How to unstuck my grinder's burrs

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Espressofilo
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#1: Post by Espressofilo »

In 2001 I bought a Gaggia MDF grinder, in conjunction with my Baby Gaggia.
Around ten years later I decided that a stepped grinder did not satisfy my needs and I applied the stepless modification.
This involves eliminating the spring-loaded pins that mark the steps and adding some Teflon tape to the thread which governs the burrs' distance, lest the grinding size changes during the grinding operation.

Recently I dismounted the upper burr holder, I cleaned the inside chamber accurately, I cleaned both burrs accurately, and I re-screwed in the upper burr holder with the same teflon tape, I did not remove the old teflon tape. The result is that the burr is stuck, certainly due to some coffee powder which I did not correctly eliminate from the threading.

I have bought a new grinder in the meanwhile but I would like to salvage my MDF, one possible option is to devote it to the morning de-caffeinated Moka, while the other grinder is devoted to the after-lunch and afternoon "caffeinated" espressos.

I am asking your help regarding how to unstuck the tefloned thread. I am trying with a lubricant, MD-40, in the thread (the part that I can access) but I don't manage to apply force enough to unstuck it even if I applied way too much lubricant.

I suppose I have to find a way to eliminate the Teflon from the thread. Instinct would suggest to get a needle, and lift some part of it and pull it hoping that it will come out from inside the thread. My fear is that there is a good and a bad way to do that, and that I will do it the bad way, and the Teflon will remain inside the threads forever.

Is there any trick to do the job? Some chemical substance that dissolves Teflon? (some acid, I don't know, something). Is there a best technique to pull the Teflon away?

Alternatively, I need to find a tool that I can insert inside the upper burr holder, in place of the hopper. I have no idea what I could use.

I know this looks very dirty, it's months I am trying to solve the problem. I had the same problem when I applied the modification, I solved it with a lubricant such as MD-40, but it seriously took more than one month.

Picture:

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baldheadracing
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#2: Post by baldheadracing »

You could try putting the whole grinder in a freezer - preferably a deep freezer - overnight and then seeing if the assembly will unscrew with a drift pin/screwdriver or similar tool. (The brass will shrink a very little bit in the cold.)

Good luck!
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

Espressofilo (original poster)
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#3: Post by Espressofilo (original poster) »

Thanks, I'll try that.
Both parts are in brass but it might be that the Teflon tape will lose its sealing properties with the cold, who knows. Good idea.

I must buy a specific screwdriver to separate the grinding mechanism from the rest of the grinder. I am thinking about heating the metal as well to see if I can do the job. I should try to heat the lower part more than the upper part, in fact. I could place it in a pot with hot water up to the lower thread.

I will try the deep freeze trick in the meanwhile.

Thanks!

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Jake_G
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#4: Post by Jake_G »

I have had success with heating the entire grinder in the oven at the lowest setting (around 200°F) and then shrinking the burr carrier/adjustment collar by sticking a plastic bag filled with ice in the throat. With the teflon tape serving as a bit of a heat break, hopefully you can get enough thermal growth and shrinkage to allow you to back the carrier out.

Good luck!

- Jake
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Espressofilo (original poster)
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#5: Post by Espressofilo (original poster) »

Another good idea! I will certainly try that if the deep freeze trick doesn't do the trick. Thanks!

RTM
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#6: Post by RTM »

Jake_G wrote:I have had success with heating the entire grinder in the oven at the lowest setting (around 200°F) and then shrinking the burr carrier/adjustment collar by sticking a plastic bag filled with ice in the throat. With the teflon tape serving as a bit of a heat break, hopefully you can get enough thermal growth and shrinkage to allow you to back the carrier out.

Good luck!

- Jake
good idea! I was thinking a heat gun on low as another option

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Jake_G
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#7: Post by Jake_G »

RTM wrote:good idea! I was thinking a heat gun on low as another option
That's a great option!

Espressofilo wrote:Another good idea! I will certainly try that if the deep freeze trick doesn't do the trick. Thanks!
I wish you luck with freezing, but beware that heat makes things bigger and cold, well, smaller.

When two parts are interfaced with one another, and made of materials with similar coefficients of thermal expansion, the space between them will also grow with heat and shrink when cold.

The only time a deep freeze will work better than heat is if the material of the part on the inside of the interface has a much higher thermal expansion than the part on the outside. So, aluminum threaded into brick masonry would be a good option.


In the case of aluminum or brass, they are quite similar, but I wish you luck all the same!
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baldheadracing
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#8: Post by baldheadracing »

Freezing is just an easy-to-do first step, as I am assuming that it is old coffee in the threads that is causing the jam.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

Espressofilo (original poster)
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#9: Post by Espressofilo (original poster) »

Yes, I am aware that if I cool down both parts the net results should not change. I was hoping to diminish the stopping quality of the Teflon tape, but that did not work.

I still have to try with the selective heat-cold application.

edgndg
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#10: Post by edgndg »

Others here more expert than me on grinder repairs, but just to say there are a variety of cooling sprays available that might allow you to first heat the overall grinder as previously described and then selectively cool one of the parts. Also noting that the parts are sort of reminiscent of an old bike freewheel and wondering whether a bike shop might have a pin spanner or other tool/idea re how to gain some leverage.