Overview of common pipe dimension and threads used in espressomachines

Question

Is there a good lookup table for universal espresso parts and common pipe dimensions?

I have been servicing some entry level espresso machines and noticed a lot of similar components (Francis Francis X1, Ascaso Arc, Saeco Starbucks Sin006, Krups 874). As example the first three use an Ulka 5 pump.

However i struggle with determining the dimension of pipe-threads and etc. As an example i wanted to block the steam outlet with an end cap (they never used it) on a Saeco Starbucks Sin006, but could not identify the thread (~16mm OD and 24tpi).

Also the silicone valve in the boilers (right above shower screen) seems to be identical on X1 and Sin006, but was uncertain if i could just swap.

Is there any source that describe the most common dimensions used for pipes, universal parts and etc.?

So far my best source have been this site on espresso parts, but still do not feel confident ordering parts unless the model is mentioned.

Answer 1

There are lots of ways to make mistakes with threads.

European machine screws will be metric. But the diameter of the male thread will be smaller than the nominal size. For instance, a 8mm bolt is 7.78mm diameter, and a 6mm is 5.82. Also, these are dangerously close to Imperial 5/16” and ¼” sizes, so imperial nuts will sometimes spin onto metric bolts for a few turns.

If that weren’t bad enough, there are different thread pitches for a given metric bolt diameter. There are different “official” thread pitches. For instance, there are 5 different pitches listed for 10mm metric screw threads.

Get yourself a Nut and Bolt Thread Checker from Amazon.

Another pitfall is metric pipe threads. They don’t exist. Well, the standard does exist (DIN 158) but manufacturers almost always defer to NPT (American) pipe threads. But sometimes metric manufacturers use the ISO standard which is actually BSP (British) pipe threads.

NPT and BSP have different thread pitches, but are close enough that they can be mixed up, with leaky results.

ISO pipe threads come in 2 forms: parallel and tapered. Parallel are the more common, and seal with a washer, not on the threads.

Machine screws are named by the nominal size of the stock that male threads are cut from. A 10mm thread will be cut from 10mm stock, even though it is 9.74mm diameter.

Pipe threads are named by the size of the pipe they are designed for. Pipes are named by the INSIDE diameter, not the OUTSIDE diameter where the threads are. Say you find a pipe thread on a coffee machine which measures exactly 10.0mm.You are well informed enough to know it is actually an NPT thread, and 10mm is 3/8" so you reach for a 3/8NPT fitting, right? No. This is a 1/8"NPT because it is made for pipe with a nominal 1/8" inside diameter.

No wonder you are confused.