Stainless Steel Replacement Bolts

Put a micrometer on the threaded section. The thread outer is the metric number (i.e. 8mm outer = M8 bolt).

If you don't have a micrometer, borrow one, drop into an engineering shop or ask at a show.

Both Stainless and Aluminium form a protective Oxide coating over their surfaces, so in normal use they won't corrode if put together. That is certainly the case on our trailer which has stainless and aluminium extrusions in very close proximity.

Peter

or buy some known nuts and bolts and see if they fit

Thanks for all the advice

If you are unsure what to order on the net, take the bolts in to a yacht chandler (and they are not only on the coast) and ask them for replacements.

On the other hand, stainless is V expensive, and can still corrode. It doesnt sound as if what you are looking at is structural in any serious way, so why not just go down to B&Q and get ordinary ones.

I am not sure you can say Stainless steel and Aluminum will not corrode if put together. How quickly two metals corrode when in contact depends on how far apart they are on the periodic table, and Aluminum is particularly at risk when with iron and especially copper. This is the problem with, for example, Discovery 1s and Range Rovers where aluminum skins are mounted on steel frames. they are supposed to have a mastic to separate them, but if carelessness in the building, and time allows water to bridge between them the aluminum will corrode quite quickly. If possible it is best to use non metallic washers to prevent contact when bolting aluminum with steel or stainless steel fixings. Corrosion is a complicated and interesting subject, but in essence if two metals are together and there is any damp, one of them will corrode.