Rifling the 7" Treble-Banded Brooke Seacoast and Navy Rifle

[seacoastartillery]

     When we made the rifling head which holds the hook cutter of Swedish tool steel called   'FAGERSTA  WKE45', we had no idea that Brooke Slant-Hook Rifling was going to be superior to Parrott conventional square cut rifling.  The cutter was the result of endless computations, mock-ups and trial grindings.  To cut rifling in the trial tubes and first prototype, we used our inferior BIPICO BP 202 5% Cobalt  Made in India tool steel which required 3 sharpenings to cut a single tube VS the Swedish tool steel which cut 3 entire Brooke tubes, more than 2,400 strokes of 22" each on just the original sharpening. 

     We hope a few of you have some questions about the movie clip which shows a part of the rifling process which is very surprising visually and we hope, a bit provocative.  It provokes several questions in our minds, at least.

Other videos showing use of the rifling machine will follow as we learn to use the new Free-trial Video manipulation software.

Enjoy!

Mike and Tracy


The low-light condition of the clip is caused by the 600 frames per second speed of filming, Not the fact that we didn't pay the electric bill last month!  A 100 watt bare bulb was just 5 inches away and the whole ceiling is loaded with fluorescent troffers, hence the background flickering.  Click on image.

[RocklockI]

Nice little chip spray ! 
Gary

[dan610324]

the fagersta wke 45 is probably one of the best tool steels in the world today
its an molybdenium - tungsten high speed steel with a minimum of 11% cobalt
I guess its a tiny bit better than the indian steel 
the manufacturing company is located in an small town called fagersta located just 20 miles from me
but I got a chock when I checked the prices , 1 piece of 1/8 X 5/8 X 6" is more than 30 dollars
I guess that all my boxes with that steel is worth something today 

is the cutting edge at the lower part of the bore and the chips just comming up from the square hole in the tool ?
no oil ??

[GGaskill]

Quite interesting for only 41 seconds.  You should put some witness lines on the shaft so the rotation shows more.  Can't really tell it is rotating until the cutting head shows up. 

What causes the bounce as the head finally exits the bore?  Seems like it is opposite to what I would expect.

[dominick]

Can you get chatter if the bit dulls or is it just more difficult to draw the bar?  I saw a demo of a rifling machine at the Cabin Fever Expo and it looked as if he had a problem with it.

[rampa room artillery]

very cool,  but is that the only pics we get for now??   why so secret ?
   

[Soot]

why so secret ?

To keep the Yankees from stealing the technology.

[seacoastartillery]

    Thank you Dan!  Look everybody, there is some new information about our choice for rifling cutter tool steel.  Very interesting, Dan, and only 32 km away from your house.  FAGERSTA WKE45, fellas, if you ever need a long lasting cutting tool, this is the steel to make it from.  Dan, the 'How to Make a Rifling Machine' thread with all the photos and diagrams of the Rifling Head internal construction is in the Forum Stickies, but temporarily unavailable,(I checked today).  When it becomes available agin, you can go there to page four and look at the drawings and see that all the cutting is done bt the cutter which protrudes out of it's slot which is just in back of the chip recess.  Enough cutting oil is brushed on the Rifling Head body, just prior to running the tool into the tube and bottoming it which sets the cutter height and then retracting the tool from the tube during it's cutting stroke.  Gary, you are right about that, quite a spray!  Just one more reason to wear safety glasses ALL the time in the shop.  Dom, it is definitely more difficult to turn that chain drive hand-wheel when the old bits got dull.  Chatter, in our experience, has more to do with cutter geometry, mainly rake angle, than anything else.

