Today while upgrading from drum brakes to disc brakes I came across a stripped out rear caliper carrier.  Of course it is crucial that it has both securing bolts to hold the caliper carrier to the spindle...I decided to do what I've always done before. I back-filled the stripped threads with a bit of weld - ground down the excess, center punched it and attempted to drill down into it with my drill press.  Strangely the weld is far harder than I've ever encountered before and I can't seem to drill into it.  It needs to be M10x1.25 (the hole size needs to be 11/32 for the tap).  So I started off with a pilot bit of 1/4".  It went down maybe 5/32" and decided it wasn't going to go any further.  I sharpened the bit up and went at it again with more cutting oil.  Nothin'.  So I decided to bring the speed down to around 200rpm from 390rpm and still it won't bite.

Short of taking it to a professional machinst, does anybody have any tips they want to give this young guy?

-Rob

Quoted: Today while upgrading from drum brakes to disc brakes I came across a stripped out rear caliper carrier.  Of course it is crucial that it has both securing bolts to hold the caliper carrier to the spindle...I decided to do what I've always done before. I back-filled the stripped threads with a bit of weld - ground down the excess, center punched it and attempted to drill down into it with my drill press.  Strangely the weld is far harder than I've ever encountered before and I can't seem to drill into it.  It needs to be M10x1.25 (the hole size needs to be 11/32 for the tap).  So I started off with a pilot bit of 1/4".  It went down maybe 5/32" and decided it wasn't going to go any further.  I sharpened the bit up and went at it again with more cutting oil.  Nothin'.  So I decided to bring the speed down to around 200rpm from 390rpm and still it won't bite. Short of taking it to a professional machinst, does anybody have any tips they want to give this young guy? -Rob

Draw down

Hard materials require very low speeds on the drill and very high pressure on the feed.

Have you tried annealing it ? fire the torch up heat it up and bury in insulation to cool slowly ? another trick is charcoal brickets  bring it up to temp with the coal and let it burn out and cool for a day.

What kind of insulation is suggested?

Quoted: What kind of insulation is suggested?

ashes work if you have enough to form a good heat barrier around the part.

ok, thanks Strat!

Quoted: Today while upgrading from drum brakes to disc brakes

I'm not very mechanical, but I think I understand the post..drum brakes and disc brakes are some kind of codewords for disconnector or auto sear or some such--right?

And you didn't drill  the hole larger, tap for and install a keensert because????

ETA:  In case you don't know what a keensert is and how it works

Sand will work for slow cooling also. Try a carbide drill bit with a high twist rate or possibly the Irwin Turbomax will get through it.  Weld is very hard to drill and likes to destroy tyypical HSS drill bits in no time.

...because I didn't have a heli-coil in that size available at the time.  I also needed to get my auto sea...I mean...my brakes fixed tonight .  I need a car. I don't have a spare.



buuuut....it wouldn't be a bad idea to get a set at this point with all the work I do...
-Rob