How do I get compressed air to my rivet gun and air drill?

 

This seems like an easy question, but there are several subtleties that make the answer more difficult that it first appears. There are three problems, connectors, hoses and pressure regulation:

 

·         The thread on aircraft air tools is not the same as the connectors available at B&Q or Machine Mart;

·         The connectors provided are heavy and the hoses are stiff;

·         It is beneficial to vary the air pressure between drilling and riveting, the regulator supplied with most compressors doesn’t really like being adjusted.

 

See this page for more information on compressors.

Most compressor shops will sell an air hose  may have sold you an air hose with an appropriate male fitting to engage, and may even have sold you a fitting for your rivet gun and drill (but the threads probably don’t engage very far). Apart from the compressor (see this page)

 

Connectors

Any DIY compressor sold in the UK will almost invariably be supplied with a female ‘PCL’ connector.

This is a female PCL connector and is often known as a ‘Coupler’

It mates with this, an ‘Adapter’ or ‘Plug’

 

Extraneous Details

There are 2 types of PCL couplers – Airflow and Vertex – this is a Vertex. It has a lip on the left hand side (the side the adapter plugs in) which stops disconnection if the hose is on the floor. Airflow couplers, which use the same plugs, are better suited to fixed installations.

 

Couplers and plugs are each available with a male or female thread or a hose tail (of various diameters).

 

Both the coupler and plug here have female threads.

This plug has a male thread (left hand end)

 

PCL plugs usually have BSP (British Standard Pipe) threads - see below for types of thread used.

PCL adapter hosetail.jpg

This has a hosetail

 

This PCL plug has a ‘hosetail’ that is designed to push into the end of a hose – various diameters of hosetail are available.

 

There is nothing wrong with these connectors, except they are heavy. The problem aircraft builders have is that airtools supplied for aircraft building purposes don’t have the same thread.

The air tools supplied by Gloster Air Parts are sourced from the USA and have NPT (National Pipe Thread) threads – which is the standard for this type of connection in the US. PCL connectors almost invariably are supplied with BSP (British Standard Pipe) threads. The threads are similar, and some advocate graunching a BSP fitting into an NPT thread with plenty of PTFE tape, but compressed air can be dangerous stuff so we recommend using connectors with the correct thread.

 

Gloster Air Parts can supply adapters to convert NPT threads to BSP

 

Adapter ¼“ NPT Male to ¼“ BSP Female. Part No 3021

 

For use with a Male PCL plug

 

Adapter ¼“ NPT Male to ¼“ BSP Male.

Part No 3022

 

Female PCL plug also available.

Part No 3023

 

The least expensive method to connect your drill or rivet gun to the supply from the compressor is to buy an adapter above and to use PCL connectors with a heavy hose supplied by the compressor shop – but least expensive is usually not optimum.

To build an aeroplane will entail drilling thousands of holes. A light weight drill will make the whole experience much more pleasant. The drills we sell are not cheap, but we believe they represent good value – a high quality and light weight product with excellent balance and teasing trigger; a Gloster Air Parts air drill typically weighs 680g (1.5lb).

With the adapter above, the PCL male/female connector pair weighs 190g. When added to the weight of the hose it’s a considerable addition to a lightweight drill.

A far better solution is to use a ‘mini-coupler’ which is much lighter – 45g for male and female parts together, that’s 145g lighter than the PCL method (over 5oz lighter in old money). The mini-couplers also work better and allow a much lighter hose to be used. By ‘works better’ we mean that connecting and disconnecting is easier. Most PCL connectors need to have the collar pulled back to engage. A mini-coupler will plug straight in and latch.

A mini-plug in the drill & rivet gun and a mini-coupler on the end of the hose will make using these tools much more pleasant. A PCL plug at the other end of the hose will connect up to the compressor.

 

Mini-plug, available with
- Male ¼ NPT thread (pt no 3015) – this is suitable for most US origin air tools

- Female ¼ NPT thread (pt no 3013)

- Male ¼ BSPP thread (pt no 3026)

- Female ¼ BSP thread (pt no 3027)

Mini_plug_3015.jpg

 

Mini-coupler, available with
- Male ¼ NPT thread (pt no 3011)

- Female ¼ NPT thread (pt no 3014) – this is suitable for the light-weight hose below

- Female ¼ BSP thread (pt no 3028) – suitable for ‘store bought’ hoses with BSP threaded ends

- 8mm hosetail (pt no 3029)

Mini_coupler_3014.jpg

 

This picture gives a comparison of the size of a Mini-coupler compared to a PCL coupler. The mini-coupler is on the super light-weight hose described below.

