Broken drill

[mgbrv8]

A friend of mine brought over a cylinder head that he broke off a drill bit in one of the exhausts bolts that he broke off any advice on how to get it out? It not flush it's about 3/8 deep

 

[don-tucker]

What Dia is it,when they break off below the surface I have had success with tapping down with a small pin punch and breaking it up,but it depends on a lot of things and watch your eyes
Don

 

[doc1955]

What was the bolt size? Drill size?
Hss or carbide drill?
If it was a HS drill bit you could drill out carefully with a carbide if you don't have a carbide drill you could use a masonry carbide tipped drill.
But with carbide you will need to be careful I've used masonry bits in the past for this but it is slow and you need to use extreme caution and back out of hole a lot to clear chips when I've done it in the past I had to re-sharpen several times to complete task. Plus works best if you can either clamp to drill press table so things do not move or clamp in vise on mill. Doing this by hand or letting part move around does not work real well as carbide does not take any flexing.

 

[Admiral_dk]

Or are we back to chemical removal here ...?

If the head is aluminium, you can remove steel chemically without any disturbance to the ali - it's been discussed several times before on this board.

 

[dalem9]

Just as Admrial said , I am assuming that their is a bolt broking off that he was trying to drill out . If you have alot of time you can get it out with alum. A food processing chemical. It will eat the iron but not the aluminum . I t will take some time but it does work . any questions PM me and I will help you . Don't put the whole part in the Alum cause it will eat the cylinder too if it is iron . Dale

 

[rake60]

If the head is aluminum, I'd go the alum route.

If it is cast steel, I'd take it to your local machine/welding shop.
An experienced welder will know how to use a tool steel welding rod.
A tool steel welding rod will only stick to metal that it is contacting.
(That is where experience becomes the key word)

I have witnessed broken drill bits being removed in this process.
The welder built up a puddle using a tool steel on top of the broken bit, then
laid a hex nut on the puddle and continued to weld it fast.
A few dental like twists on the nut freed the broken drill bit.

The foreman was very pleased with the recovery.
The welder told me, "It wasn't me, it was the basic characteristic of the tool steel rod."

Never the less, I was just as impressed!

Rick

 

[mgbrv8]

I ended up using my small Magbased drillpress and a small carbide bur to punch a hole through it

 

[doc1955]

Good deal!
That is what I should of called it when I referred to masonry drill (punched through it) I have done that for a 3/8-16 tap I broke and it took some doing but did get through it.