Rail (625Wh) you may want to watch this #TREKRAIL

[Wilbur]

So I've done a little research on replacement M5 screws for Gen 1-3 Bosch motors. The originals are black M5 x 16mm flanged security head (T25 5-pt pentalobe). The 11mm flange is not serrated. The head is ~3mm tall. They don't appear to be thread-forming as the tip isn't blunt-tapered, (even so, Bosch recommend not removing the screw completely when tensioning/resetting in order to preserve the threaded aluminium material). The coating appears to be black oxide or maybe zinc.

Ideally I'd like to replace them with a M5 x 16mm flanged and serrated class 12.9 cap screw.

• Flange is important as it spreads the load on the aluminium brackets.
• Serration would be good to improve screw grip in the presence of vibration.
• Class 12.9 is the highest tensile strength alloy steel available (170,000 psi) and a cap screw can have a 4mm allen socket, instead of the annoying pentalobe head.
• Flanged cap screws are a little taller (5mm vs 3mm) than the original heads so I need to check frame clearance

This is what I'm thinking would work:

Class 12.9 non-serrated:
McMaster-Carr

Or Class 8-10 serrated :
McMaster-Carr

 

[Stihldog]

So I've done a little research on replacement M5 screws for Gen 1-3 Bosch motors. The originals are black M5 x 16mm flanged security head (T25 5-pt pentalobe). The 11mm flange is not serrated. The head is ~3mm tall. They don't appear to be thread-forming as the tip isn't blunt-tapered, (even so, Bosch recommend not removing the screw completely when tensioning/resetting in order to preserve the threaded aluminium material). The coating appears to be black oxide or maybe zinc.

Ideally I'd like to replace them with a M5 x 16mm flanged and serrated class 12.9 cap screw.

• Flange is important as it spreads the load on the aluminium brackets.
• Serration would be good to improve screw grip in the presence of vibration.
• Class 12.9 is the highest tensile strength alloy steel available (170,000 psi) and a cap screw can have a 4mm allen socket, instead of the annoying pentalobe head.
• Flanged cap screws are a little taller (5mm) than the original heads so I need to check frame clearance

This is what I'm thinking would work:

Class 12.9 non-serrated:
McMaster-Carr


View attachment 114164

Or Class 8-10 serrated :
McMaster-Carr
View attachment 114170

I wonder if those heads might be too tall for clearance’s in the motor compartment?

 

[Wilbur]

I wonder if those heads might be too tall for clearance’s in the motor compartment?

They are about 2mm taller - I need to check clearance...

 

[Formulasuper]

”Loctite”.

 

[Wilbur]

”Loctite”.

290 or 243?

 

[Stihldog]

290 or 243?

Reminds me of a scene from “Mr Mom”.
220, 221 …whatever it takes.

 

[Wilbur]

Reminds me of a scene from “Mr Mom”.
220, 221 …whatever it takes.

 

[Formulasuper]

290 or 243?

Blue is for fasteners you’ll be removing again, red is for permanent.

 

[Stihldog]

View attachment 114228

I guess s it’s blue then since I’ll probably have to remove it…no wait, it’s red 🫣

 

[Chairman]

Drilled out my broken m5 and and tapped in an m6

 

[Wilbur]

Good job - looks like there is sufficient material for that. Are the holes blind or did you dump a pile of swarf into the motor?