Author Topic: Stuart 10H grub screws.  (Read 3181 times)

Offline Gas_mantle

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Stuart 10H grub screws.
« on: September 11, 2016, 09:04:30 PM »
Hi,

I'm trying to restore a Stuart 10H that I got at a bargain price and wanting to remove the eccentric, also the grub screw that is in at the moment needs replacing but having never had a Stuart engine before I'm unsure of its size or what Allen key will fit.

I understand Stuart favoured BA threads, is anyone able to please suggest what size the screw is likely to be and what size key will fit ? The smallest key I have at the moment is a 1.5mm but I assume I'll need a much smaller Imperial key ?

Any ideas where I can get small replacement grub screws ?

Many thanks
Peter

Offline Admiral_dk

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Re: Stuart 10H grub screws.
« Reply #1 on: September 11, 2016, 10:13:11 PM »
A very good question at work we have more than 8 different size Allan keys around 1.5mm. where I can't see the difference in size with the naked eye, but certainly feel it when I try it on the guitar or Bass that needs repair. From 1.0mm. to 4.0mm. we have more than 30 different sizes in the toolbox - most of those are Imperial sizes. I really haven't got a clue why there is that many, but using the wrong one almost always destroys the screw/bolt and the key (at least a bit).

We got most of ours along with different instruments - as most of them can't be bought in a shop.

Haven't got a clue what size is supposed to be used on the Stuart - but I hope that you find it.

Offline Gas_mantle

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Re: Stuart 10H grub screws.
« Reply #2 on: September 11, 2016, 10:21:37 PM »
Thanks Admiral,

I'm assuming the original builder used a Stuart screw but can't be certain - I have no BA tools at the moment and as yet can't remove it, my only concern is the size of the Allen head - it is pin prick sized so I'm hoping it's a standard screw that I can get a key for.

Offline derekwarner_decoy

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Re: Stuart 10H grub screws.
« Reply #3 on: September 12, 2016, 01:44:28 AM »
Peter............look at the W dimension....or the AF sizing.......... tables may assist........ Derek
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Offline AOG

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Re: Stuart 10H grub screws.
« Reply #4 on: September 12, 2016, 02:28:08 AM »
i happen to have an unbuilt set of 10h castings in my closet of castings. According to the parts list its a 5BA x 5/16.

Tony

Offline Jasonb

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Re: Stuart 10H grub screws.
« Reply #5 on: September 12, 2016, 08:46:02 AM »
Depends on the age of the kit but they did favour slotted grub screws so you may have a job finding a hex key to fit ;)

6BA on the eccentric, which if hex would need a 0.050" key often now sold as 1.3mm

Offline Gas_mantle

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Re: Stuart 10H grub screws.
« Reply #6 on: September 12, 2016, 09:52:08 AM »
Hi,

Many thanks for the replies.

I'll order a set of smaller keys in both metric and imperial and hope I can remove it. At the moment it's difficult to get a micrometer at it accurately but it seems to be about 2.75 mm OD but the Allen socket appears to be smaller than 1.3 mm when comparing my 1.5mm key.

Depends on the age of the kit but they did favour slotted grub screws so you may have a job finding a hex key to fit ;)

Jason - are there any things to look out for that can give an approximate age to these engines? this one has counterbalances on the crank that fit over the webs - it's difficult at the moment to tell if it's a solid or fabricated crank shaft.

It looks to be well made so I'm assuming the counter balances were added by a skilled builder and not actually a Stuart feature ?

Offline Johno

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Re: Stuart 10H grub screws.
« Reply #7 on: September 12, 2016, 10:38:44 AM »
Peter,

Stuart's favoured BA threads. Grub screws having slotted heads. Parts list (including fixings) for the present kits are available as downloads on their web site They will also sell you a drawing of their engines listed within the 'spares' section which may assist with the refurbishment. Regards the size of the grub screw on your engine  you can not assume the original builder followed the drawing as he (or she) was working to at the time and may have substituted the specified size for what was at hand in terms of size of tap/grub screw.

