Setting lathe compound angle

[BelgiqueB]

Currently attempting to make a holder/seat for schaublin W25 collet's i bough second hand recently, I found a data sheet for the collet and it states that the collet has a 15° taper up front.

I've set the compound angle using the technique described by Joy Pi in this youtube clip:

I used Fusion to determine the vertical leg angle, then mounted a dial gauge to my lathe and did exactly as described in the youtube clip. After a couple of tries i got it so that the numbers on my DRO for the cross slide were within 0,01 mm.





However the result is this, after i made a test piece i cut it in half to see what te result was, the angle is way off from the collet 15°:



So my question, what am I doing wrong? As a disclaimer I have a form of discalculia so I struggle with angles and numbers, so it might be something simple. Am I setting my compound wrong, am I reading the plan wrong? All help is greatly appreciated.

Christof.

 

[BelgiqueB]

Forgot to add in the previous post, as stated i set up the compound to 15° with the technique used in the youtube video, however the markings on my compound are only at 7°?

 

[Hood]

Not watched the vid so not sure what he is doing but...

If you have a collet then chuck it up. Put a dial indicator on the compound and adjust the compound roughly the angle required. Wind the compound and check the movement on the dial, adjust the compound until yo see no movement on the dial as you wind the compound back and forth.

 

[Hood]

BTW just in case that is not clear you would put the end of the dial gauge on the taper of the collet.

 

[Seadog]

The angle is inclusive. You need to set the compound to half of the nose angle. I nearly made the same mistake when trying to set my taper attachment up for the first time.

 

[mtt.tr]

Like hood haven't seen the video.

If im working to an angle i cant compare then use laws of sine as your diagram
Travel the hypotenuse 50mm and expect the see the perpendicular to the axis distance move in a predetermined amount. 12....mm



Your diagram looks incorrect, of you can draw in cad print it as a PDF with no scaling

 

[mtt.tr]

The angle is inclusive. You need to set the compound to half of the nose angle. I nearly made the same mistake when trying to set my taper attachment up for the first time.

Well spotted

 

[RichardM]

You need to set compound to 15 deg, according to the Schaublin drawings in #1 the inclusive angle is 30 deg, then dial it in as per Hoods description.

 

[Seadog]

So it is

 

[BelgiqueB]

The method I used and is described in the video is the one using the Sine law calculation to set the compound.

I think i found my problem, my DRO is set up to read diameter, so if I move the crosslide forward and the DRO reads 20mm (diameter), in reality it only moved 10mm (radius). Will try again tonight and report back my succes or failure!

 

[BelgiqueB]

The angle is inclusive. You need to set the compound to half of the nose angle. I nearly made the same mistake when trying to set my taper attachment up for the first time.

You need to set compound to 15 deg, according to the Schaublin drawings in #1 the inclusive angle is 30 deg, then dial it in as per Hoods description.

How do you know from the plan if the given angle is inclusive or not? Probably quite clear i don't know how to read machining drawings .

What about the markings I circled in red, I would assume this is a tolerance on the given 15" angle in minutes of an angle? However that would mean you can have a tolerance from -3' to -8', which doesn't make sense to me. Logical would be from 0 to -3' or 0 to -8', or am i missing something here (most probably ).

 

[Agroshield]

I think you are absolutely correct when you say it is because of the way the DRO reads and well done for spotting it. You can check it by putting a parallel piece of bar in the chuck and the test indicator on the compound. Then, as you move the compound, the indicator gives a direct reading.

The angle you have stated is correct. It is 15 degrees per side, so 30 degrees included. Mr Seadog misread the drawing (see post No. 9).

The tolerance is stated the way it is because errors which result in a lesser angle are less serious than errors that result in a greater angle. You would set it up for 15 degrees and then give it a finely-judged percussive adjustment of approximately 1 RCH in the lesser direction, hopefully arriving in the middle of the tolerance band at 14 degrees 54 minutes 30 seconds.

To me, telling a machinist to set up for 14 degrees 54 minutes and 30 seconds and then allowing 2 1/2 minutes either way tolerance is a nonsense way to proceed.

 

[RichardM]

You also have and Alpha on the other side of the collet to take into account if thinking about an inclusive angle.



Set the compound to 15deg then dial it in with the dial gauge to the actual collet. Just use the DRO for your base diameter

 

[Brad93]

You’re gonna have to make it and blue a collet and mate them together to see if you’ve got the right fit. Quite difficult to hit the exact angle with a lathe as there’s always some sort of deflection etc.

double boost has a couple of good videos on YouTube, where he makes a 5C collet holder and a tapered back plate to fit his L00 taper spindle. worth a watch

 

[Brad93]

 

[Shox Dr]

The method I used and is described in the video is the one using the Sine law calculation to set the compound.

I think i found my problem, my DRO is set up to read diameter, so if I move the crosslide forward and the DRO reads 20mm (diameter), in reality it only moved 10mm (radius). Will try again tonight and report back my succes or failure!

I watched a similar ut video the other day, using Sine. Like yourself I have great difficulty in understanding angles, I’d never heard of Dyscalculia before

 

[Shox Dr]

That works but everything else needs to be bang on as well.

 

[mtt.tr]

I watched a similar ut video the other day, using Sine. Like yourself I have great difficulty in understanding angles, I’d never heard of Dyscalculia before

Dyscalculia really is a thing, im dyslexic my sister no doubt has Dyscalculia shes got a bachelors in English and im pretty good at maths, a real crack team

 

[Shox Dr]

Dyscalculia really is a thing, im dyslexic my sister no doubt has Dyscalculia shes got a bachelors in English and im pretty good at maths, a real crack team

Im Dyslexic, and cant remember more than 3/4 numbers, any more I might remember them but not in the right order

 

[mtt.tr]

Im Dyslexic, and cant remember more than 3/4 numbers, any more I might remember them but not in the right order

I have to write things like that down, my workshop walls are like a maniacs scribblings


As you know that has its own problems