Garden Railway Forum

Does anyone know anything about bolt threads?

Im trying to work out the threads for the banjo bolts for my osmotor, 1st thought was 2ba but this was wrong, theres about 4 threads on the bolt to every 3 on the 2ba bolt.

Ive now got one of the bolts and my calipers out and had a proper measure up.

The dia of the bolt is 4.4mm or very slightly under 3/16" and the length of the threaded part of the bolt 4mm from the start of the 1st thread there are 7 threads over this distance, or measuring over 2/16ths 6 threads with the ruler from the sart of the 1st thread. So this should give a tpi of 48.

Does this ring any bells or does anyone have any ideas?

sounds like a metric thread to me

Just had a quick word with dad and it is not possible to have 48tpi as that makes the distance between each thread 20thou. If it is that fine it is more likely to be 3/16 ME which has 40 tpi

Thanks Mat and Dan, a few people have said possibly 3/16 x 40me so will give that a try. Next question

Where is the best place for bolts? not too worried about banjo bolts at the moment just want to prove what the thread is first.

your local auto factor. Being into classic cars I have found they have a huge range of nuts and bolts in all shapes and sizes. Failing that you local tools shop should know. I live down the road from a screwfix and BAPP.