I tried using aluminum prop screws awhile back back and quit using them after two screws got bent in a crash. They did not break but I was afraid next time they might and I did not want to try to remove the broken part out of the motor bell housing.

Another possibility worth looking into are "peek" screws although they are rather expensive. I am going to try some for motor bolts in my 75mm whoops... 12 1.4 x 3mm bolts  come in at 0.1 grams. 12 of them in steel come in at 0.49 grams, almost a half a gram savings.

(18-Feb-2024, 07:34 PM)skywanderer Wrote: Problem for me with aluminum screws is the head breaking off from crashes. Have not tried in m2x7 prop screws configuration tho...

Hi Skywanderer,

That is interesting. Are these frame column bolts or motor mount bolts?

I guess I am going to have to break down and buy some aluminum bolts
and give them a try; see if I break any. 

Of course, I have never had a steel bolt break off anywhere especially
not the heads. I have bent long bolts in landing gear applications, but
they did not break. 

By the way, about 98 percent of my bolts are M2 in size as my primary focus 
is the sub-250 gram, FAA category 1, UAS (drones). I rarely use anything 
larger than M2. I have lengths from 2mm to 20 in 1mm increments and then 
some 25mm, 30mm, and 40mm lengths. I have both black steel and stainless
steel in the shorter sizes, but the longer ones are stainless steel. 

Later, iFly  

(18-Feb-2024, 07:34 PM)skywanderer Wrote: Problem for me with aluminum screws is the head breaking off from crashes. Have not tried in m2x7 prop screws configuration tho...

Probably not made from T7075. Supposedly if you put some scrapings in a sodium hydroxide solution (drain cleaners) and it turns black, then it is T7075, otherwise its just some other cheaper alloy.
If you did want some in real 7075 maybe this is a reliable source but who knows how many you'd have to order.
https://www.kdfasteners.com/aluminum-707...crews.html

Quote:7075 Aluminum Uses

• Bicycle frames
  
  
• Worm gears
  
  
• Aircraft wing panels
  
  
• Structural beams
  
  
• Rock climbing equipment
  

And yes I think these 1-2 grams savings doesn't really make any difference on a 2", only for a 1S tiny whoop.

(18-Feb-2024, 08:05 PM)brettbrandon Wrote: I tried using aluminum prop screws awhile back back and quit using them after two screws got bent in a crash. They did not break but I was afraid next time they might and I did not want to try to remove the broken part out of the motor bell housing.

Another possibility worth looking into are "peek" screws although they are rather expensive. I am going to try some for motor bolts in my 75mm whoops... 12 1.4 x 3mm bolts  come in at 0.1 grams. 12 of them in steel come in at 0.49 grams, almost a half a gram savings.

This is a large part of the reason I use flat head screws and not bolts.  They are low profile and less likely to catch on stuff.  I only use steel ones.  I don't run anything 1S for the most part so weight is irrelevant in terms of screws.

(18-Feb-2024, 09:31 PM)mstc Wrote: Probably not made from T7075. Supposedly if you put some scrapings in a sodium hydroxide solution (drain cleaners) and it turns black, then it is T7075, otherwise its just some other cheaper alloy.
If you did want some in real 7075 maybe this is a reliable source but who knows how many you'd have to order.
https://www.kdfasteners.com/aluminum-707...crews.html


And yes I think these 1-2 grams savings doesn't really make any difference on a 2", only for a 1S tiny whoop.

1-2 grams on a 65mm whoop = huge difference.
1-2 grams on a 75mm whoop = big difference.
1-2 grams on a 85mm whoop "2 inch" still makes a difference, just not as big. Just my opinion...

(18-Feb-2024, 09:56 PM)Pathfinder075 Wrote: This is a large part of the reason I use flat head screws and not bolts.  They are low profile and less likely to catch on stuff.  I only use steel ones.  I don't run anything 1S for the most part so weight is irrelevant in terms of screws.

These are phillips pan head screws (low profile) and I think the damage was from the prop taking the hit which bent the screws...

I always thought pan head were the ones that looked like a mushroom on top. The ones I use are flat on top, like the image below. But if the damage was caused by the concussive force of the prop striking something and applying maybe torsion to the screw and bending it out of shape, the shape of the head would not play any part in the problem.

(18-Feb-2024, 10:22 PM)brettbrandon Wrote: 1-2 grams on a 65mm whoop = huge difference.
1-2 grams on a 75mm whoop = big difference.
1-2 grams on a 85mm whoop "2 inch" still makes a difference, just not as big. Just my opinion...

8x of the screws i use weigh 0.64g, so not much more than half a gram.

(18-Feb-2024, 10:59 PM)Pathfinder075 Wrote: I always thought pan head were the ones that looked like a mushroom on top.  The ones I use are flat on top, like the image below.  But if the damage was caused by the concussive force of the prop striking something and applying maybe torsion to the screw and bending it out of shape, the shape of the head would not play any part in the problem.  




