Measuring conical register?

[chap]

Over the years (often when i've been swapping the chuck on the lathe) i have wondered how you can manufacture the register into the back of the chuck to fit the conical upstand on the spindle-nose.

Say i wanted to produce my own face plate or the like, how would i measue the 'nose and get some measurements?

My first instinct is that i could use two peices of ground bar on opposite sides of the cone, that sit tangentially to the cone and also the face (at the base of the cone), then i magically sprout 6 arms to hold this against the spindle-nose and i could somehow mic. across the outside of the bars to give me a value.
Next, cut the conical pocket undersize in the blank material, use a pair of ball bearings the same diameter as the bar, hold these on opposite sides of this pocket and somehow measure the distance between these (6 arms again), account for the dia of the ball/bar and this would tell me how much meat is left to take off.

Does this sound feasable, or even make any sence?
Is there a standard way to do this in industry?

Cheers
Nathan

 

[Tigman]

I`ll pass on that one

 

[chap]

lol
I've not needed to cut a conical taper yet, but when i do...

 

[brightspark]

lol
I've not needed to cut a conical taper yet, but when i do...

clock the taper up with a dti gauge on the topslide

 

[piman]

Hello Nathan,

I'll expand on Brightspark, as I assume he's thinking as I am. Set your cross slide as close to the taper angle then check and adjust by running the clock pointer up and down the taper until it stays at zero over the length.
Do this on the back of the taper as this will then be right to machine the taper. If you do it on the front you'll need to swing the cross slide to the same reading but opposite angle which could give some error.

Alec

 

[brightspark]

Hello Nathan,

I'll expand on Brightspark, as I assume he's thinking as I am. Set your cross slide as close to the taper angle then check and adjust by running the clock pointer up and down the taper until it stays at zero over the length.
Do this on the back of the taper as this will then be right to machine the taper. If you do it on the front you'll need to swing the cross slide to the same reading but opposite angle which could give some error.

Alec

thats a better explanation for anyone that doesnt know what a d t i gauge is.= dial test indicator . it measures runout on on shafts ect . i should have elaborated

 

[graffian]

I have made several spindle mounted tools. Here's How I do one.
To turn the taper set the topslide like mentioned above, you want a Verdict type indicator.
Look at the figures for the spindle in machinerys handbook[think that's where I found it], I did check my spindle and it seemed bang on the printed figs for D1-3.
Mount the blank on a face plate, face both sides and taper bore to size.
Measure the depth of the bore then chuck two ball bearings in the hole and measure the bore between the two ball bearings; do bit of maths and figure out the size of the bore, I have just made an educated guess with a digital caliper and got it within a few thou.
If your confident with your measurement aim for bang on size; I aim for a for a thou or so over then try the blank on the spindle. If the taper bore is oversize measure the radial clearance if it's undersize measure the axial clearance with pairs of feelers.
Do a tad more maths[if you had radial clearance] and wack it back on the face plate and face it off to make it to size, I try and make it so I have to face it, rather than bore it as it saves time.

Is that understandable?

The measuring is like you say. Measure the diam over two ground cylinders, and then you need to measure at another position in an axial plane, either a spacer under each cylinder or two larger cylinders. Trigonometry is your friend.

 

[MrFluffy]

Interesting :-
http://books.google.co.uk/books?id=...crometer#v=onepage&q=taper micrometer&f=false

 

[chap]

clock the taper up with a dti gauge on the topslide

I knew that!

Looks like Graffian has done it the way i was thinking.

 

[brightspark]

I knew that!

Looks like Graffian has done it the way i was thinking.

even though its not as easy as it sounds if the tools a few though out of center height the taper will be wrong and need fine adjustment to corect

 

[Pete.]

Set the top slide to the correct taper using a dti, then fit a chuck and use the top-slide to turn a taper on a piece of scrap to mimic the spindle nose. Use this as a gauge when you are making your backplate/faceplate.