Measure internal taper

[Gordon]

How would I accurately measure an internal taper? This came up as I was trying to determine the taper inside the headstock on my South Bend lathe. It is either #5 or a SB special taper. I was thinking about making an adaptor to fit 5C collets instead of the external holder I now have.

I have the usual dial indicators but there is no way to get the large dial indicator inside the hole and the indicator with the arm only has a very limited range. I have a digital scale on the X axis so I can move the carriage a known distance but I don't know how the measure the distance on the Y axis. If I decide to make the adaptor I would want to set the compound at the correct angle to fit the taper. The only thing I have come up with is to make a lever type arm to fit in the hole and measure the distance that the lever moved on the other end. Not a must have but I have been wondering how this could be done.

Gordon

 

[Asm109]

The rocker arm lever is a standard accessory that you can purchase for a travel indicator. Hole Attachment, Model Number 196F, for Starrett Back Plunger Variance Indicator | McMaster-Carr

 

[Gordon]

The rocker arm lever is a standard accessory that you can purchase for a travel indicator. Hole Attachment, Model Number 196F, for Starrett Back Plunger Variance Indicator | McMaster-Carr

OK Thanks. That is basically what I was thinking about with the lever arm.

 

[clockworkcheval]

Sir, as I understand the #5 taper is 0,0526 inch per inch and the SB special taper has the size of about a #5 taper but the angle of a #3 taper, or 0,0502 inch per inch. The difference is 0,0024 inch or 0,06 mm. As you can enter a dial indicator with an arm easily about an inch or 25 mm into the internal taper and because you can read the dial indicator with an accuracy of plus minus 0,01 mm it seems to me to suffice to make a direct measurement of your internal taper with your dial indicator mounted on the carriage.

 

[goldstar31]

[QUOTE="clockworkcheval, post: 358163, member: 37758
Sir, as I understand the #5 taper is 0,0526 inch per inch and the SB special taper has the size of about a #5 taper but the angle of a #3 taper, or 0,0502 inch per inch. The difference is 0,0024 inch or 0,06 mm. As you can enter a dial indicator with an arm easily about an inch or 25 mm into the internal taper and because you can read the dial indicator with an accuracy of plus minus 0,01 mm it seems to me to suffice to make a direct measurement of your internal taper with your dial indicator mounted on the carriage.
[/QUOTE]
Ooops but for the morse taper it is certainly NOT to the foot( 12 inches)
I did a lot of research and discovered it was to a 10 inch sime with an 1/8th of an inch againdst the hypotenous. No, in practice ot isn't . Some credit is due to Colin Johnson writing as Strangbela' woth the design for taper turning device on his early Myford ML7.
Sadly, Colin is no longer with us. The Morse taper seems to be a result of poor machining-- from the Original Propositions of Euclid.
If you do it all on a slide rule and accept a bit of number crunching it is from a sine of 10 and not 12

Regards

Norman

 

[xpylonracer]

You could use 2 ball bearings of known diameter, 1 to be slightly larger than the small end of taper and 1 to be below the nose of the spindle when placed in the spindle.
Fit the small ball in the taper and measure the distance from the spindle nose to the OD of the ball, note the distance and remove the ball.
Then do the same with the larger ball and note the distance, you now have the dimensions needed to calculate the amount of taper in the spindle.

 

[oldengineguy]

Gordon : I made a 5C adaptor for my heavy 10 a few years ago and thought it was morse5 until I recently bought a generic Chinese 12x36 King lathe and found my adaptor did not fit. When I made it, I offset the tail stock using a dial indicator on the plug that holds the SB dead centre as a guide. I have no idea what the taper per inch /foot is but it fits nicely.I made an adaptor for the new lathe on the old SB with the tail stock offset at .052 pe inch, it fits the King but not theSB. By the way ,using a hollow drawbar through the headstock with 5C collets works very well. Colin

 

[nautilus29]

When measuring make sure you are on centerline, you will get an inaccurate reading if you are off of center.

 

[Gordon]

I had not thought about the importance of being on centerline but you are correct. In looking online I can find all kinds of information on what the taper is on my 13" SB. No two of them the same. When I bought the lathe 10+ years ago I got a sleeve with #3 MT and I think #5 OD but I am not sure. Whatever it is it seems to fit but apparently the #5 and SB are close so perhaps I just think that it fits. It is perfectly possible that the large end fits and there is actually a few thousands slop at the small end and as long as the forces are forces are only longitudinal it does not show up.

