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Chasing threads in heat block  

Rob Miller
New Member
Chasing threads in heat block

First, let me just say that this is my first 3d printer (my wife got me a Mk3s+ for Christmas) and so far I love it. The first prints with PLA were great, then I decided to try some Hatchbox PETG. The first fes prints were great, but then I had a clog and the hot end got all gummed up. I am assuming the nozzle had been improperly tightened. I disassembled it, cleaned it all up and reinstalled it. The first print went well, but then I noticed a significant leak above the heat block. So I disassembled and reassembled it again (twice) before I stopped the leak (so far). In any case, during cleaning I decided I needed to clean up the threads in the heat block, so I chased them with a tap. For this I identified the thread count and pitch (1.0) using a gauge I have. However, when I ran it through the threads I had a not insignificant amount of aluminum shavings come out. My intention was just to clean out any excess plastic that was left in the threads so I was pretty surprised to see this and somewhat concerned when I noticed the heat break seemed sort of loose in the hole when I screwed it back in. I suspect I will soon be buying a new heat block but I would like to know what is the correct tap to use for cleaning the threads. Can anybody help with this?

Posted : 19/02/2022 4:11 am
Famed Member

Oops!  Your tap was riding the plastic and biting the metal ...

Once you have plastic in there you have to do any work on it at molten plastic temperatures.  You are almost certain to need a replacement as the leak will now get worse 🙁

For future reference, look at this page and pay particular attention to the diagrams at the bottom:


Posted : 19/02/2022 4:52 am
Chicago Keri
Estimable Member
RE: Chasing threads in heat block

Unfortunately, it sounds like you will need a new heatblock.  I suggest the E3D plated copper one.

Be very wary of chasing threads with a tap!  Nearly all taps that are easily available outside of industrial supply cut a very loose tolerance thread, which is probably why you got the metal chips.   A thread chaser is less aggressive than a tap and is less likely to alter the existing thread.

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Posted : 19/02/2022 8:36 pm
Illustrious Member
RE: Chasing threads in heat block

I just run the heatbreak through a few times with the block heated up to clean the block threads out.

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Posted : 19/02/2022 9:32 pm
Estimable Member
RE: Chasing threads in heat block

Certainly sounds like new heat block time, unfortunately. Silver lining is you can take the opportunity to upgrade to a copper version, as Chicago Keri suggests.  You could go the extra mile and pop a titanium heat break in too.  E3D can supply both these parts, but you can potentially save some money by purchasing compatible replacement parts.  Polisi, for example, manufacture and sell a beautifully made copper heat block and titanium heat break / throat that are a direct swap and, in my experience, work perfectly and just as well as the E3D versions.  Just a thought.

Good luck.

Posted : 20/02/2022 9:33 am