     Thanks for that suggestion, George, maybe we can paint some lines on that shaft next time.  I'm really glad someone noticed that bounce of the Rifling Head after it emerges from the bore.  We will explain why it does that below the following two photos:






     The reason for the bounce is simply a lack of solid support of the Rifling Head weight after it leaves the cannon's bore.  The reason we did not provide any is more complicated.  In the upper photo you can see a rectangular steel pillar at the tube's end.  This was originally designed to be dual-purpose.  It was supposed to block the tube from being drawn to the right, out of it's two, greased, carbide-faced, V-Blocks and indexing collar.  It performs this function today.  Also it was supposed to support the Rifling Head after it came out.  We decided it would have to be a very complicated assembly, with extremely close tolerance parts to do this job correctly, especially if different sized heads were used which they are.  Also we were concerned that it would perhaps be an obstacle and possibly cause a hump for the head to go over if it were sized just .0001" higher than the bore's bottom.  This could cause the cutter to dig in near the muzzle, the most critical area of the bore.  Not good.

     In addition, you can see that the two inches of tube near the muzzle is turned so it can fit that bearing block for the gundrilling, chamber drilling, and reaming operations, (Reaming Op. is shown).  We added two extra inches for these ops and the muzzle-end clamping during the rifling operation.  These extra two inches are cut off after rifling is complete, so that any rifling irregularities due to the head being unsupported can be discarded.  The bore is indicated and centered with a 50 millionths test indicator during the last bore related operation, that of crowning.  We make a 45 deg. crown, carefully cut with a razor-sharp, left-hand, lathe bit, held in the compound.

     That's about it.  Thanks Soot for your comment, That, of course, is the real reason.     Rick, please re-read our first post's last sentence; the answer you seek is there. 

Mike and Tracy

[dan610324]

my father lives in fagersta 

[Soot]

When you cut the rifling, are all passes of the tool the same direction, breech to muzzle, or is it reversed every pass?

[seacoastartillery]

     Soot,   Another good question.  Our next video will show the adjustments made before each of the seven grooves are cut to the next depth of cut.  Both of the adjusters are forward of the Rifling Head body, and the  'Waterfall Cut Actuator"  is adjusted with a slight rotation of that 10-32 Cap-Screw head you see trailing the Rifling Head body as it comes out of the bore in the movie clip.  The other adjustment is a 'Hook Cutter' depth adjustment which moves the hook out by .000140" (one ten-thousanth and 40 millions of an inch) each time the seven grooves are to be cut to the next, depth of cut.  This is done by rotating a serrated steel disk on the 10-32 screw in front of the tool.  Each groove is cut a little bit deeper after the head bottoms out in the bore, pushing the adjusted screw and disk back against the front end of the Rifling Head body, actuating the adjustments. The actual cutting of each groove, in turn, happens only on the withdrawal stroke. 

Mike and Tracy

[Soot]

So before the rifling head is withdrawn, it is adjusted to the new depth.
That's how I thought it worked, but what I don't understand is how does it simply not deflect the tool until it is withdrawn some and given a chance to start cutting?
It seems that you would end up with tapered rifling, with nearly none at the breech end because of deflection. That's why I thought the tool was reversed at the end of the stroke so you would get the full depth of cut all the way back to the breech end.
Hold on.

The rifling head fits snugly across the lands to prevent deflection and the depth of cut is so shallow that the tool just cuts in.
I should have paid more attention to the now inaccessible rifling machine thread.

[Double D]

I should have paid more attention to the now inaccessible rifling machine thread.

None of the threads are inaccessible, they are all still there.  Right now you just have use the search function to find them...Matt is in the process of writing a redirect script to fix the problem.

[Double D]

http://www.gboreloaded.com/forums/index.php/topic,108012.0.html

[Soot]

Thanks for the link, I'm only semi confused now.
I guess the rifling is tapered.

[seacoastartillery]

   Take heart Soot!  Mike and I were completely confused by this hardest part of the rifling to visualize, to design tooling for, and to actually cut effectively.  In short, rifling a blind hole ain't easy, until you get all the learning curve behind you.  Making the Rifling Head assembly and it's parts, especially the Hook Cutter geometry took the better part of 6 months and the testing and improvement phase took at least 4.  Making the structure of the machine was easy and only took 2 months to accomplish.

