Screw thread query

[pophops]

I'm hoping someone can help me identify what brass screws to order.

I don't know what thread size or type has been used throughout the boat but they all seem to be the same.

They have been used to attach hinges, portholes, mushroom vents, etc

.I also need to order a tap and drills of the correct size.

The boat is about 25 years old and the screws seem to be an imperial size.

I have taken a photo for comparison.

The screw on the left is M5.

As you can see, the one on the right is very slightly narrower and the thread seems a little finer.

BA ? BSF? BSW? BSP? UNF? Whitworth? I'm confused

Thank you for any help you can give.

 

 

[Tonka]

you need thread guages and a dzus book of threads

[RLWP]

Probably 2BA

 

Richard

[Timleech]

2 BA, M5 and 3/16" BSF are all pretty close to one another

 

Tim

 

Edit to add:-

 

M5 x 0.8, 5mm dia, 31.75 tpi

2BA, 4.7mm dia, 31.35 tpi

3/16" BSF, 4.76mm dia, 32 tpi.

 

All different thread forms, of course.

Edited October 27, 2014 by Timleech

[Black Country Lee]

If my memory serves me correctly a little under 5mm in imperial is the 3/16"BSF. Not sure on the metric measurement for the 3/16" as I don't have my Zeus book here but working it out approx 4.76mm. It looks a bit course for a 2BA but I'm happy to be proven wrong lol.

 

Lee.

 

ETA:- Spelling mistooks!

Edited October 27, 2014 by Black Country Lee

[dmr]

Lay it down next to a ruler, take a good digital photo, zoom, and count the "threads per inch".

But Richards probably right, so get a 2BA nut (eBay) and see if it fits.

 

.............Dave

[by'eck]

Good guide to identifying threads here

[Slim]

I've got a thread size app on my Android tablet. I used it once in anger and it worked for me

 

I'm on my laptop so can't try and identify it at present. I'm pretty sure I found it on Google Play and know for a fact that it was free.

 

As you might gather I'm no IT wizard

 

 

Frank

[springy]

They could also be #10 available either coarse - 24 threads per inch, or fine - 32 tpi, just

a gnats smaller in diameter than M5 but #10-32 is slightly coarser ?

 

springy

[egret]

why not take it to a nut and bolt supplier and ask them after all you will have to go to buy them anyway.

[Bee]

Somewhere on an industrial estate near you there will be a place that sells consumables, brushes, tools, swarfega, nuts and bolts, all the stuff that big and small factories and workshops use. They can help.

[Timleech]

Trying to be practical, all the likely threads are very close to M5 and all slightly smaller. If you're just wishing to refasten fittings with new screws into the cabin steel, buy an M5 tap, run it through the existing holes and use M5 screws.

 

My money is on 3/16" BSF, BTW.

 

Tim

[hovrin]

Taking measurements from the picture, (highly inaccurate I know), I think the one on the right is 3/16 BSF.

 

However, as others have said, it would be easier to obtain 5mm bolts and fittings these days and just use them.

 

If you really want to replace like with like then find your local bolt stockist or general engineering firm and ask them to match the one you have - much easier and more accurate than working from a photograph.

[RLWP]

2BA brass screws here: http://www.ebay.co.uk/itm/BA-Brass-Countersunk-Slotted-Head-Machine-Screws-2BA-4BA-/371148860736?pt=UK_DIY_Material_Nails_Fixing_MJ&var=640304389588&hash=item566a322d40

 

£7 for 100

 

Richard