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Part 69a-c: Grub screws

As with the set screws, these parts weren't included separately in each outfit, but were included where required in the brassware.  Only the very short grub screw, part 69c, was included in outfit 10 from its introduction in 1937.

69a	Grub screw, 5/32''	1912	-					Included in bosses
69b	Grub screw, 7/32'' (long)	1922	-					Only with part 63a
69c	Grub screw, 7/64'' (short)	1937	-			12	N°10	5/64'' pre-war

The parts

Another tricky part to spot, there are in fact three different lengths of grub screw, as shown in the picture to the right.  Part 69a is by far the most common, supplied with most brassware such as collars, gears, couplings and so on.

Part 69b is a special long grub screw originally supplied with the octagonal coupling part 63a, but later available also as a spare part.  Part 69c is a short grub screw that is very useful in complex gear mechanisms as it doesn't stick out from the boss of the gear.

The easiest way to identify the smallest grub screw is by its concave end.  You can see in the picture to the left the concave end of part 69c (left) compared with a standard grub screw part 69a on the right.

For many small gear trains, particularly with 19-tooth pinions, you will need part 69c to avoid the grub screw fouling on the teeth or boss of nearby parts.  The photo to the right shows part of a gear train – the grub screws in the top pinion and the socket coupling must both be part 69c to avoid them fouling each other.

The long grub screws, part 69b, can be used for various trickery in small spaces as they are long enough to hold a nut on one or both ends.

Chronological variations

As with the set screw, this part didn't have its own number until 1916 even though it was supplied with collars and other parts from 1912.

Initially plain steel, these parts were very soon supplied in blackened steel (from at least as early as 1915), and almost all examples are like this.  Grub screws are found in nickel, and brassed.  It is very difficult to date these parts as they, like set screws, get mixed up in outfits rather easily!

However, William Irwin identifies the last Binns Road period, as usual:

...and now thanks to Richard we also have an example of the iridescent 69b.ir in the table below.

Very short grub screws

The short grub screw in fact had two different lengths.  When introduced in 1937, it was 5/64'', as shown by the label on the tin to the left, and in the 1937 parts listing.  Immediately post-war, the lists show this part as lengthening to 7/64''.  Thanks to William for spotting this.  The very small grub shown below might well be one of the very short ones.

This length change might well make sense in combination with the concave ends to the short grub screws.  If the very short grub screw has a convex end, it would have to be around 5/64'' long to avoid the head protruding from the boss.  However, if made with a concave end it can be made longer and thus easier to handle, and still perform its function.

But of course it's not as easy as that, is it.  It seems that the majority of pre-war part 69c do indeed have concave ends, and are slightly shorter than the post-war versions.  Note that these parts are only supplied in the pre-war outfit 10 and as spare parts, so they're hardly common.

Perhaps the convex-ended part 69c are an early variation, soon changed to concave ends, and the length was increased to 7/64 post-war once they realised that it was easier to have them longer.

Variations and oddities

John Nuttall sends us a couple of weird ones – a long 69b with a concave end and a short 69c with a convex end.  These appear to be one-off mistakes, rather than deliberate parts.  They could conceivably be from another system altogether, of course.

And to prove you can't keep a good man down for long, Ed comes back to us with some even more strange variations.  Here's a spigot-ended short grub screw (which is thought to have come from the model room at Binns Road), and a very very short version of the 69c.

Yet another oddity is shown right – a standard grub screw with a rounded end and a strange indentation in the bottom.  Again, no idea where these are from, or even if they are Meccano.

One of the most annoying thing about grub screws is that the heads can break rather easily while you're tightening them up.  If this happens you can end up with part of a grub screw stuck in a boss and almost no way of removing it.  The solution is to put the part in a strong acid such as supplied for swimming pools (33% hydrochloric acid).  The grub screw will dissolve leaving the brass gear untouched.  You must make sure that the part you're removing the grub screw from is entirely brass, of course!

Dealer spare parts boxes

The picture to the right shows a dozen grub screws in a white box (early 50's), in a dark yellow box (late 50's), and in a light yellow box with white label (60's).