     Thanks to Double D.'s link to the A to Z Rifling thread, we are able to post the 3 diagram/drawings that explain how the Rifling Head works.  The 'splainin', (Rocklock1 lingo), is done via captions.

Tracy and Mike


This first diagram shows you the only tapered portion of the rifling.  It extends from the forward edge of the bore dia. chamber to a point only a bit more than one-half inch from there.  The remainder of each of the 7 grooves is all at the same .0231" depth.  After the test barrels and first prototype, we changed the depth of each step in this 'Waterfall Cut' to .00014" rather than .00022".  This made it physically much easier to pull the cutter out of the bore, but also increased the number of strokes to over 800 per Brooke tube.




This drawing shows how the adjustment to the 10-32 Cap Screw of 1/6 turn advances the Hook Cutter toward the muzzle .0052 for each new depth setting in the 'Waterfall Cut'.  The hook cutter position changes when the screw head goes from the forward, hook cutter retracted position to the back position where the serrated flange is tight against the front of the Rifling Head body.




The notched wheel is rotated 2 notches from top dead center to adjust the Hook Cutter's depth for each step in the Waterfall Cut.  This adjustment is also made before the head is run into the bore and is actuated by the gentle impact with the chamber bottom.  More than 100 of these adjustments are made.  Any further questions will be answered after I get back from the annual town Easter Egg Hunt with J. whose basket will be full, I'm sure.   

[gulfcoastblackpowder]

I'm not sure if this was asked or answered yet, but I'm assuming by the looks of it, and by the versatility of being able to cut different amounts of rifling for different applications, that this is a single cutter design.   I think you said that it cuts from the breech to the bore, so this makes me wonder how you handle indexing the start points of each groove so they are uniformly distributed around the bore.  I guess maybe you have a nifty trick using some feature of the lathe?  I know each one wouldn't start at the same point as it ends, because that would be straight rifling, which isn't very common.

[rampa room artillery]

my question is why did you choose to only cut one grove at a time?  ken kurt cuts his fullscale liners all the groves at once.    all three groves for a parrot at once and so one for other guns.   didnt know if there was a reason?

rick bryan

[seacoastartillery]

     Gulfcoastblackpowder,   You are correct, it is a single cutter machine, please remember what I just explained about going to a shallower cut to make pulling the cutter through it's 800 strokes.  A Hook Cutter bite .00014" deep is much easier to pull than a bite .00022" deep even if it means more than 100 extra strokes.    Indexing is facilitated by a precisely made indexing collar that is bolted to a rear journal that is oversize compared to finished cascabel dimensions.  The following pic shows how very precise indexing is accomplished.


Here is the 9 position indexing collar for the 100 Pounder Parrott Rifle.  The collar is accurately turned on the lathe for a running fit onto the tube's rear journal and then 9 accurately spaced holes are drilled on the mill with the collar centered on the rotary table which provides 40.000 degs. of separation for each hole.  A 60 deg, countersink is used at each position to accept the same shaped tip of a powerfully, spring-loaded, position-locking bolt.  For each new groove, this bolt is withdrawn and the tube rotated to the next indexed position on the collar, then locked again.  We use a dedicated, home built, Rifling Machine to do rifling of artillery bores, not a lathe.

I know each one wouldn't start at the same point as it ends, because that would be straight rifling, which isn't very common.

