Need to add a threaded vent to a tube.

Joined
Jun 27, 2021
I hope I am posting this in the right area.

I bought a used full scale 1841 Mountain Howitzer. It is a steel lined bronze barrel with a 3" bore. The outside diameter around by the vent is 6.2" The vent was a direct vent. The vent hole is getting out of spec in the .25" range. I need to have a threaded vent made and the tube drilled/threaded for the new vent. So I have a bunch of questions. Friction primers are the source of ignition.



What size vent plug should I use? Does 1" sound correct?

What thread is used? Straight or tapered?

Fine thread? Class of thread?

Material of thread? Copper?

Would the machine shop rebore the area where vent protrudes down in barrel to make it flush or just screw it down to flush?

Should be no problem to couture top portion of threaded vent plug?



The more info I have to give the machine shop the better off I am.

cannon1jpg.jpg
 
I hope I am posting this in the right area.

I bought a used full scale 1841 Mountain Howitzer. It is a steel lined bronze barrel with a 3" bore. The outside diameter around by the vent is 6.2" The vent was a direct vent. The vent hole is getting out of spec in the .25" range. I need to have a threaded vent made and the tube drilled/threaded for the new vent. So I have a bunch of questions. Friction primers are the source of ignition.



What size vent plug should I use? Does 1" sound correct?

What thread is used? Straight or tapered?

Fine thread? Class of thread?

Material of thread? Copper?

Would the machine shop rebore the area where vent protrudes down in barrel to make it flush or just screw it down to flush?

Should be no problem to couture top portion of threaded vent plug?



The more info I have to give the machine shop the better off I am.

View attachment 406244
There are several different approaches to this problem. They make a .25 sleeve to go around the friction primer which will tighten it up in the vent hole. Or putting a plug would work but that is a pain and you never know if it will blow as there is a LOT of pressure on the vent. Could you post a photo of the vent hole?
 
You are correct, replacing the vent is a job for a machine shop. I know of a set of drawing based on original specs. I will post them if I can get a copy.

When the vent plug was replaced on one of Stones River’s 1841 model 6 pdr’s we faced an unusual problem. The tube of the friction primer would stick in the vent after firing. Occasionally, we had to use a vent punch to knock it down into the breech. Until you get it shot in, you will want to search the vent after every round.
 
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You are correct, replacing the vent is a job for a machine shop. I know of a set of drawing based on original specs. I will post them if I can get a copy.

When the vent plug was replaced on one of Stones River’s 1841 model 6 pdr’s we faced an unusual problem. The tube of the friction primer stick in the vent after firing. Occasionally, we had to use a vent punch to knock it down into the breech. Until you get it shot in, you will want to search the vent after every round.

We have had this problem quite a bit. We had primers from 2 different sources ( one batch had red tops, the other black). We noticed that only the red top ones would stick. On examining the primer tubes, the ones that were sticking were made from tubing with an obviously thinner tubing wall. we also noticed that on the tubes that were sticking, the bottom of the tubes were flared out. It looks like when the primer was set off, it dropped into the vent hole and when the charge in the bottom of the primer tube went off, it flared the end of the primer tube. We have altered our drill so that after firing but before we worm #3 checks the vent with a brush to make sure it's clear and the primer tube did not remain in the vent.
 
We have had this problem quite a bit. We had primers from 2 different sources ( one batch had red tops, the other black). We noticed that only the red top ones would stick. On examining the primer tubes, the ones that were sticking were made from tubing with an obviously thinner tubing wall. we also noticed that on the tubes that were sticking, the bottom of the tubes were flared out. It looks like when the primer was set off, it dropped into the vent hole and when the charge in the bottom of the primer tube went off, it flared the end of the primer tube. We have altered our drill so that after firing but before we worm #3 checks the vent with a brush to make sure it's clear and the primer tube did not remain in the vent.
During a battery program at Chickamauga a non-park service gun had friction primer stick in the vent. They drove a small Phillips screwdriver into the vent… apparently, it fit right nicely inside the primer tube, spiking the gun. I had never seen that done & found it interesting.

When they had worn themselves out trying to extract the screw driver, a competent individual fixed it. He cut off the screw driver flush. He had to use a 2 pound hammer & a punch of proper diameter to drive it through. He really had to whack it.

We carry an authentic vent punch in the limber tray. Sometimes there is nothing like having the right tool for the job.

Historically, I read that they would drill a hole in the spike, thread it & seat a ring bolt. They used leverage to pull out the spike. Of course, to do a through job of disabling the gun, a long spike would be inserted & then a ball would be rammed down to clinch it & wedge the ball. That must have been a real pain to fix.
 
I'm not sure where you are located, but Steen Cannon could take care of that for you and it will definitely be done right.

http://steencannons.com
I tried to purchase a copper threaded vent plug from Steen. Called them and was told to send some info and pictures to an email address given to me. Sent email, waited 2 weeks emailed again and then I sent a text to their cell number with pictures and info. I guess they are real busy. So it is time for me to move on. I was willing to send the tube to Steen but they will only sell me the plug. I am back to square one.
 
There are several different approaches to this problem. They make a .25 sleeve to go around the friction primer which will tighten it up in the vent hole. Or putting a plug would work but that is a pain and you never know if it will blow as there is a LOT of pressure on the vent. Could you post a photo of the vent hole?
The sleeve becomes a part of the tube or added to the friction primer? Here is a pic of vent hole.

20210528_190539 (1).jpg
 
I tried to purchase a copper threaded vent plug from Steen. Called them and was told to send some info and pictures to an email address given to me. Sent email, waited 2 weeks emailed again and then I sent a text to their cell number with pictures and info. I guess they are real busy. So it is time for me to move on. I was willing to send the tube to Steen but they will only sell me the plug. I am back to square one.
Sorry to hear that. Our battery members have had excellent luck with steen. One of them had some custom ( and complicated) wheel repair done by them, but that was before the owner passed away. You could also try trail rock ordnance.
 
I tried to purchase a copper threaded vent plug from Steen. Called them and was told to send some info and pictures to an email address given to me. Sent email, waited 2 weeks emailed again and then I sent a text to their cell number with pictures and info. I guess they are real busy. So it is time for me to move on. I was willing to send the tube to Steen but they will only sell me the plug. I am back to square one.
If you have the plug, a machine shop can install it. If you think about it, delivery & return shipping costs will be steep. Any local shop can drill the hole & thread it.
 
Ranger Jim Lewis kindly sent me the specs from the new vent plug to our Shelly six pounder. Sometime in the distant past a very poor substitute had been installed. It was a disc about an inch thick. The machinist drew up the plan went to a lot of trouble to return Shelly to the proper form. The printed page is from the manual. You will be able to take your Steen vent plug & gun to a machine shop & have the job done. The 80 degree angle of the vent pitches the primer tube forward, away from the limber. & the horses.


Vent Plug #1.jpeg


Vent Plug #2.jpeg
 
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