Grub screws

As long as you know the size thread and length yes Engineers supplies. But as you don't mention which ones might they be from Gears, then the gear Manufacturer would be worth a check.

Sounds like you're treating these as if they are to hold the Forth Bridge together! They really don't need any great force to tighten. You'd need to be just a little bit specific as to what your paericular grub screws are for before anyone can advise you where to get replacements. Your Caterpillar Tractor stockists will keep a good range, same for engineering shops and R/C car stockists. ;-)

Greg.P.

Try using socket set screws instead - no slot to break off!

thanks for suggestions, yes should have said they are for gears - ones supplied with gears, and I do try to be gentle with em.

Cheers Simon

Are you filing a flat on the axle?

MBQ

I sheared off the grub screw the first time I fitted a replacement Ultrascale Mainline Warship gear. Luckily the gear was in the right place and enough of the screw was left to hold the gear in place. It was my fault and I didn't do it with the other three. So be careful! :)

By the way the Ultrascale gears transformed my Mainline Warships.

Are you filing a flat on the axle?

MBQ

Have done recently and make sure know where it is :-) Didnt to begin with, possibly why got so many gears without grubscrews.

Cheers, Simon

trouble is once screw damaged then tempted to fix in place using glue or threadlock but then cant remove gear so axle has to stay in place unless cut it out.

Cheers, Simon

It's also a problem of the grub Screw being too long, It should be inside the threaded hole supporting the bit with the slot.

I use hex drive ("socket head") grub screws. And I prefer the ones with ring tips to the pointed ones:

In real life we generally put two, at right angles, into the gear boss, but I've only seen that a few times in models. One instrument maker I know puts in two, at 120 degrees.

Like MBQ says, a flat on the shaft helps a lot.

Wow modelfixings, now theres a site ! All need to do now is find out size of screws, buy a pack of fifty and never break another one.

Thanks, Simon

Two useful sites there, thanks Bob.

I think the real reason why you should use a flat is that if you don't, the point or cup on the screw chews up the shaft and you can't get it off (or if you do, you can't get it on again).

If you want to avoid damaging a shaft but don't want to put a flat on it, try putting a little disc of copper or brass in the hole, diameter just below the clearance size, length need only be about the same or less, This will avoid damaging the shaft but still grip quite well. If you hit it with a punch it will swell and grip the thread just a bit and then it won't fall out when you remove the screw or the shaft, but still move enough to grip when you tighten the screw.

You also need to be careful to get the shaft a good fit in the hole, or the grub screw will push it to one side.. If it's undersize (say if you use stock mild steel in a reamed hole) you may be better using Loctite, which has reasonable centring properties.

David

Believe flat used to avoid pushing against axle in one place thus putting gear slightly out of alignment and eccentric.

Cheers, Simon

I *think* as well that the grub screw shouldn't be done up tight against the flat, so that the flat and grub screw provide a key rather than a friction fit. This is what avoids the gear going slightly eccentric.

I may be wrong though!

Yep, thats what was trying to say, but you put it better.

Cheers, Simon

In article , simon writes

Sorry, that won't fly; if the shaft is a few thou undersize (as it will be, if it's stock sized mild steel) then the grub screw will push it off centre whether there is a flat or not.

David

In article , simon writes

Still won't fly; if the screw has any contact with the flat, it will exert a wedging action on the shaft and displace it. Also, if it is not tight into the flat, the shaft can rotate somewhat, which you mostly want to avoid.

David