     That's right, what you described would be 'straight rifling'.  Some experimental shotgun tubes have used it, but we have no idea if it was effective.  And we have created very short runs of it in Parrott tubes, because they are 'Progressive Rifling' or 'Gain-Twist Rifling' which starts out straight at the point of tangency between the large radius of the curved, arc-segment,  sine bar and a line parallel to the bore axis and quickly turns tighter and tighter until the final, stabilizing-twist is achieved at the muzzle.  The Brooke has straight-twist rifling at a rate of one turn in 55".  The sine bar is straight, so you start with 1 in 55" and end with 1 in 55".

my question is why did you choose to only cut one grove at a time?  ken kurt cuts his fullscale liners all the groves at once.    all three groves for a parrot at once and so one for other guns.   didnt know if there was a reason?

rick bryan 

     Rampa room artillery,    For our first Rifling Machine, we chose to concentrate on making it as accurate as we possibly could so it would cut very accurate rifling grooves in the tube which had been gundrilled extremely straight and reamed smooth, with a consistent, precise size so they would shoot well when a precision size and weight bolt was fired in them.  We just didn't want to complicate things with hydraulics and making vastly more intricate, 'broach-style', or ‘poker chip-style' cutters with multiple cutting teeth.  Remember, our machine is man-powered with a mechanical advantage of only about 3 to 1, hand-wheel dia. to chain-drive, sprocket dia.  All of these considerations, combined, are the reason, Rick.

Mike and Tracy

[rampa room artillery]

very cool, ok, i thought you had a hydraulic powered unit.  hand powered, that makes it take longer but have more control over the rifling.  no wonder your cuts are so small at a time. and take so many pulls on the machine. 
  very cool,

rick bryan

[seacoastartillery]

     We figured maybe we needed to get the breech of the Brooke rifles shaped before we spent too much time on a rifling movie.  This very careful machining results in a hemispherical curve that starts within the reinforcing ring area, not at the breech reinforce face.  The reverse radius is tricky too and would be almost impossible to do without 2 full pages of numbers from a computer program.  All the lathe cuts are done manually after rotating the cranks to move the lathe bit over a little and down a little as the tube is spinning.

Tracy




The excellent Excel program can do it all and generate all those numbers in about 20 minutes as you plug in your distance,  depth and degree dimensions.  We make a cut for each degree in the two quadrants required ( one large radius and a smaller reverse radius) or 180 degrees total.  Microsoft Excel is great, we used it all the time when we were aerospace inspectors.

[dominick]

Mike,  Now I see how this works better and this is very interesting.  You had mentioned the Excel program back during your visit in 2008 when we were discussing radiusing breech OD's. These are 2 dimensional cuts, X & Z ?  Do you first make a rough cut to eliminate excess material or do you remove each layer entirely with either the X or Z dimension?

[seacoastartillery]

     Dom,     When we turned the lights off in the shop, Mike was talking to Gary who is quite windy on the phone.  I will take a stab at your question.  As assistant to the 'Master Machinist', I am allowed to do this.   The axis parallel to the spindle axis is always Z, whether it's a mill or lathe.  For the lathe, the axis that controls the diameter is always X.  So when we turn a radius on the lathe like that big, o.s.r. (outside spherical radius), we move the end of the tool path away from the breech ring in a +  -Z- axis direction and away from the existing surface in a +  -X- axis direction. 

     All material is thus removed a little bit at a time using depth of cut and end of cut, dimensions generated by the computer program for Radii which we wrote using the Microsoft Excel software.  There are no stair-step, roughing cuts, necessary, except the conventional left-hand tool, surface reducing cuts to waste the material above the hemisphere shape to be created.

     With the tube rotating at low RPM, a 6", medium, half-round, second-cut, file removes the minor ridges left after the lathe work is complete.  This takes but 5 minutes.  This is a low-tech method we use to do this work, but when you only make 4 or 5 cannons a year, it makes good financial sense to forego the fancy computer assisted lathes and mills.

For our low volume operation, this method is accurate and efficient, as well.

Tracy

[dominick]

Tracy,  Thanks for clarifying the X - Z direction.  I also see that from the start measurements on the Excel sheet.  I like to try this method.  I don't have an accurate measuring device for my lathe's bed travel.  I may experiment with the hand crank on the lead screw along with a dial indicator.  Don't own a dial indicator either.  I now have an excuse to buy one.       Thanks for the info.  Dom

[seacoastartillery]

     Dom,   To try one out, you could always move your lathe's compound  slide so it's parallel to the -Z- axis and use the graduations on that crank along with those on the cross-slide.  We have used a 6", .0005" Grad. Travel Indicator to do precise linear work on our Mini Lathe and it works great while magnet mounted on the farside flat way with the tip against the tailstock side of the saddle.  Eyeballing the barrel of the indicator probe parallel to the backside way's edge is plenty accurate considering the trigonometry of any possible error.

