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Today I am reviewing the Ko-ken 3756z Z-series or Zeal quick spinner. It's a Japanese-made unit and is 9.5mm or 3/8" drive on both the male and female ends. Here's how mine arrived:
The brand is visible on the upper side, and you can see that the finish here is textured rather than being smooth chrome:
The country of origin is clearly labelled below it:
Inside the female end - where the male 3/8" drive of the ratchet wrench goes - there are detents for ball bearings:
The corners are rounded so that the driving force is transmitted to the flanks of the drive square rather than the corners:
The knurling has been done nicely and provides good grip, even with oil-covered fingers.
There is a ball bearing in the male end:
So, what is the purpose of a quick spinner? It sits between the ratchet wrench and an extension:
The wider diameter as compared to the extension in this example combined with the knurling give you much better grip for quickly spinning the socket and fastener - this is particularly handy when the fastener is not on tight enough to trigger the ratcheting mechanism and you are working in confined spaces where there is not a lot of space to get a good grip on the socket/extension.
I find the quick spinner particularly good in those situations as I have arthritis in my fingers which makes firmly gripping a probably-oil-covered extension difficult. The knurling and larger diameter make life much easier there. As an example, replacing a distributor on a Toyota 5S-FE motor the other day was made a good deal easier by having the quick spinner on the end - the bolts on the underside were easily reached with an extension on the socket but repeatedly turning the narrow extension was not ideal. Adding a quick spinner into the mix made the job quicker and easier thanks to the knurling and increased diameter.
Speaking of the diameter, the 3756Z is about 28mm edge to edge:
In terms of weight and length the 3756z weighs 40gm and is 25mm long from end to end - though it does not add 25mm to the length of your ratchet, as the male drive part sits inside the female of the spinner. It instead adds:
Koken's Z-series or Zeal lineup feature tighter tolerances than required by the ISO/DIN specs, meaning that they should have a very close fit to not just fasteners but also the male drive square. Ko-ken's brochure shows this like so:
There is another quick spinner option in the Koken Zeal lineup - there's this one, the 3756z, and also a 3756zs that is the same length but with a knurled section diameter of 7.7mm less. The 3756zs also weighs 26gm compared to the 40gm of the one I'm looking at today.
Ko-ken also have a non-Zeal quick spinner in their 3/8" range, part number 3756. It's a hair longer (25.5mm), slightly heavier (47g) and a little larger in diameter (30.5mm) than the Zeal option - and presumably has "regular" tolerances for the square drive sections. It's also approx. $26AUD (1,996JPY).
In terms of value, the 3756z is currently listed for around $18-19AUD (approx. 1,500JPY) at Mutsuura and i-Tools - which seems pretty decent value to my mind. They also come up from time to time on eBay AU. Other options include quick spinners from another Japanese company, KTC - there's one on Amazon for $12USD which converts 1/4" to 3/8" drive, which - while not exactly the same - may be of interest.
Snap-on have a similar product in the FRS70A - there's usually a few vintage ones of those available on eBay US, and their new list price is around $35USD (a touch over $50AUD at the time of writing).
It's a small tool but it complements a quality extension and ratchet wrench set nicely - I have used mine more than I expected since it's purchase and feel that it was $18 well spent. Recommended. Prefer Nepros? They have a similar (28mm diameter) quick spinner in the NBEC38 (Rakuten).
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