metric fastener help needed

I am looking for an M12 X 1.50 pitch 20 or 25 mm hex head bolt in 12.9 specification, and I am starting to believe that they don't actually exist.
Can anyone help with a source, or tell me that they are unobtainium?
Maybe 12.9 specification is only for socket head screws, not hex head?
Thanks, Brian
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Reminds me of fiat twin cam flywheel bolts. Can't be sure they are 1.5mm pitch though and I haven't got one to hand at the moment to check. I may be able to in a day or so. You might try some part places and see as flywheel bolts are that sort of spec in my experience.
Brian wrote:

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These are indeed for a flywheel application, on a BMW M10 engine where I want to install a racing flywheel that is a lot thinner than the stock flywheel, so the stock bolts won't work. Good tip on looking at other flywheel bolts, though.
Brian

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Simply purchase a stock set and shorten them.
Jim
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In my limited eperience they are only threaded the amount needed as they are specials for the manufacturer. Cutting extra thread with the likes of a die won't produced the quality of thread in this critical application.
jim rozen wrote:

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says...

Correct. That plan only works if they are fully threaded to start with.
If they are high strength waisted fasteners then threading extra along the shank is of course impossible anyway. Die cut threads will not work in that application.
What *do* the flywheel bolts actually look like?
Jim
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They are high strength waisted fasteners, basically.
Brian
David

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OK, you are *not* going to find a regular fastener house to sell you those bolts. The car manufacturer makes them up special and I'd be willing to bet a coke there's no off-the shelf solution, which is what you're looking for.
You might possibly call Metric and Multistandard Components in Elmsford, NY and ask them to quote to make some of them. Be prepared to supply a sketch of the exact part you want and be prepared to supply money.
If you could find a fully threaded fastener you could of course machine the waist in it yourself.
Jim
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Jim, you really honestly think that if that was even remotely possible, I wouldn't have already done that?
Stock bolt is threaded only at the end, somewhat like a NAS or MS bolt. It can't be usefully shortened.
Brian
Brian says...

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If you can't find the shorter bolts what about using the standard and having the flywheel modifed so the central boss is thicker. The extra mass in the centre will have negligable effect on the performance unlike the mass at the periphery.
Brian wrote:

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Basically, the idea here is to use a light steel flywheel that I already have rather than making one up. The bolts have to fit under the clutch plate, and the thickness of a hex head bolt is basically what the flywheel was designed for. It's a PITA. I have ordered a bunch of 10.9 spec bolts, I figure that I can loctite them in and toss them after one use. the bolts are basically in tension only, the flywheel is located on a center spigot and a dowel. The race flywheel/clutch combo is about 1/3 the weight of the stock setup, and that will raise any torsional vibration frequencies and lower their amplitude reducing the overall stress on the bolts, although I don't know how to predict that.
I phone the Tacoma guys, they don't have them. I now believe that the 12.9 spec is only for SHCS.
Thanks, all. I appreciate the help.
Brian

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I just had a look at the fiat bolts from a Lancia Beta 2L and they are M12 x 1.25 unforetunately. Marking on the head were as follows
-- ---- ------ --------
R12
Thats 4 lines one above the other sort of forming a pine tree shape with R12 beneath it. Not sure what the R12 is but it doesn't really matter for you now anyway.
Brian wrote:

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brian.evans@mci%%%.com (Brian) wrote:
<snip>

<snip>

I just did a quick check of my reference books (e.g., Industrial Fasteners Institute Metric Standards Book) and supplier catalogs and it appears that your assumption is correct: 12.9 is for SHCS only and 10.9 is the highest grade of hex head cap screw (aka bolt).
If you really want the 12.9 grade with a lower head height, you could try looking for a socket BUTTON head cap screw; a button head looks like a pan or round head but has a hex recess like a socket head. The M12 socket button head has a head height of 6.24 - 6.60mm, which is much lower than a M12 SHCS and even a little lower than a M12 hex cap screw (7.24 - 7.76mm). However, I don't know how readily available the M12 SBHCS is with 1.50 pitch.
Let me know if you need further assistance with this.
HTH, Will
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Washers?
Spacer under the heads?
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On Thu, 14 Oct 2004 09:02:10 -0300, "jtaylor"
||
|| ||> These are indeed for a flywheel application, on a BMW M10 engine where I ||> want to install a racing flywheel that is a lot thinner than the stock ||> flywheel, so the stock bolts won't work. Good tip on looking at other ||> flywheel bolts, though. ||> ||> || ||Washers? || ||Spacer under the heads?
The heads are recessed to just below the surface, and the clutch disc covers that surface, so he cannot space the heads higher.
What about cutting the heads off the bolts to make studs out of them, then threading them from the backside of the flywheel and using nuts to retain the flywheel? Texas Parts Guy
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Assuming you are in the US, Maryland Metrics has a very good selection at 800-638-1830.
-- Regards, Carl Ijames carl.ijames at verizon.net

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M12X1.75 is the normal pitch. You may be able to find 1.5 at a dedicated fastener house. JR Dweller in the cellar Brian wrote:

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Try Tacoma Screw Products in Tacoma, WA. They have a big selection of metric oddities.
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