 

PCL_+_Mini-coupler.jpg

 

 

Pressure Regulation

Compressors typically deliver air between 120psi (8 bar) and 150psi (10 bar), but most air drills and other devices want 90psi (6 bar) supplied to them, so the compressor output must be regulated (for information on compressors see this page). Usually the regulator supplied with most compressors is relatively basic, although the output pressure can be adjusted it is awkward to use for frequent adjustments. It is advisable to leave this set at around 95psi, assuming 5psi is lost in the pipe work to the air tools.

However, when riveting 1/8” and 3/32” solid rivets (typically used in the construction of homebuilt aeroplanes) most builders find that using 60 and 40psi (2.5 to 4 bar) results in easier riveting with much better results, so the air supply pressure must be adjusted regularly. It is possible to use the compressor regulator, but it is a much better idea to invest in a separate regulator that can be sited in a convenient position, this regulator often includes a water trap to remove any moisture in the air.

To avoid having to adjust the pressure all the time it is also worth investing in a manifold block and taking one output to the separate regulator with the others running at full pressure.

Machine Mart and others sell reasonable regulators for around £30. They often are supplied with large diameter inlets & outlets (eg ½“ BSP) – ensure that the connectors bought with the regulator have the correct thread, or an adapter is also ordered. For example an 8 or 10mm hose tail for the inlet and a PCL female for the outlet, the hose tail may be available only with a ¼“ thread so a ½“ to ¼“ adapter would also be required. I have included a sketch below of a straight forward set-up.

 

Manifold.jpg

 

Gloster Air Parts 3 Port Manifold
Part Number 3030R

MM_Regulator.jpg

Machine Mart Regulator

 

The Machine Mart regulator above is connected up using 10mm push fit tubing – Gloster Air Parts can supply the tubing and the fittings required, although it has taken us 20 years to take the plunge and connect up our system using this method!

 

Hoses

DIY and compressor shops usually sell air hoses that are heavy and somewhat inflexible. They will take a lot of wear and tear, but not really the best thing to use with a lightweight air drill or rivet gun. A much lighter and more flexible hose is required. A light hose (and connectors) will make the whole aircraft building process much more enjoyable.

We offer two types of hose for connecting to tools, a lightweight and super lightweight. The lightweight hose is imported from Avery Tools in the US while the super lightweight is made up in our workshop. Both hoses are not as robust as the ‘store bought’ hoses, but are entirely suitable for aircraft homebuilding needs.

We can also supply hoses made from 8mm and 10mm internal diameter (12mm & 14mm outside diameter) reinforced PVC hose. These hoses are stiffer and heavier than the lightweight hoses, but are a third to half the price. End fitting are the same. The saving on an 8m hose is £10. Mini-couplers are not available with 10mm hosetails.

 

 

Lightweight hoses

Supplied with ¼“ male NPT fittings moulded onto each end, and available in 2 lengths only,

12’ hose – part no 3012

25’ hose – part no 3025

 

Mini-coupler and PCL plug (with adapter) available separately.

 

Super Lightweight hoses

Supplied with Mini-coupler and PCL plug already fitted. Available in 2 lengths,

Standard, 4m, part no 3044

Long, 8m, part no 3048

These hoses are also available at any length up to 30m to special order.

Super Lightweight nose part no 3040

Super_Lightweight_3040.jpg

 

Reinforced PVC hose

Available per metre in

8mm id (12mm od) part no 3041

10mm id (14mm od) part no 3042

Plus end fittings – shown here with PCL plug with 8mm hosetail (part no 3024)

 

 

Recommended set up

 

It is essential to have 2 air outlets available so that a drill and a rivet gun can be hooked up at the same time. If a pressure regulator is used, as suggested above, it is then useful to have an additional outlet available for those other activities – for example pumping up the car tyres. The set up below uses a Gloster Air Parts 3 outlet manifold (part no 3030, pictured above) to provide these additional outlets. The lengths of the hoses can be adjusted to suit your own workshop.

Compressor hook up.jpg