How do I measure a spindle taper?

[AdeV]

I'm getting fed up with the runout in my chucks, it's impossible to get anything even remotely re-centred, and even if you do the chances are it's at a funny angle, so whilst I can work fine so long as everything can be done without having to turn the workpiece around, as soon as one needs to reverse a part to finish off the backside, it's all out of true.

I'm 99.9% sure the problem is a worn out chuck - all my chucks are second hand at best, and quite bashed about & worn, so it's not entirely surprising they're past their best. The final solution will be to buy a new chuck.... but that'll have to wait a few weeks until I can raise sufficient spare funds.

So - in the meantime, I'm pretty sure the spindle taper is an MT5: I've got an MT5 to MT4 sleeve, and MT4 to MT3, and my ER32 collet chuck has an MT3 arbor on it. Put them all together, and I should have a super true-running chuck 

Er, no chance. Seems the spindle isn't MT5 after all. So.... question is.... how do I measure the taper? Given that it's deep into the spindle, which is only a couple of inches across at best..?

[seadog]

I would use two DTIs. One to measure longitudinally and the second to measure radially.

Set one square against the plate and the second bearing onto the start of the taper. Advance say one or two inches and take the readings. You can then easily calculate the taper per foot and look in tables to find which taper that corresponds to.

[AdeV]

Presumably the DTI which goes up the spout (so to speak) has to be a finger type? The problem being I've only got little ones of that style, send them an inch up the bore and I'm not sure i'm even going to be able to read the dial.... Also, wouldn't it need to be dead nuts on centre to read accurately?

I had wondered (earlier today, long after I wrote that message) whether I could use my telescoping bore gauges:



Send into the bore, lock, extract, read; return it to the bore, advance one inch (or two, or whatever), lock, read. The hard bit of course, being to return the gauge to the exact same point between readings... which I think I can do by throwing together a tool holder for my QCTP.

[seadog]

Yes, it would need to be a finger type. I've an old Starrett plunger type that has a lever arrangement so would be capable of going in an inch or so. It definitely has to be bang on centre.

The problem with the telescopic gauge is that the contact area won't be along the axis of measurement.

Rethink - maybe that won'k matter, the error will be the same since the contact point willstill be the same at any point on the taper. It may just work, but you'll need to clamp the gauge bang on centre and will still need an accurate way to measure the depth.

[AdeV]

Centre height is easy enough for me to manage - I can use a dead centre in the tailstock to sort that; has to be eyeball, but I'm assuming that once I'm pretty close to the taper, the numbers will suggest what it really is (e.g. if it's 4.007" per foot, one can be reasonably sure it's actually 4" per foot... for example).

I don't need to be cock-on the centre of the taper (so long as I'm on centre height), as the arms of the gauge can expand independently, so as long as they're contacting on centre height, the reading should be good.

I'll use the compound slide to measure my inch, it's got a decently graduated dial, and about 6" of travel.

[Pete W.]

Hi there, AdeV,

I suggest that your task would be easier if you were dealing with a male taper.  Therefore, I'd coat the taper with some sort of release agent (e.g. wax furniture polish) and take an impression with some suitable material.  You'd also need to plug the mandrel through hole.

Plasticene probably isn't stable enough.   Devcon would set stable enough but might defeat the release agent and be difficult to extract.  Ditto epoxy putty.  Plaster of Paris might do or maybe even expanding polyfoam.

How about David's Isopon (aka 'Bondo')? 

You wouldn't need to totally fill the taper, you could use a cardboard tube core to economise on material.

Then you'd be able to measure more easily before referring to the Tapers section of Machinery's Handbook. 

[AdeV]

I reckon I've been over-thinking this...

Those bore gauge things are self-centering, that is, provided you're somewhere near, so I figured if I used the gauge hand-held, with a sharp tool to give me a reference point... it might do...

First measurement: 1.9095 thou

Move compound 1" in.

Second measurement: 1.8595 thou

That looks a LOT like 600 thou per foot to me!

Now all I need to do is try to work out what the hell taper that is! Where's my machinery handbook gone.....?

Edit to add: Aha, looks like a Jarno taper to me Somewhere between a #15 and #16, a #15 1/2 if such a thing exists... but I reckon a #16 would be my best bet.

[mattinker]

Adev,

what are you trying to do? I seem to remember that the spindle dimensions are on the manual (i have the .pdf on another computer which isn't accessible at the moment!)!
I've made a series of taper blancs to be able to make various ER40 and ER32 holders. I "copied" the spindle taper to the compound slide using a rule to get it in the ball park and the tweaked it with a dial test indicator. The spindle had a rusty zone, so I re-cut the spindle at the same time. I digress, what do you want to do!!

