More reliable connectors

In Postbag ME 4501 p254, Phil. Bellamy advocates using a metal sleeve on wiring connections. For those interested they are known as Bootlace Ferrules and can be obtained from RS Components. They are colour coded for size in relation to the thickness of the wire. White being the smallest and black the largest.

When used the bare wire is located in the metal sleeve and the insulation into the coloured part. It should be crimped onto the wire before inserting into the connection. Don't rely on the securing screw in the connection to crimp the ferrule.

Bootlace ferrules make for a neat installation, prevent strands of wire getting where they shouldn't and stop the screws of some connectors from damaging the strands. They are a great idea if you have some, although sometimes the plastic barrel can get in the way if you are inserting more than one into a single connector. I see that CPC also stock them. And Maplin.

Another means of terminating stranded wires is the pin crimp or flat blade crimp if you prefer the red/blue/yellow system.

On the subject of stranded wires and compression terminals, don't ever be tempted to tidy up stranded wires by solder tinning them before inserting them into screw terminals. It all looks neat and tidy when you finish the job but unfortunately, solder is prone to "cold flow", whereby the solder flows due to the applied pressure over weeks or months. The result is a loose connection, no matter how hard you originally tightened it. This in turn can lead to intermittent connections and more importantly, the risk of fire if the wiring is passing high voltage and current.

As this is a well-recognised problem, it's now unusual to see tinned wires in new products. However, I have seen one or two in recent years. They should be cut off and reterminated.

Murray

Gentlemen,

I use bootlace ferrules in my everyday job and agree with what has been said but it should be made aware that the ferrules are cheap but a good crimping tool can be expensive, I use another tool to do the crimping but dare not tell you what for fear of the backlash

Martin P

Yeh, what's wrong with pliers or the heel of a shoe?!

Ref. Crimping, years ago I was working in electronics where I had to check out 140 units that produced an alarm signal, in the end I found 38 units ware "alarming". It turned out that the bootlace crimps had been done with a proper tool but with the wrong dies fitted so the wire had been severely "over" crimped and in some cases it was only the PVC sleeving that held the wire in place.

I once had to crimp 48 wire together (in pairs) at home, I used a £4 tool which was very painful on the hands and had to replaced afterwards. I then bought a proper one (red,blue and yellow crimps) for £25, best thing I did. Comparatively, its a joy to use.

If you buy the proper tool you feel the pain when you buy it. If you buy a cheap tool, you feel the pain every time you use it.. (Practical Machinist)

Frank

The pin crimp and flat blade crimp mentioned above are secured by crimping the coloured section. Boot lace ferrules are secured by crimping the metal section.

The pin and flat connectors use a crimping tool whilst the boot lace ferrules can be secured using a pair of wire cutters, not your teeth that Martin P probably uses

I actually use wire cutters but thought that might not go down to well, you have to remember not to squeeze to hard though my teeth aren't up to lots of wires.

Martin P

An interesting point that is often not appreciated is that a really good crimp connection will actually result in cold welding of the wires to the connector.

Neil

Hello all,

In the industrial environment I work in we took the decision about 30 years ago to standardise on bootlace terminations. We considered that they had a significant advantage over the red/blue/yellow type because the bootlace crimp is generally held in a terminal which exerts pressure on it so if the crimp is not as good as it might be the clamping action of the terminal will help maintain integrity. On the other hand with the red/blue/yellow pin crimps are such that if not properly formed will be a bad termination because the terminal grips the pin.

However bootlace terminations are no good for a stud termination, very good for clamp terminals but not much else - the r/b/y type are available in many forms, eye, fork, faston etc. The use of bootlace terminations is now standard across all our suppliers for clamp terminal interfaces, not because we insist but because they prefer to use them.

Back to the workshop, for lower scale installations I can recommend stripping the end of the cable, twisting it and then tin it with solder, simple but very effective.

Regards,

Michael

I would have been sacked for crimping your way.

So far:

It's good practice to use a ferrul when terminating a wire in a terminal. Agreed

Its ok to crimp with wire cutters! I don't think so. I hope Martin does't work in the aircraft, automotive or medical industry for example.

Contradictory advice re soldering the ends of wires - it sounds good but the reason not to do it given by Muzzer is sound advice. Also there is increased risk of a fracture where the non soldered/soldered point meets.

