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Drilling hardened rod

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dbq49

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Yes this is an age old issue. Here goes- Broken off hardened steel rod on a dozer throttle 1/4" rod , 3/8" deep I think. Drills don't drill hardened steel. CAN I heat the stub to soften the rod and then drill it out. I am not sure it can be removed from the dozer at this time. Any help, Please!
 

kb3guy

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If you heat it up past the Curie temperature (usually dull red) and let it cool slowly (covered in ceramic wool helps), you might have some luck softening it. You can test it with a file afterwards to see if it works.



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MrWhoopee

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Yes. It is unlikely that the material will air-harden, so simply heat to red and allow to cool. No special care or treatment required, just don't quench it with water.
 

P. Waller

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How hard is the question, if it is very hard a carbide drill or end mill will do it but I would not try this with anything other then a stout milling machine.

I often reduce the shanks of taps with carbide tooling, your part is unlikely to be full hard HSS but you never know until you try. Straight flute carbide die sinking drills are excellent for this sort of work. They are very fragile so do not use them in a low cost drill press or mill as you will break them easily.

https://www.mscdirect.com/browse/tn/Holemaking/Straight-Flute-Die-Drill-Bits?searchterm=die+sinking+drills&navid=4287923630
 

extropic

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Doesn't it seem unlikely that a throttle linkage rod would be hard (un-drill-able)?
Is something else going on here?
 

dbq49

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It was on a governor throttle. Broken and destroyed 8 bits trying to get a pilot hole created.
 

brino

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Is there any way you can remove that bell-crank arm for "processing" elsewhere?

-brino
 

Silverbullet

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I'd try diamond burrs , the type used by dentist, only other way is to abrade it away with edm or lazer..
Diamond drill ???
 

aliva

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use a carbide drill bit go slow as to not chip the drill, and lots of coolant
 

TonyRV2

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^^^ I agree. I sure would try a carbide bit before I start trying to anneal an unknown piece of steel with a torch.
 

chips&more

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I would try a cobalt bit first. A carbide drill bit will break just looking at it (metaphor).
 

dbq49

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Well, I put on the smallest acetylene tip and heated the steel stud. No heat past the casting, so spring not effected. Used my drill press and drilled a size F hole. Tapped the hole with a 5/16-18 tap. Cleaned the pivot of rust and made sure it would pivot on the grade 8 bolt solid shaft. Cut the threads off so that nothing extended past the casting and ground down the thickness of the head so that it would fit under the lid swivel post. Working great and back on the engine. Thanks for all the suggestions
 

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KBeitz

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For heating something like that I use my stick welder.
I turn it on high and stab the rod on the broken part and hold it tight.
Induction heat. Works great. I use a 1/4" rod.
 
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