Thread: Measuring angle/diameter of a bottomed internal taper

I know normally id measure internal tapers with gage balls, but this taper is too large and i dont want to try to source 3" balls. How would you go about measuring the angle and the diameter at the small end of the taper? I figure i can make a tapered plug to check diameter(i would size and angle the plug using two rings) but whats the best way to accurately measure the angle of this bore? The tolerance is only +-30' but i'd prefer to be able to reliably measure it within ~5'. The print should be attached. This is just a personal project for myself as a newer machinist so I would like to execute it as precisely as possible

Sine plate

Originally Posted by Booze Daily

Sine plate

Lol thanks now im having a "duh" moment. Just stack the blocks for the sine and indicate the low spot at two points in the taper to ensure parallel with the base, right?

Yep. Though in this case you may want to clamp your part to an angle plate so your gage block stack isn't so high.

Cool, thanks again!

Re angle then a sine bar is best. Re the bottom diameter of the taper then that won't be as easy. What do you have available to measure with?

Jeez! This is a cavity in the bottom of a bench block. I would measure the angle with a protractor. I would get the big end diameter as close as I could with calipers and, if necessary calculate the dia. at the small end. Anything else is a wast of time.

Originally Posted by Illinoyance

Jeez! This is a cavity in the bottom of a bench block. I would measure the angle with a protractor. I would get the big end diameter as close as I could with calipers and, if necessary calculate the dia. at the small end. Anything else is a wast of time.

I suggest you look at the drawing. While you're at it read the OP.

What the OP wants to do and what you suggest are two very different things.

Originally Posted by Gordon B. Clarke

I suggest you look at the drawing. While you're at it read the OP.

What the OP wants to do and what you suggest are two very different things.

A great example of over tolerancing a drawing.

Find someone with a CMM? if not, remember you need to be on the exact centerline of the taper to get an accurate measurement- being off center has a huge effect on the angle you will measure.