Tap and Die

[diditrain]

Hi all, is anyone familiar with re-tapping?
I need to replace a bolt on my multi fuel stove as the old one snapped.
Is there a general rule of thumb?
e.g. if i wanted to use a 3.5mm bolt what size drill bit would i use and then what size tap would i use?

Many thanks for any responses

 

[randyrat]

If you havent a clue, get a tap you think will be about right, and a bolt to match it. Get your box of drills out, and offer up the shank of a few to the thread on your bolt. By eye pick a drill that appears to be the same size as the bolt without its threads.
Drill yer 'ole, tap yer 'ole and fit yer bolt......doddle
Obviously you could refer to standard thread sizes and screw pitch and match it up dead right......but if its a non-crirical assembly I would just use "by eye" if I were you.

Hope this halps
Randyrat

 

[uksel]

for an M4 bolt, use a 3.5mm HSS bit to make your hole, then tap
for M6 bolt, use a 5.5mm HSS bit

 

[montybaber]

try this link

Tap Drill Sizes