[lindum]

Firstly I'm a complete beginner where tap and dies are concerned. I have a set, but up to now its either been done before I get the part or I got a mate to do it for me. But I can't keep asking people for help every time I need to tap something. So I'm starting to do this myself, with a bit of help from you guys.

I've bought 2 fencing panels so I can fence off part of my backyard as I don't have a garden shed but do have a lean too at the back of my Bungalow but its open to any one who walks up the garden path, hence the panels. One of these panels need to be anchored to a concrete post so I have to make a wire clamping gadget (to buy one cost £70) out of bits and pieces but this entails drilling and tapping a couple of holes to take an M5 bolt.

I found a Tap and Hole calculator at Theoretical Machinist . com (see Attachment), but it might as well be written in Klingon as I have no idea what the calculator is asking for.

All I really wanted to know is how big a hole do I have to drill to tap for an M5 bolt.

[awerby]

The short answer is 4.3mm. See https://www.boltdepot.com/fastener-i...rill-size.aspx That calculator would have gotten you there. It was asking a lot of questions you didn't know the answers for, but you could have figured them out by measuring your bolt. Or gone back to Google...

[109jb]

What the program is asking you:

Basic Diameter - The bolt diameter
Threads per inch - Number of threads in 1 inch of bolt length (Imperial threads)
Thread pitch. - Metric threads don't use threads over a given length, but the distance from one thread to the next in mm
Thread percentage - You can't really form a 100% thread or the tap will break. Plus, above about 75% you don't gain much strength anyway. 75% or so is normal for threads

Cutting tap drill size - The drill to use for a tap that removes metal (Normal tap you get from the hardware store.)
Cold forming tap drill size. A cold form tap doesn't cut metal, but "bends" it out of the way to form the threads and need a bigger starting hole

[Bvbang]

This is the formulaMajor diameter) - (pitch distance) = tap drill size. (for 75% internal thread). It works on imperial or metric, any size.example for 1/4"-200.250 - 0.05 = 0.200. #8 drill (0.199) or #7 drill (0.201) will work. 0.05" = pitch distant, 1/20example for M5 x 0.85.0 - 0.8 = 4.2. 4.2mm drill is the tap drill size for M5 x 0.8.BB

[Bvbang]

This is the formula. Major diameter) - (pitch distance) = tap drill size. (for 75% internal thread). It works on imperial or metric, any size. example for 1/4"-20. 0.250 - 0.05 = 0.200. #8 drill (0.199) or #7 drill (0.201) will work. 0.05" = pitch distant, 1/20. example for M5 x 0.8. 5.0 - 0.8 = 4.2. 4.2mm drill is the tap drill size for M5 x 0.8. BB

[lindum]

Thanks
The Bolt Depot list is easier for me to get my head around.

Thanks again for the replies guys.