Truing trunions

[rusty barrels]

I can see on guns that are lathed its a matter of just welding them on but in the case of cast guns how are they machined since they are already a part of the barrel?

[freddo]

 Thats a question that has always bothered me.I did think about jigging them up vertically in a mill and machining them with an adjustable boring bar but i have never tried it.I too would like to know how.

[Tropico]

On cast cannons with a trunnion poured in place I find it easiest to use a caliper and find the diameter then get a pipe that is the same or a little bit bigger (not much) then carefully use a die grinder to smooth any casting lines., (Better than a die grinder is a 50 grit sand paper and rubber disk for your drill) that is a bit more controllable and still fast. when the pipe can spin fairly smooth I can weld on two ears for bolting to the carriage. Many times I will use a pipe a little longer than the trunnion. This allows me to build the carriage from heavier guage wood for a more buffed carriage.  I hide the shorter trunnion by welding a cap on the end of the pipe. Now this trunnion cap allows me to grease pack it. Especially useful for the cannons on our boat as well as the sea wall wherethey are exposed to salty weather.






I hope this helps. For me it simplifies my life. Provides a greased maintenance free trunnion and altho is not exactly correct., its close enough for most and out weighs most because of the benefits.

[GGaskill]

The following is all speculation but reasonable speculation. 

A good casting is good enough for a block mount since the barrel is essentially unmovable.  Since these things weren't turned out by the hundreds per day, there was enough time to use hand tools and templates to get them round enough, even for those which were adjustable for elevation.  The models of 1861 with centered trunnions were more amenable to machine finishing since they were a lot closer to being balanced than the early end trunnion style.  Look at saved ones to see if there are center holes in the ends of the trunnions which would point to lathe turning.

[guardsgunner]

The trunnions on original guns were turned.  The barrels were mounted to the side of a wheel of sorts which was turned with the cutter comming from the side.

[freddo]

Thats a good idea Tropico.I tried the pipe thing but I welded two ears to the sides and then tried to split the pipe to form a cap square and bearing surface-made a complete balls up of it -Hard to believe that it never occured to me to just weld one ear as you did and leave it.Too focused on authenticity I suppose.All a waste of time because the solution that I eventually adopted to get the fit that I wanted is not authentic anyhow.But I did get a fit that I am more or less satisfied with.
   I shall post a picture of the finished result That is if [god willing] I live long enough to get a finished result.
Making my field carriage has been something of a 'Pilgrims Progress' although I have encountered  more 'sloughs of despond' than Bunyon ever dreamed of.

[Michael Az]

They could easily be done on a vertical mill {Or horizontal}. You would set up the barrel, with the trunnion pointing up. Then just a matter of centering up the trunnion to the spindle and use a boring head with a boring bar to make the cut. I'm just saying that's how I would do it with what I have.
Michael

[freddo]

I think thats the way I would do it Micheal.I would also set it up in a dividing head to get  both trunnions true to each other.

[Michael Az]

Yes, the dividing or a indexing head will maintain your 180* apart and be sure to set up the barrel with the bore horizontal to the mill table and the trunnions will be true {90*} with the bore.
Back in the old days when there weren't any mills and lathes they had files and craftsmen. Amazing what they could do with a file!
I remember reading that when Holland and Holland gun company wanted to take on an apprentice they would give the young man a round piece of steel and a file, ruler, and square. He had to come back with a 1" cube.
Michael

[freddo]

A good sharp file is a precision cutting instrument and in the gun trade it was  a seperate trade-a man so occupied was a called a lock file Holland and Holland would have expected their lock files to work to a tolerance established by the thickness of a layer of soot left on the work by a smoky candle.One can only do accurate filing by watching the play of light on the cuts.I cannot file well it takes a bit of practice -like half a lifetime on the one tool.

[CU_Cannon]

I would have to say that the file is the most abused tool in the shop.  There are very few who take proper care of their files and even fewer that can use them well.  I have heard of German apprentices being given a ball bearing and a file and expected to make an accurate cube.

[GGaskill]

Wernher von Braun told of his first "training" in the machine shop.  He was given a file, a square and a large lump of steel and told that when he had produced a cube (must have had a scale too), he would be trained on using the machines.  When finally achieved, the cube was much smaller than the inital lump.

[freddo]

It is not too difficult to produce a cube accurate to within a thou by filing.I have done it.
What I find is impossible for me to do is produce a cube of desired or nominated dimensions.