Weak bolts

[BrendAn]

Where can I buy good quality bolts in Vic.

I purchased grade 8 bolts for my prop hub from a local bearing service and they seem to be brittle .

I snapped one without even trying. 8mm X 120. Would Bert flood carry special bolts for this task.

 

 

 

[BrendAn]

I screwed the broken piece out with my fingers. I couldn't believe an 8 mm bolt would snap like. I have never had it happen before

 

[facthunter]

Gotta be rubbish metal. You don't want them near an aeroplane.   Nev

[Thruster88]

Unfortunately AN bolts don't come in metric as far as I am aware. Commercial bolts now are a lucky dip, lowest bidder gets the wholesale.  

[facthunter]

You could have them made from appropriate bar stock. I often have to do that. Some metals may require heat treatment and that must be spot on. .Nev

[BrendAn]

20 minutes ago, Thruster88 said:

Unfortunately AN bolts don't come in metric as far as I am aware. Commercial bolts now are a lucky dip, lowest bidder gets the wholesale.  

yes. i tried the lame workshop first but they did not anything to match.

 

[BrendAn]

17 minutes ago, facthunter said:

You could have them made from appropriate bar stock. I often have to do that. Some metals may require heat treatment and that must be spot on. .Nev

thanks. might have to do that if nothing is available.

[Blueadventures]

55 minutes ago, BrendAn said:

Where can I buy good quality bolts in Vic.

I purchased grade 8 bolts for my prop hub from a local bearing service and they seem to be brittle .

I snapped one without even trying. 8mm X 120. Would Bert flood carry special bolts for this task.

 

 

 

What brand prop are you fitting?  The manufacturer should be able to supply bolts.  I also recall that Bolly had a supply of some metric thread bolts.   Good you found out now and terrible they aren't grade 8.

[Bosi72]

Did you try 

 

http://www.propbits.com/

 

They are in YMMB, but you need to know exact part number that you'd normally look on aircraftspruce. 

 

 

[BrendAn]

Just now, Blueadventures said:

What brand prop are you fitting?  The manufacturer should be able to supply bolts.  I also recall that Bolly had a supply of some metric thread bolts.   Good you found out now and terrible they aren't grade 8.

warp drive . i have the original bolts that were fitted without the  hub extension. they seem to be a good quality black bolt, i did not like the look of those plated bolts when i got them.

[BrendAn]

5 minutes ago, Bosi72 said:

Did you try 

 

http://www.propbits.com/

 

They are in YMMB, but you need to know exact part number that you'd normally look on aircraftspruce. 

 

 

thanks bosi. i will call in there tomorrow and see what they have.  but would they do metric rotax stuff.

[Thruster88]

I would try and get some unbrako socket head cap screws, they are the real deal. There is always a possibility of counterfeiting a name brand. Available in metric 8.8 and 12.9 grade 

 

https://www.unbrako.com.au/

[BrendAn]

4 minutes ago, Thruster88 said:

I would try and get some unbrako socket head cap screws, they are the real deal. There is always a possibility of counterfeiting a name brand. Available in metric 8.8 and 12.9 grade 

 

https://www.unbrako.com.au/

excellent, i forgot about them, they are only 10 minutes from my flat. i will try them in the morning.

[Bosi72]

TBH I don't know, but if these are the bolts you're after, I would be asking if they have them (Part# 05-06757
MFR Model# 01-60-001)

 

https://www.aircraftspruce.com/catalog/appages/duc_swirlwindspn-hardware.php?clickkey=212019

 

 

 

 

[BrendAn]

10 minutes ago, Bosi72 said:

TBH I don't know, but if these are the bolts you're after, I would be asking if they have them (Part# 05-06757
MFR Model# 01-60-001)

 

https://www.aircraftspruce.com/catalog/appages/duc_swirlwindspn-hardware.php?clickkey=212019

 

 

 

 

they maybe what i am after. if unbrako can not help i will try them. those duc props are a nice bit of kit, lots of good information on the website.

[onetrack]

Brendan, that bolt is not a Grade 8 bolt, which is an SAE standard - and Grade 8 bolts are a medium carbon low-alloy steel with a tensile strength of 150,000 psi (1034 MPa)

Your fractured bolt is a Metric 8.8 grade, which is only equivalent to Grade 5 in SAE, which has a tensile strength of 150,000 psi (827 Mpa).