Cheers, Matthew

[AdeV]

Hi Matt,

It probably is in the manual (doh! Never thought of that....). First job is to make a sleeve adapter to take a 3MT so I can use my ER32 collet chuck without it wobbling all over the place (as it does if I put the non-tapered body into a chuck). After that.... who knows! Most of my stuff is 3MT (for the tailstock), so that'll be the most useful item.

Cheers!
Ade.

[chipenter]

                         Standard Tapers
           *  *  *  ALL DIMENSIONS IN INCHES  *  *  *

Taper Name              Large    Taper/  Taper/ Angle   Small   Length
                        End      Foot    Inch   From    End
                                                Center
-----------------------------------------------------------------------
#0 Morse                0.3561  .6246   .0521   1.4908  0.2520  2.00
#1 Morse                0.4750  .5986   .0499   1.4287  0.3690  2.13
#2 Morse                0.7000  .5994   .0500   1.4307  0.5720  2.56
#3 Morse                0.9380  .6024   .0502   1.4377  0.7780  3.19
#4 Morse                1.2310  .6233   .0519   1.4876  1.0200  4.06
#4-1/2 Morse            1.5000  .6240   .0520   1.4894  1.2660  4.50
#5 Morse                1.7480  .6315   .0526   1.5073  1.4750  5.19
#6 Morse                2.4940  .6257   .0521   1.4933  2.1160  7.25
#7 Morse                3.2700  .6240   .0520   1.4894  2.7500  10.00
-----------------------------------------------------------------------
#1 B&S                  0.2392  .5020   .0418   1.1983  0.2000  0.94
#2 B&S                  0.2997  .5020   .0418   1.1983  0.2500  1.19
#3 B&S                  0.3753  .5020   .0418   1.1983  0.3125  1.50
#4 B&S                  0.4207  .5024   .0419   1.1992  0.3500  1.69
#5 B&S                  0.5388  .5016   .0418   1.1973  0.4500  2.13
#6 B&S                  0.5996  .5033   .0419   1.2013  0.5000  2.38
#7 B&S                  0.7201  .5015   .0418   1.1970  0.6000  2.88
#8 B&S                  0.8987  .5010   .0418   1.1959  0.7500  3.56
#9 B&S                  1.0775  .5009   .0417   1.1955  0.9001  4.25
#10 B&S                 1.2597  .5161   .0430   1.2320  1.0447  5.00
#11 B&S                 1.4978  .5010   .0418   1.1959  1.2500  5.94
#12 B&S                 1.7968  .4997   .0416   1.1928  1.5001  7.13
#13 B&S                 2.0731  .5002   .0417   1.1940  1.7501  7.75
#14 B&S                 2.3438  .5000   .0417   1.1935  2.0000  8.25
#15 B&S                 2.6146  .5000   .0417   1.1935  2.2500  8.75
#16 B&S                 2.8854  .5000   .0417   1.1935  2.5000  9.25
#17 B&S                 3.1563  .5000   .0417   1.1935  2.7500  9.75
#18 B&S                 3.4271  .5000   .0417   1.1935  3.0000  10.25
-----------------------------------------------------------------------
#2 Jarno                0.2500  .6000   .0500   1.4321  0.2000  1.00
#3 Jarno                0.3750  .6000   .0500   1.4321  0.3000  1.50
#4 Jarno                0.5000  .6000   .0500   1.4321  0.4000  2.00
#5 Jarno                0.6250  .6000   .0500   1.4321  0.5000  2.50
#6 Jarno                0.7500  .6000   .0500   1.4321  0.6000  3.00
#7 Jarno                0.8750  .6000   .0500   1.4321  0.7000  3.50
#8 Jarno                1.0000  .6000   .0500   1.4321  0.8000  4.00
#9 Jarno                1.1250  .6000   .0500   1.4321  0.9000  4.50
#10 Jarno               1.2500  .6000   .0500   1.4321  1.0000  5.00
#11 Jarno               1.3750  .6000   .0500   1.4321  1.1000  5.50
#12 Jarno               1.5000  .6000   .0500   1.4321  1.2000  6.00
#13 Jarno               1.6250  .6000   .0500   1.4321  1.3000  6.50
#14 Jarno               1.7500  .6000   .0500   1.4321  1.4000  7.00
#15 Jarno               1.8750  .6000   .0500   1.4321  1.5000  7.50
#16 Jarno               2.0000  .6000   .0500   1.4321  1.6000  8.00
#17 Jarno               2.1250  .6000   .0500   1.4321  1.7000  8.50
#18 Jarno               2.2500  .6000   .0500   1.4321  1.8000  9.00
#19 Jarno               2.3750  .6000   .0500   1.4321  1.9000  9.50
#20 Jarno               2.5000  .6000   .0500   1.4321  2.0000  10.00
-----------------------------------------------------------------------
#0 Jacobs               0.2500  .5915   .0493   1.4117  0.2284  0.44
#1 Jacobs               0.3840  .9251   .0771   2.2074  0.3334  0.66
#2 Jacobs               0.5590  .9786   .0816   2.3350  0.4876  0.88
#2 Short Jacobs         0.5488  .9786   .0816   2.3350  0.4876  0.75
#3 Jacobs               0.8110  .6390   .0532   1.5251  0.7461  1.22
#4 Jacobs               1.1240  .6289   .0524   1.5009  1.0372  1.66
#5 Jacobs               1.4130  .6201   .0517   1.4801  1.3161  1.88
#6 Jacobs               0.6760  .6229   .0519   1.4868  0.6241  1.00
#33 Jacobs              0.6240  .7619   .0635   1.8184  0.5605  1.00
-----------------------------------------------------------------------