 

[nautilus29]

I would probably indicate the bottom if I were you. You can put the indicator on the bottom and then use the x axis to find the low point.

You don't necessarily need a full inch of travel to figure this out. You could trynto move a half inch or .25". The only issue is .002 is already a small amount and at .25 you'd be at a half a thou difference between the two. Idk if I'd feel confident enough with my reading.

Check going in both directions as you can get indicator variance.

 

[Gordon]

I am not sure what I have proven so far but after several attempts I have come up with .024 in 1" of travel which does not line up with anything. I will try again and try to do a better setup.

 

[goldstar31]

Gordon, it is Morse Taper but the number can only be determined by giving the diameter of the widest part of the spindle.

According to my 'Bible' which is the geo Thomas Model engineers Workshop Manua;

No2 is 0.070 and Number3 is0.938"

Somebody should have ha said ve you that you needed a nose diameter( given here_, the length of the taper ( the Hypotenuse) and the length of chuck side. This is a truncated cone.



Regards

Norman

 

[Gordon]

Norman
I am not sure what you are saying but I am pretty sure that it is not a morse taper. If I have specifications showing taper per foot it should not matter if the diameter is 1" or 10". The difference between the two points 12" apart should be that value

 

[goldstar31]

Norman
I am not sure what you are saying but I am pretty sure that it is not a morse taper. If I have specifications showing taper per foot it should not matter if the diameter is 1" or 10". The difference between the two points 12" apart should be that value

Oh Ye of Little Faith!

 

[ThomasJ.]

I have a Samson, Tida etc. lathe that had a Morse 4 1/2 taper. Very common on these lathes. I bored to MT5 and reamed to 5MT. I'm reluctant to bore the spindle to 1.5 inches however ! Also bored and reamed the tail stock ram to MT3.

 

[MachineTom]

Awhile back I made some spindle adapters for Rockwell lathes and others. The common problem is folks confuse taper angle, with taper size-MT. Each Morse Taper # has an angle and a size. When used in the spindle bore, the Morse ANGLE my match a certain MT, but the size is not even close.
Morse tapers are listed as Inches per foot. A morse taper #4 1/2 has a taper of .62400 or .052 per inch, the half taper would be .0260". The Half taper is what you have when measuring the bore with a DI or other means.

A easy way to measure a taper on the part you are making is remove from lathe, using a sine plate, flat surface, gage blocks, height gage. Set the work on the sine plate with .2600" blocks, The height gage should show 0.000 variance end to end.

Be sure to Blue the spindle, and test the adapter before calling it done, a thou or two will be too loose.

 

[Gordon]

Gordon, it is Morse Taper but the number can only be determined by giving the diameter of the widest part of the spindle.

According to my 'Bible' which is the geo Thomas Model engineers Workshop Manua;

No2 is 0.070 and Number3 is0.938"

Somebody should have ha said ve you that you needed a nose diameter( given here_, the length of the taper ( the Hypotenuse) and the length of chuck side. This is a truncated cone.



Regards

Norman

Still not sure what the diameter has to do with the taper. South Bend says that it is a taper of .602/ft and several others have said that some South Bend came with a 4 1/2 or a #5 Morse taper. The hole at the chuck end of the taper is 1.629 dia. A #0 MT is .3561 dia and .6246/ft and a 4 1/2 MT is 1.5 dia and .6240/ft so dia does not seem to enter into the calculation.

Perhaps (not actually perhaps) I am just dumb as a rock but I do not see what diameter has to do with taper per ft. A drift pin has a taper and there is no diameter involved.

 

[chrsbrbnk]

A fair number of digital readouts have a taper measuring function , also thought about if you had a dial bore gage you could mount it in a tool holder , using the active side of the gauge you could tell when it touched the inside of the bore that in combination with your readouts would give you pretty accurate picture

 

[goldstar31]

1 My tables do bot have 4 1/2 MT and I cannot read the print on Machinert's 1941 Edition

I'm in a state of macro degeneration- one wet one dry

 

[MachineTom]

If SB shows a .6020 taper that is what you need to know. If making an adapter for a center, I suggest making it a bit smaller at the large end, that way it will be recessed, about -.010 dia. should be enough.

Norman #4 1/2 morse taper is about 5.375 long [gage line} Big end 1.5", taper of .6240" per foot.