Are set screws dangerous?

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EVBiker2000   100 W

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Are set screws dangerous?

Post by EVBiker2000 » May 18 2010 8:06pm

I want to mount a hubbed sprocket on a 1" keyed steel shaft. The sprocket has a 1/4" keyway and a set screw. My motor is 48V, 1000W from monster scooter parts.

Do you guys think it would be dangerous to use this sprocket with set screw on my jack shaft? I'm worried a sprocket with set screw would begin rattling loose over time.
sprocket.gif
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BLUESTREAK   1 kW

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Re: Are set screws dangerous?

Post by BLUESTREAK » May 18 2010 8:28pm

Just replace the allen screw with one that is 5/16in or3/8in longer and put a nut on it to lock it down and it will stay. :mrgreen: :mrgreen:

dumbass   100 kW

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Re: Are set screws dangerous?

Post by dumbass » May 18 2010 8:48pm

BLUESTREAK wrote:Just replace the allen screw with one that is 5/16in or3/8in longer and put a nut on it to lock it down and it will stay. :mrgreen: :mrgreen:
No, no, no...You should never do something like that. The nut is flat sided and the sprocket is round so the contact or locking serface of the nut is very small and will not hold.

Set screws have been in use for a long long time on sprocket. When used properly there is nothing wrong with them. Always use the longest set screw possible. But never use a set screw that extend out of the threaded hole you are putting it in. This may cause the "hex" hole to snap or crack when tightening it.

Of course the shaft should have the matching key size as the sprocket. If the sprocket does not have a keyway then drill a dimple hole in the shaft using the set screw hole as a guide. Then reinstall the set screw. I would also recomend using loctite on the screw.

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rkosiorek   1 MW

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Re: Are set screws dangerous?

Post by rkosiorek » May 19 2010 7:51am

but no set screws usually do not work loose. if you are worried just use a drop of thread locker glue on the threads.

or if you prefer you could use the set screw hole as a guide to drill a hole for a shear pin.

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EVBiker2000   100 W

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Re: Are set screws dangerous?

Post by EVBiker2000 » May 19 2010 1:01pm

If I use the thread lock glue, would I still be able to unscrew the set screw later if I wanted to change out the hub sprocket? I never used that stuff before.

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rkosiorek   1 MW

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Re: Are set screws dangerous?

Post by rkosiorek » May 19 2010 1:19pm

depends on the kind of thread locker you buy. check the label. they come in various strengths, from "light" to "when hell defrosts after it froze over"

on small screws the medium is fine. you could also pre-assemble the screw, tighten just enough to mark the shaft with the screw.take it apartand drill a small dimple into the shaft . just enough sothe tip of the screw has something to bite into. then re-assemble.

don't overtighten as you will break out the socketpart of the setscrew.

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cassschr1   10 kW

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Re: Are set screws dangerous?

Post by cassschr1 » May 19 2010 7:33pm

The thread locker still comes loose if heat is applied ... so you can always take it apart.

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coln72   10 W

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Re: Are set screws dangerous?

Post by coln72 » May 19 2010 10:06pm

If you have enough thread, use two set screws.

Screw the first one down so it is tight on the shaft as per usual. The screw the second one down on top of the first. Kinda like using using a lock nut. Will never come undone but may have to use to short set screws.

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Mark_A_W   100 kW

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Re: Are set screws dangerous?

Post by Mark_A_W » May 19 2010 10:18pm

EVBiker2000 wrote:I want to mount a hubbed sprocket on a 1" keyed steel shaft. The sprocket has a 1/4" keyway and a set screw. My motor is 48V, 1000W from monster scooter parts.

Do you guys think it would be dangerous to use this sprocket with set screw on my jack shaft? I'm worried a sprocket with set screw would begin rattling loose over time.
sprocket.gif

I do not think a set/grub screw (or even 2 at 90 degrees), is a suitable engineering solution to your problem.

Can you put a pin clean though the whole thing?
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BLUESTREAK   1 kW

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Re: Are set screws dangerous?

Post by BLUESTREAK » May 19 2010 11:18pm

If you look at all SCHWINN ADULT TRIKES including the MERIDIAN and the IZIP TRICRUISER thay all have the sprockets bolts and set screws locked down this way. I have been doing this for over 45 years and have never had one to split or come loose. try it it won't hurt. :mrgreen: :mrgreen:

EVBiker2000   100 W

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Re: Are set screws dangerous?