[mattinker]

i made Morse 3 and 4 adaptors for my colchester master using five to three morse adapters the Colchester has a 4 1/2 morse taper! I think a morse 6 to 3 adapter would be a good start! My project is long term, I have made the plugs in order to make the ER 40 and 32 chucks, two advantages, over the morse three Er 32 etc It's not too difficult to make the ER tapers (16° I think) The other advantage is making a through collet holder with a tubular draw bar allows longer stock to be held. The ER40 range usually goes up to 26mm, but up to 30mm collets are available!

Cheers, Matthew

[Jo]

It might help if we know what the Lathe is... Colchesters have their own tapers that are just bigger than a 5MT and have adapters to take them down to 3MT. Have you checked if it mentions the taper on Tony's site?

An ER32 collet holder up the nose of a lathe that size 

Jo

[Anzaniste]

Measuring a taper bore can be done with two ball bearings. A big 'un that will just fit in the larger end of the taper and a little 'un that fits the small end. Put the little one in place and measure with a depth micrometer or similar the distance down the hole using a suitable reference point. Do the same with the large ball. Knowing the ball diameters and their separation a bit of geometry calculates the angle.
I can't explain the geometry in simple words but somewhere in my notes I have a nice diagram if only I could find it.

I will look.


Here we go I just googled it:-  http://mathscinotes.com/2014/09/taper-measurement-using-gage-balls/

[PekkaNF]

I have quick and dirty method: to measure the angle, but you still have to connect the dots.

Pat playdough halfway (centre height), you only need two ridges.....then take two utility knife snap-off blades and gingerelly pres sharp parts snugly inside the taper, sharp part out. Then use our favorite zap (or epoxy glue) between the blades and after the has has set, pull out the "wedge". Now that is brittle and usless for measurement, but set it on something flat and put good dollops of glue to glue it down on each end of the blades and then you can measure it. Not accurate enough to make replacement, but good enough to identify taper.

Pekka

[mattinker]

It might help if we know what the Lathe is... Colchesters have their own tapers that are just bigger than a 5MT and have adapters to take them down to 3MT. Have you checked if it mentions the taper on Tony's site?

An ER32 collet holder up the nose of a lathe that size 

Jo

I'll answer for adev, as i have the same Edgwick mki that he has. It's a proprietary spindle nose taper. the spindle bore is 1 3/4 inches so we are over Morse 5. I think Er32 and 40 could be very useful on this lathe especially as it a 1940's modle, so chucks are pretty worn out!!

Regards, Matthew

[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  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!!! 

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...

[mattinker]

Adev,

Step drill to remove bulk, boreing bar to get it close, or even finish the taper or finish it with a morse taper reamer. Aluiminium is too soft for the job in hand, mild steel would be better!

Cheers, Matthew

[AdeV]

Hi Matt,

That's what I thought, I was trying to avoid the step drill step! But I guess it wouldn't hurt to try.

Agreed about the aluminium - this is a prototype to prove (to myself) that I can cut the level of accuracy right; also, I want to make sure the thing runs true before I commit it to steel.

[chipenter]

Why not make a collet chuck yourself then you can get long stuff up the spindle , 8degree taper use your exsisting collet chuck to set the angle .

[AdeV]

Why not make a collet chuck yourself then you can get long stuff up the spindle , 8degree taper use your exsisting collet chuck to set the angle .

You mean make an ER32 compatible end on my "sleeve"? Not a bad idea actually.... I hadn't really thought of that.

I will still need an MT sleeve at some point, so I can turn between centres, but that can be for the future, if I can be sure this spindle sleeve goes in concentric and true every time, then I'll be a lot happier about making such a thing. 

[mattinker]

My project is long term, I have made the plugs in order to make the ER 40 and 32 chucks, two advantages, over the morse three Er 32 etc It's not too difficult to make the ER tapers (16° I think) The other advantage is making a through collet holder with a tubular draw bar allows longer stock to be held. The ER40 range usually goes up to 26mm, but up to 30mm collets are available!

Cheers, Matthew

Adev,

i did suggest the ER40 and ER32 chucks a little way up the thread, I included my reasoning!

Cheers, Matthew