I'm sharing my experience with converting an older stepped Macap grinder to stepless. ~$50 and the final result works just like the stepless Macaps.
I have an older Macap MX. Like others have noted, I find the steps are too large. I tried the stepless mod that involves gluing a rubber brake on to the step pin, but found it wanting. To keep the break from slipping, I had to use so stiff a spring that it was hard to press down. Also, the rubber brake had to be pretty thick not to compress down onto the pin, which left little room to turn the upper burr carrier once I did get the pin pushed down. Fortunately, retrofitting the grinder with the new stepless system is pretty straight forward.
This has previously been done with a newer machine in which the upper burr carrier (UBC) was already designed to accept the gear collar:
Switching Macap M4 from stepped to stepless - DONE!
So this description also involves mounting the gear collar onto the UBC.
-Adjusting screw and gear collar ($40 from Chris Coffee). Gear collar must fit your machine. Part #C0007M162A is for the MX (OD is 10.5 cm); there is a different collar for the M4/5. Adjusting screw (part #C0007M11700) fits all machines.
-Mounting screws and matching drill bits and taps:
For collar: 7/64" or #36 drill bit; #6-32 tap; #6-32 x 3/8" screws qt. 3
For adjusting screw: 5/32" or #21 drill bit; #10-32 tap; #10-32 x 1/2" screws qt. 1 or 2
1. Unplug grinder
2. Unscrew upper burr carrier (UBC) and remove step pin & spring - you won't be using them anymore.
3. Remove burr from UBC so it doesn't get damaged.
4. Remove grind setting decal from UBC so you won't drill holes in it in case you ever want to reverse your mod.
5. Center gear collar on top of UBC. The contour of the top of the UBC is different from the bottom of the gear collar, so they'll want to slide around. I used three clamps to hold them, avoiding covering the holes.
6. Drill 3 holes in UBC for gear collar attachment. Gear collar holes are ~1/8", so I used a 7/64" bit, which corresponds to a #6 screw/tap. I didn't bother with marking - just used the gear collar holes as a guide. Drill press makes this easier. Still, I found it was hard to get the holes exactly aligned. Though they might have been good enough, I decided to make them true by redrilling the gear collar holes to fit the UBC holes I had just drilled. I did this by selecting the UBC hole that best aligned the gear collar and UBC, tapped it and screwed the collar into that hole, then used the other UBC holes as guides to enlarge the drill collar holes. (I didn't tap all three holes at once in this case because I didn't want to risk damaging the new threads with the drill.)
7. Tap the UBC holes
8. Attach gear collar. Tighten screws until outside edge of gear collar touches UBC; leave gap at inside edge so gear collar doesn't get distorted. Reinstall upper burr and screw UBC all the way down into grinder until burrs meet.
9. Decide where you want the adjusting screw to go. I put mine where the step pin had been. This was the only place that would work for me, as my grinder is situated in a corner, and in the front the doser is in the way. I decided to use one of the existing motor mount holes, so I only had to drill one hole. The side vent cover was sort of in the way, but I'm missing a vent cover anyways, so this worked out perfectly for me.
10. Set the adjusting screw into position. From the side, notice that when UBC is screwed all the way down the plane of the gear collar is ~3/16" above the plane bisecting the adjusting screw. I made a shim to raise the adjusting screw. I used a paint stirrer, carved into the shape of the adjusting screw base, then clamped it to the adjusting screw and drilled out the holes.
11. If you're using one of the existing motor mount holes, go ahead and attach the adjusting screw and shim, tighten the motor mount screw and position the adjusting screw until it is tangent to the gear collar.
Be careful not to make it too tight. Then drill the second hole in the housing, using the adjusting screw hole as a guide. You'll have to drill a little bit into the motor housing underneath in order to have enough clearance to tap the hole. I drilled a bit too far - no problem.
You can set up a vacuum around the hole to catch any aluminum filings; fortunately, my hole was right above the vent opening. If your hole isn't near an opening, you'll want to be careful to collect all the aluminum filings from the inside.
Having now done this, I would suggest NOT using one of the motor mount holes, as I mounted it too tight - see space between gear teeth and screw in these before and after pics:
The easy fix would have been to loosen the mounting screws, but this isn't an option with the motor mounting screw. So, I had to enlarge the adjusting screw mounting hole with a file. If you don't use a motor mount hole you will have more margin for error.
12. Tap the hole(s) and attach adjusting screw.
Put on adjuster knobs and... voila! It really works.
One full turn of the screw equals one tooth of the gear collar. There are a little less than two teeth per old step, so there are around two turns per old step. This allows you to make adjustments that are around 50 times finer than what could be done with the old steps.
New adjuster working well. I find that I rarely make adjustments finer than half a turn of the worm adjuster.
For single-shot dosing, you need something to tamp down the beans and prevent popcorning. I have found that a large can of cooking spray works really well. It's the right diameter (2.75") and has a concave bottom that avoids the motor spindle.
I had wanted to convert this to a doserless grinder, but there's so much hang up of grounds in the throat that I don't know how that could work, without making a mess every time. I am still looking for a great brush - the top of the doser is above the throat, making it difficult for a brush to sweep the top of the throat (where grounds accumulate). I have a short brush that will fit inside the doser, but it is uncomfortable to use.