The nut that keeps a fitting where it belongs
A lock nut does no work; it prevents work. It secures a fitting against loosening and at the same time determines how far a connection protrudes from the wall or the panel. Anyone who has ever moved, lifted or transported a machine knows how quickly something shifts without a lock nut.
Rocket lists the number A329905087 for the 1/4-inch version. It is a typical part that gets lost during servicing, ends up in the drip tray or comes out of the machine with worn edges because someone used the wrong spanner size.
When it is due
A connection that can be turned by hand is no longer locked. This rarely means an immediate leak, but it does mean that the connection behind it loosens a little with every movement.
Rounded or torn spanner flats are the second case: the nut can still be turned, but no longer tightened properly. Helping out with pliers only makes it worse.
And finally the classic: it is simply missing during reassembly. In that case, better to order a new one than to leave the fitting unlocked.
At a glance
| Type |
Nut, 1/4 inch |
| Installation location |
on fittings in the water and steam circuit |
| Fits |
Rocket machines for which the manufacturer lists the number A329905087 |
| Scope of delivery |
one nut, without sealing ring |
| Part number |
A329905087 |
| Version |
Metal, 1/4 inch |
| Installation |
Installation by a specialist recommended |
| Brand |
Rocket |
Important for installation
The nut sits on connections that carry water or steam. Before working, disconnect the machine from the power supply, depressurise it and let it cool down. Always work with the correct open-ended spanner and hold the counterpart so that the pipe behind it does not turn as well.
Who it is for
For anyone who has lost a small part during servicing or wants to replace a worn nut properly.
The spanner size is not specified in the documentation for this item. What is known is the thread size of 1/4 inch – we do not claim more than that.
The fittings in the Rocket catalogue
Fittings differ in shape, thread and connection type – and on the outside, many of them look confusingly similar. That is why the part number is always what counts. We list twenty items individually:
Reducers
Elbows and L-pieces
Straight connectors and quick connectors
T-pieces
Connectors and small parts
What goes with it
The counterparts include the lock nut for the drip tray drain plug and the lock nut for the drain elbow.
The matching fittings are right alongside: 90-degree elbow fitting with male thread on both sides and I quick connector with two male threads.
The whole range can be found in Rocket accessories and spare parts.
A small workshop rule from Zurich: we do not put removed nuts and washers on the work surface, but in a shallow bowl next to the machine – in the order in which they come out. Sounds excessive, but it saves searching during reassembly and prevents a 3-franc part from holding up an entire repair. This is our routine, not a manufacturer requirement. For the final test we grind some Very Nutty, because the crema shows immediately whether the pressure is back.
No returns
Original spare parts are excluded from exchange and return. They are procured to order and cannot be resold after installation or a test fit on the machine. So before ordering, check the model, year of manufacture and serial number of your machine – or drop us a line and we will clarify the fit together. Your rights in the event of defective goods remain unaffected.
Frequently asked questions
What spanner size does the nut need?
The spanner size is not specified in the documentation. Measure your removed part or ask us, stating the model and serial number.
Is a seal included?
No. Only the nut is supplied. Sealing rings are separate items.
Can I use a nut from a hardware store?
We advise against it. Material and surface are not arbitrary for parts in the water circuit, and 1/4 inch comes in different thread forms.
Do I need one or several?
That depends on how many fittings you open. The item is supplied individually.
Can I look at the part in your showroom?
Our showrooms in Bern (Gerberngasse 44) and Zurich (Hagenholzstrasse 50b) show a wide selection, but not our entire range – the display changes. Drop us a quick line at [email protected] before your visit, and we will check whether the product you have in mind is currently there.
Questions about the fit or the serial number of your machine? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
