VMC300 Toolholder question

[Proteus]

Still looking around :-x
Measured the angle and although it might not be dead accurate, it reads 21 degrees.
(Se Attached sketch)



I just hope Coventry feedback next week will tell me something...

[magicniner]

I've measured one of my Coventry Easy Change at 20 degrees

[m_c]

Standard BT tapers are 7/24, which going by my calculation, works out at 16.26 degrees.

[magicniner]

Standard BT tapers are 7/24, which going by my calculation, works out at 16.26 degrees.

I've measured Coventry Easy Change and BT30 for comparison/reference with a Moore & Wright Angle Thingy, here's the photos -

I used BT30 because it's the "Taper Which It Definitely Isn't" which keeps getting rolled out here, it mystifies me and I was tempted to use a MT3 taper, but I'll go with the flow ;-)

[m_c]

It really wouldn't surprise me if Boxford used a custom taper and holder design, just so you had to buy holders from them.

[magicniner]

Knowing a change in diameter over a fixed height it's a really easy bit of fag packet sketchery and school trigonometry to calculate the taper angle -
Sine - Opposite/Hypotenuse
Cosine - Adjacent/Hypotenuse
Tangent - Opposite/Adjacent

Do they still teach the basics at school? I meet so many people who don't seem familiar with them I do wonder,

- Nick

[Proteus]

I've measured one of my Coventry Easy Change at 20 degrees

This is why i suspect the tool holders to be Coventry.
My measurement was not accurate holding 2 steel rulers along each side and then measure With a School Plastic 180 Degree Protractor.

[Proteus]

It really wouldn't surprise me if Boxford used a custom taper and holder design, just so you had to buy holders from them.

I think Boxford and Coventry used to collaborate previously(at least) on toolholders.
I seem to remember a chap talking about some Coventry toolholders for his VMC190, and i think it`s the same toolholder.
Still havent got any answer from Neville at Coventry yet though.

[Proteus]

Knowing a change in diameter over a fixed height it's a really easy bit of fag packet sketchery and school trigonometry to calculate the taper angle -
Sine - Opposite/Hypotenuse
Cosine - Adjacent/Hypotenuse
Tangent - Opposite/Adjacent

Do they still teach the basics at school? I meet so many people who don't seem familiar with them I do wonder,

- Nick

This is basic Math Nick, but the Challenge is to measure 100% correct top diameter on the taper and correct distance in between(the taper top i slightly rounded).
Tryed to improve my measurements and got lower dia at 31,61, top dia at 20,9 and length at 30. This gives a Cone angle α = 20.24° = 20°14' , taper 35.7%.
This is definately no standard taper in my opinion...

[magicniner]

This is basic Math Nick, but the Challenge is to measure 100% correct top diameter on the taper and correct distance in between(the taper top i slightly rounded).
Tryed to improve my measurements and got lower dia at 31,61, top dia at 20,9 and length at 30. This gives a Cone angle α = 20.24° = 20°14' , taper 35.7%.
This is definately no standard taper in my opinion...

Your dimensions are almost exactly what I get off the Coventry Easy Change if I try to measure where you have using digital calipers.
Because of the problems measuring the top edge of a frustum with calipers I chose to measure the OD in two places where an easily measured OD is available, at the bottom edge of the taper and the top edge of the groove, with a micrometer then measure the vertical distance between the two with a vernier, that gives me a calculated angle of 10.02 degrees. (Once I'd downloaded a decent calculator with inverse functions to my phone - what's the use of sine without arcsine Mr Samsung!)

If you super-glued your two steel rules together in alignment with the taper you could draw a nice big triangle on a piece of A4 and measure/calculate the angle ;-)
- Nick