Gallery, Projects and General > How do I??

How do I measure a spindle taper?

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Pete.:
I would use the two balls method and draw it in CAD. Use the measuring tool to get the angle.

AdeV:
Thanks again all for the useful (and surprisingly varied!) techniques on offer. I've seen the 2-ball method used on Youtube - albeit in a taper cut in some ali, not a spindle nose, but the theory's the same, just keeping your balls securely in the hole could be an issue  :lol: sorry...rude...

Anyhoo... now that I'm happy with my measurement of 0.6"/foot, or 50 thou per inch, the next question is.... how accurate do I need to be with my cuts? I've mounted a DTI on the lathe, set the approx angle, reset the DTI so it's parallel to the bar & measured, fiddled, measured, fiddled rinse & repeat for the better part of an hour, and now I'm within 1 thou per inch, according to the DTI. However, if I grab hold of the compound and twist it, I can induce more than 5 thou +/- error... presumably this is down to worn gibs. I've tightened them up a bit, to the point where the handwheel is getting a tad stiff, but I can still twist it and produce an error. So, the question is, what sort of accuracy will I get away with? I'm sure I could keep going and get "dead nuts", presumably I'll be OK if I only take very light cuts & maybe squidge the gibs up a little more?

mattinker:
I think it's a sort of try it and see. cut a taper, blue it and see where it's transferring! You can adjust with emery cloth!

regards, Matthew

AdeV:
Just a quick update on this one..... So, I set my topslide over to measure 0.050" per inch to cut the taper, cut the taper which came out very nicely thank you (lovely smooth finish on the ali). And, as some of you will have already realised.... at completely the wrong taper of 0.1" per inch!!!  :palm:

Then I had a 2 week holiday.

Having a spare few minutes the other day... I tried my new taper out & discovered my glaring error. So, back to the topslide, re-set for half the previous angle, as measured with a DTI on some freshly squared up stock. Cut the new taper, crossed fingers & clenched backside, removed the chuck, cleaned out the spindle tube & popped the freshly cut aluminium taper jobby into the spindle. A sharp tap with the plastic hammer seated it beautifully, hurrah! In fact, it took some fairly hefty beating on the back face to get it back OUT of the spindle!

I blued the spindle with some Stuart's Micrometer Blue, and popped it in again. And when I did finally managed to smack it out, it looks like it's contacting all the way around for a good 2", so I'm going to call that "good".

Whacked it in again, faced it & turned down the outer diameter so it's running true, and drilled a 1/2" through hole (I'll open that up a bit further yet), but this leads to my next question!

What's the best way to cut a decently accurate internal Morse Taper (#3 for what it's worth)? The idea is this sleeve will convert my spindle to MT3, so I can mount my ER32 collet chuck, ideal for holding smaller stock, and hopefully a tad more accurate than my 3-jaw chuck. In fact, I'm hoping it'll prove that the part wobble/unconcentricity I seem to suffer from all the time IS in the knackered old 2nd hand chucks I've got, which will persuade me to part with some hard-earned & buy a new chuck...

AdeV:
I should have added...

It looks like there's 2 main methods: 1) Topslide at correct angle, boring bar, go for it; or 2) buy a set of MT reamers and use them.

MT reamers are around £30 from China, so I've no problem with that (but wish I'd thought of it the other week while I was actually over there, damn!)

I've got a small boring bar which, albeit with some scary stick-out, would probably get deep enough into an MT to hold the chuck.

PS: I only took light skim cuts, but I drilled straight through @ 1/2", and the taper held so well I didn't need a drawbar or any other form of workholding. Although I was scared for the entire operation...

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