Almost the luckiest escape. (method I used for removing broken long series drill)

[thehomeengineer]

Hi All

I took on a private job to fit a decompression valve to a 2 stroke motor bike head that the old boy couldn't kick over. Then the dreaded words came out "can't get another one of these cylinder heads anywhere as they don't make them anymore, so we have only one shot at this" (WE?) (I should have walked away at this point).

However the customer had marked up the position where the hole was to be spot faced and drilled. The material was only aluminium, and this had been preformed on other heads, so what could go wrong!

The head was set up on the mill and aligned to the marked out position and the job positioned under the spindle. Slideways then locked off and proceeded to centre drill and drill. The hole was only 3/32" diameter and a long series drill was going to be required to finish the hole.

While drilling there was a funny crunching noise so stopped the drilling process. Nothing obvious so I wondered if it was porosity? Went slightly deeper and it then stopped. Then disaster! with only a 1/16" of depth to go to break through the drill end broke off in the head. The cold sweats and that sinking feeling quickly hit me and the words "so we have only one shot at this" were ring in my ears.

So first things first how do I remove a broken long series drill without causing anymore damage

It was impossible to drill from the other side so a had to come up with another idea . Lets take the broken drill bit and place it in a battery drill and run it backwards to see if I could dislodge the broken part of the drill. To my surprise some swarf was dislodged, but the drill was still firmly in place. I couldn't use a magnet so was stuck having to confess to the damage to the head with no solutions to solve the problem.

Then another moment. I thought maybe just maybe could I could hydraulically remove it .
So the hole was filled with oil and the shank end or the broken drill used as a piston. The hole was charged and refilled several times until a good pressure was felt/achieved and a slight tap with a hammer this moved the broken part of the drill and I was able to then blow it out with the airline.

Total relief short lived!

WHY DID OIL look like it was coming through to the coolant passage A torch was then used to shine light into the coolant chamber and to my horror there it was I had drilled into the coolant cavity. The casting wasn't flanged as I was told but was hollow. So the porosity I thought I had broken into, was actually the coolant cavity. The drill must have then wondered on re-entry to the casting and broke off the end of the drill bit.

The dreaded phone call was then made and the customer said he would pop over straight away. When I said "you showed me a YouTube video of this modification and they didn't have any issues with it braking into the coolant chamber": His response " that might be because that was a different head assembly from the one I gave you. The video was for a Honda not a KTM".

To overcome this I will need to sleeve and weld the head so coolant cant enter the piston.

What a nightmare.

Thank you for reading and sharing my pain.
The Home Engineer

[bruce.desertrat]

" that might be because that was a different head assembly from the one I gave you. The video was for a Honda not a KTM"

IOW, he didn't know the casting was hollow, either, or he picked the wrong place to drill (or both) I am feeling your pain...hope the sleeve&weld works!

[Toolmaker51]

I wonder, has there been a tally of misinformed owners relying on mistakenly chosen video materials, informing someone else to not get undesired results?

[WmRMeyers]

I wonder, has there been a tally of misinformed owners relying on mistakenly chosen video materials, informing someone else to not get undesired results?

One of the things I like, and comment favorably on, is the guys who make mistakes, show those mistakes, and show how they overcome them. I find I learn more from those than the ones where everything goes right.

Bill

[mklotz]

One of the things I like, and comment favorably on, is the guys who make mistakes, show those mistakes, and show how they overcome them. I find I learn more from those than the ones where everything goes right.

Look on the bright side...

The ones where everything goes as it should provides a fabric on which to imagine all the things that could go wrong if you were to try it and mentally concoct actions you would have to take to avoid making such mistakes.

[Toolmaker51]

I, the OP stated "I wonder, has there been a tally of misinformed owners relying on mistakenly chosen video materials, informing someone else to not get undesired results?"

One of the things I like, and comment favorably on, is the guys who make mistakes, show those mistakes, and show how they overcome them. I find I learn more from those than the ones where everything goes right.

Bill

I'm in agreement, mistakes teach; perhaps better than complete success.

I was referring to those asking us to perform some job, that a requestor has insufficient background information to insist guides a process; and then fault us when things go awry.

[WmRMeyers]

I, the OP stated "I wonder, has there been a tally of misinformed owners relying on mistakenly chosen video materials, informing someone else to not get undesired results?"


I'm in agreement, mistakes teach; perhaps better than complete success.

I was referring to those asking us to perform some job, that a requestor has insufficient background information to insist guides a process; and then fault us when things go awry.

That is probably more often the case than not. I've used not quite correct data more than once. Had the opportunity to do technical order validation on an Army-managed satellite antenna, an OE-361 QRSAG, which had been in service by then for about a dozen years. Found one of the drawings that were critical to getting the antenna aligned was upside down. https://picryl.com/media/an-oe-361-q...ir-wing-7a3204

So it doesn't just happen on YouTube Videos, or people messing around with old equipment. That particular system was where I developed the notion that engineers needed five years experience as a mechanic, and five more years experience as a machinist before they're allowed to design things for sale to the public or Government.

Bill

[thehomeengineer]

Hi Bill
unfortunately I have 40 years experience but I do agree with you about the time spent before designing items. However I do feel responsible for the error as I didn’t check for myself. I don’t change a lot for doing odd jobs as it gets reinvested back into the workshop. Fortunately (and I don’t want to blow my trumpet) when doing private work things don’t go wrong. But a simple error like this just checks the complacency that is there and reinforces the old saying check twice cut once!

[WmRMeyers]

Hi Bill
unfortunately I have 40 years experience but I do agree with you about the time spent before designing items. However I do feel responsible for the error as I didn’t check for myself. I don’t change a lot for doing odd jobs as it gets reinvested back into the workshop. Fortunately (and I don’t want to blow my trumpet) when doing private work things don’t go wrong. But a simple error like this just checks the complacency that is there and reinforces the old saying check twice cut once!

You still work with the data you have. Your guy told you it was THIS way, and it turns out it was really THAT way! Had that happen a few times, too. Fortunately for me, not on something irreplaceable. Yet. But it could happen today.

Bill

[bruce.desertrat]

So it doesn't just happen on YouTube Videos, or people messing around with old equipment. That particular system was where I developed the notion that engineers needed five years experience as a mechanic, and five more years experience as a machinist before they're allowed to design things for sale to the public or Government.

Or it's just the person who produced the manual was not competent.

I'm reminded of the part in "Zen and the Art of Motorcycle Maintenance", where the author was talking about his freelance job doing technical writing, when he was hired to write an instruction manual for a lawnmower, and the higher-ups at the company decided to pair him with a line worker who assembled the things to assist. The line foreman promptly assigned his worst man to the task, mainly to get him off the assembly line where all he did was screw things up.

One of the only things I remember from that book...must have read it 45 years ago or more...