Sizing of 1/4” hex shanks

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Sizing of 1/4” hex shanks

This topic has 15 replies, 12 voices, and was last updated 8 October 2024 at 20:04 by Bill Phinn.

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21 September 2024 at 14:54 #754855
Bill Phinn
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@billphinn90025
Michael’s recent question about the declared shank sizing of Dremel bits (the motivation for which seems to have been slightly misinterpreted by some) put me in mind of a quite different sizing issue that I’d be interested to have people’s views on.

About six months ago I bought a set of HSS 1/4” hex shank 3-flute countersinks. As you can see from the two photos, the across-the-flats measurements are rather short of the declared size. My feeling is that this size discrepancy isn’t acceptable, whether the intention is to use the bits in a hex bit holder or a three jaw chuck.

I should point out that:

a). none of the eighteen AF measurements in the six-bit set is as big as 1/4”, the biggest being 6.29mm, and the smallest 6.07mm, with half being under 6.2mm.

b). all three of each of the six bits’ AF measurements are different from one another by between a perfectly acceptable (to me, at any rate) minimum of 0.03mm and a surely unacceptable max of 0.20mm.

c). some of the bits are, as you’d expect, a decidedly wobbly fit in a 1/4” bit holder.

d). the seller gave me a full refund whilst being quick to point out that he’d sold hundreds of these sets and nobody had ever reported the problem I was reporting. I am perfectly prepared to believe him, though if his reply was intended to be reassuring it wasn’t.
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21 September 2024 at 15:21 #754859
DC31k
Participant
@dc31k
Please look up ISO1173.

https://cdn.standards.iteh.ai/samples/23588/ab32510c11f74bfbb198fcd63d2b9a04/ISO-1173-2001.pdf
21 September 2024 at 15:23 #754860
Tony Pratt 1
Participant
@tonypratt1
Sadly it doesn’t surprise me at all, nowadays the consumer is the quality control. I suppose they do the job as you say?

Tony
21 September 2024 at 15:42 #754865
Hopper
Participant
@hopper
I would have thought those were intended for woodworking use in handheld pistol drills, so unlikely to be of the levels of precision we are more used to in precision metalworking kit?

Likely made undersize so they go in and out of the typical carpenter;s quick change 1/4″ hex holder quickly and easily? A bit of slop never slowed a carpenter down. As long as they don’t fall out, he will be happy.

And if they are cheap ones, quite likely all over the place in line with low cost manufacturing standards.

For more precision suited to use on steel etc in milling machines for model engineering etc, I think I would be looking at the more expensive countersinks with the ground round shanks.
21 September 2024 at 15:42 #754867
Bazyle
Participant
@bazyle
Edited out previous reply. I was thinking of screwdriver bits where the working bit is smaller than the hex shank.
21 September 2024 at 16:06 #754874
JasonB
Moderator
@jasonb
Looks like you picked up a bit of a Lemon, measured an assortment of mine for comparrison. If you are putting them into a cordless with built in hex recess holder then there is more risk of wear to the holder, if you are just using a separate hex recess holder or even a drill chuck not such an issue.

From The Top

Trend 5mm TCT drill/csk

Trend 4mm TCT drill Csk

Kreg Pocket Hole drill

Bosch Lip and spur drill

haffle sprung jig drill

Screwfix drill bit

Toolstation Drill bit

Tec Driver

Wera #2Pz

All except plain shank jig drill quite close to 6.35 and withing the upper and lower limits of DC’s table 5 which is the recessed one
21 September 2024 at 16:07 #754876
Bill Phinn
Participant
@billphinn90025
Thanks a lot for the replies.

Yes, I intended them mainly for woodworking (though I would also have liked to use them in my mag drill). Other 1/4” hex shank tools I own by Wiha, Milwaukee, Dewalt et al. are probably mainly intended for woodworking too. After a quick measuring session all but one of about a dozen I’ve measured is within the spec DC31k has provided.

