Set screws - why wont they EVER come out? - Page 2 - RC Groups
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Jul 17, 2012, 04:18 PM
jackerbes's Avatar
The tolerances in the sizes of the sockets and the tolerances on the sizes of the wrenches are such that it you have a dozen wrenches one of them will fit the best. And that is the one to use. There there is all of the other qualities like the quality of the steel each is made from, the heat treating, and just about everything else.

I probably have a bag of 20 1.5mm wrenches and various numbers of nearly every size I have. When I put a wrench in a socket I always twist it from side to side and check for play. The leass play you have the less likely you are to strip a socket.

And there are no rules as far as needed to use inch or metric wrenches on only inch or or metric sockets, if there is a rule it is that you need to use the one with the closest fit regardless of how it is marked.

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Jul 17, 2012, 05:53 PM
Space Coast USA
hoppy's Avatar
Originally Posted by Bare
'possibly' due to crappy grub screws,
but it's IMO far More likely that your Allen wrenches are the crap element. Especially incriminating when it happens on more than one grub screw. A tight fit into the hex hole IS critical.
Quality varies dramatically on those wrenches.. more so than in the screws actually..something I've learned over the years.
I agree 100% with you.....all my allen screws have been stronger than my wrenches so far. I've never owned an "Allen" wrench.....I see Sears carries them, maybe I'll treat myself......but, it's better to have the wrench fail than the screw, right?
Jul 17, 2012, 06:09 PM
Wake up, feel pulse, be happy!
Piece's Avatar
Why do we even use these stupid things anyway? I know slotted setscrews exist; I have them in my GWS pinion pullers. They work excellent. (They're all over the Interwebs, too, after a quick search).

I see no advantage to hex hardware in this case.

What size are the ones normally used in our motors? Specifically, ~28mm outrunner bells? Seems like they're the same size across the board, so buying a minimum-order bag of slotted ones should have me covered.
Jul 17, 2012, 08:21 PM
jackerbes's Avatar
They are 3mm diameter x 0.5mm pitch socket head set screws, generally about 4 to 5mm long. They would be called 3mm-0.5 x 4 or 3mm-0.5 x 5 in Eurospeak.

And I replace some of them with 6mm long 3mm button head socket head screws that have a 2mm socket instead of a 1.5mm socket. I've done that on a couple of motors that were a little on the "troublesome" side as far as staying tightened.

The 2mm socket will take quite a bit more tightening and general abuse than the 1.5mm sockets will.

You can find the screws I use in the Traxxas RC cars parts assortments in a LHS that carries that stuff.

You can see the screws and see them installed on a motor and also on the motor mount in the images.

I cut the screws to get rid of any excess length when I fit them. You can put a 3mm nut on first to set the cutting point, hold them in a plier, and cut them to length with the Dremel tool and abrasive disc.

Jul 17, 2012, 09:25 PM
I'm All Thumbs
AirBornOne's Avatar
Originally Posted by jackerbes
And there are no rules as far as needed to use inch or metric wrenches on only inch or or metric sockets, if there is a rule it is that you need to use the one with the closest fit regardless of how it is marked.Jack
The rule is you start with the appropriate tool for the job.Afterwards comes the improvisation.
Most likely there is inferior metalurgy involved with the 'stripping' set screws.And possibly over torqueing as well.
Jul 17, 2012, 10:21 PM
Registered User
flypaper 2's Avatar
Maybe it's time to bring in the square Robertson screwdrivers. More flat surface area than the hex screws. Was at Home Depot a while ago and saw many different sized sheet metal screws with Robertson heads.

Jul 18, 2012, 10:10 PM
Registered User
MIP Thorpe drivers have very hard tips and tight machining
they will often remove a set screw which mangled other drivers.

They are not that much more expensive and you really only need a couple in the very small sizes anyway.
Jul 20, 2012, 06:06 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Thanks for all the advise guys.. So eventually i did get it sorted. I did it the brutal way I drifted out the shaft with the screws still in, this wasn't actually so difficult but I did take care to support the end of the can so as not to deform it.

I then tried to spin the screws out with a 2mm drill but this didn't work. Eventually I ended up drilling right through one set screw (by quenching the tip of the drill bit to make it glass hard and re grinding the tip several times). Even once drilled through it wouldn't budge so I tried a 2.5mm drill which got a better bite and spun the screws out without any problem leaving the thread in the motor intact.

All fixed now and ready to fly again... but it was a real pain.

Jul 20, 2012, 06:45 AM
Proud to eat Kraut ;-)
Julez's Avatar
I was just about to propose to drive the shaft out directly. If the shaft has a slot where the screw sits, pushing it back and forth may loosen the screw a little.
Another method is to use metric hex keys at inch-sized screws and vice versa. The next bigger key that just won't fit can be driven in with a hammer, and can deliver more torque then.
There is also a compound called screw grab, it is like toothpaste with small diamond bits which increase friction.
I used this to get stripped screws from the maintenance hatches of real planes.

Whenever I insert new scews, I grind the bottom part flat, if there are shaped like a cutting ring. These rings are for axial fixing only, which we hardly need.
This way, my shafts get less scratches.
Jul 20, 2012, 09:11 AM
Registered User
43851E's Avatar
For some reason I'm seeing and hearing of so many oversized setscrews (drive hex) so I too have maintained an oversized wrench, which flyes in the face of my Bohndus sets of wrenches.

For slotting a stuck screw w/ a cutoff wheel, use a smaller diameter - worn out wheel to reduce the danage to adjacent material. All priceless responses RGC! I have nothing to add ~

Jul 21, 2012, 11:00 AM
Space Coast USA
hoppy's Avatar
Seems to me I read about a guy who dipped the end of his hex wrench in epoxy and glued it into the socket. Anybody ever try that?
Jul 21, 2012, 09:07 PM
Wake up, feel pulse, be happy!
Piece's Avatar
I'd end up getting epoxy in the threads and then snapping off the wrench at the screw when trying to turn it.
Jul 22, 2012, 07:40 AM
Life begins at transition
Tried it a few days ago. Fail.
Dremelling a slot worked a treat
Jul 22, 2012, 12:46 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
Originally Posted by hoppy
Seems to me I read about a guy who dipped the end of his hex wrench in epoxy and glued it into the socket. Anybody ever try that?
If you can take the corners of an alloy steel allen key then I'm afraid epoxy doesn't have a hope.
Jul 25, 2012, 07:17 AM
You know nothing....
Stuart A's Avatar
If you use button heads as suggested earlier Torx type heads are more positive than hex,not sure if the go small enough for a grub screw at your size

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