Grabbers for plated-through holes - Page 1
Forum section: electronics / general

author: cdw
author_rank: Contributor
timestamp: April 28, 2025, 12:57:21 pm
content: I'm a u-boot contributor, and from time to time, I want to connect to unpopulated 0.1" serial port headers on the boards of routers for unbricking/debugging/porting. My current bodge for doing this quickly is to place little 'hoop' test points (attached a picture) into the holes and then carefully use small hook grabbers on the hoops without dislodging them. It works surprisingly well but is a bit fiddly: very easy to knock out the hoops as you attach to them. I can't solder headers onto the board properly because it's usually a borrowed device.Does anyone make little grabs that expand to grip the inside of a through-hole when you release them, rather than gripping a wire from the outside, kind of like the way the hoops themselves grip the inside of the hole? I had a search but didn't turn anything up. It's entirely possible I just don't know the right description to Google though.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: April 29, 2025, 12:19:44 am
content: My bodge for this is to use a 0.1" header row, placed through the holes, and then gentle side pressure applied so it makes decent contact. Only works with single row headers unfortunately.A protoboard with pogo pins would work, you'd need to make one for each model of router you deal with. Something heavy on top would allow hands-free connection.

author: cdw
author_rank: Contributor
timestamp: April 29, 2025, 06:42:17 am
content: For your amusement, yesterday's horrific bodge with grabbers and test points that inspired my question!Of course, they're invariably in awkward spots like this. (Despite the implausible mess, this was a good enough 3V3 serial connection to get the mt7981 to uart-boot ARM tf-a and u-boot so I could tftp a kernel and initramfs.)I did wonder if I could even bend the end of pieces of single-core wire into a shape that was narrow at the tip and widened as it went further in, but I guess I ideally want something more springy.Anything I do really needs to be adaptable as I see a lot of routers but rarely for more than half an hour each - unless they're my own in which case they get proper headers. Generally they're three or four pin unpopulated 0.1" headers, GND/TX/RX (in some order, with or without a VCC to avoid). Something that applies gentle pressure on three header pins as you describe could work, or maybe a modified set of long header pins bent somehow would hold in unassisted?

author: tooki
author_rank: Super Contributor
timestamp: April 29, 2025, 10:52:34 am
content: Quote from: cdw on April 28, 2025, 12:57:21 pmYep, XG25, XG31, and XG40 “E-Z Micro-Lock Hook” from EZ-Hook.https://e-z-hook.com/test-hooks/micro-hook/xg25/https://e-z-hook.com/test-hooks/micro-hook/xg31/https://e-z-hook.com/test-hooks/micro-hook/xg40/This reminds me that I wanted to order some of those…

author: artag
author_rank: Super Contributor
timestamp: April 29, 2025, 11:34:04 am
content: I think I've seen something like this in the past, probably a relation of one of those ez-hooks that HP were selling at hundreds of pounds for a small set.https://warwickts.com/1710/E-Z-Hook-X2015-Double-Micro-HookFor larger holes a simple cheap minihook (the type with a single hooked end) pushed through the hole can work, but they slip off and the holes are often too small.A couple of possibilities though - Geoff-AU mentioned pogo pins and the difficulty of keeping them in place. This type might be helpful though the jaws aren't deep enough for all pcbs.https://vi.aliexpress.com/item/1005006609750088.htmlIf the board is small, or has nearby holes that can be used as anchors, 3d-printing a fixture for an array of pogo pins can work. I use this to connect to the programming pads on Seeed Studio's little Xiao boards.For something closer to the original request, these are comparable to the very small minihooks -https://vi.aliexpress.com/item/1005007717859380.htmlAnd these are a different mechanism I haven't tried yet :https://vi.aliexpress.com/item/1005007723049477.htmlAll the above though seem to be tweezer-like. They open wide and clip to a point. Maybe deliberately twisting the tips so that when they close they cross over and open out into the hole would work ? Or poking the tweezer pins through and locking them on to a short piece of wire placed across the hole on the far sideto stop them withdrawiung ?

