Making reamers and cutting radii

[gitano]

As mentioned here : http://thehunterslife.com/forums/showthread.php?t=16720&page=2 j0e_bl0ggs sent the radius cutter to me that he bought, troubleshot, and fixed. FedEx brought it last night, and after a few minutes on Skype, I was out in the shop making my first "pointed rod" - the start of a point forming reamer.

JB had been particularly unhappy with the device from the moment he received it, and he was also more cautionary about what to expect from it than he usually is. He was right. The best that can be said about it is that is will allow one to cut radii in round stock.

That said, that is a big deal. There is a world of difference between "can't do it" and "can do it but it's a challenge to get it right". One CAN DO IT with this tool. And, it can be done with some level of precision with respect to the radius of the ogive. In other words, if you want an ogive with a radius of 8 calibers, you can "do the math", and get the device set up to get 'pretty close'.

You can only get 'close', because the way the device sits in the lathe and the spatial relationship between all the various pieces - headstock, rod, toolholder, tool, etc., it is darn near impossible to get a "nice" smooth cut. You can only get close with a fairly rough finish. By the time you get finished with file and sand paper, you will only be "close" to where you calculated the radius of the ogive. Fortunately, "close" is good enough when it comes to ogive radii.

Here's a picture of my first effort. This is an 5.66 caliber radius for .358 caliber that started out to be a 6 caliber radius for a .338. I started out calculating the ogive radius by using .338 - the caliber and DIAMETER - then multiplying by 6 for a radius of curvature setting on the device of 2.028".



That point is on the end of a 3-foot, 0.375" rod. I was going to part the point off, but that "spear" looks kinda cool. :D

Anyway, the device works, and I thank JB for working out the problems with the original, fixing them, and giving me the thing. I WILL be making point forming reamers AND round-nosed jacket drawing punches with it.

Paul

[drinksgin (deceased)]

It can cut a secant but is there a modification to cut an ellipse?

[gitano]

I wasn't thinking about the math between tangent and secant ogives. The way I presented the math in the first post suggested a secant ogive, but I was kind of bassackwards with all of it. I have corrected everything now I think. I don't know how it would be modified to cut an elliptical profile other than an elliptical cam on the rotating axis.

Paul

[drinksgin (deceased)]

Hum, I thought a tangent was just a point.
I was confusing a segment of an arc with a secant, which is really the same as a chord, oh well, it has been too many years since geometry classes,about  55 or so.

[gitano]

This explanation is fairly succinct. http://www.accurateshooter.com/ballistics/tangent-vs-secant-vs-hybrid-ogive-bullets/

Paul

[drinksgin (deceased)]

I seem to recall a device in mechanical drawing class,( we actually drew with pencil and ink), that would generate an ellipse, it had several arms and pivot points.
If it could draw one, seems it could be built to use a bit rather than a pencil or pen.

[gitano]

Here's a 6R .338 point. That's the good news. The bad news is that it is in 12L15 steel, not tool steel. 12L15 cannot be hardened meaning that this piece is no good for a reamer. However, I knew that when I made it. I wanted to work in some "machine" steel and see if I could work some math out. I did.

Finer cuts - 0.005" max - and this "machine steel", and I didn't have to use a file to start the finishing. I just went from 220 to 400 to 600.  It's pretty, but essentially useless other than exercise.



Paul

[gitano]

One can draw an ellipse with two nails in a board and a string tied in a circle with a diameter larger than the distance between the nails. I couldn't turn that into a machining tool. However, you very well might be able to. :)

Paul

[j0e_bl0ggs (deceased)]

The foci needed for an ellipse (or even partial ellipse) difficult to achieve in this type of tooling, now with CNC dead easy!
The secant ogive cut is just the position of the centre of your radius in relation to the cut you make.
I.E. you do not start or finish your cut in the same position as the 'tangent', your start or finish point will be 'behind' the cut see following picture with hi-lighted 90º line;

[j0e_bl0ggs (deceased)]

Well done Paul, points look good, now need make some reamers for real....
Did not notice any 'red' so must assume sticky out bits are all still intact?

[gitano]

Yup. Still got all my fingers and toes.

I just got some Biopar stuff dumped on me, so I will give the actual reamer making some time to 'percolate' before diving in.

I need to get some stock for die bodies and get a burr that will give me a proper taper into the jacket drawing die so I can make some the dies to draw the .43 and .45 caliber jackets to .338.

Also trying to get boat back to sea-worthy for spring bear.

Plate is over-flowing.

Paul

[drinksgin (deceased)]

I suppose you use small salmon for bait, how heavy a line and how long a leader do you use?
Trolling or sight casting?
;<)

[gitano]

Actually.... I bought the boat primarily for bear hunting. Only about 40% for fishing.

In the spring when the bears come out of their dens, the snow is still deep except on the shoreline, so they come down to the shore to eat grass and seaweed. You can spot them 'cruising the beaches'. Used to be, you could shoot from a boat whose motion due to a motor has completely stopped. However, since the powers that be decided that no one was stopping their boats before shooting, they made it illegal to shoot from a boat. So now, when you spot a bear, you have to land the boat before shooting the bear.

In Prince William Sound - where we will go first - the bag limit is one black bear. On the southern end of the Kenai Penninsula the bag limit was changed last year from "no bag limit" to "six per year". I intend to take as many as I can get in my sights and the law allows. I'll be using the Remington Classic in 8x57 loaded with ANVB bullets.

Paul

[drinksgin (deceased)]

Oh, I thought you were fishing for bears.

[gitano]

Here's the next 'installment' on making a reamer.

This is a 'true' 8R, tangent, .338 point in drill rod.



As usual a photograph shows things you can/don't see with the unaided eye. Those scratches on the nose are not visible to my unaided eye, before or after the picture was taken.

Next step is to cut it 'in half' to make a D-type reamer. Then to the kiln/oven for heat treatment - hardening and then tempering. Maybe I'll get the profiling done tomorrow.

I cut this from the first .358 point I made.

Paul