VMC300 Toolholder question

[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]

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

[Clive S]

I am not into math but the way I see it is that you could put the tool holder into a known dia. hole in a piece of thin stock to measure the top di. then it would be easy to measure the distance to the bottom. Just my 2p worth.

[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.

[m_c]

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.

The Coventry Easy Change system was fitted to lots of machines, however it doesn't use a pullstud, which is why my money is on some form of Boxford specific custom holder.
Boxford aren't exactly renowned for using established standards.

[magicniner]

The Coventry Easy Change system was fitted to lots of machines, however it doesn't use a pullstud, which is why my money is on some form of Boxford specific custom holder.
Boxford aren't exactly renowned for using established standards.

The presence on the Boxford holder of the locking ring groove in the same place as on the Coventry holder when with a pull stud it isn't required makes me suspect the Boxford is a modified Coventry, anyone conversant with, say the BT30 holders would recognise that the slot is redundant and that it would be absent on a fully custom-ordered part ;-)
Also there are the suspiciously thin walls above and below the tool changer disc slot, intriguingly designed to fit into the standard Coventry holder drive disc size and position :D

I'll put a fiver on the Boxford being a modified Coventry

[Proteus]

Got answer from Coventry today.
The toolholders are custom made for Boxford.
Production stopped in 2012, but they can make them at 156£ each with the groove. However, i strongly belive it's the same as their standard Easychange toolholder(without the groove).
I will order 1 and check similarity with the ones i have. For nearly 60£, i could could even fix that groove myself in my lathe.
The pullstuds however is a Boxford product according to Coventry.
Will have to make them myself ��

[magicniner]

Jurassic Tools have an ER32 Coventry Easy Change in stock at a good price -

http://www.jurassictools.com/store/s...se=easy+change

- Nick