drilling help needed

[souljah]

ok i had to repair a stripped thread so i drilled it oversize then inserted a 10mm bar and welded it both ends now i need to drill it in the center for a 6mm hole problem is the bright bar i used now wont drill couse its to hard .i havent got a clue were the bar came from just some i had lieing around, are there any special drill bits that i can buy or any ideas

 

[Ratty]

Welcome souljah. You don't say what the stripped thread is in nor what depth it needs to be, if you can get the welded bar out again maybe a threaded insert would work. If not this company does have other types of insert that might just do the trick.

 

[souljah]

hi ratty its on a kit car subframe and needs to be 15mm deep and i cant get the bar out now im gonna try a TCT bit to start one suatable for stainless steel this quick faviour job is gonna cost me time and money

 

[Paul.]

Even if you manage to drill it maybe with a cobalt drill, how will you tap it?, Time to start again I think, use a material of known specification, or as Ratty suggests a threaded insert if the application is suitable, or a helicoil.

 

[souljah]

yea good point well presented but it cut ok with a hack saw and files ok so it cant be that hard can it

 

[irondarren]

Good quality drill bits will drill it. dormer or similar, a cobalt will no doubt work. If its hard drill it slowly, slow speed drill will do fine

 

[Paul.]

Try drilling the off cut, see if its really that hard, it might just need a decent sharp drill and some cutting oil, If it is a piece of medium or high carbon steel then the welding will have hardened it, but if only mild steel then a decent drill should cope with it,

 

[Justme]

Wont it have hardened when you welded it?

 

[gavuk]

I've done the same before , rather than risk tapping i managed to drill a hole ,then use that hole to centre a holesaw to dril out the offending bar and put in an even bigger slug .....hope u sort it !

 

[souljah]

I've done the same before , rather than risk tapping i managed to drill a hole ,then use that hole to centre a holesaw to dril out the offending bar and put in an even bigger slug .....hope u sort it !

yea thats kinda the idea i was gonna choose cheers

 

[rikrobson]

you could try annealing the plug it may have work hardened. This should soften the steel and be easier to drill. With hindsight it would have been easier to have drilled the insert 1st Doh!

Have you also tried to drill a smaller pilot hole?

 

[Welderpaul]

Can you cut out the offending area, weld a little piece of plate in, grind flush and start again. Probably quicker in the long run.

 

[Drains]

It's possible it's a bit of EN8 or similar and the welding has hardened it. It'll only be a shallow harden though, maybe, so tapping it may be possible, once you've drilled through the hard stuff. If it was well bright then it could be stainless, in which case you need to drill it right and not let it work harden, or your bugg3red.

What size pilot you using?

 

[souljah]

tried all sorts of pilot hole sizes from 1mm to 4 mm i got one out ithe otherone is a pig i couldnt tap it or pre drill it as there was only 2mm wall thickness after tapping and the hole would have filled with weld and theres only acces from the outside for a tap wrench gonna get the dremmel out on the otherside with some stone wheels and take as much weld of then try and knock it through but will have tpo knock it from the outside and cut bits of inside as i go couse its to loong to come out in a oner

 

[KTMMICK]

I know it is to late this time but drill it first next time.......

 

[KTMMICK]

Ok you posted up before my reply........why not use a bigger piece of bar then? You only need a pilot hole in it so it wont matter of you get weld in the hole.