help with turning (or otherwise shaping) a small dome

[Jimsehr]

When turning brass, the top of the tool is always horizontal and roughly on center height. You adjust the tool rest height for that. When turning all other materials, the tool rest is lowered so that the tool is at about a 10-15 degree angle. As you say, its a feel thing but when its right, the tool cuts. I mean it really cuts, not scrapes. You will be amazed at how fast you can remove material with a graver.

In that thread I linked to there is some info on making gravers by WR Smith. Have a look.

sooo... I'd have to grind a form tool that is at least slightly over 0.5" wide cutting edge for a 1" dia round stock...
But I think that is pushing it for my little lathe and the little AXA tool holders you think ?

Or am I misunderstanding.[/QUOTE

sooo... I'd have to grind a form tool that is at least slightly over 0.5" wide cutting edge for a 1" dia round stock...
But I think that is pushing it for my little lathe and the little AXA tool holders you think ?

Or am I misunderstanding.

sooo... I'd have to grind a form tool that is at least slightly over 0.5" wide cutting edge for a 1" dia round stock...
But I think that is pushing it for my little lathe and the little AXA tool holders you think ?

Or am I misunderstanding.

sooo... I'd have to grind a form tool that is at least slightly over 0.5" wide cutting edge for a 1" dia round stock...
But I think that is pushing it for my little lathe and the little AXA tool holders you think ?

Or am I misunderstanding.

After reading post #5 I went out and made tool and cut shape on a 1 inch piece of alum. I used a 3/8 HSS tool that should work in your tool holder. It could be ground on a 5/16 tool if you like. I did this guicker then I could have using a graver. Plus I did not have to heat treat anything. bbaley is the part I made ,about what you wanted?

 

[mikey]

Hah, I forgot about Jimsehr. Should have just told you to PM Jim and have him whip a tool out for you!

 

[Jimsehr]

Hah, I forgot about Jimsehr. Should have just told you to PM Jim and have him whip a tool out for you!

He is welcome to use the tool I made.
Jim

 

[bbaley]

Jimsehr - yes thank you I did not forget about your post. I am pretty new to grinding my own tool profiles other than some pretty standard flavors - but I was contemplating this - in your previous post you mentioned might be "a bit much for a small lathe" which is what I have (a PM-1030V).

My goal with this is to use a steel that I can at least minimally harden, e.g. so I am not sure what I can get away with as far as such a large form tool - meaning I have to experiment and try it!

Question - what did you use to grind the profile of your form tool?
I haven't experimented with convex/concave/radii when grinding tools with that type of shape - specifically the concave part. did you dress/shape a grinding wheel or ?

As for the part you produced - yes, spot on....

 

[Jimsehr]

Jimsehr - yes thank you I did not forget about your post. I am pretty new to grinding my own tool profiles other than some pretty standard flavors - but I was contemplating this - in your previous post you mentioned might be "a bit much for a small lathe" which is what I have (a PM-1030V).

My goal with this is to use a steel that I can at least minimally harden, e.g. so I am not sure what I can get away with as far as such a large for tool - meaning I have to experiment and try it!

Question - what did you use to grind the profile of your form tool?
I haven't experimented with convex/concave/radii when grinding tools with that type of shape - specifically the concave part. did you dress/shape a grinding wheel or ?

As for the part you produced - yes, spot on....

You will never know if the lathe can do it till you try. If you have a back gear, I think it will work. How many parts do you need? PM me if you would like to try my tool.for free
And I just freehanded the tool on a plain bench grinder. But I have ground thousands of tools by hand. I’m old school and in my day you could not buy tools that are common now. And I often grind brand new drills before I use them. And also grind new drills to make them flat bottom drills. Where I drill holes without a predrilled starter hole. It took me years to learn how to do this. And 99% of the drills I use in my home shop are from the famous Harbor Freight drills. And I have never used a tool and cutter grinder.

 

[ttabbal]

Off topic but....

No man should ever go without a forge! even a tiny one.
here you go;

Thanks!

I've thought about building a little one with plaster/sand or maybe something like the larger ones with glass wool. I even have some O1 around that would be interesting to experiment with. I've never worked with the stuff, but it looks easy enough to deal with.

 

[P. Waller]

Hi,
I am just getting started researching how one might turn or form a small "dome".
By dome I mean not a full radius half-dome (ball end, etc)

but a convex shape for which the radius would be MUCH larger than the piece being machined.
The convex dome need not be a specific dimension with an exact tolerance.
I am imagining a piece of 1" round stock on which the end is shaped a dome where the center/highest point is maybe 2.5mm / 0.1"

My first thought was to make some sort of jig to hold a cordless drill that I could use on the belt sander - where the jig bottom plate had a bolt and a slot (cut with router and large circle jig) such that I could "turn" the part on this large sweep/radius... but I am figuring there is some lathe option possibly ?

I have seen lathe ball turning attachments and the like - but those seem a) to be for small radii , and also complicated to make (for me).

what would you do ?

View attachment 281473

You have not included the MOST IMPORTANT bit of data which is HOW MANY PARTS.
This is a 2 tool part, an OD/Facing tool and a parting tool, a mechanical screw machine from the 40's would knock out dozens of such parts per minute 24/7.
In your case it would be
Advance stock
Form tool
Parting tool
Done

Such a machine would beat the pants off of a CNC machine on such a simple part, if you only have to make a handful of them on a manual lathe then grind a form tool and have at it.