G-clamp bolts

[dwh]

Most of the generics I use are fairly (very) old, at least old enough that they have imperial bolts between their yolks and G-clamps... I'm looking to fit some new G-clamps on them, and generally modernise/standardise them. Is there a general standard for the bolts that go between? They look currently to be a bit smaller than M12, and the (new metric) G-clamps I have kicking about have holes a bit bigger than M12 (can easily fit an M12 bolt through, but I doubt a 14 would fit through) as well... So would M12 be a fair guess, as a bolt size for KW Sils, Fresnels, etc? Also, I'm about to thread them all after I re-dril them... Is it worth it? I would think probably, but you never know!

[Brian]

IIRC the old standard was 3/8" Whitworth. Today most people use M10.

[Stu]

Most people use M10 bolts, I certainly very rarely see anything bigger than this on 1kw lanterns, some people do use M12 for 2/5kw fresnels, Sil 10s etc but M10 will be fine for your application. Some lanterns with imperial drilled holes will probably be (I think this the right measurement) 3/8th Witworth, which is slighly smaller than M10 so if you are looking to use M10 bolts in these lanterns then you will defintely need to drill the holes out!

 

Although this can be found on other threads in the BR, my chosen method for the placement of washers/splits etc on lanterns is

 

M10 bolt -> washer -> yoke of lantern -> washer -> hookclamp -> washer -> split washer -> M10 bolt or wingnut

 

This way you can then tighten up the lantern so it'll move when focussing but not move if slightly knocked (maybe with an additional 2nd tightening when focussed to be sure).

 

HTH

Stu

[Michael Beere]

At the moment most lanterns up to a 1.5k the hook clamp arrangement is M10. Bolt, washer, trailing arm, washer, G clamp, washer, spring washer and nut. Anything bigger than 1.5k is M12 with the same arrangement and also used with a heavy duty G clamp.

 

Hope this Helps

[dwh]

Thanks a lot guys :-) Very helpful!

 

How about the threaded vs straight hole for the yoke?

[Martin]

As Brian said, they are probably 3/8" Whitworth, which look very similar to M10's but are slightly smaller. Just don't get them mixed up, as an M10 nut will fit on a 3/8" bolt, but it won't be very safe. So I'd advise binning all the 3/8" stuff to avoid confusion. It's also very frustraiting when focusing, as a quad spanner doesn't fit the 3/8" bolt heads. Screwfix sell a box of 100 M10 bolts for less than a fiver. Go for the 40mm bolts.

[david.elsbury]

I find threaded holes in yokes a PITA. It takes forever to take the bolt out, and it prevents the lantern spinning properly if the nut has been over tightened.

 

David

[gareth]

I can only agree with what other people have said - M10 for smaller lanterns (up to 1.2k - what the heck is a 1.5k lantern, MBSLX?!), M12 for anything bigger. And don't go with threaded holes in trunion arms, either.

[knotted]

we drill all of our yokes out to 13mm holes so they'll take C-Clamp bolts (US style, M12 appx)

 

as for washer arrangement, our standard is

 

Bolt Head>Flat Washer>YOKE>Flat Washer>Spring Washer>Flat Washer> Hook> Flat Washer> Nyloc

 

All in M10, with a 40mm bolt, heavy duty hook clamps from J.Thomas ENG.

 

Having the spring washer on top of the hook is a real pain as it can be extremely hard to get undone when torqued up. And as we prep 100's of lanterns at a time, with 7 possible hanging arrangements it pays to have something that is reasonably easy to undo whilst still doing the job.

[robloxley]

Beware that M12 wing nuts don't spin fully in a 'standard' G-clamp.

Personally I like threaded yoke holes (or headlocks) but it seems to be very much personal preference.