thread repair

[firebird77clone]

This is a follow up to something I had posted about a while back: welding in a hole and re drilling and threading it.

I had decided that next time I would over drill the hole before I welded it back in. Well, the hole had already been oversized from an M4 to M5 and the threads were wallowed out, and I wanted to get back to the original fastener.

The hole was already oversize, the part was 5 mil thick mild steel. I used a copper flat bar between the part and the bench, and migged the hole shut. This time, I did NOT quench it! While it was still toasty, I ground the weld flat, and let it air cool from there. A badly abused transfer punch gave me center with the cap plate set in place. The tap index was missing the drills, so I eyeballed a drill laying about, and drilled it nice and slow using the end mill as a drill press; the vice on the drill press is junk. No problem drilling through the weld. The tap was a little tougher, and more than once I questioned the wisdom of not having miked the drill. But it was a nice spiral. The tap, and I went slow, no problems. The cap plate I left with oversized holes, it's not critical, and a couple washers under the fasteners will make it all good.

To sum up, the oversized holes seemed to make it go easier.

[MelloYello]

If I may ask, did you not opt for a heli-coil because you wanted to get back to original fastener size?

[jerry clayton]

heli coils don't work good in thin stuff----he said 5 mm---just over 3/16 inch

[M.T.]

Ive been through this several times in the past with the same good results. I tried Tig welding them closed once with the same wire that I Mig with E70s6 wire. No way I could drill through that weld. I think the using Mig and letting it cool naturally is the key. For what ever thats worth?

[40FordDeluxe]

I've experienced the same as MT in I had a heck of a time trying to drill through my mig weld. I think the key is to walk away and let it cool all the way off. That isn't easy to do when you want to get it done.

[pat mccarthy]

timeserts just pick up some 1/4 by 1/4 so they make them short not a big fan of hei-coils but still have some but use more timeserts now that i found them i am hooked on them . some stuff is a pain in the ass to thread . i need a 3/4 -16 hole drilled and tap in the nose of a new callies magnum crank to drive the oil pump mandrel only $1700 crank if i screwed up.. tap was crying as i lube the hell out of it.. i have some lube stuff will rust and thing it sets on or raw steel by it. but it works . as the tap is letting me know how much it is not liking the heat treated 4340 steel i was thinking it.s was going to rip and not thread or tap was going to bust off . but it did tap and never again

[jerry clayton]

I did a crank for my Monza Pro stocker oil pump drive years ago and left here without the bolt headed to Michigan US 131 drag strip---got the bolt over there somewhere at a supply house-----------lots of big mosquitoes there-----------

[pat mccarthy]

I did a crank for my Monza Pro stocker oil pump drive years ago and left here without the bolt headed to Michigan US 131 drag strip---got the bolt over there somewhere at a supply house-----------lots of big mosquitoes there-----------

yep and some are now packing heat