DIY Compak K10 Doserless Conversion Guide

While I was getting busy in the garage making the bottomless portafilters I decided to also have a go a converting my Compak K10 WBC Edition connical burr grinder into a doserless.

Why? Well, again there a couple of very good reasons:

• If you grind to order, then it's faster to prepare the shots. Twice as fast.
• Less coffee wastage
  
• Absolutely no stale grounds, no matter who is operating the grinder. It falls into the basket as it is ground, the only chance for the grounds to go old is in the throat of the grinder, and that's not a lot.
• Less chance of developing repetitive strain injuries from pulling that doser so many times.
• Much easier clean up at the end of the day.

Without further ado, below is my guide for converting this grinder (and perhaps other models too) into a doserless.

1) Obtain the necessary screwdrivers and remove the dosing chamber from the grinder.

2) Measure the vertical drop from the chute/throat to the spot where your basket would be resting on the portafilter forks. This will need to be at least the vertical height of the funnel you will be buying. Make sure that there is room for the grinds to dome/pile up above the portafilter and enough room for you to lift the portafilter from the rest to give it a few thwacks and remove.

3) Measure the horizontal distance from the chute/throat to where you would like the coffee grinds to drop into the centre of your basket. This will need to be the radius (half the width) of your funnel.

4) Source yourself a suitable sized stainless steel funnel from a kitchen shop. I got mine at a commercial kitchen supplier in South Brisbane.. It came with a little metal handle which I thought was a nuisance, but ended up making the job super easy. Cost $58.

5) Using a suitable tool (I used an angle grinder) cut the bottom of the little handle. This will act as a hook to hold the funnel onto the grinder. Screwing the plastic chute/throat back onto the grinder then holds it securely in place. You may/will need to bend the metal handle appropriately to get it to hook insode the grinder neatly.

 

6) Fashion a suitable bracket to hold the bottom of the funnel the correct distance out from the grinder. I got a peice of metal noramally used for nailing two peices of wood together for house framing from the hardware shop for about $2. I drilled two holes in line with the pre-existing holes in the grinder and then bent it at a right angle over a lip of cement. I then used an angle grinder to shape it to hold the funnel spout. It was getting dark at this point, so the pictures stop here...

7) With the funnel now in place securely mark on the spout where to cut it off so the portafilter will fit underneath it. Then...chop it off with a suitable tool. Again, I used an angle grinder. Probably best to start long and shorten it to the perfect point. The picture here shows the grinder without the holder and without the spout chopped short, but i'm sure you get the idea.

There you go, a doserless grinder for $60 and a couple of hours labour.

This post is written retrospectively and I can now say we have been using this successfully at the markets in a super busy environment for the last month with no dramas.

It is literally twice as fast to prepare the shots. We no longer dose, then thwack, then dose, then level and then tamp. We simply turn the grinder on, thwack the portafilter twice as it is coming in, then turn the grinder off when the dose is right and tamp the mound. We can see the extractions with the naked portafilters and they are great and even.

The only problem now is slightly inconsistent dosing due to human timing errors when turning off the grinder. So if anyone has a source for an electronic timer I can plug the machine into, that then plugs into the power point, then let me know.

That said, dosing is pretty consistent, maybe just as consistent as when we actually used the doser. But it would be another improvement if I can source a suitable electronic timer.