using ferrule to join two wires? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2019, 10:16:31 am
content: So a ferrule that goes over a wire end for a screw terminal, is it acceptable to join two wires with it so long you meet cross sectional area requirements in total for the wire gauge range?

author: madires
author_rank: Super Contributor
timestamp: December 17, 2019, 11:36:44 am
content: No, because it's easy to pull out the wire. Are you asking about mains wiring or some low voltage stuff?

author: JackJones
author_rank: Regular Contributor
timestamp: December 17, 2019, 11:39:19 am
content: I recall reading something about there being a maximum distance you can parallel mains wire like this. You'd have to ask someone who actually knows for any details.They do sell double ferrules that fit two wires so it can't be a complete nono.

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2019, 01:19:15 pm
content: I meant to make a linear splice, so one wire from each end, just as a easy way to join them with heat shrink. I know the tool does not come off.I wonder if its more resistant to bending them making a solder joint. It compresses the wire much more nicely then the other kind of crimp tool used for these joints. One without the insulation.The difference is, it would be pulled from both ends. So you need to make something longer and you don't want to solder in a uncomfortable area.

author: madires
author_rank: Super Contributor
timestamp: December 17, 2019, 01:23:05 pm
content: Quote from: gabinetex on December 17, 2019, 11:43:41 amAs the family's repair shop I've seen too many wires easily pulled out of twin-wire ferules or just barely kept in. And I would assume the manufacturers of the machines used professional crimping tools.

author: wraper
author_rank: Unknown
timestamp: December 17, 2019, 01:28:02 pm
content: Quote from: madires on December 17, 2019, 01:23:05 pmIf it can be easily pulled out, it means not properly crimped. I've seen very expensive equipment (100k+ EUR) where connector/wire cross section did not match. As long as total cross section is the same, there is no difference for holding strength if there is one or two wires.

author: Berni
author_rank: Super Contributor
timestamp: December 17, 2019, 01:50:14 pm
content: I don't see why it would be bad to use a ferule to join wires.From my experience when using a good crimping tool these things are pretty much impossible to get off again. When crimping connector pins onto wires i always test the first one by grabbing it with pliers, wrapping the wire around my finger once and pulling apart as hard as i can for one or two seconds. If the wire starts slipping from my grip instead of pulling out i call that a successful crimp (For tiny non power wires i do a similar test but pull much less since otherwise id tear the wire itself in half)Its important to test the first crimp you make with a given tool and wire combination. If you use the wrong setting or wrong die on your crimping tool you might end up with something that looks crimped perfectly fine, but will pull out with relatively little force. Sure your setting might match the ferule/crimp you got, but if the wire is not filling the whole ferule/crimp then it won't grip it inside.If there is more force than that being exerted on your wires then you have installed your wiring harness wrong.Also you can remove the plastic part of the ferule by pushing the metal part towards the plastic part and then grabbing the plastic with pliers and ripping it off. This lets you make nice low profile crimps for when space is important. If you are worried about pullout then put both wires into one side, this makes the pulling force sideways when you pull the wires apart, so the wire itself will always break before the ferule breaks.I have used ferules for joining before, but yeah its not what ferules are intended for. The correct thing for splicing wires are these crimp butt splices:https://uk.rs-online.com/web/p/crimp-butt-splice-terminals/0534288A/As a bonus they also are already insulated so no heatshrink needed.

author: Gyro
author_rank: Super Contributor
timestamp: December 17, 2019, 01:55:31 pm
content: Yes, go for butt splices as above. In addition to being fully insulated, the metal is thicker, probably improving the lasting quality of the crimp (I don't know how much ferrules rely on terminal pressure to keep them tight).

author: coppercone2
author_rank: Super Contributor
timestamp: December 17, 2019, 02:21:44 pm
content: but the ferrule is compacted from 4 (or 6) sides by 4 anvils pressing against each other, it does a better job then the ones that squash it with a single anvil. The butt splice crimp tool is poor and its sooo ugly

author: tooki
author_rank: Super Contributor
timestamp: December 17, 2019, 04:42:25 pm
content: Quote from: Gyro on December 17, 2019, 01:55:31 pmThat would be my concern as well. As I understand it, the reason for ferrules is simply to prevent wayward strands from shorting adjacent terminals. As such, the pressure of the terminal is critical, but the ferrule itself is not crimped hard enough to form a cold weld, as in a crimp terminal.Quote from: coppercone2 on December 17, 2019, 02:21:44 pmIt’s telling that square and hex crimps aren’t used for crimp terminals. But single point ones are, as are four- and eight-point crimps, where a tube is crimped by 4 or 8 anvils which create only dimple-like indents (this is very common in military and aviation). And one certainly can get butt splices using that system.

author: madires
author_rank: Super Contributor
timestamp: December 17, 2019, 05:12:14 pm
content: Quote from: tooki on December 17, 2019, 04:42:25 pmThere are multiple reasons. One is to prevent single strands to break off when the wire is fastened with a screw. Another is to keep the strands together for optimal contact. When fastened with a screw some strands wont be caught by the screw and therefore won't make proper contact which causes burned terminals in high power applications.

author: Kalin
author_rank: Regular Contributor
timestamp: December 17, 2019, 05:42:34 pm
content: They are much faster to work with than just the stripped stranded wires, also they make the connection much more secure in a screw terminal which makes it much safer working inside a control cabinet since the wires are much less likely to pull out accidentally when trying to trace one wire in a duct full of them.

author: thm_w
author_rank: Super Contributor
timestamp: December 18, 2019, 01:41:21 am
content: Quote from: Berni on December 17, 2019, 01:50:14 pmOr uninsulated:https://www.aliexpress.com/item/32425525831.htmlSince the correct part uses much thicker metal, it would make me think that ferrules have inadequate metal thickness. But these use single point crimp vs. ferrule which may be say 4 or 6 "points".Trying it here between two thin wires, the ferrule is incredibly strong (ratchet crimp), I would trust it over a hand-crimped splice. Thicker wire might not be as good (due to the relative thickness difference with the larger butt splice crimps).Good test for someone with a force gauge.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: December 18, 2019, 02:11:35 am
content: Quote from: tooki on December 17, 2019, 04:42:25 pmNegative. For butt splices, cable lugs and blade terminals (insulated), the Mil/Aero-orescribed crimp is the same as everywhere. (M22520/5-01 with Die M22520/5-100 /101/102/103 or M22520/10-01 with Die M22520/10-100...10-104). I prefer to have them use uninsulated ones (B-.crimp) in that case, but on the industrial side only.

author: wraper
author_rank: Unknown
timestamp: December 18, 2019, 07:03:05 am
content: Quote from: Kalin on December 17, 2019, 05:42:34 pmNot only that. Stranded wire likely will be held only by a few strands pressed by screw, the rest flapping loose. If current is high that will cause overheat and might even cause burning.