo above), enabling the plunger/weight to ride all the way down to that washer while leaving 1/16" clearance above the burrs. (Note: the hardware and burr sets seem to vary depending on the vintage of individual M7Ks, so the particulars of your own burrs and their hardware may vary.)

Again, UHMW is great to machine, so if you're equipped with the tools and patience, you can probably mill the burr end very specifically, even enabling the plunger to extend down within the open space below the top of the burr set to eliminate even more pop-corning area. With the big slow burrs augering the beans down anyway, I'm unsure how much difference this extra step would make. (But hey, if you've read this far, there's a pretty good chance you're certified OCD anyway, so why leave such an opportunity unexploited?)

You'll see in the photos I've added a pair of black neoprene washers to the plunger/weight. These keep it centered nicely within the hopper tubes, and prevent bean shards from creeping up along the sides or possibly causing the plunger/weight to stick in place, surely causing popcorn chaos to ensue. I intend to rout out a shallow groove just above the plunger's bottom edge so the lower washer won't move around, but you can easily roll the upper one up or down to best match the particular cylinder/tube length you're using at the moment.

Now - if you're not too stoked on caffeine - it's time to get some sleep and look forward to using your tamed Titan to grind your morning coffees. I'm sure that many improvements can be made to this overall design and I'd like very much to hear what you come up with - and of course I'll be happy to do my best to answer any questions you PM or post here.

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#5: Post by Bluecold »

Don't you think that a large chute is actually not that handy since the speed of the grounds in the chute is lowered, which makes the grinds pile up in the chute?
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

Anvan (original poster)

#6: Post by Anvan (original poster) »

Interesting point!

I don't think that the chute acts like a nozzle in a fluid context, where a constricted opening accelerates the exit speed. Rather, I suspect the exit speed is more a function of the burr/sweeper's RPM, and here the M7K at 400 RPM doesn't spin them out with a lot of velocity. For example, comparing the M7K to the smaller Macap M4 with its roughly similar overall head design but much higher-speed motor, the M4 spits out the grinds much faster, although in much lower volume (that is, the M4 doesn't output nearly as many grams per second).

I do suspect that this is a design factor leading to the M7K's wide chute. Given a very high output volume at relatively slow exit velocity, a narrow chute would likely result in the coffee getting packed during exit, with attendant clumping.

Assuming one's routine is to clean out the chute per dose, I'm not sure the amount of coffee left in the chute to brush out really matters. Brushing out a few grams more or less takes or saves no additional time or effort (at least assuming the "3 bump & brush" method described) and brushing breaks up clumps as opposed to creating them, so no harm there either.

One thing for sure, though, is that the big, wide chute does make brushing much easier, faster and more thorough due to the improved access and room to use a bigger brush.

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#7: Post by TomC »

Very nice mod! I'd be curious though, if you discover a slight dusting of free floating coffee "powder" in front of the grinder where you lowered the cylinder wall. Even if 99.9% of the exiting grounds are firing off to the lower left, I imagine static electricity or just microfine particles might tend to escape. But it's only a blind guess. You'll know with certainty soon enough. I do like the open access to the chute though.

It would be nice if these companies could embrace the home barista community a bit more by having modular upgrades available as an option ( ie, anti-popcorn tube, etc) that doens't require one to hack at it with a saw and blow torch in order to make changes.

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Anvan (original poster)

#8: Post by Anvan (original poster) »

Tom, thanks for your comments. I haven't noticed any of the micro-dust you mention. Maybe it's just a little beyond my perception or more likely it gets mixed in with the other inevitable stray grounds from the process that get swept off the counter after each session. I'll pay more attention and see if something like this is happening.

Also, it took some getting used to, but these slow-RPM grinders just don't seem to throw much coffee around. On this one, for example, the grinds just sort of fall out of the chute - very different from my earlier grinding experiences where the coffee was spun out in a thin stream but with quite a bit of velocity.

Yeah, it would be nice if some standard factory mod components were available. I'm guessing there just isn't enough of a market for the manufacturers to bother (or put up with the criticism that they still got it wrong). I wonder what percent of high-end grinders are purchased by home baristas. Five percent maybe? Less? More perhaps for the Versalabs but that's almost its own category. I'd sure be curious if anyone has even reasonable ballpark numbers on that question.

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#9: Post by Bluecold »

Anvan wrote: Also, it took some getting used to, but these slow-RPM grinders just don't seem to throw much coffee around. On this one, for example, the grinds just sort of fall out of the chute - very different from my earlier grinding experiences where the coffee was spun out in a thin stream but with quite a bit of velocity.
That's not just rpms but mostly chute design. The chute of my Faema is more tangential than radial so grounds really fly out. Even at 300rpm, the tips of 8cm long vanes go roughly 7.5m/s or 27 kilometers per hour.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."


#10: Post by mitch236 »

I've been following this thread to find out how the column weight is working? I decided against using a column weight and just keep at least an inch of beans in the column. (you can read my thread here Grind consistency of column with weight vs. stock hopper)

I found that as the beans emptied below the effect of the weight, the grind became much coarser causing distribution issues. Granted, I was using a very heavy weight and yours seems lighter but I found when using a column, you only need an inch or so of beans to prevent popcorning. I also never let my column run empty (at least that's the plan!)