Simple way of checking thread size of stainless hex head bolts

Hmm. I acquired a metric/imperial thread gauge around 65 years ago! Lots of choice on line.

Having identified the thread, you need a chart giving the tapping drill/clearance drill sizes etc.

A quick look found this

Why not keep a labelled box of bolts, all sizes, if the screw fits...

Otherwise, I use a USB microscope and ruler.

I meant nuts,

The Screwfix item is cheaper

I also have one of these

Thanks. The eBay item looks promising. I was doubtful abut the Screwfix item as it seemed orientated to screws, not bolts.

Cheers

Dave R

Theo

Fix a range of nuts, and bolts, onto a strip of timber/metal, etc., label them with the size. The nuts will enable you to identify bolts, the bolts will enable you to identify nut sizes.

I didn't read carefully, I was actually thinking pitch.

For diameter, I too use a digital vernier calliper. And maybe look at manufacturing tolerances if in doubt.

I would make a cone of clear celluloid sheet and calibrate with marker pen lines for different known thread diameters

I've always used a digital caliper for diameter. To get the pitch: either use a thread gauge or roll the thread in plasticine (or similar) and then count the bumps over a reasonable distance and divide appropriately, depending on whether it turns out to be metric or imperial. Checking the thread angle needs a thread gauge.

Ordered the eBay item. It turned up today and at first test does exactly what I wanted. It will make sorting through my box of mixed bolts much simpler.

Cheers

Dave R

I have seen such a thing on sets of plastic wallplugs. You have a recommended drill size for each size of plugs and a recommended screw size for it when using it, and the idea is that if you can't tell an M3 screw from a No8 screw then you slide the screw down the carrot and see if it is the right size.

I have never seen the equivalent for larger bolts though

Hmmm! I call an M3 a machine screw/bolt whereas a No6 wood screw is 3.5mm Ø & a No8 wood screw, 4mm Ø approx.

I just picked numbers out of the air. It was the principle I was trying to get across.

(I can tell a woodscrew number (at least from 4 to 12) by looking at it, but I have no knowledge of the exact measurements).