     Now, if we can get you to take another 4 hour coffee break when we next see you, you can teach us to be expert welders!  Then, the possibilities are endless; we can be super-cannon makers!   

Tracy

[dominick]

I like the 4 hour coffee break!  I'm NOT an expert welder though.   

[dominick]

Turning the compound slide will work.  I do that when cutting a taper and there is enough travel to cut a complete curve.

[seacoastartillery]

     I finally found time to edit and organize the clips of rifling operations on the 1/6 scale 7-Inch Treble-Banded Brooke Seacoast and Navy Rifle.  There are four short clips posted below and, despite their being shot by a beginner movie-maker, they impart some pretty important information.  The more general shots are in the first two clips and the last two get up close and personal with the details of the sine bar, follower and the rack, also the all-important, Rifling Head adjustments.

     If you have any questions we will provide detailed answers.  If there is enough interest we might be talked into providing other clips on requested topics having to do with rifling cannon tubes.

Mike provided error-free operation of the machine while my filming and commentary can only be described as 'dorky'.

Tracy and Mike


An over-all view.   Click on the image to display these clips.




A little closer to the action.




A close-up of what the follower does.  It follows the sine bar and drags the rack to the left or right, rotating the pinion gear and the rifling head shaft, imparting twist to the grooves.




Some dialog with this clip attempts to answer a few basic questions about rifling.  No rehearsal here!  Just raw footage!  The dialog ends abruptly here.  My fault.  I cut it off a bit too short and the remainder of the dialog went on to say, "which creates a 1 in 10, 1 in 22, or 1 turn in 55" twist which is what the Brooke rifle has."  Our 1/6 scale 100 Pdr. Parrott Rifle has a gain or progressive twist going from zero to 1 turn in 36"within the length of the tube.

[keith44]

Ok, you may have already answered this question, and I just missed it.  You are cutting one groove per pass correct? With the set-up you have and the number of rifling lands you are after would a button type rifling cutter not work faster? (note I did NOT say better)  or is the number of lands compared to the bore diameter preventing the use of that type cutter on your tubes?

[seacoastartillery]

     Keith44,    When Mike and I started rifling cannon tubes in 2004, there was quite a bit of information on cut rifling, but very little of it was very practical.  There was no information available on how to rifle cannon size bores except the large naval cannon of 12 to 16 inch size.  Today there is a lot more out there on small bore rifling, but still very little on rifling 25mm to 40mm tubes. There may be some article somewhere about button rifling bores larger than 50 cal, but we have not found it.  Roto forging is used to produce small to medium sized modern tubes, but requires a nation's military budget to afford the equipment.

     The hydraulic equipment required to push or pull large carbide buttons through 1.000 to 1.500 inch bores is way beyond our budget and understanding.  Cut rifling is much easier to understand and can be done by hand which is our preferred method.  It produces the most accurate tubes; (Krieger Rifle Barrel Co.) has proved that and is by far the least stressful method for producing grooves.  Even broach cutters stress the barrel because of the hydraulic pressure necessary to force the multi-tooth tool through the tube.

     The last reason we use a single point rifling cutter is the fact that, with our production of 5 or 6 cannons per year, it would be silly of us to try and save a few hours on tube rifling.  The difference in cost would be not worth any consideration. 

Besides there is a lot of satisfaction to be had when you walk down to your 100 yard target and find a five shot clover-leaf group of less than 2 inches, from a table-top cannon!!.............  Accuracy is our goal and we persue it vigorously and singlemindedly. 

Tracy