Originally Posted by HardWorkingDog
Those stainless steel bolts are OK (pricey), but my solution to finding longer good quality flange head metric bolts is my local Honda car dealership's parts department.
The local Ace Hardware has metric flange bolts but they are generic Chinese crap with poorly made threads and rough finishes--not something I trust to hold critical loads or look at and feel like
Turns out Honda's parts numbering system for bolts is readily decoded, and they use the same parts numbers for both motorcycles and cars. An 8x55 flange bolt is 95701-0805508. High quality Japanese-made, beautifully formed and spec'd. to meet the strength needed here. Call your nearest Honda car parts department, ask for that number, if they don't have it in stock they'll get it usually the next day. I paid about $1.25 per bolt, well worth it.
95701 = flange head bolt
08xxxxx = 8 mm dia.
xx055xx = 55 mm length
xxxxx08 = thread pitch??? (less certain about this...)
In reading this, I had some thoughts since I've had to deal with metric hardware in a sideline project making cam chain tensioners. If you did some digging might find the 8 is a rounded M8-.075 fine thread pitch. They do two fine pitches, M8-1.00 and M8-.075 threads per millimeter. But I'm guessing. The coarse 8mm thread is M8-1.25 threads per mm.
Here is a link to the ISO charts
I buy bolts at Fastenal, where they can be ordered individually (if not in stock and usually not). Problem is washers and nuts are not sold in singles. Just pointing out the alternative. I am fortunate in having a really good old style hardware store for the goofy or single stuff. I use Fastenal for my quantity purchases though.