8x of the screws i use weigh 0.64g, so not much more than half a gram.

That is about what they look like.



Are those prop screws or motor screws?

I just weighed 8 of the aluminum screws (M2 x 8 as I couldn't find 7mm length so I just flied them down to 7mm) and they come in at 0.55 grams. That would be only about a tenth of a gram difference (if you are showing prop screws)...

Technically mine are flat headed bolts and they are neither motor or prop, just generic M2x7mm flat headed bolts. I picked them up from an engineering firm I buy parts from that specialise in obscure fittings.

I don't like things sticking up from the top of the props, I do have some pan head hex bolts in the same size, but the heads are far from aesthetically pleasing, so i found something else that was more streamlined. They work for me in the builds I've done. But I can't guarantee they would work for others.

I like to use these low profile screws. Much better than phillips head, and the top is <1mm. Cheap too, but they are steel.


https://www.aliexpress.us/item/3256803454126880.html

(18-Feb-2024, 08:19 PM)iFly4rotors Wrote: Are these frame column bolts or motor mount bolts?

They were standoff screws, replaced with cheap at the time sale @ RDQ: titanium m3x8. Funny just saw those @ Amazon for like $8 for a bag of 20.

Not easily finding m2x7s atm...

(18-Feb-2024, 09:31 PM)mstc Wrote: Probably not made from T7075. Supposedly if you put some scrapings in a sodium hydroxide solution (drain cleaners) and it turns black, then it is T7075, otherwise its just some other cheaper alloy.
If you did want some in real 7075 maybe this is a reliable source but who knows how many you'd have to order.
https://www.kdfasteners.com/aluminum-707...crews.html


And yes I think these 1-2 grams savings doesn't really make any difference on a 2", only for a 1S tiny whoop.

Pretty sure they were not, thinking I remember 6061 anodized? Not sure really atm, been a long time since ordered...

(18-Feb-2024, 05:32 PM)skywanderer Wrote: Where do you order them from, grade 2 or grade 5?

Info here, they take quotes for orders but no prices listed so expecting high?:
https://www.extreme-bolt.com/titanium-fa...anges.html

...wish were possible to inexpensively order a 100 pack of m2x7 for prop nuts, and others likewise for motor mounting...

Titanium screws M2*7, Gr2,
https://sl.aliexpress.ru/p?key=MB4POnD

I compared the weight of titanium and steel bolts. Titanium screws are approximately 40% lighter than steel screws. I only use titanium where I want to save every gram. I have only three quadcopters with titanium, the rest with steel.

(19-Feb-2024, 07:09 AM)LiPoFly Wrote: Titanium screws M2*7, Gr2,  
https://sl.aliexpress.ru/p?key=MB4POnD

I compared the weight of titanium and steel bolts. Titanium screws are approximately 40% lighter than steel screws. I only use titanium where I want to save every gram. I have only three quadcopters with titanium, the rest with steel.

I have just weighed some M2 * 7mm black steel bolts. According to my
scales, they work out to be 0.2 grams each. I figure that this is a pretty
good average (some bolts being a bit shorter and some longer).

I have roughly estimated 32 bolt equivalents * 0.2 = 6.4 grams; 40
percent is 2.56 grams so let's round that to 3 grams which would be
about what I would save by replacing all of the steel bolts with Titanium
ones.

Now the question: Is that worth over $1 per bolt??  Hmmm.

Hi LiPoFly,

Well, that is interesting. Do you have a weight comparison between 
the Titanium screws and Aluminum screws?

I have been looking into the Titanium M2 bolts (that is the only diameter
that I use). So far, the Titanium bolts are running between $ 1 USD and
$ 3 USD depending on size and vendor. I also am discovering that many
of the suppliers Do NOT carry the 7mm length. Hmmm. Wonder what is
up with that? Anyway, I will keep looking. 

Perhaps another thing is that I live in the USA and pretty much try to
avoid the Chinese shopping sites such as AliExpress and others. I have
just heard too many horror stories about folks using the Chinese, "eBay"
type, clearinghouses. I am not sure that I want to go there just for bolts.

That said, if I do break down and decide to try AliExpress, I will likely
add some Titanium bolts to the order. The 7mm ones will likely work 
for the props and frame. The motors depend on the frame thickness,
but 4mm or 5mm seems to work in most cases since most of my frames
have an arm thickness of 3mm or less. 

Thank you for getting that information on the Titanium bolts.

I will keep looking; maybe bite the bullet.

Later, iFly  

M2*20, titanium and steel. In the photographs there are four screws. And very dark shadows.


GepRC Phantom/Smart 25 2.5" HD: The weight savings from replacing steel screws with titanium screws was 3.2 grams (5-top, 5-bottom, 16-motors, 8-props, 4-FC, 2-camera).

I have almost no problems with Aliexpress. And in those rare cases when problems arose, all problems were solved. From the link above - I bought titanium screws there myself.