Math for making baffle on lathe, help please

[mr fixit]

Questions, part the first:
As a matter of fact, math is not my strong suit. I bet this is likely very simple but apparently so am I.

What I need to figure out is how much to move the saddle, or compound if that is a better way to do it, in order to make a baffle with a specific thickness.

For instance, I have a piece of 17-4 in the lathe. I have drilled the center hole and used boring bars to cut the inner surface of the baffle. I have a little chatter, but overall looks pretty good, a nice 60* cone. Now I need to work on shaping the outside of the baffle. So I need to figure out how much to move the carriage in order to make the wall thickness .100". This will be the blast baffle for a direct thread can.

Is there a formula for figuring this? I bet there is and I bet it involves trig. I never had trig, only algebra and geometry.

Question, part the second:
On a related note.....My lathe is a 12" Logan Turret lathe (2537). I don't have DRO's. When I move the carriage left or right, is there any way to tell how much it is moving? The cross slide and compound have dials, so I can see that, but how do I measure the travel of the saddle?

[fishman]

Trigonomerty or CAD. Take your pick.

Draw your baffle and give the known dimensions and I can do the trig

[T-Rex]

CAD FTW

As far as carriage movement sans DRO's, there are a couple easy ways.
1) Layout fluid the exterior and use calipers to set distance lines
2) Mount parting tool and use caliper's depth gauge to measure an offset from the tailstock end of workpiece
3) Use a carriage stop micrometer and bars of known length

[yondering]

There are lots of machinist apps for smartphones that do the trig for you. "Machine It" is one I use, but there are lots of them.

[ECCO Machine]

I don't have DRO's. When I move the carriage left or right, is there any way to tell how much it is moving? The cross slide and compound have dials, so I can see that, but how do I measure the travel of the saddle?

Spend $80 on an Igaging DRO for Z and stop wasting time doing it the hard way and making mistakes.

[mr fixit]

I don't have DRO's. When I move the carriage left or right, is there any way to tell how much it is moving? The cross slide and compound have dials, so I can see that, but how do I measure the travel of the saddle?

Spend $80 on an Igaging DRO for Z and stop wasting time doing it the hard way and making mistakes.

Great advice there. I plan on doing that, when finances allow

As far as the distance, I was able to figure it out. Turns out, with 60* sides, the wall thickness is double the carriage (right left).
So, 1.face the end and hollow out the inside of the cone at 60*
2. move the saddle to the left (toward the headstock) double the thickness of the cone's side wall
3. contour the outside of the cone.

[fishman]

I've done work on a lathe that didn't have a dro or a dial. The bed had a sliding stop with a dial adjustment and 0.001" increments. What a giant PITA.

[MoNkEy]

These magnetic dial indicators can be stuck in places and used to measure carriage and cross slide movement. They're pretty cheap, sometimes I drop them and don't feel bad like when I drop a Mitutoyo indicator.
http://www.shars.com/magnetic-indicator ... -indicator