Grub screws in packets are very common, as they were often needed to replace lost ones.  Even today, there is a good market for grub screws both Meccano and reproduction.

To the right, a packet of the shorter grub screws, part 69c.  As usual with unpainted parts, these boxes with yellow labels continued right through the medium red/green and light red/green eras, so these parts could be as late as the mid-60s.

Individual part numbers

Part numbers for the parts on this page are as follows:    Unique part numbers
For identification, each variation has been given a suffix to the main Meccano part number. These suffixes consist of a two-character code for the colour, and if there are many variations, a further number and sometimes letter code to identify each variation. See the bottom of the 'Parts' page for further details.

You don't need to worry what the codes are, just click on any one for a photograph.

The button above turns on and off the display of DMS numbers (where they are known). The DMS (Development of the Meccano System, Hauton and Hindemarsh) published in 1972 and added to in 75 and 82, suggested part numbers for every variation of every Meccano part. These numbers aren't perfect, but they are recognised and also referenced in the EMP (Encyclopedia of Meccano Parts, Don Blakeborough).

Description	from	69a	69b	69c
Plain steel	12	.st
Blackened steel, convex end ¹	??	.bs	.bs
Blackened steel, 5/64'', concave end ¹	37			.bs1
Blackened steel, 7/64'', concave end ¹	45			.bs
Nickel plated	??	.ni
Brass plated	??	.br		.br
Zinc plated	78	.zn	.zn	.zn
Iridescent	79	.ir	.ir	.ir
Blackened steel, allen head	89	.bs1		.bs2
Zinc plated, allen head	89	.zn1		.zn1
		ALL	ALL	ALL

Notes:
¹  Almost all grub screws are blackened steel.

Please send us pictures of missing parts! Hints and tips for pictures
Take a picture of the part in very good light, preferably on a plain yellow background, without a flash but with a tripod.
Ideally, trim the picture to about 150 pixels per inch of the Meccano part (unless the part is particularly big or small), save it as a reasonably good quality jpg file with a filename of exactly the part number, for example 19b.ni1.jpg, and email it to us by clicking on 'Contact us' at the top of the page. Thanks!

• A greyed-out box shows that no part exists for that colour combination.
• Part number codes with a green background have an attached picture of the part, just click once on the code to show a photograph of that part in a separate window.
• Parts marked "†" were temporary or economy parts, or existed only within specific themed outfits. The previous part continued throughout or afterwards.

Further information

Total number of messages on this page: 8.  This is page 1 of 2.   

Johnny Meccano      (at 6:06am, Sun 12th Apr, 15)

Hi Graeme. I am in Australia as well, but I found it easy to purchase 100 allen key grub screws from John Thorpe in the UK. I'm sure he sells slotted as well as allen key. They don't weigh much so postage isn't too expensive. You can browse his website at http://www.meccanohobby.co.uk/

Graeme      (at 12:04am, Sun 12th Apr, 15)

I am requiring some 69a wheel grub screws. Do you have these available and could you please tell me the cost plus postage to Australia? Thank you.

Paul Hughes      (at 12:12pm, Fri 30th Jan, 15)

The grub screw breakage is an issue. I've found that for painted parts, clamping the blocked tapped hole vertically then pipetting concentrated HCl onto the the broken grub screw surface can avoid damage to the rest of the part. Might need a few goes at it though.

Barry Gerdes      (at 2:04pm, Thu 9th Sep, 10)

I have had trouble with hex grub screws getting rounded. I bought one of those kits of wrenches with all those star type wrenches. I found a star wrench that could be forced into the damaged hole. This remove the screw without any problem.

Rick Moore      (at 5:09am, Thu 9th Sep, 10)

To remove a steel screw from a brass gear wheel or pully you can soak it in Hydrocloric acid. (or battery acid) This will desolve the screw but not harm the brass. Parts like a crank even though partly steel can be done with care if only the brass part is submerged. Coat the steel part with grease for extra protection. Always wear gloves and gla** for your safety.

gail      (at 4:43am, Thu 9th Sep, 10)

i have a grib screw stuck as the allen key end has somehow become a circle!! how will i remove it?

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