There's a lot I don't know about crimping but I do know that the crimp and the wire must match and the only tool to use is one of the ratchet types designed for the crimp in use. Otherwise it's a disaster.

A grey area for me is use of crimps on solid wires and the voltage ratings of crimps. Can any one give some sound authorative advice on the subject of crimping please.

I too use bootlace ferrules at work. I mainly use the uninsulated type but do use the others. Don't get to fixed on the colours as the french (I think) have a slightly different colour scheme and they often get mixed up. Also worth noting is the fact that you can get a twin version of the insulated crimps that will take two wires.

I bit the bullet and bought a proper pair of crimps, which are a joy to use and well worth looking out for on ebay etc.

Regards.

David.

When I worked in satellite communications, we often used coaxial cables and had to fit connectors on the ends. The connectors were several pounds each, but much cheaper as a crimped version. The correct tool for crimping them on was about £125. However, my chief engineer didn't approve, he said he couldn't take them apart to see how well they had been assembled!

Geoff

Is it just me that detests the plastic shielded crimps?

Once crimped they look ugly, so I strip the plastic off and use heat shrink tube where necessary.

Agree with Frank's last sentence/quote and David about using the proper tool as it makes crimping a pleasure, so much so, that I'm actually looking forward to re-wiring the Austin Seven.

Cannot believe I used those blade crimping tools in the past - abomination are they after using the 'proper' ones.

Geoff - Waiting for Workshop to heat up.

Edited By OuBallie on 07/02/2015 09:45:04

I agree, using crimp connectors makes wiring up something like a motor or inverter easier and safer (less worry about loose strands). A bit like discovering the joy of push-fit plumbing when you have a long, complicated run of pipe in inaccessible spaces!

Neil

We use both bootlace crimps and the RYB eyelets, fork and blade crimps at work on lamp circuits that run at 950V 4A and have a strike voltage up to 2KV. this arrangement passes both UL and CE low voltage directive via independent test house in UK, so that should give some idea. They do insist on the correct ratchet tools that have to do a pull test on a sample every year or 6 months depending on use.

As others have said soldering ends of wires going into clamp terminals is a no no now days however neat it looks.

Best connection is the spring clamps found on many terminals and increasing numbers of components, gets rid of the screws working loose during shipping.

Steve

Many years ago we had to do a survey on different wire connections, this was for building an enduro bike. I worked in aerospace at the time so had a lot of info. The best connector electrically is a twisted joint, next crimped . Do not solder the ends, this causes stress raisers and for a dynamic situation is the worst possible. Neil- push fit plumbing is the invention of the devil, Just wait until you have a little dribble in one of those inaccessible places.

If you properly tin the cable end the solder flows up into the insulation providing stress relief with the support of the insulation. My suggestions have been to help a model engineer who has a few cables to terminate without the outlay to buy crimps and the expense of the crimping tool.

Of course a correct crimp termination is better, some time ago I was involved in a project where the customer questioned the integrity of the installation because no crimps were used, the terminal supplier, Klippon now known as Weidmuller replied that their terminals are designed for bare wires. I would not advocate that but just wish to make the forum members aware.

Regards,

Michael

As Michael says Weidmuller terminals are designed for bare wire, they are clamp type, the screw operates a clamping plate, not to be confused with more widely used screw connectors where the screw end can if overtightened cut through multi stranded cable and indeed solid conductors.

Emgee

I think the most important point is to use the cable termination that is suited to the terminal on the device you are connecting to, bootlace ferrules do indeed make a neat and reliable connection but can prevent full insertion into some terminals, they can also crowd some relay terminals where two wires are required but intended for bare wire connection. For speed of installation many control devices use spring terminals designed for bare wire, the time taken to strip fit and crimp ferrules costs money. Insulation displacement connectors are now very popular on much equipment especially communication type wiring for telephone and ethernet cables. Ribbon cable would be a nightmare to have to strip and solder compared to the speed and reliability of IDC systems. Even some power wiring systems use IDC termination now. The trouble with many termination systems is the are very specific for the cable and connector, use the wrong ones and the mismatch will give a poor electrical and mechanical termination.

Mike