288 8L Bolt size

[carringtonw]

Hi All;

I've got a stooopid question here. After spending about 20 bucks (thanks to Home Depot) on sets of bolts for my "new" 288's I've decided to come to the source for answers. I'm using the inner three bolt ring for an adapter that I purchased from Werner Jagush (the maker of the Jabo Horn on eBay) to mount his horns. I've tried 3/8" coarse and fine as well as 8mm x 1 0 and 8mm x 1 25 (along with some larger sizes that didn't even come close). The metric screws seem to come the closest but both of them don't seem very secure (it may be because I tried to use 3/4" or 20mm first which isn't long enough). I really don't want to strip these guys - can anyone steer me in the right direction?

Thanks very much in advance,

Carrington

[bfish]

Fine outside, but course tappings inside. The correct studs have dissimilar threads end-end. The tapped holes are 3/8"x16 UNC, bored one half inch deep. The exterior is 3/8x24 as Jim said, and should extend 1" when tight. A shoulder at the transition should taper the last threads so it's a taper-fit instead of "bottoming out".

[bfish]

Like this.

[bfish]

Shoulda mentioned, the local auto parts is where to look, a request for a double-ended stud at HD will just get you funny looks.

If you don't like the feel of the fit, add a couple wraps of teflon tape. Works as anti-sieze to boot.

[valhallax]

or you could just call bill at great plains audio and have him send you a stud kit

[carringtonw]

Ok;

First of all thanks for all you replies. You guys are what makes this place such an amazing resource.

I must not be getting something here. I'm going into the inside circle of three, not the outside 4. I've tried 3/8 coarse and fine and neither even fit into the hole. Which is why I went to try some metric bolts instead (they fit but not tightly). I don't need to use double ended studs, these adapters work just fine with bolts. But the 3/8" didn't seem to fit at all (on the inside three bolt pattern - I thought the inside was the same as the outside which is why I got 3/8's first). What am I missing?

Thanks again,

Carrington

[jnorv]

The studs sticking out of my 288-8K's are 3/8-24 (fine)

Jim N

[GM]

Originally posted by carringtonw:
But the 3/8" didn't seem to fit at all (on the inside three bolt pattern - I thought the inside was the same as the outside which is why I got 3/8's first). What am I missing?

<font size="2" face="Verdana, Helvetica, sans-serif">Greets!

Good question, all seven holes are supposed to be tapped 3/8-16 and use the studs bfish listed, so if yours is different there could be a specific app variation or whoever was doing the tapping that day screwed up and QA either didn't notice or didn't care.

Bottom line, sounds like you'll have to either figure out what thread it is or either re-tap it or drill it out and install an insert.

Me, I'd make the proper studs work some way just in case I ever wanted to sell them.

GM

[carringtonw]

GM,

I think you're right and I'm in trouble. The inside three don't take 3/8" coarse or fine (the coarse at least grabs a foothold and goes in about a half turn) and they don't take 8mm coarse or fine either (they slide around within the first 1/8" and then start to grab, the fine goes in about a 3/8" inch and then seizes and the coarse goes in all the way but has a bit of "play"). I guess someone was asleep at the wheel that day - I wonder if there is a 8.5mm out there or perhaps an 11/32" coarse... I don't have the facilities to re-tap something and I wouldn't have the faintest as to where to go to attempt something like that. Maybe I'll try to stick with the 8mm for now and see how that works.

[GM]

The fact that you can at least start a 3/8-16 indicates this is what you want to pursue. Any automotive repair and/or machine shop can do it or you can go to the nearest well stocked auto parts or hardware store and buy a tap and handle, then all you need is some Vaseline to lube the tap/retain the filings and a spray can of brake cleaner for clean-up, though the shop may charge less than all these cost.