 

A lot of fasteners are produced today with unsatisfactory quality, and of course, they come from China. This is not to say all Chinese fasteners are poor quality, you just need to ensure the fastener brand name is a quality brand name.

 

Unbrako socket head fasteners are a guaranteed product, and their standard socket head grade is Grade 9 in SAE, which has a tensile strength of 170,000 to 190,000 psi (1172 to 1310 MPa), depending on the fastener shank diameter.

 

The metric equivalent of Grade 8 in SAE is 10.9, and the metric equivalent of Grade 9 in SAE is 12.9.

 

Below is a website with inch and metric fastener head markings and their grades.

 

https://www.aftfasteners.com/grades-of-bolts-bolt-grade-markings-bolt-strength-chart/

[BrendAn]

8 minutes ago, onetrack said:

Brendan, that bolt is not a Grade 8 bolt, which is an SAE standard - and Grade 8 bolts are a medium carbon low-alloy steel with a tensile strength of 150,000 psi (1034 MPa)

Your fractured bolt is a Metric 8.8 grade, which is only equivalent to Grade 5 in SAE, which has a tensile strength of 150,000 psi (827 Mpa).

 

A lot of fasteners are produced today with unsatisfactory quality, and of course, they come from China. This is not to say all Chinese fasteners are poor quality, you just need to ensure the fastener brand name is a quality brand name.

 

Unbrako socket head fasteners are a guaranteed product, and their standard socket head grade is Grade 9 in SAE, which has a tensile strength of 170,000 to 190,000 psi (1172 to 1310 MPa), depending on the fastener shank diameter.

 

The metric equivalent of Grade 8 in SAE is 10.9, and the metric equivalent of Grade 9 in SAE is 12.9.

 

Below is a website with inch and metric fastener head markings and their grades.

 

https://www.aftfasteners.com/grades-of-bolts-bolt-grade-markings-bolt-strength-chart/

thanks. going to unbrako in the morning.

[walrus]

Be careful! An M8 grade 8.8 bolt should be just fine. There is something else going on. Your torque wrench sounds dodgy.

 

‘’Furthermore, if you over specify the bolts to a higher grade, you may lose fatigue strength.

[Blueadventures]

48 minutes ago, walrus said:

Be careful! An M8 grade 8.8 bolt should be just fine. There is something else going on. Your torque wrench sounds dodgy.

 

‘’Furthermore, if you over specify the bolts to a higher grade, you may lose fatigue strength.

Good point. I work mine on a know bolt a  few times (usually a hangar bolt for example and also do a calibration with a spring balance at regular intervals.  Like you mention he should test the tension wrench. Also I have seen people mix up the readings and almost over tension.

[440032]

Nobody has asked "what torque is required and what did you actually take it to?" ???

 

[BrendAn]

Nothing to with being overtorqued. 

Just crap bolts. 

And the torque setting is 175 inch pounds.

Thanks for that.

[facthunter]

You can't lockwire or tab an unbrako. They are top quality though. The design of bolt you had put's all the load on the threaded bit where it becomes thicker.If there's any bending or shear load that's where it is also. The prop should be clamped by the bolts not driven by them. Nev

[Thruster88]

18 minutes ago, facthunter said:

You can't lockwire or tab an unbrako. They are top quality though. The design of bolt you had put's all the load on the threaded bit where it becomes thicker.If there's any bending or shear load that's where it is also. The prop should be clamped by the bolts not driven by them. Nev

This type of propeller attachment has nyloc lock nuts on the rear of the flange.  No lock wire.

Edited September 27, 2022 by Thruster88

[BrendAn]

i just went to unbrakos warehouse in dandenong. nothing there. so i went to a bolt place and they said unbrako packed up and moved to india 18 months ago.

[onetrack]

As with all Global Corporation manoeuvres, Unbrako was sold to Deepak Fasteners Ltd from India, in 2008. Unbrako still own manufacturing facilities on every continent and their products still have top-level certification and testing.

As with all corporate takeovers - retail locations, headquarters and offices, change on a regular basis, you just need to find an Unbrako retailer. Look up "bolt and nut suppliers" for your area.

 

https://www.globalfastenernews.com/indias-deepak-fasteners-buys-unbrako-global-fastener-news-usa/

 

https://www.unbrako.com.au/

 

 

 

Edited September 27, 2022 by onetrack