CMS-Japanese Motorcycle Supply Parts

Ko-ken 3756z Z-series Zeal Quick Spinner Review


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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:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

The brand is visible on the upper side, and you can see that the finish here is textured rather than being smooth chrome:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

The country of origin is clearly labelled below it:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

Inside the female end - where the male 3/8" drive of the ratchet wrench goes - there are detents for ball bearings:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

The corners are rounded so that the driving force is transmitted to the flanks of the drive square rather than the corners:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

The knurling has been done nicely and provides good grip, even with oil-covered fingers.

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

There is a ball bearing in the male end:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

So, what is the purpose of a quick spinner? It sits between the ratchet wrench and an extension:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

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.

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

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:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

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:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

Approx 13.5mm.

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:

Here's a review and some photos of a Koken or Ko-ken 3756z 9.5mm or three-eights quick spinner, which is made in Japan.

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).

Liked this review? Check out some of my other tool reviews! or take a look at the video review of the quick spinner.



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