Optimum Vent hole size?

[carmy53]

With so many cannon barrels being sold without the vent hole being drilled I was wondering if there is some sort of formula for deciding how big a vent hole to drill? 

[Cat Whisperer]

Approximately 1-1/2 times the diameter of the fuse being used works. 

[Artilleryman]

If it is a lined barrel, a vent piece should be installed to provide a continuous passage.  If not a gap can erode in the vent passage between the liner and the barrel which could be potentially dangerous. 

[carmy53]

Approximately 1-1/2 times the diameter of the fuse being used works.

What I mean is - what size hole is optimum for a particular size bore barrel?
 

[carmy53]

If it is a lined barrel, a vent piece should be installed to provide a continuous passage.  If not a gap can erode in the vent passage between the liner and the barrel which could be potentially dangerous.

The barrel is not lined.
 

[GGaskill]

what size hole is optimum for a particular size bore barrel?

As small as possible commensurate with the fuse fitting easily.  Or the friction primer.  For loose powder (not recommended), 1/8".  Can be bigger with full scale bores.

[Mike H.]

As small as you can reliably drill without snapping off the bit and ruining the piece because you can not get the tip back out.  I have snapped a lot of 5/64 bits recently.....   

[seacoastartillery]

     For cannons with wall thicknesses of 1.500" or less we prefer the No. 46 drill bit which drills an .081" dia. hole.  This allows us to use either the 1mm or the 1/16" dia. fuse.  Why drill a larger hole and waste the powder pressure generated?  2.5" deep holes of this size can be drilled with aircraft length, No. 46 drill bits. 

Tracy

[Double D]

I make my vents for my Golf ball mortars and larger all .177 diameter.  This size will fit the  quill and most friction primers as well as the 1/8 inch standard cannon fuse.  Most cannon fuse sold is  1/8 inch.
 
Some where I saw a rule of thumb for making the vents, equaling 1 1/2 times diameter of the fuse. The reason given was so the that you could be sure that the fuse could be fully inserted inthe charge. That should not be an issue if you properly worm the vent

For years the only fuse we could get was the 1/8 inch green cannon fuse. It was used with most  model cannons sold and with out any concerns reports of lost of pressure. 

When you get into the smaller cannons under 45 caliber then you might have some concern about pressure lose with the bigger fuse.  The smaller firecracker cannons for  example would better served with the smaller pyrotechnic fuse of 1/16 inch.

A good source for cannon fuse is Cannonfuse.com.  They are located in Montana and give excellent service--same day or next day shipp via U.s. Mail.  They also have in the past supported our cannon shoot here Montana.

Before you drill your vent determine where you are going to get your fuse its size and drill for that size fuse.  It won't do you any good to drill a small vent hole for a  small fuse and all you can get is larger.

Some thing else to keep in mind is the burn rate of the fuse.  Standard green cannon fuse burns at the rate of 30 seconds a foot.  There is faster fuse.  You will need a longer fuse with fast fuse to get your self clear  before the cannon fire.

Lately I have been using FFFFg intstead of fuses in the SAMCC gun with good results.

[flagman1776]

 

[Cat Whisperer]

AND when you drill, go very slowly at the end of the hole.

IF you hit the curve at the bottom of the bore, it is likely that you'll break a bit.

Many of us have experienced it.

[shred]

FWIW,  I just got done running down some fuse for my micro-seacoast mortar and found 1/16" fuse can be somewhat tricky to source.  I ended up ordering off a link posted here that worked, but going to the main site didn't show the 1/16" size at all.  At least I have 300' now

[Ex 49'er]

FWIW,  I just got done running down some fuse for my micro-seacoast mortar and found 1/16" fuse can be somewhat tricky to source.  I ended up ordering off a link posted here that worked, but going to the main site didn't show the 1/16" size at all.  At least I have 300' now

Was that the link for Pyrocreations?

[Double D]

Here is the link to Pyrocreations fuse page. http://www.pyrocreations.com/ignition___fuses

Here is Cannonfuse.com  fuse page.  http://www.cannonfuse.com/store/pc/viewCategories.asp?idCategory=2

1/16" in fuse is the 1.8mm size.

[shred]

FWIW,  I just got done running down some fuse for my micro-seacoast mortar and found 1/16" fuse can be somewhat tricky to source.  I ended up ordering off a link posted here that worked, but going to the main site didn't show the 1/16" size at all.  At least I have 300' now

Was that the link for Pyrocreations?

Yeah.  I couldn't find it in a regular run around their site, but there was a link posted here that worked.  Some older posts suggest e-mailing them to be sure in advance of ordering which is probably a better idea.

My next stop was the 1.8mm if I couldn't find 1/16" anywhere as I wasn't sure they were the same and I drilled the touch hole a tad tight.  Are they actually both the same size? 

[Cannoneer]

1.8mm is slightly larger than 1/16". I recently got 65' of 1.8mm premium green Chinese visco from CannonFuse, and it burns 32 seconds per foot (good stuff).

[carmy53]

Ok, I've ordered some .116 green visco fuse. I'll wait until I get the fuse to decide between drilling a 1/8" (.125) hole, a 5/32" (.15625) hole or a 9/64" (.140625) hole.
What is the best drill bit to use for drilling a steel barrel? Cobalt, carbide, titanium or something else?

[GGaskill]

What is the best drill bit to use for drilling a steel barrel?

With the exception of carbide which will drill harder materials (requiring more down force also), they will all work.  The important thing is procedure; let up on the down pressure when you feel the drill breaking through the bottom.  Also, don't let the chips accumulate in the drill flutes; take the drill out frequently.  It is worth a little more drilling time extracting chips versus trying to extract a drill broken because the chips jammed.

And should you break the drill in the hole, there are places that specialize in removing stuck bits using an electric discharge machine.  Don't give up an expensive work piece just because you stick a drill or tap in it.

By the way, I don't mean to say that carbide won't work; just that it is not necessary for this application.

[Mike H.]

And if it starts to chatter or chirp, STOP and clean the bit and hole thoroughly. That is just before breakage.  I have had much better luck with titanium nitride in the tiny sizes  The cutting tip seems to say cleaner.

[Cat Whisperer]

...
What is the best drill bit to use for drilling a steel barrel? Cobalt, carbide, titanium or something else?

Keep you speed up.  Speeds and feeds - the key to smooth cutting and long tool life.  There are charts per material and size of bit for the recommended speed and rate of feed.

(General rule of thumb is for the smaller bits to be turning faster.)

[flagman1776]

Use cutting oil.  I got mine from Browell's. 

[irishman]

The multiplier is .03937. ie. 1.8 MM X .03937=.0709, which is what we recommend for our barrels 50 Cal and less. We cut a 3/32 (.093) fuse hole and it works great. We recommend 1.4MM on our micros fitted with a 1/16 fuse hole.
 
                                      Michael

[flagman1776]

 

[carmy53]

This is no longer an issue for me. I have shipped my barrel to one of our sponsors to have him drill the fuse hole for me.

[little seacoast]

Smart move.

[flagman1776]

 

[RocklockI]

For the guns I make @ .075" - .080" ,it's really not that big a deal . But then again I like 1.8mm or 1/16" fuse .
 
Gary

[flagman1776]

Better too small a vent, than too big. 

[Double D]

I wish the vent on my signature piece was a bit smaller, but it's not enough over to mess with it.   

Why? Aesthetics or function?

[flagman1776]