author: TERRA Operative
author_rank: Super Contributor
timestamp: April 29, 2025, 11:37:10 am
content: In Japan I can buy these off the shelf, I haven't used them myself, but they apparently work quite well.Test Wire for Through Hole (Male to Male) (TTW-200)Test Wire (Female-Male) (TTW-201)Test Wire (Female-Female) (TTW-202)Test Wire (Male/Breadboard - Male/Spring Pin) (TTW-203)Maybe there's something similar available locally to you?

author: cdw
author_rank: Contributor
timestamp: April 29, 2025, 05:07:14 pm
content: Thanks, some great options to buy and try out there.Another idea I had was a 1x3 row of press-fit headers, gentle pushed into the holes so they just start to grip but aren't locked in properly. Although I haven't seen press-fit headers for years...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 29, 2025, 06:39:52 pm
content: Quote from: Geoff-AU on April 29, 2025, 12:19:44 amor a 0.1" header with long pins, and alternate pins bent to provide tension against the sides of the holes

author: thm_w
author_rank: Super Contributor
timestamp: April 29, 2025, 10:29:48 pm
content: We had a thread but I can't find it again either, fairly sure it was tooki that suggested the XG40 there too. At $8 its expensive, but if you have a use for it it works well, specifically being unable to solder.But you could consider other options like some kind of spring pogo pin holder:https://www.electromaker.io/shop/product/pogo-pin-probe-clip-6-pins-with-254mm-01-pitchIf the connector is always on the board edge.I do use the bent header pin option myself usually.

author: cdw
author_rank: Contributor
timestamp: April 30, 2025, 06:57:37 am
content: Yes, the bent pin option is super-simple, cheap, and doesn't involve me buying anything, so will try that next time I have a borrowed router on my desk!I can't try it out on any of my own boards as I've already soldered headers to all of those, but it seems to work nicely on a piece of 0.1" protoboard. I did wonder if it would grip at all with only three pins and only one bent out of line, but actually it seems okay...

author: coppercone2
author_rank: Super Contributor
timestamp: April 30, 2025, 07:01:45 am
content: Imagine a tiny screw with a rounded bottom, with a loop on top, that you can insert into a via and thread a tiny nut on so you have a measurement loop for a via that is robust but also removableA 0000 screw is 0.53mm.Do they have smaller long screws? Like say 0.2mm??

author: Someone
author_rank: Super Contributor
timestamp: April 30, 2025, 09:00:28 am
content: Quote from: cdw on April 29, 2025, 05:07:14 pmPlenty of options still available and stocked, even from the brand names:https://www.samtec.com/products/pht

author: 5U4GB
author_rank: Super Contributor
timestamp: April 30, 2025, 12:50:55 pm
content: Quote from: coppercone2 on April 30, 2025, 07:01:45 amYou can get screws in those sizes for use in eyeglasses (larger sizes) and wristwatches (smaller sizes), but they're an enormous pain to work with, you need a magnifier with a ring light and steady hands and tweezers and a relatively soundproof room so your comments while trying to do it don't kill the houseplants.

author: coppercone2
author_rank: Super Contributor
timestamp: April 30, 2025, 01:37:43 pm
content: If its modified to have a loop on top, you can use an applicator. And the "nut" for it can be substantially long to make it easier to handleBecause I don't know if you tried them, true micrograbbers (the ones that cost $30 each) are also similar to use, when you destroy the grabbers on a 0.5mm pitch part you will put a hole in the table

author: julian1
author_rank: Frequent Contributor
timestamp: April 30, 2025, 10:16:29 pm
content: The XG40 grabber DS says the part is designed for holes 0.040 - 0.042" (1.02-1.07mm).That is a tight tolerance/manufacturing margin.What are the chances they work for a metric 1.0mm PTH CAD footprint, without change?

author: thm_w
author_rank: Super Contributor
timestamp: April 30, 2025, 10:40:03 pm
content: Quote from: julian1 on April 30, 2025, 10:16:29 pmThey fit in a 1.1mm hole but not a 0.91mm hole, 0.93mm its a moderate friction fit. So 1mm should be OK.Stupid ruler has 1.2mm and 1mm "drill size" but doesn't tell you what the actual hole size is, I measured but it might not be dead on.I think they could have designed it differently to fit a larger range of hole sizes, but this design is very simple.

author: langwadt
author_rank: Super Contributor
timestamp: April 30, 2025, 11:26:30 pm
content: there must be something that works like a cleco