Gallery, Projects and General > How do I??

Math for machinist tapers...

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BillTodd:
Hope this is clearer.

A spindle nose diameter of  (3.4993 - 3.4986) is also specified

RussellT:

--- Quote from: AdeV on February 08, 2013, 06:29:59 AM ---Russell - that's what I thought.... but the reason we're wrong is actually relatively easy to show using a diagram; see attached.

--- End quote ---

Ade

I think you were right the first time - I've attached a diagram. :scratch:

The triangle ABC is the taper we are trying to make.  It starts 7 units wide and over a length of 24 units tapers to 0.  (I've drawn it to a point to make it easier to visualise).  The triangle ABC has no right angles so we cant simply apply arctan.  We need some extra lines.  To get the included angle we could draw a centre line from the midpoint of AC to B to give us two right angled triangles.  They would be the same shape as the triangle BCD and the angle would be arctan(BD/CD).  So the included angle is 2arctan(BD/CD) and the angle to set your topslide to is arctan(BD/CD) or in this arctan (3.5/24).

I hope I've got that right.

Russell

NeoTech:
Setting the angle with a dial seem to be the "easy" solution here..  I have one of those dual DTI thingys to make sure the spindle head is square to the table.. would that be of any use setting the angle of the topslide? If i square that in a toolholder to a piece of ground roundstock, it should be able to set the angle with it .. wouldnt it? =)

DMIOM:

--- Quote from: NeoTech on February 08, 2013, 10:34:44 AM ---Setting the angle with a dial seem to be the "easy" solution here..  I have one of those dual DTI thingys to make sure the spindle head is square to the table.. would that be of any use setting the angle of the topslide? If i square that in a toolholder to a piece of ground roundstock, it should be able to set the angle with it .. wouldnt it? =)

--- End quote ---

You woud need to know =exactly= the spacing between the two indicators, and you would have to align the beam parallel to a test bar (not just in&out but also in height at both ends so that probes touch on the same point of the circumference) - seems like adding extra complications and extra opportunities for errors to creep in.

Dave

RussellT:
To address the real issue, rather than just the maths, the most important thing you need is some way of testing the taper without removing it from the lathe - for example a suitable socket.  You set the angle to about 8 degrees and cut the taper, then try the socket and see which end is loose and adjust the angle to suit.  Repeat until it's right. It's fiddly rather than difficult.

Russell

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