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Machine Shop and Tool Talk Shop Equipment, fabrication, repairs, how to fix it, which tool to use for the job. Machinist shop talk, straight to the point.

Machine Shop and Tool Talk

Can not Enlarge Hole in SS With Drill Bit


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  #1  
Old 06-21-2017, 01:47:22 PM
sdowney717 sdowney717 is offline
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Default Can not Enlarge Hole in SS With Drill Bit

I had a 5/16 threaded hole in a piece of polished Stainless Steel.
The bolt snapped off, so I wanted to go to a 3/8 bolt.
I could not properly drill the hole, the sharp bit smoked hot, and the SS seems to be like a rock.
So I tried the 3/8 tap, it wont catch the metal, it just bounces off the Stainless

I can not file the inside of the hole.

What if I heated the SS red hot? Would that help to soften it at all?
I was thinking, heat it red hot, then slam a grade 8 3/8 bolt thru the center just for fun.
Then I could put a nut on it.
Right now I am stuck.
Infact pretty mad this happened. I may have to get a new part and stay with the 5/16 bolt. But before I did that, I was thinking use a torch and have fun. Machine shops are $75 per hour and this part is maybe $10.
I have drilled SS before successfully.
If I heat the thing, can I make it shine again?

I am sure a grinding stone cut cut this, but do they come that small diameter that it would not self destruct?

Apparently, it can be heated red hot then quenched in water to soften it.
http://weldingweb.com/archive/index.php/t-23897.html

Last edited by sdowney717; 06-21-2017 at 01:59:26 PM.
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Old 06-21-2017, 02:21:34 PM
stufforbud stufforbud is offline
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Default Re: Can not enlarge hole in SS with drill bit.

There are so many kinds of stainless that it would help to know what you're working with. Some will work harden if you dwell/rub the surface without cutting, others are percipitation hardening and you wouldn't know if heat would anneal it. You may strike out even if you had a carbide drill. I would go get a new $10 part.
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Old 06-21-2017, 03:12:04 PM
sdowney717 sdowney717 is offline
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Default Re: Can not enlarge hole in SS with drill bit.

Total strike out, tried heating, got it red hot, and only moved in 1/8 inch, could not slam a bolt through with a 3 lb sledge.

I did find my dremel with small diamond grinder tip can slowly grind the hole.

This is the part, 316 SS. The ones I got from a seller cheaper he has sold them all.
http://www.ebay.com/itm/Heavy-Duty-D...dU9iYn&vxp=mtr

This SS metal is tough to work with, I learned my lesson, never again.

I have enough of a hole, I could go back to 5/16 SS bolt and a nut. Could use a SS acorn nut on the outside and epoxy the bolt in the hole.
Bu of course it is now seriously discolored.

I had some high wind, it pulled out the bimini eyes from the poles and pushed so hard it snapped off the bolt on one side.
My plan is to get rid of setscrews trying to hold SS tubing, drill a hole and run in a 1/4-28 bolt using the existing threads in the eye. Or use a #12 SS sheet metal screw, screwed into the tubing through the set screw hole.
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Old 06-21-2017, 03:55:50 PM
Andrew Mackey Andrew Mackey is offline
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Default Re: Can not enlarge hole in SS with drill bit.

You should be able to polish out the discoloration, if you spend the time. Might be easier to just replace - by the time you finish monkeying with the part, you probably will have more invested than replacement cost.
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Old 06-21-2017, 04:20:00 PM
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Default Re: Can not enlarge hole in SS with drill bit.

You work hardened the metal by going too fast with the drill. Stainless is not hard to work with but certain alloys and esp 316 will work harden if your tools are dull or running too fast or even feeding too slow. Scrap the part and get a new one.
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Old 06-21-2017, 05:00:37 PM
Greg Mosley Greg Mosley is online now
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Default Re: Can not enlarge hole in SS with drill bit.

Greetings All, Possibly a diamond bit and some clorox for cooling. Very slow rpm. Enuf said.
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Old 06-21-2017, 05:41:16 PM
akuna akuna is offline
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Default Re: Can not enlarge hole in SS with drill bit.

I think the part is not worth saving. By heating it up you changed the corrosive properties of the 316. I believe you will need to dunk it in acid to make it so it will not rust. More then you ever wanted to know about pacification of stainless steel. http://www.mmsonline.com/articles/ho...ss-steel-parts

Stainless also work hardens as has been mentioned. Could have been you, or the first manufacturing steps.

Buy better bolts maybe for the other mounts. And a replacement mount unless you want to mess with this one.
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Old 06-21-2017, 07:14:54 PM
randyjaco randyjaco is offline
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Default Re: Can not enlarge hole in SS with drill bit.

Quote:
Originally Posted by stufforbud View Post
There are so many kinds of stainless that it would help to know what you're working with. Some will work harden if you dwell/rub the surface without cutting, others are percipitation hardening and you wouldn't know if heat would anneal it. You may strike out even if you had a carbide drill. I would go get a new $10 part.
Plus 1.
In the end you are going to be much more happy with a new replacement. You have probably already paid more to fix it than the price of a new one.

Randy
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Old 06-21-2017, 07:50:26 PM
pedalcola pedalcola is offline
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Default Re: Can not enlarge hole in SS with drill bit.

If a replacement part is not avl. try taking it to machine shop to have the bolt EDM burned out. Some shops have what they call tapbuster. Good luck
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Old 06-22-2017, 07:44:46 AM
sdowney717 sdowney717 is offline
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Default Re: Can not enlarge hole in SS with drill bit.

No bolt is stuck inside, it is the hole I cant fix.
One fix would be to take an old bronze screw for filler, and silver braze it into the runed hole. Drill and tap back to the original 5/16 sized thread. I have had good results with Harris 15 and staysilv flux. A stick of Harris 15 is $4, and I have old bronze screws.

I took some fine sand paper and sanded it till it got shiny again. I suppose it could even be polished.

I had a stone in a dremel, that did work grinding on the hole till the glue holding the stone to shaft failed and it went flying.

See a machine shop for this part is not worth it. They charge $75 per hour, go figure, a new part is around $10-$15 off ebay.

I got an old thin sterling silver piece my grandkid who is 3 mangled. That I could cut into strips and use as welding rod for the torch.
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