Engineering Help Needed.

Iwasgoodonce

Old School Grand Master
Hello all, I need to ask a simple question. More will undoubtedly follow and as ever I thank you in advance. I have to construct a new door handle for the patio doors. The World's most heavy handed woman ripped the damn thing clean apart and, thanks to the handle design being very obsolete, I can't find a replacement.

So I need to make one. I have problems welding but that will improve with practice. My first question regards tapping a thread in a hole in 5mm flat mild steel. If I want a threaded hole to take either an M8 or M10 bolt, what size hole do I drill? Does it need to be 0.5 or 1.0mm smaller than the thead? I only have access to basic DIY tools.

Thanks!
 
You can always drill the heavy handed woman to make a lighter touch :)
 
royboy2cv":1ltz70ij said:
Those books are going for £4.50 :evil: ,Google is FREE , yes i'am tight , i'am an Engineer ;)

You can download a Zeus book if you want, I can tell you were it is if you can't find it.
Simple rule of thumb which is never far out, tapping drill size will be OK if you go for nominal diameter minus pitch. So M8x1.25 will need a 6.75mm[17/64ths in real money] drill.
 
speaking as a bodger, make sure your drill bits are up to it otherwise you'll just nibble whatever it is you are drilling.
 
Thanks again everyone. After practising yesterday, I wasn't too happy with the results.

Also as a Bodger, I think I'll weld an M10 nut to the plate in line with the hole. This will give me a better result I think. I have even found a spring that will give the lock lever some tension!

All I need to do now is find somewhere local that will sell me a small quantity of 30 x 5mm mild steel flat.
 
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