Math Question

[Uncle O]

Anybody have a cad program that could whip me out an answer ?

Material .063" thick. 82* countersink, upper dia .307" lower dia. .197"
If you dropped a .3125" ball into the countersink, how much of the ball would be protruding above the surface ?

Material starts out at 3/16" thick, but gets milled down to the .063" dim. from the opp side, down the length of the part (15")
The lower Dia. of the countersink is +.000 -.005 .If the lower dia. tolerance is blown, the part is scrap. At .063" the material is too bendy to clamp in the vise and too springy to drill reliably, so the countersinks have to go in first, then mill, and still keep my fingers crossed that I haven't over-tightend the vise and cause the part to deflect while milling, scrapping the part.

With the ball height I can at least reliably set the CS depth, then worry about bringing in the thickness.

Any help appreciated
kerry

[torker]

Just curious why you can't clamp a 1/2 thick plate in your vise...then clamp the part to that. That'd get rid of the bowing you'd get from clamping the part in the vise.
Russ

[toastydeath]

I did it by hand, but my numbers seem to check out. I'd scan my papers for somebody else to proof, but I don't have a scanner. Maybe try this out on a scrap piece?

To get a .197 +.000/-.005 bottom diameter:

From the .1875 plate, drill .3005-.2979 deep with an 82 degree countersink.

When you drop the ball in, it should stick out .0940-.0966 above the plate.

To adjust the drill depth for a varying plate, just add or subtract the difference from .1875 from all the tolerances.

[Evan]

Sounds like a gear door.

[Astronowanabe]

countersunk BB protrusions

I am eyeballing .21802 on the big side and .03148 on the small side
unless I am misunderstanding the question.

ah ... that it the protrusion *after* it is .063 thick

[Paul Alciatore]

I did it with CAD as you asked.

First, with your dimensions for the lower diameter and thickness, I get 0.306" for the upper diameter.

I drew both limits for the lower diameter (0.197" and 0.192" and the corresponding countersink for each. So I have the limits for the upper protrusion:

0.2181"

and

0.2210"

I hope that helps.

[Mekanizm]

I agree with Paul Alciatore.

I did it on CAD as well.

[Forrest Addy]

I didn't do the math but it appears the first two responses forgot to add the ball radius to the center height above the work surface.

[aostling]

Ah, trigonometry, so much easier than the blasted income tax forms I'm also struggling with today.

[clutch]

I used your numbers.



Sorry, didn't dimension the 0.063.

Clutch

[Mekanizm]

Clutch,
Why not 82 degrees exact? Maybe I don't know the truth about an 82 degree countersink?

[clutch]

You gave the upper and lower diameters. I used those values.

Clutch

[Mekanizm]

I see now. Thanks. Just wanted to make sure that 82* wasn't a 'nominal' for something else (I learn a lot of things the hard way )

That was the O.P.'s numbers and it looks like round off on the .307. I used the smaller diamerter hole with tolerances and the countersink as the controlling variables. Just carried everything out to tenths because his ball was specked in tenths.

p.s Clutch, How did you get the CAD drawing into the post? Cut and Paste or something? Sure helps with clarity.

[clutch]

Well I used a pdf printer driver that outputs pdf files. Then I selected and pasted the image in the pdf file into irfanview and saved it.

Pictures worth many words.

Clutch

[Mekanizm]

Thanks Clutch

I have saved this procedure so I can go try it.