Creating Customised Threads in Fusion 360

As ever this started off with a need and from the need came some learning.  In my experience such needs are always welcome for the resulting learning benefit but inevitably lead to a few hours of frustration.

We have a small Jacuzzi spa at our home in France.   It has two cartridge filters that are screw mounted into the sump of the spa.   The threads on the cartridges are plastic and are loosely defined as 2” SAE spec. (I think SAE is a fine pitch thread (?) and as the filter threads are around 5mm thread to thread pitch, they don’t seem to me to be fine pitch).

When filling the spa from empty, Jacuzzi recommended that the filters are removed and the filler hosepipe nozzle is wedged into the outer vacated of the two filter holes. The nozzle has to be jammed in place by packing a cloth or sponge around it.   Filling via the filter mounting ensures the spa fills from the bottom up with minimal potential for an airlock in the pipework.

The problem with this is that the filler hose tends to have a mind of its own and when your back is turned it will liberate itself from the filter hole and whiplash round like a demented cobra and give you an unexpected bath.

After one such soaking I resolved to stop this happening.   What was needed was an adapter plug to fit into the “2” SAE” socket that would accept a standard hose push fit connector.  This would hopefully keep the rampant serpent retained during the filling process.

I opted to use a standard commercial male hose connector for the interface to the filler hosepipe. These have a DIN Pipe thread specification (G26.441 x 1.814 mm).   This left me with the need to model the 2” SAE from scratch which on inspection appeared to take the form of a pseudo Acme profile but with an asymmetric thread to valley ratio.

Having failed to find anything helpful on the Internet I set about creating a custom thread in Fusion 360. New experience ….

Here is the resulting adapter. 

The attached ZIP file below has the full write up, the STL file and the source Fusion file.

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2 Replies to “Creating Customised Threads in Fusion 360”

    1. Hello Peter, well you tend to get a different view of the world when you have Fusion 360 and a 3D printer ….
      PS – Your piano wire posted on Friday by snail mail so should be with you by Christmas (?)

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