Regards

Ian

Offline AOG

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Re: Stuart 10H grub screws.
« Reply #8 on: September 12, 2016, 11:00:03 AM »
i happen to have an unbuilt set of 10h castings in my closet of castings. According to the parts list its a 5BA x 5/16.

Tony

I was one number off on the parts list, that's for the flywheel. The eccentric is 7 BA x 3/16 inch. Mine appears to be slotted but this is an old kit.

Tony

Offline Gas_mantle

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Re: Stuart 10H grub screws.
« Reply #9 on: September 12, 2016, 11:13:54 AM »
Thanks,

7BA sounds nearer to the size but I'm starting to think it's a non standard screw in the engine - I could remove it by force but I'm trying to avoid damaging the eccentric as I think redrilling to a larger size will spoil it and I'd don't want to make a new eccentric if I can avoid it.

Offline Jasonb

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Re: Stuart 10H grub screws.
« Reply #10 on: September 12, 2016, 12:45:44 PM »
That 2.75mm dia also makes it sound more lihe 6BA which is 2.8mm. I'll have to go and unscrew mine to check though I may have gone larger as its such a shallow depth the thread may have stripped in the past.

0.035" is the next imperial size key down from 0.050"

Offline Jim Nic

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Re: Stuart 10H grub screws.
« Reply #11 on: September 12, 2016, 02:35:22 PM »
My 10H is assembled from a factory machined kit purchased direct from Stuarts in 2010 so can be assumed to be made to drawing.  I have just this minute disassembled the relevant part and can tell you that the eccentric is secured by a 7BA grub screw using a hex key measuring 1.25mm across the flats.
As to dates the crankshaft is a pinned assembly, presumably but not confirmed, as Loctited as well, it has no counterweights.  The shaft on my 10V made from a casting set purchased in 2012 I made similarly.
Jim
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Offline kev

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Re: Stuart 10H grub screws.
« Reply #12 on: September 12, 2016, 05:50:02 PM »
Should be a 7BA x 1/8 slotted head grub on the ecentric (5BA on flywheel) unless its before 1945-50 ish when it could have been a BSW. If it has a hex hole in the top its none standard as 7BA are only available with slot heads as far as I know (and thats what stuart themselves supply/use). When I make 10H 10V or d10 engines I use either 6ba with a hex socket head or if I need smaller use metric.

If anybody knows of a source of 7BA hex heads please prove me wrong and let me know :)

Offline Gas_mantle

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Re: Stuart 10H grub screws.
« Reply #13 on: September 12, 2016, 06:05:24 PM »
Thanks guys, I've ordered a set of small Allen keys in both metric and imperial so hopefully will be able to remove it and hopefully have a better idea what thread / size it is.

Online Jo

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Re: Stuart 10H grub screws.
« Reply #14 on: September 12, 2016, 08:33:23 PM »
If anybody knows of a source of 7BA hex heads please prove me wrong and let me know :)

You can get away with M2.5 hex head grub screws. The pitch difference is 0.03mm which will not matter on such a short length and yes I know the thread angle is also wrong but once you tighten it up it won't be for long  ::)

Jo
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Offline kev

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Re: Stuart 10H grub screws.
« Reply #15 on: September 14, 2016, 08:32:45 AM »
Never thought of that joe, great tip, off to order some 2.5's then :)

Offline pgp001

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Re: Stuart 10H grub screws.
« Reply #16 on: September 14, 2016, 11:01:23 PM »
2.5mm are huge. If you want some really small ones look here.

https://knupfer.info/shop/index.php/deutsch/gewindestifte/mit-inbus-stahl.html

I have just ordered some fasteners from them and they came from Germany to the UK within two days.
They posted them out before any payment was made and I paid with Paypal when they arrived.

Phil