For quality work I’ve just bought these, which, interestingly, come in two versions: a round shank version (mine) and a triple-flat shank version:
8 October 2024 at 16:08 #758002
Bill Phinn
Participant
@billphinn90025
Well, here we go again, this time with square drives on two recently purchased offset handles. Do either the 1/4” or 3/8” come within a recognised standard?
8 October 2024 at 16:40 #758007
ega
Participant
@ega
As to the hex shanks, Festool offer their “Centrotec” holders which centralise the bit and minimise wobble. They are intended for Centrotec bits but standard ones can be turned down slightly to fit.
8 October 2024 at 17:05 #758013
Michael Gilligan
Participant
@michaelgilligan61133
On 8 October 2024 at 16:08 Bill Phinn Said:

[…] Do either the 1/4” or 3/8” come within a recognised standard?

“Easily Detachable” perhaps

MichaelG.
8 October 2024 at 17:11 #758018
Neil A
Participant
@neila
BS 4006 covers the size of square drive sockets and wrenches.

1/4 square drive. 6.260 min 6.350 max

3/8 square drive. 9.435 min 9.525 max

All in millimetres of course.

I was always told that BS was the lowest common denominator of the manufacturers. That was by someone who was on some of the committees!

Neil
8 October 2024 at 17:19 #758021
old mart
Participant
@oldmart
I have been lucky with the 1/4″ hex shank toolbits which are intended to fit in screwdrivers and small impact drivers. I have just bought one of the 12V Lidl drills with the 10mm chuck which comes off to reveal the 1/4″ hex drive. It comes with a good set of drills and screwdriver bits and the drill box for £13.99, they were £ 16.99 before. You have to already have the charger and battery, though.
8 October 2024 at 18:59 #758034
Pete
Participant
@pete41194
Many of these tool shanks are designed and meant to be a slip fit. That spring loaded ball on the square shank is what does the retaining well enough for whatever tool is on it to not to fall off. It’s there, but on lower priced tools I’ve seen a few that don’t work at all to help retain the tool. A lot of those hex shanks are also meant to be used with a magnetic driver that again does the retention well enough to hold the tool in use and still be removed and replaced by hand. I have dozens of hex shank tool tips and either use them directly in the drill chuck or with that separate magnetic driver in the chuck when I need to change to various tips often enough to make it worthwhile to use that set up. But the inconsistent sizes that started this thread sure seems to indicate poor quality control for the forging dies and finished product. Building down to meet a very low price point doesn’t work for retaining repeat customers either.
8 October 2024 at 19:37 #758036
Robert Atkinson 2
Participant
@robertatkinson2
A loose fitting square or hex connection reduces the effective contact area under load (torque). This increases the stress and thus increased wear and probability of failure.
That’s apart from location issues and perfomance of the tool combination.

Robert.
8 October 2024 at 19:46 #758039
Pete
Participant
@pete41194
Of course that’s true Robert, I’m not stupid. But EVERY square drive mechanics tool including Snap On’s best use that spring loaded ball for socket retention. So obviously there’s a tolerance to keep the square slightly under size to meet that slip fit requirement, but not too far under. The same would hold true for hex drive tool tips that are magnetically held in the driver.
8 October 2024 at 20:04 #758043
Bill Phinn
Participant
@billphinn90025
Thanks for the feedback, everyone.

It was, as Michael’s post anticipates, the ease of detachability of sockets that first suggested something wasn’t quite right, though the four ends aren’t equally bad, possibly because of the different strengths of the springs behind the ball bearings. The short end of the 1/4” one is the worst: put an extension and a deep socket on this and they will drop off merely under gravity.

The 3/8” short end doesn’t drop sockets so easily but the degree of “backlash”of the square drive within a socket is disturbing. Who needs a wobble bar? Just make ordinary square drives undersized. Maybe that’s their logic.

Essentially for the reasons Robert gives, I’ll be returning these.

It’s notable that 1/4” and 3/8” offset (or L) handles aren’t nearly so common as 1/2” and 3/4” versions. Not sure why.
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