A Comparison of Molex KK 0.1″ Crimp Tools

I was recently discussing some equipment repairs and refurbishments with a new sub-contractor and the subject of replacing a number of leads came up. These leads were terminated on one end by the common 0.1″ molex KK connectors and I enquired whether they had a crimp tool for these. As they hadn’t, there followed a discussion on the options which basically fell into two camps: buy the genuine Molex crimp tool (63811-8200) for the eye-watering price of £240, or go for a cheaper more generic crimp tool.

It’s worth at this point, taking a moment to consider the other option, which of course is to solder the crimp contacts. This is a very common practice amongst Makers and one that I used myself on many occasions. Why bother to crimp? On the face of it, it seems barking mad – squeezing some metal around a wire and expecting it to hold fast and create a good electrical contact. Surely soldering is better?

I must confess to thinking that crimping was mainly about speed for volume production and that crimping was an expensive luxury. Whilst crimping is faster, it also creates a more reliable, consistent connection. One of the problems with soldering our friendly old KK contact is that the solder inevitably wicks up the wire and this makes for a brittle junction around the top of the contact. This creates a common point of failure, especially for wires that get regular flexing or vibration. For this reason you’ll seldom find anything other than crimped contacts on cars. So whilst it’s not the end of the world to solder a contact (meant to be crimped), you should crimp these where possible.

To return to the burning crimping question: Is the Molex tool needed and what advantage it would confer over a cheaper alternative? I had managed to pick up a used 68311-8200 from eBay some time ago and thus decided to do a comparison with my trusty old generic crimper.

The Test

The generic crimp tool that I tested was the PA-09 from Precision Hand Tools. This currently costs £41.99 + £1.99 P&P in the UK and whilst not exactly cheap, promises to do a whole raft of different contacts and is just about within reach of the hobbyist.

Molex 63811-8200 KK crimp Tool

Cost: £236.36
The crimp contacts that I used were Molex 0.1″ KK ones, part number 08-50-0032

This crimp tool is a ratcheting tool that crimps the contact in a single movement and so can be very quick. I selected the “C” jaw and timed several crimp operations. From a stripped wire, it took me around 15 seconds per crimp and I reckon with a bit more practice, I’d easily get this down to 10 seconds or less. The quality of the crimp was very good with no failures (always do a “pull” test to check mechanical strength).

PA-09 Universal Crimp Tool

Cost: £41.99
The crimp contacts that I used were Molex 0.1″ KK ones, part number 08-50-0032

Using this crimp tool, you need to crimp the contact in two distinct phases: first you crimp the bare end of the wire and then you crimp the insulation. From the instructions, they recommend that you use a set of calipers to measure the width of the contact and then select the correct jaws to use based on the measurements. I duly did this and came up with a measurement of around 1.6mm for the main part of the contact and around 2.0mm for the insulation. I thus chose the 1.6mm jaw for the wire and the 1.9mm jaw for the insulation.

From a stripped wire, it took me around 40 seconds per crimp. It was a lot more fiddly that the Molex crimper, but nonetheless the results were reasonable for Maker use.

Conclusion

From the close-up image you can see that the red wire from the PA-09 is not quite as tidy as the Molex (black wire) and it takes longer to crimp. However, speed is seldom the issue for the average Maker and the result is ok, far better and more reliable than soldering. Coupled with the fact that the PA-09 is very flexible and will crimp a whole range of other small crimp contacts, it’s a reasonable choice here and would recommend for most Makers.