Post by EVBiker2000 » May 19 2010 11:21pm

Well, I suppose I could put a pin through it. I'm a little worried about that because I don't have a drill press, just a hand drill. Not sure if I can get all the way through the 1" shaft with a hand drill. Maybe after a lot of bits I could. :lol:

I suppose I can try the double stack set screw idea. Its interesting. If I find that solution doesn't work then I can resort to putting a pin through the shaft. What size pin? The keyway of the shaft is 1/4 inch. It seems like drilling a 1/4 inch hole all the way through takes away the strength of the steel shaft.

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Re: Are set screws dangerous?

Post by swbluto » May 19 2010 11:53pm

Mark_A_W wrote:
EVBiker2000 wrote:I want to mount a hubbed sprocket on a 1" keyed steel shaft. The sprocket has a 1/4" keyway and a set screw. My motor is 48V, 1000W from monster scooter parts.

Do you guys think it would be dangerous to use this sprocket with set screw on my jack shaft? I'm worried a sprocket with set screw would begin rattling loose over time.
sprocket.gif

I do not think a set/grub screw (or even 2 at 90 degrees), is a suitable engineering solution to your problem.

Can you put a pin clean though the whole thing?
I wonder why?

I've used a set-screw before on a shaft and it was a similarly torquey motor and it worked fine. The key is to use loctite (Loctite blue is what I use - it's a thread-locker, so it can be manually opened with enough force. It's not "a strenuous"/I-feel-like-i'm-going-to-break-something amount.). I used to have problems with the set screw coming undone and then the sprocket would just stop spinning suddenly. It didn't matter how hard I secured it. After applying loctite, that problem never came back.

On my shaft, the set-screw was set inside a dimple, which I've heard is the best. Flats are OK, but they don't secure along the axis of the shaft.

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Mark_A_W   100 kW

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Re: Are set screws dangerous?

Post by Mark_A_W » May 20 2010 12:09am

Because a set screw doesn't have a proper interlock with a shaft.


We use them at work, for small stuff. Never for high torque applications.

Also, they damage the shaft, making it difficult to remove the gear/pulley. (The answer to that is a machined recess in the shaft, but that's more work).
Under construction: Giant DH Team, MAC Shanghai, Infineon 18 FET controller, 64v Headway battery. LINK!!

Retired: Kona Dawg Dually + Bomber Triple Clamp forks with Nine Continents front hub motor, 48v 10Ah Headway LiFePO4 Pack + 12v 10Ah Headway LiFePO4 booster pack (nominal 64v).

Powered by the sun :)

Dead: Jamis Dakar frame, Mongoose Pro Downhill frame, cooked Lipo booster pack....and various other bits and pieces...

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rkosiorek   1 MW

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Re: Are set screws dangerous?

Post by rkosiorek » May 20 2010 12:53am

i think that i agree with Mark_A_W about the set screws. i also prefer to pin onto the shaft.

for small sprockets a 1/8" or 3/16" diameter roll pin would likely be sufficient. it would also hold better than the set screw. the shaft on these motors is usually quite soft. it should be easy to drill through with a sharp HSS drill bit. even if you do it by hand.
PRO-Roll Pin.jpg
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rick
DISCLAIMER:
We will not be responsible for damage to equipment, your ego, blown parts, county wide power outages, spontaneously generated mini (or larger) black holes, planetary disruptions, or personal injury that may result from the use of this material.
- Samuel M. Goldwasser -

dumbass   100 kW

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Re: Are set screws dangerous?

Post by dumbass » May 20 2010 7:53pm

cassschr1 wrote:The thread locker still comes loose if heat is applied ... so you can always take it apart.
If that sprocket gets so hot that it loosens the thread lock he has a bigger problem to worry about.

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v_tach   100 W

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Re: Are set screws dangerous?

Post by v_tach » May 20 2010 8:41pm

Been using set screws for years. Use em on the drive sprockets of my 40+ mph stand-up gas scooter without ever having any issues after thousands of miles with the constant vibration of a 2-stroke. I do favor self-locking set screws over using thread locking compound and I always use a new one if I remove a sprocket and reinstall.

Poor fitting sprockets either bored too much or installed on a galled shaft are a recipe for problems.

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