Introduction
Crimping is a popular topic at Element 14, it seems we all love our crimping tools.
A slightly more uncommon tool for hobbyists, but very common for industrial, military, automotive and aerospace purposes, is the pin crimping tool. It is used with circular pins, and indenters push into the pin from multiple sides. It is a bit like a ferrule crimping tool, but for smaller pins that may be used in connectors such as DEUTSCH, D-Sub and circular connectors with often dozens of pins, and for the center pin for some coaxial connectors. Often I have to use the solder bucket versions, or try to solder as best as I can, but a crimp tool would make life easier, and produce a reliable result.
(Image source: Farnell website)
A popular set of tools for crimping pins for some of these connectors is available from Daniels Manufacturing Company (DMC). Typical examples are the AF8 AF8 and AFM8AFM8. They look like very useful tools – the amount of indentation can be adjusted for suiting different diameter pins, and the position on the pin (i.e. how far up or down on the pin) can be selected by using a ‘positioner’ – these are available for different pins, or an adjustable positioner can be attached.
The photo below (from the DMC website) shows a couple of the tools, and how they are used; a positioner is fitted, and then a pin is inserted from the other side of the tool, and then a wire is fed in and then the handles of the tool are pressed together.
(Image source: DMC website)
I unfortunately do not own one of these tools, but I wished to crimp small RF connector pins such as SMA connectors.
I took a gamble and purchased a used tool called DMC MH800 from ebay. This was very cheap, because it is intended for a special BT (British Telecom) connector, and perhaps BT has phased it out, because there are a lot of used MH800 tools on ebay. The tool looks very similar to the more standard AF8 and AFM8, but with some slight differences, since the MH800 only needs to work for a single connector and doesn’t need configurability.
Anyway, this short blog post just shows a teardown of the MH800 tool, and I will try to modify the tool to suit my specific RF connectors need in a later update.
Currently, this video shows how the tool works. I eyeballed the pin position, and fortunately the indent depth seems reasonable for the diameter of the pin I was using (it was the center pin for an SMA RF connector). The video was accidentally shot with a very poor shutter speed : ( but it is still clear how the tool is used.
Exploded View
The photo here shows the tool mostly entirely disassembled. I’ve tried to name each part, so that it can be more easily discussed in text. Everything can be disassembled using a couple of hex keys, of size 1/16” and 3/32”. The main tool frame arm and a few other bits are made from steel, and the rest is mostly aluminium, it’s a very lightweight and comfortable tool when assembled!
The tool had seen a lot of use, I cleaned it all up for these photos.
Indenting Mechanism and Pin Positioner
The way it works is straightforward to understand. The wire is inserted into the pin, and then the pin is inserted into the opening in the tool, from the side shown in the photo below. When the arms of the tool are pressed together, the crimp actuator lever causes the light-colored circular part of the tool to rotate, and the cam and springs cause the four indenting dies to move inward, crushing into the pin from all sides. At a high-level, that’s really all there is to it. Of course, precision is required in the tool (because the pins can be tiny, less than a millimetre in diameter, and just a few millimetres long), hence the cost.
I didn’t try to disassemble the indenting mechanism further, in case the cam and springs popped off and went flying : ) It was possible to clean it all without disassembling further.
This particular MH800 tool has very small indenter dies, I think the expected pin diameter was of the order of 1mm or so (for instance SMA connector center pins). The MH800 tool cannot be adapted for larger pins such as D-Sub pins, because it would just tear into the pin. So, the MH800 cannot replace the general-purpose DMC tools intended for larger pins.
Shown below is a photo from the other side; a positioner piece is normally attached there, to fix how far deep the pin is inserted. The red cylindrical thing, the positioner body, is used for that purpose. A steel shaft of the correct size is fitted inside the positioner body along with a spring. I don’t know why the spring is there, I guess it’s not needed for the more normal general-purpose positioners.
Indent Depth Stop
The photo below shows the ratchet mechanism. More importantly, the photo also shows a circular piece of metal which I’ve called the ‘indent depth stop’, and a screw alongside it for fine-trimming.
The indent depth stop piece and the screw together determine how much of an indent occurs. In order to make a deeper indent into the sides of the pin, then the circular piece would need to be larger, or the screw would need to unscrewed from the other side slightly.
On the more normal AF8 and similar tools, the indent depth stop is not a fixed circular piece of metal, rather it is a rotatable adjustable piece. That’s a major difference between the normal tools, and the MH800.
The photo below shows the circular indent depth stop piece, and the fine-trim screw, more clearly from the other side.
The photo below shows where a 3/32” hex key can be inserted, to remove the indent depth stop elements just mentioned. They are hidden behind plastic plugs that are easy to pop off.
As you can see in the photo below. the indent depth piece is actually composed of a thick washer located in place using the other piece shown in the photo.
Summary
The DMC pin crimping tool looks like a great problem-solver for dealing with miniature pins for connectors. Although I need to do some work on it, I’m hoping with some modifications I can use it for RF connector center pins, because it gets tiresome soldering those. I suspect those with a few machine tools, or even a 3D printer, could easily modify such a tool to give it a new lease of life for hobby use.
The larger pin tools such as AF8 or AFM8 could be extremely useful for all the popular connectors such as D-Sub and circular connectors.
Thanks for reading!
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