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On 10/4/2021 6:21 PM, Carl Bukowsky via
I have to say you may not get results you are looking for by
working the ER-40 collet chuck-to-spindle engagement last.
Ideal sequence is make the spindle threads first, then make the
collet holder while mounted to the spindle.
Making a collet chuck in the reverse order, spindle threads
last, you loose the concentricity relationship inherent in the
single operation of creating the collet holder while it’s
attached to the spindle.
All your spindle-to-chuck concentricity you cut will be
independent to that of the collet block holder. Any small
error in your chuck, and any error in centering the work
piece in the chuck, will all be added into the spindle
threads you cut.
I just made an ER-40 collet chuck on my SB 9” from 2”
piece of 4140 and it’s not that complicated.
You can make your own ER-40 nut if you don’t want to
cut metric threads. I went metric using some 3D printed
change gears-my metric threads worked great with the ER-40
but I bought. For the plans I bought a back issue
Machinist’s Worshop (Feb/Mar 2015, Vol 28 No 1). Good
Sent by my iPhone
I'm thinking of making a ER40 chuck
for my 10K. Because I don't want to set up to thread
metric and bore the 8 degree internal taper (best
ground, no grinder) I was thinking of using a ER40
hex block. I would have only one operation a
internal 1.5"-8 thread of which I've done a bunch in
aluminum and mild steel.. Now the problem is these
blocks are hardened to 40-45 HRc. I'm not really
sure how hard that is comparatively speaking. I have
some 5C blocks which seem pretty hard. I'm sure I
could use carbide to bore it out (not a lot of
material as they are already bored) with no problem
but I'm not sure how well the threading would go. I
know I would need carbide for this too and besides
the block itself would be my only expense. Has
anyone had any experience doing a internal thread on
hardened steel? I can not thread mill it. If nobody
has tried this does it sound feasible to anyone?
I'll be going over to my local machine tool shop
(1/4 mile away) and ask them what they think too
lots of knowledge with the guys who work there plus
I can buy my carbide threader (Solid or insert?)
there too. My only other "SMALL" problem would be
getting it perfectly aligned which shouldn't take me
much more than a day at most. :(
Bill form Socal