In article ,
David Billington wrote:
DoN. Nichols wrote:
[ ... ]
And interesting thing is that the taper of an R8 and a 30-taper
is identical, as is the larger diameter end of the taper. An R8 taper
stops sooner, at a larger minimum diameter. But, with a drawbar, you
can hold a 30-taper into an R8 spindle. Unfortunately, you lack the
keys to prevent spinning -- both under cutting load and when trying to
unscrew the drawbar.
I believe your comment about R8 and 30 taper being the same is
incorrect. 30 taper is 3.5"/ft or 7 in 24 whereas R8is about 3.555"/ft.
I was helping my neighbour make an R8 spindle earlier and had to check
this.
O.K.
The info on the www seems incorrect or misleading, my bridgeport
manual shows the taper as 16 degrees 51 minutes, yet some web pages show
16.51 degrees. 16 degrees 51 minutes works out at a taper of 1 in 3.375
on diameter or 3.555"/ft or 16.85 degrees included. This was checked
against an R8 taper and verified.
*Which* was verified? The Bridgeport manual's 16 degrees 51
minutes, or the 16.51 degrees? I presume the former.
O.K. I'll accept that, as you have done the measurements. I
had read it some time before, and I simply tried hand-fitting a 30 NMTB
into an R8 spindle. It felt free of rocking, but I did not have
spotting die at the time, so I did not test it beyond that point.
I had received the information from an article here some years
ago, and after a cursory check, took it as valid information. I
obviously need to stop that. :-)
An attempt to use a bevel protractor seemed to come out with the
same figures, but an R8 collet is a rather springy thing to try to
measure.
While _Machinery's Handbook_ has the precise taper of the 30
taper (and the rest of that family) documented, the set of drawings and
tables for the R8 (and similar) spring collets does not bother to
document the precise taper -- at least in either the 24th edition or the
25th edition.
Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. |
http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---