Ways to bore a cannon barrel

brasssmanget

brasssmanget

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I am working on a steel cannon and have managed to drill into it the full needed length of 15.50" - but only with a 7/16" extended drill. Took quite awhile going .50 " at a time and then clearing chips and re-lubricating with cooling juice. My problem now is how to complete the larger bore size to that length? I stepped up with a 5/8" / then 1" / and finally a 1.125" shorter drill getting in almost 6.0" total, but all these larger drills are very short, and I'm not sure how to extend them safely. Boring bars might be an answer, but right now at 7/16" I have nothing long enough or small enough to fit into the existing hole. Any ideas / suggestions on how to proceed with this task would be appreciated. I'm working with an older Heavy 10 with a 4' bed, so reach is not an issue as long is any tool doesn't exceed 16" - but I would thing there would be a lot of flex in a boring bar that long and narrow enough to work in the existing hole....

Thanks in advance....
 
I have an extension I made for a S+D drill that is just a piece of 3/4 round stock drilled to 1/2 on one end with 4 set screws to hold the drill shank. 2 set screws in line and 2 at 90 degrees. Mine is 6" but you could be made any length needed. Then the other end is turned down to 1/2 for the drill chuck.
once you get to the 1.125 size then proceed with a boring bar.
 
brasssmanget said:
I am working on a steel cannon and have managed to drill into it the full needed length of 15.50" - but only with a 7/16" extended drill. Took quite awhile going .50 " at a time and then clearing chips and re-lubricating with cooling juice. My problem now is how to complete the larger bore size to that length? I stepped up with a 5/8" / then 1" / and finally a 1.125" shorter drill getting in almost 6.0" total, but all these larger drills are very short, and I'm not sure how to extend them safely. Boring bars might be an answer, but right now at 7/16" I have nothing long enough or small enough to fit into the existing hole. Any ideas / suggestions on how to proceed with this task would be appreciated. I'm working with an older Heavy 10 with a 4' bed, so reach is not an issue as long is any tool doesn't exceed 16" - but I would thing there would be a lot of flex in a boring bar that long and narrow enough to work in the existing hole....

Thanks in advance....
Click to expand...

I used a Plumber's/electrician s extended 3/4 drill bit here is how I did mine:
http://www.practicalmachinist.com/vb/south-bend-lathes/cannon-barrel-boring-266384/




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Thanks for the replies. rgray what you suggested is just about what I had been contemplating. I guess I just needed to hear someone else say it too. :tranquility: I am definitely leaning that way, but will wait for any other ideas that may arise....
Jeffers thanks for your link. I had seen that while over on that forum awhile back and was impressed. You did a fine job on that project. I am a little worried about too much chatter - may have to go with idea #1 to ease my concerns....we wil see, and I will keep the thread updated....
 
I've used Sterling gun drills with great success, but I don't believe they will work with a predrilled hole. You might consider a core drill, or it might take 2 to get to your size. They have a generous blunt, non-cutting center and are expected to be used only to enlarge existing holes.

If you choose to make an extension for a twist drill, try to turn the shank back far enough to get into the back end of the flutes. You will have less problem getting coolant in and chips out. Yes, it does get harder as you remove the MT if that's what you start with, but it can be done. Or you can gouge out some semblance of flutes in what remains of the smooth drill OD with an angle grinder for the same purpose. It doesn't have to be pretty to work.
 
I spent some time working up an extension today - had to remove the cannon body from the 3 jaw to work on the bar, so I'm continuing with other parts before re-chucking the large piece - for now anyhow.....
I will have to manufacture a sleeved front end to slip over the front as I had to turn that part down to fit my steady rest - only accepted 3" or less Diameter....bummer.....
 
This all sounds exciting but your pics are not showing up?!
Robert
 
I might be able to help you, I have a piloted step drill that is 1.25 OD and threaded for an extension shaft, overall length is about 14" and I would be willing to loan it to you. I made it for a job and used it once to drill a 30" bronze cannon barrel back in 1979. If interested let me know and I'll see if I can find it.
 
Rick Berk said:
I might be able to help you, I have a piloted step drill that is 1.25 OD and threaded for an extension shaft, overall length is about 14" and I would be willing to loan it to you. I made it for a job and used it once to drill a 30" bronze cannon barrel back in 1979. If interested let me know and I'll see if I can find it.
Click to expand...

I really appreciate that offer, and I am actually very interested in at least seeing a picture if you have one available. Sounds like an interesting drill. I am going to try my extension and see how successful that is - if no luck I will contact you about your offer.
 
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