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Posted: 3/28/2006 6:17:45 PM EDT
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
Link Posted: 3/28/2006 6:23:16 PM EDT

Originally Posted By SKSGuy:
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
Link Posted: 3/28/2006 6:23:33 PM EDT
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.
Link Posted: 3/28/2006 6:32:41 PM EDT
What kind of insulation is suggested?
Link Posted: 3/28/2006 6:37:43 PM EDT

Originally Posted By SKSGuy:
What kind of insulation is suggested?



ashes work if you have enough to form a good heat barrier around the part.
Link Posted: 3/28/2006 6:56:44 PM EDT
ok, thanks Strat!
Link Posted: 3/28/2006 7:31:13 PM EDT
[Last Edit: 3/28/2006 8:13:40 PM EDT by CarbineMonoxide]

Originally Posted By SKSGuy:
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?
Link Posted: 3/28/2006 7:59:42 PM EDT
[Last Edit: 3/28/2006 8:02:07 PM EDT by headpulper]
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
Link Posted: 3/28/2006 9:05:39 PM EDT
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.
Link Posted: 3/28/2006 9:36:22 PM EDT
[Last Edit: 3/28/2006 9:37:23 PM EDT by SKSGuy]
...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
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