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Discussion Starter · #1 ·
Hallo folks,


I screwed up. Rather a friend of mine screwed up while I watched him.


I got a hern iron works barrel (good piece by the way) with a steel liner in a cast 6 pounder, a 2/3 scale.


Went to drill a vent hole, and we missed. It's behind the breach by 3/8". I don't think it ever reached the steel, but I'm not sure.


Then he went ahead and drilled a second hole where it's supposed to be, and got the 1/8" drill bit broken off inside.


I can deal with a broken drill bit, but what do I do with this second hole? Have I rendered it useless? If I cut the hole all the way through and screw a fine thread bolt into it, will it be good? I don't think I could bring myself to shoot it live fire, but will it be good for a blank load?


Don't tell me what I want to hear, just say it as it is. I already think it's unsafe and that I just made the biggest paper weight money can buy. I don't say that lightly because it's hard earned money and I could barely afford to buy it in the first place. The lesson I've learned is always take it to the professional. If I'd brought it to the gunsmith I talked to and he screwed it up, he'd be paying the $800 bucks to replace it. I brought it to a friend of a friend who does maintenance and has a few tap sets and a lathe. Dumb idea.


Oh, and it's supposed to be shot off at a wedding on Saturday. Specifically my wedding....


Thanks for the help
 

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How deep did you drill? Did it come out the other side?
Seriously, I don't think the wrong vent is a big deal. Upsetting as ****, but not serious. Spiked guns & guns with worn vents had them plugged & redrilled back in the day. I see no reason you should not do the same.
Drill it with a proper tape drill size, tap properly with a bottoming tap, epoxie a bolt in, cut it off, grind it smooth. You could even weld it over & grind again.
Now, you know that a lined barrel should have a vent liner. Originals were copper. I used a SS 5/16" cup point set screw, center drilled it in the lathe, threaded it in the hole until it bottomed into the liner. For 1/8" fuse (with needed clearance) I used a #29 drill about 0.136" for the vent but I like a tight vent for the size cannons I use. Some prefer 9/64" = 0.140
 

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Find a soft iron rod the same diameter as the drilled hole. Drive it in and peen it flush. File smooth, paint.

Fuse or vent holes are supposed to be 1-1/2 calibers in diameter. Standard 1/8" fuse needs a vent hole no less than 3/16".

Large and full scale guns use .200 vent.

There seems to those who feel the need for to small a vent. This practice requires close attention to vent cleaning, and can be hazardous if not done correctly.

To tight of vent makes fusing harder and short fusing and the possibility misfire increase.
 

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Your big problem is going to be digging out the broken drill which is hardened tool steel, lottsa luck with that. Your problem is one that i have worried about over the years having drill many touch out, so" far" i have not had your problem.
 

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In the past I have used a punch on a broken drill bit or tap. Find one that will just fit the hole, insert it untill it touches the the broken bit and give it a right smart whack, this should shatter the bit so You can blow it out. If You can find a good welder with a cutting torch he may be able to blow the bit out.
 

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Discussion Starter · #9 ·
Eh, like I said, the drill bit was't an issue. We went on to get another drill bit stuck after that.


Right now the plan is fill the hole, put a bolt into the already threaded top portion, and green locktight.


Here's some "in process" pics
 

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I sure hope you mount that barrel so the trunnions are over or slightly to the rear of axle. The trail will kick up when fired the way the barrel is resting now. The axle housing looks pretty weak also.

I also hope those are not the actual wheels you are going use. The wheels shown have no strength and will come apart very quickly, perhaps at first shot.

For this pattern of gun and carriage, I suggest you Google British 6 pounder and click on images to see what this carriage should look like.

A very helpful book for this type of cannon is John Muller's Treatise on Artillery, available as an e-book.
https://books.google.com/books?id=v...Al6#v=onepage&q=Treatise on artillery&f=false
 

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I'm sure you are past this point now but the broken bits may have resulted from less than optimum technique or equipment. If you are using a hand drill, that can change its alignment easily and break a bit. I'd never want to drill a vent freehand unless it were the only possible way. Best to use a drill press that you and position over the vent and fix in position so it won't move relative to the workpiece. Other advantage of drillpress is variable speed. Metals including cast iron should be drilled at a low rpm-you can find charts on the web that tell you speed to drill cast iron for various drill diameters, the rpm used is much slower than you would use to drill wood, for example. Also don't use more feed pressure than needed to advance the bit; too much feed pressure that may be a reason for broken bits, cast iron is soft relative to drill bits and the bit can bind up in the cast iron under excessive feed pressure.
 
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