Roundness

[Powder keg]

Hi, I just finished a new toy for my lathe. A large radius attachment. This cut my time in half on this opertion. Once I figured out how to use it. I can do up to a three inch radius with my new attachment. I was taking cuts .05 deep without any trouble.  The barrel is a Beer can mortar that I am building for someone. I might build a larger one later, maby?

[intoodeep]

It amazes me to watch the projects and progress of any of these cannons. To look at the technology that we have today and the creativity to do a project and make fixtures for each. I can't even fathom the thought of doing the originals over 140 years ago. My hat goes of to those who create and can re-create..... :grin:

[Cat Whisperer]

Looks good, dude!

I like the offset for attaching the lever-arm - to keep out of the way of the work.

Is the board underneith for extra support?

What did you use for bushings/bearings on which to turn?  Looks like a good quality bolt with a sleave.  

Slick use of the cylinder on which the cutter holder rides (for up-down movement).

How about a pix or two detailing the tool holder mechanism?

Does it seem like I've accumulated enough steel (stainless 1/2 plate) to build one?

[gary michie]

I like the way you transferred some of the cutting pressure down to the ways. I use a 8D Holdridge radii-cutter and I get a little chatter if I push it. If you can put your cutter in the vertical round bar you'll be able to cut concave and convex.
 gary

[Powder keg]

Hi, The attachment chattered a bunch And the 2X4 fit purfect. I can cut innies and Outies, but not full innies. I tried for a ball mold. I can't get a full concave radius. The bushings for the pivot are tapered split brass bushings. I can tighten them up. I'll post some pictures tomarrow. I got the plans out of a Home shop Machinist mag. Later

[kappullen]

PK,

That is a good tool you have built. You mentioned ball mold cutting tools some time ago I believe.

I made this tool some years ago when asked to make a couple of ball molds by some nssa guys.
To do balls as you know, the pivot pin has to go into the bored hole.
When built, I had a Monarch lathe with a big square turret.



The bar mounts on the far side of the turret, and the old home made lathe milling attachment on the
Headstock side.   Moving the milling slide rotated the cutter head by the link connecting the two.
This could also be actuated with a bar from the tailstock.



This piece of junk was built in a couple of hours using excess tooling and junk with the welder
and a little milling.

The pivot pin can be set from the face with a parallel and depth held with a long throw indicator.
The center has to be adjusted by comparison of depth and diameter.
The tool block has a couple of reamed holes to cut different ranges of holes.



I did do a couple of ball molds but finally had to get a real job at the instrument company.

Reinactors are seldom happy with what you do for them. They wanted molds to size and round
within a couple thou.

I sent them to a cnc shop.

They say (probably true) that molds have to be spherical on the outside as well as the inside.
Theory is that a square block mold will draw more heat from the corners of the molten balls
than the thinner areas causing out of round balls.

Using your tool and mine, we may be able to make a good mold.

Cheers

kap

[Powder keg]

Thats a cool tool!!! Need one for the bottom of my mortar barrles :wink:  I wonder if ther is room to do that? The angles would have to be diffrent to get a full swing in the bottom of the barrel.  You got me thinking again Kap.

[Powder keg]

Been thinking of rounding the bottom of bores. Kaps neat little gizmo has a limited depth I think. mabe a worm gear arrangment might work? The tool would hook to the crown gear and the worm would have a shaft exiting the bore, with a hand crank on it. It works good in my head  Guess I'll have to add this to my to do list. Thanks for sharing your wealth of knowledge with us Kap!!!

[Cat Whisperer]

Been thinking of rounding the bottom of bores. Kaps neat little gizmo has a limited depth I think. mabe a worm gear arrangment might work? The tool would hook to the crown gear and the worm would have a shaft exiting the bore, with a hand crank on it. It works good in my head  Guess I'll have to add this to my to do list. Thanks for sharing your wealth of knowledge with us Kap!!!

There's potential there!  I was just thinking the same thing - take a gear of smaller diameter than the bore, mount a cutter on it and put it at the end of the boring bar - using the teeth of the gear to rotate it the 90 degrees needed to  radius the bottom of the bore.

[kappullen]

Guys,

Thanks for the compliments.
This is all old knowledge and I don't claim to have thought of any of  it.

Before the invention of cnc machines, the machinist, and toolmaker
had to devise many innovative solutions to problems that can now be simply programmed away.

I started this trade just when the nc tools were being introduced so have  been lucky to have known some of the machinists that won ww1, ww2 and korea (draw?) without that cnc stuff.

There is still info on doing things the old way in republished books and manuals.

Check out this site!

http://www.lindsaybks.com/

This site has a wealth of information for the home machinist, and home foundry operations.
You could, should put him on your resource list.

cheers,

kap

[Powder keg]

Here are a couple more pictures of my radius attachment. There is a close up of the pivot bolt with tapered split bushing. and a close up of the tool clamp.