Ratcheting wrenches for small fasteners (≤M4)

  • December 15, 2023
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Today’s story begins a few weeks back. While tightening up some loose kitchen cabinet and drawer handles and the screws that attach drawer sides to drawer slides, I replaced several of the handles’ countersunk Phillips-head screws with hex-head bolts and washers. Phillips-head screws that were easy to reach straight-on with a screwdriver were snugged-up and left in place. The ones I swapped out were those that were hard to reach or obstructed to some degree by other cabinetry parts. The handle screws were all M4.

Animated GIF demo showing an example of a situation where a socket wrench is too girthy and a spanner-style wrench is needed.
This may take a moment to fully load. It’s an animated GIF demo showing an example of a situation where a socket wrench is too girthy and a spanner-style wrench is needed. The fastener is an M3 hex-head bolt identical to the one shown alongside an M5 and M4 bolt in an image below. The socket and the wrench shown, blurrily, are Wera 5.5mm models.

After preliminary finger-tightening, some of the replacement fasteners were easy to finish up with a hex socket. In a few instances, however, like the handle attachment screws on what seems to be commonly known as an oil pull out, which were close to some thin c-channel on one side and the bent-wire frame of the topmost storage basket a few centimeters directly behind the heads of the fasteners, there wasn’t enough headroom to get a socket wrench with a socket installed into place.

Reflexively, I dug up my set of nice combo wrenches with offset ratcheting heads and a switch on each to change it back and forth between tightening and loosening mode (6001 Joker Switch Ratcheting combination wrenches, with switch lever) — only to find that the 8mm wrench is the smallest one in the set. Pliers to the rescue.

Here’s an image showing three 304 stainless steel hex-head bolts:

Some hex-head bolts (M5, M4, and M3) with their measured dimensions.
Some hex-head bolts (M5, M4, and M3) with their measured dimensions. The heads of the larger two bolts bear the grade marking A2-70, in which A2 indicates that it’s made of 304 stainless steel and the 70 denotes its claimed tensile strength (≥ 700 N/mm2).

Discerning readers may question the accuracy of the measurements taken by yours truly with a pair of digital caliper measurements and included in that graphic. If you plug one of those numbers for one of the fasteners’ heads into the correct field in a hexagon properties calculator (e.g. Calc Resource’s Regular hexagon calculator), the value that it spits out for the other distance won’t be exactly equal to what I’ve posted.

For a perfect hexagon, the relationship between the face-to-face (yellow in that image) aka height (h) and point-to-point (green) aka width (w) distances is described by a very simple equation: h = cos(30°)*w. My numbers for the M5 and M3 bolt heads are close to the ideal, but for the M4 bolt they’re a bit off. If the face-to-face distance is 6.85mm, then the corner-to-corner distance should be 7.9-ish mm or, if the c2c is 7.8mm, then the f2f number should be about 6.75mm. On the other hand, we’re talking tenths of a millimeter. Moving right along…

Once the immediate problem, the issue of the floppy drawer handles and shaky drawer slides, was solved, I wondered whether Wera made any sub-8mm 6001 Joker combo wrenches. At present, all of Wera’s spanner-style wrenches bear a name of the format Joker 600X. The 6001 Joker wrenches — with their slightly offset, switchable ratcheting heads — are the most featureful line right now. Sadly, some poking around on the Wera site indicates that there are no 6001 Joker wrenches smaller than 8mm. What about the other types of Joker wrenches? The smallest switchless (and hence no-offset) 6000 Joker ratcheting combo wrench is 8mm as well. The 6002 Joker wrenches are non-ratcheting models with two fastener sizes on each wrench (e.g. 8mm and 10mm or 10mm and 13mm) and the smallest of those has one 8mm head.

Some hex-head bolts (M5, M4, and M3) with their measured dimensions.
From left to right, the three smallest 6003 Joker combination wrenches: 5.5mm, 6mm, and 7mm. The rightmost wrench, included for purposes of comparison, is the smallest 6001 Joker, the 8mm (#05020064001).

Wera does sell smaller, but they’re of a barebones, non-ratcheting type: the 6003 Joker combination wrenches. I went ahead and got one of each of the three sub-8mm 6003 Jokers from Amazon. The 5.5mm model (#05020190001 , the one with an orange band of paint) fits M3 hex-head bolts of the sort shown in an earlier photo and the 7mm wrench (#05020199001, banded with gold) fits the M4 bolt. The M5 bolt can be manipulated with the 8mm 6001 Joker (#05020064001).

Some hex-head bolts (M5, M4, and M3) with their measured dimensions.
All of my new sub-8mm spanner-style wrenches from left to right in order of increasing size, including the the 6003 Jokers and capped by the same 8mm 6001 Joker. New in this image: two no-brand flex-head ratcheting wrenches (a 6mm [labeled FHR6] and a 7mm [labeled FHR7]) and a 6mm Craftsman ratcheting wrench (model # ‎CMMT39240).

Ratcheting is a very useful feature because it means that you don’t have to remove and re-seat the wrench on the fastener head repeatedly. The narrower the arc through which you can turn the wrench, the more you tend to appreciate a ratcheting head, even if it’s got some slop. So I looked online for sub-8mm wrenches with ratcheting heads and got a 6mm Craftsman ratcheting wrench on Amazon and two no-name ratcheting wrenches with flexible heads, a 6mm and a 7mm, from a Taobao seller.

Bahco makes some ratcheting wrenches smaller than 8mm. One product is of particular interest: the S4RM-4-7 aka 4-7 mm Ratcheting Ring Wrench with Chrome Finish 115 mm. It’s the smallest wrench in the 4-in-1 Ratcheting Ring Wrenches with Chrome Finish [S4RM] series and, if it’s like the larger models (for which I can find more information and photos), it seems that it’s supposed to do 4mm, 5mm, 6mm, and 7mm duty. I couldn’t find it available for easy purchasing online, but Bahco is owned by Snap-on and the Hong Kong Snap-on office has responded favorably to my initial inquiry, so perhaps I’ll be able to buy a S4RM-4-7 and pick it up in person.