metric fastener help needed

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

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

Simply purchase a stock set and shorten them.

Jim

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

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

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

They are high strength waisted fasteners, basically.

Brian

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

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

Washers?

Spacer under the heads?

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|| ||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

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 l>Basically, the idea here is to use a light steel flywheel that I already

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