Screw Sizes Imperial/Metric Confusion

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  #1  
Old 08-09-15, 08:41 PM
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Post Screw Sizes Imperial/Metric Confusion

Hi, I purchased a variety of screws at a hardware store. I asked the guy for a mixture of #8 and #10 and some #5 screws. I'm confused about the relationship between Screw Gauge and diameter size and the differences between Imperial and Metric sizings.

The screws which are supposed to be 5 x 80mm (metric) have a large diameter (almost 12mm), larger than the diameter of the 10 x 2 1/2" (imperial) screw.

Furthermore, the other screws that were supposed to be 5s have a large diamter too. Is there a chance her gave me 12mm screws by mistake?

I am having trouble figuring out the screws by measuring, eg. the #8 X 3" screw has a diameter of 10 and a shank of around 4mm. I can provide pictures if necessary
 
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Old 08-09-15, 09:34 PM
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Welcome to the forums from Ireland.

I'm a little confused. Pictures may be a help. http://www.doityourself.com/forum/el...rt-images.html

#8 and #10 are sizes we use. The size determines the diameter of the threaded part.

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  #3  
Old 08-10-15, 06:30 AM
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If the guy picked the screws from an open bin then the likely hood of mix up is very high. Sealed boxes are the only sure way of knowing what your getting.
 
  #4  
Old 08-10-15, 07:40 AM
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What is confusing me is that I have a mix of imperial and metric screws.

I purchased a box of 10 x 2 1/2" online. The boxes was labelled.

Then I purchased a box of 5.0 x 80mm (http://i.imgur.com/DnGjvUD.png) and this is where the confusion started, as the 5.0 screw has a similar diameter to the #10 screw (side by side http://i.imgur.com/B5KGsHu.png) and it is 10mm wide (http://i.imgur.com/v5Hw0US.png). I thought it would be 5mm diameter?

A few days later I went to a hardware store and asked for a mixture of 5 screws. Since I assume they are metric as it is Ireland, he gave me screws from a 5mm box. However, they too are similar to the #10 screw in diameter (Comparison http://i.imgur.com/Mz4lw0L.png).

One of the screw types that was supposed to be 5.0mm has a humongous diameter, larger than the #10 screw and with a wider shank. (Comparison http://i.imgur.com/ArzhfqC.png) It's 12mm (http://i.imgur.com/zBhsHJV.png).

I am confusing myself the more I think about it.

I would be happy measuring the screws and labelling them myself. The one that has a 12mm diameter head and 50mm length, does that mean it is 12mm x 50mm or do I measure the shank instead (4mm).

Sorry about the convoluted questions.
 
  #5  
Old 08-10-15, 01:34 PM
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Screws

I asked the guy for a mixture of #8 and #10 and some #5 screws
Why would you want them mixed?
 
  #6  
Old 08-10-15, 02:54 PM
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Hi,

I mean I wanted a few different lengths of #5, #8 and #10 I didn't think there would be a problem identifying them out of the bag later
 
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Old 08-10-15, 03:01 PM
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Even if they are similar, they are still different! And many manufacturers will make there screws slightly different (the pitch and screw thread should be the same) but the head or length might vary. Also some industries will make a b*st*rd thread just to prevent repair or third party sources.
 
  #8  
Old 08-11-15, 09:25 PM
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Is it diameter or shank width that is the relevant measurement to figure out which screw is which?

Thanks
 
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