drilling a hole 12inches deep???

   / drilling a hole 12inches deep??? #1  
M

muddstopper

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been trying to figure out how to drill a 2in hole, 12inches deep in some round stock. I have a lathe, but no drill bit that size. Dont have a drill bit that will reach that far except for some aircraft bits, 3/8 I think being the larges size. Thinking about making a drill bit extender and drilling starter hole and then going with boring bar, but my boring bar wont reach 12inches in a hole. I can probably flip the piece and drill/bore from each end, but even 6in deep is a lot of peck and drill and the biggest hole i can drill is 1in. Without resorting to buying an expensive gun drill that would only be used once, anybody have any suggestions. any way I do this, it seems its going to be a long process
 
   / drilling a hole 12inches deep??? #3  
2" annular cutter in the lathe, flood cooling. Not sure what you can use to extend it once you're out of tailstock travel, but the bit itself will be kept aligned by the hole so it will not need to be real rigid, just push the bit and keep it from rotating.
 
   / drilling a hole 12inches deep???
  • Thread Starter
#4  
I thought about the tubing, but steel supplier didnt have any correct size in stock. As for the annular cutter, I've never seen one that could drill 12in deep. And I dont have one anyways. I did consider drilling the hole to 1 in and then using hole saws to cut out to size, but it would mean constant swapping of hole saws of different sizes since the hole saws I have will only cut about 1 1/2 deep. If I can get the hole big enough for the boring bar to fit in then I can probably just swap ends to get the full 12in's
 
   / drilling a hole 12inches deep??? #5  
You want to drill a 2" hole 12" deep in steel with only what you have on hand? Good luck :)

As I said, with an annular cutter you would kneed to extend it once you're out of tailstock travel. It's as simple as a 3/4" ID DOM tube with two set screws drilled 90 degrees apart.

Hole saws at 2" in solid steel are a pain in the ***.
 
   / drilling a hole 12inches deep??? #6  
You could probably make a 2" drill bit by brazing a high speed tool bit crossways on the end if a shaft that will fit in your boring bar holder. Sharpen it so it works as a spade bit. You'll need your 3/8 pilot hole first, and a 2" starter hole to help center it. I've drilled 5" holes in aluminum with flat bottom spade drills, but they weren't homemade. Interesting machining challenge.
 
   / drilling a hole 12inches deep??? #7  
go to Enco, buy a Chinese bit, Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies or MSC https://www.mscdirect.com/?cid=ppc-...41&006=27864417304&007=Search&008=&025=c&026= .

and then if you have a lathe make an extension holder on the shank so one can go up to 12 "

you will have to drill 1/2 may be 3/" of an inch and back it out,

pre drill with a smaller bit for a pilot(3/8 to1/2"). a 2" bit will have a hard time if there is not a pilot hole for the center of the bit,

and if this need some precision you may be better off getting some DOM tubing /shaft any machine shop worth it salt should be able to get for you. (DOM= Drawn Over Mandrel)

and or if the tube only needs some precision on the ends put in some bushings on a pipe, you say you have a lath.
 
   / drilling a hole 12inches deep???
  • Thread Starter
#8  
I was able to predrill the full 12 inches with a 1/4in aircraft bit. Took a while, but it just barely reached thru. I have drilled one end out with a 1in drill bit filpped it and am now drilling the opposite end. The 1in drill isnt going to reach in the middle. I most likely will make and extention to accett the 1in drill bit that will get me a 1in hole all the way thru. My boreing bar is 3/4dia, I havent measured the lenght bt it should b long enough to reach if I flip the piece. I did have a bit of run out with the 1/4 drill bit, not a lot, but enough to be noticeable. I think once the hole is bored using the boring bar, it should true up. 'This hasnt got to be real precise, but I cant wallow around either.

I know i can buy the right size drill and dom tube, but I have to order it and I am wanting this bushing now.
 
   / drilling a hole 12inches deep??? #9  
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   / drilling a hole 12inches deep??? #10  
Buy the high quality thick wall tubing from McMaster Carr, Metals Depot, or other supplier. It will be cheaper than any bit. Other than that, why not use the lathe and a boring bar.
 
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