Imperial bolt / spanner sizes

[E-wan]

Does anybody know of a table or an easy way to convert from measurements in millimetres to imperial spanner sizes

I'm looking for something to fit the bolts in the photograph below


it will need to be an open ended spanner from the larger Bolt which measures 25.8 mm

The smaller bolts measure 13.3 mm and I was hoping to use a socket with a t-bar on these ones

My digital calipers do inches and decimal points of an inch but not fractions of an inch.

Also are there different standards of imperial spanner size?

Thanks for any advice

Ewan

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[CHJ]

Does anybody know of a table or an easy way to convert from measurements in millimetres to imperial spanner sizes

This any help

Also are there different standards of imperial spanner size?

Yes there are, but with any reasonably modern equipment you are not likely to come across the older standards (wartime metal reduction etc. changed sizes)


Try this chart for starters

 

[sploo]

http://www.baconsdozen.co.uk/tools/conv ... charts.htm

13.3mm is likely 5/16 BSF, with the 25.8mm likely 5/8 BSF. Note that they might be marked 1/4" BS and 9/16" BS respectively, as you'll notice from the table that BSW (Whitworth) and BSF (Fine) have different size designations for the same actual head dimensions. Likely easiest to just get a cheap BS spanner set (ring on one end, open ended on the other).

EDIT: Chas beat me by 4 minutes

 

[sunnybob]

I gave away buckets of whitworth and old imperial spanners and sockets over 15 years ago. Now if I do coma across an oldie, i just drill the hole outand tap to the next metric size.

theres only room for so much nostalgia before it becomes a chore chasing down old stuff.

 

[t8hants]

They have started to reduce the metric head size now, beginning to see 12mm bolts with an 18mm head, being used in CE approved steel work.

 

[Cheshirechappie]

There's an old fitter's dodge for getting by when the available wrenches don't quite fit. Take the next largest open-ended wrench, apply to bolt head, and jam a coin, washer or similar between the wrench jaw and bolt flat. Not good practice, but it can get you out of a hole sometimes.

 

[MikeJhn]

Or just use a pipe wrench, throw the bolt away and re-tap to the nearest metric size.