Re: [PSUBS-MAILIST] Bad Day.

Hi James,

I have had days like that in the past and I expect some in the future too. I have had this happen a couple of times before.

Some times when a bit or tap breaks a small amount is imbeded in the bottom of the hole. If this is the case, I have sometimes had success by using a good solid punch to fracture the remaining piece. If you are sure there are no remains in the hole then it is most certainly work hardened. I usually heat to about medium red and let it cool slowly. After cooling I drill the hole to the complete depth. I then drill a hole about two sizes larger and tap the hole. At this point I place a tight fitting threaded bolt in the hole covered with locktight. After full cure of the lock tight, cut off the stud flush with the top, drill down the center of the hole with the original size and tap. This is a long procedure but it works well. They make threaded inserts usually called helicoils, but I have had quite a bit of trouble with them coming out with the bolt at a later date.

I hope this helps.

Best Regards,

Jim K

----- Original Message -----

From: James Frankland

To: personal_submersibles@psubs.org

Sent: Saturday, January 26, 2008 2:51 PM

Subject: [PSUBS-MAILIST] Bad Day.

Hi All.

I just had one of those days where everything goes wrong.

Im cut, burned and i got a splinter in my eye despite wearing my safety glasses.

Anyway, i have a problem which maybe someone can help me with.

I was trying to get my viewports complete and welded into the tower today. But, one fo the holes went really wrong.

I am drilling and tapping the holes in the viewports. I have done 29 holes and everything seemed straight forward.

But, on one of the holes, the pilot drill broke right at the start. It took me over an hour to get the broken piece out. After that, i tried to drill it with a new bit but it just wont drill. When i say it wont drill, i mean it really wont drill. I went to the shop and bought some special bits designed for stainless steel and even that wont get though it. Its like trying to drill a diamond. I dont know what has happened here. It seems such a simple job, but i'm really stumped.

I have gone through about 6 brand new bits of different sizes and types but all ive done is make a mess.

The hole is now about only 5mm deep and larger than needed. I think i may have to drill and tap it to the next size up if i can even get through it.

Does anyone know what has happaned? The steel is A516 GR70. I was using a drill press on slow speed. All the others holes were good with a long trail of swarf indicating a clean cut.

Perhaps its a "hard bit" on the steel? Does this happen?

Or, maybe it has work hardened and i now cant get through it?

I thought of a couple of options.

1. Heat it to red hot and try drilling it.

2. Drill another hole next to it and fill the mistake with something, maybe epoxy?

3. Scrap it and make it again. (very bad)

I had enough ports done to weld into the tower, but i thought i better stop today. I was so misserable i would probably make things even worse.

I may take the port to a professional shop to try and rescue it, but im not sure what they can do that i cant.

Any ideas anyone?

Many thanks as always

James.

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