Measuring the diameter of a cone

Hello,

I have a conical mandrel that is about 12" at the narrow end with a 5 degree taper. What is the best way to measure the diameter at different locations along the axis of the cone?

Thanks

Most questions like that are on Google, usually there is an app. Put in your variables and the answer comes up. Good luck. John

firm joint caliper and a scale will do the job.

Of course YOU LEFT OUT THE REQUIRED PRECISION! in your question.

I'm shooting for +/- .005"

Measure it on an optical comparator.

bw_4000 said:

Measure it on an optical comparator.

Click to expand...

A comparator with a 12 inch field of view would be rather special. (I would bet)

Really big gage spheres?

CalG said:

A comparator with a 12 inch field of view would be rather special. (I would bet)

Click to expand...

Why do you need a 12" "field of view"? You need 12" of table travel in the "X". Set your "X" zero at the tip and move down the cone measuring diameters at different gage lengths.

If it can be chucked up in a lathe a dial indicator can get you close. Set the indicator to some known diameter, maybe the diameter of the live center, and then you can accurately move in Z and comparative measure diameters along the length of the part. Provided you can get the indicator stem on Z0 of the part, on such a shallow taper the error would be small.

Derp. I was thinking female cone, not male.


Disregard earlier post.

I recently had the same problem except the taper I was trying to measure had grooves, o-rings, threads and a bunch of other annoying features that made it a lot harder.

I think the easiest method is to set it up in a rotator, like a spindexer if you have one that big, otherwise use a lathe.

Then you need a test indicator, holder and height gauge. Using the indicator you transfer the top and bottom to the height gauge to get the reading. On a lathe you can mount the indicator to the crossfeed. On a spindexer on a surface plate, you need a right angle block and a precision indicator base.

If you are very careful you could work inside the +/-.005” with a lathe, but in the past when setting a taper with real sample & taper attachment the machine almost needs adjusted to get it right after a trial cut. With grinders it's always check off the machine & adjust unless you have a mating master & blue it up. Is the 5° taper for draft or something, seems a bit large for a driving taper… Anyway;

Since the small end is 12” I assume you have a truncated cone that will lay flat on either end. I like gage blocks & 3/8” or 1/2” pins against the side on a surface plate & just OD mic over the pins. Take one reading @ 1/2” or 1” & then work your way up in whatever steps you like by stacking blocks & repeating the routine.

If all you need is the taper value then just jot the #’s down and do the math (this may tell you a lot about your machine or process BTW). If you need the dia @ certain distances then you subtract 2 x pin size.

The feeling & technique is pretty much the same as when using thread wires & a mic. I also very much prefer to do this with the small side of the cone down against the reference because things tighten up when you roll down with the mic set too small. The “feel” going the other way isn’t very good as it’s easy to lift the pins up the taper. I trust this as well as I do thread mic-ing with Van Keuren wires, which is pretty good…

A little practice you get faster, till then stay in the same spot until you can repeat the first measurement.

Good luck,
Matt

I would set it on my surface plate against a shoulder so it would not move and strike it with an indicator held in my height gauge.. move the height gauge with a 123 block or a gauge block set and strike again for .003TIR (+-.0015) or same and compare to a jo-block stack for .001... for .0003 I would blue it into a gauge mastertaper.
For only .005 (post-4) think a scribe mark and a good caliper would do fine perhaps using a loop to see the scribe lines...

+- .005 (.010) is almost an eye ball dimension with a scale and a loop.. *Having any machine with a .001 dial on two axis would be fine just mounting a test indicator and striking the part at one place then move the gauge amount and strike again. Yes take up slack to move only one way of zero on the dial so not including back lash..If travel in doubt you you may test the machine travel with a 123 block or the like. Yes a lathe, mill or surface grinder would do nicely to get closer than .002.

It is common to eyeball saw cut at .015 to the line.

A drawing would be nice.
Set it up on a B-port and 3 point plot the circles with a probe?
Might get there with gauge line block stacks and a mic or calipers if you know their corners are sharp but a .002 rad on the edge blows your .005.
Not sure what you are tying to do. Not real trusting here in using a Lathe, B-port or other machine tool as a measuring instrument.
CMM of course the easy way but who has money for that. 12" on small means a lot of standoff for a optical compartor so that is a bigger guy even though a 0.100 FOV will work just fine
You know the angle so just need small end diameter? Or do you question the angle also?
5 degrees per side or included? One is easier than the other to nail inside the 5 thou you want.