plugging a hole

[Peloquin]

One of the lads here at work has drilled some holes too big.
Would it be safe to fill the holes with weld, allow to cool then tap them. They will be subject to a decent amount of stress for a number of years.
Would it be stronger if we can find a metal plug to weld into the hole our is just weld strong enough?
Cheers

 

[rtbcomp]

What size holes and how much oversize are they?

Would a cold repair such as Helicoil do the job?

 

[norsa]

need a lot more info on it. size of hole, size drilled, thickness of material, sheer strength, torque required, application etc.
Nick

 

[norsa]

rtbcomp types faster than me, sorry to repeat.

 

[Peloquin]

The holes should be 11mm. Fatboy has drilled them at 14mm.
They need tapping at (I think)12mm for a bolt to go into.
metal is 8mm mild steel. There will be a 15kg bracket (8mm 'c' section) mounted by the bolts with a large switch attatched.
It's a spring loaded arm that once released hammers back with a fair bit of force.
The chances are it'll only ever actually be used once or twice in it's service.

 

[Tiggy_dorset]

The holes should be 11mm. Fatboy has drilled them at 14mm.
They need tapping at (I think)12mm for a bolt to go into.
metal is 8mm mild steel. There will be a 15kg bracket (8mm 'c' section) mounted by the bolts with a large switch attatched.
It's a spring loaded arm that once released hammers back with a fair bit of force.
The chances are it'll only ever actually be used once or twice in it's service.

I would probably just chop a bit of 14mm bar, V the hole and the bit of bar and weld in (both sides if possible). grind the weld flush and redrill the hole.

 

[norsa]

What tiggy say. Bit of a big ask to fill with weld. An alternative would be to drill out and insert an M12 nut, v out well and weld front and back.
Nick.

 

[outofthefire]

I'd have gone for a 14mm nut as well with the flats ground round, but if you want to teach the chump a lesson make him file the hole to a hex so the bolt fits :-)

 

[Engineer1964]

If you have an iron worker or a punch at work you could punch a load of 12mm holes in a scrap bit of 8mm plate and just pop them into the holes and weld up, The reasons for not filling the holes with weld especially if your going to drill and tap is that the area will be a lot harderer than the surrounding, The amounts of taps i've broken tring to tap a hole which has been 100% filled with weld

 

[norsa]

valid point. there is a slight risk with my welded nut that it could also harden and if it has to be retapped (heat distortion) it could also break a tap. By the way i would check what size to drill out if you go down that route. i would drill 10.3 for an M12.

 

[Peloquin]

I suggested the scrap punching thing but wanted to check it'd be ok. I'm planning to use 6mm plugs welded front and back then ground flat.
Thanks for the advice folks.

Haha I'll tell Tony to make the holes fit a nut

 

[Engineer1964]

valid point. there is a slight risk with my welded nut that it could also harden and if it has to be retapped (heat distortion) it could also break a tap. By the way i would check what size to drill out if you go down that route. i would drill 10.3 for an M12.

More like 10.2 for M12

http://www.simetric.co.uk/sidrill.htm

 

[Spark plug]

Would it not be possible to tap m16?

 

[norsa]

More like 10.2 for M12

http://www.simetric.co.uk/sidrill.htm

no wonder you snap more taps than me Gerry : i was taught:- equasion. thread size minus pitch= drill size i.e 12mm - 1.75 = 10.25 ???????? lets call it a draw.
Nick

 

[brightspark]

no wonder you snap more taps than me Gerry : i was taught:- equasion. thread size minus pitch= drill size i.e 12mm - 1.75 = 10.25 ???????? lets call it a draw.
Nick

tapping chart not that its that critical

 

[Paul.]

tapping chart not that its that critical

True, for stainless I would drill 10.5, worrying about 0.05mm on a drilled hole is irrelevant you would never get a drill to cut that close,
another chart with a slightly different view