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From: Robert Bastow <"teenut"@>
Newsgroups: rec.crafts.metalworking
Subject: Re: Chuck Threads Fit
Date: Sat, 27 May 2000 08:04:02 GMT

B & L Denard wrote:
> Robert !
>    You can lead a mule to water but you cant make him drink.
>   The thds are to hold chuck on lathe ,the Register lines it up. are we
> right.?
>  Bill D.

Dead Right!

I have been holding off on replying to the many messages on this thread.

Several reasons have involved workload and available energy level..

But the main one was that I was trying to think of a way of telling so many
otherwise apparently knowledgeable (and nice) people that they are full of
"S***" in a polite way..the other was trying to figure out why they could be so

Bingo! the light finally went on!

You theory..they are right.  Threads are the only centering device you long as they are perfect!

The problem is that there are two very different kinds of "Design Engineers"

A pre-requisite for the job is an ability to envision three dimensional spatial
relationships..preferably in full color and in full, real time movement.  In
other words the instinctive ability to envisage how two, or many more, three
dimensional parts will fit and interact together...put all the parts of a simple
..or complex...piece of machinery, together in your mind and watch it run
through complete cycles in your "Mind's Eye"

(studies and tests done, in the selecting of suitable candidates for
apprenticeship training programs, have shown that a far greater proportion of
Females possess this quality than Males!!!!  Unfortunately, in our culture at
least, a very large proportion of females rule themselves out from engineering
or machinist type careers because of a lack of (acquired) ability in quite basic
math, and/or, an aversion to any kind of job that might involve getting their
hands dirty or appearing less than "feminine" to their family or friends) Room
for a whole different thread there!!

Why then do so many "mechanically knowledgeable" people screw up on something as
simple and basic as the functioning of a threaded lathe spindle nose?

This type and many many other examples of similar thinking had me puzzled for
years...years during which I could only shake my head and either countermand it,
change it or fix it!!

Until I realized that mechanical "designers" fall into two, fundamentally
different groups!  one large..the other small..or should I say practically all
start out in the larger group..but only a few eventually cross over into the
smaller group.

The first, larger group, see all their elements and components, in their "minds
eye" as perfectly formed, sized, aligned etc....If you like, as a computer
generated "Perfect Picture"

These people are dead right..two perfectly formed, perfectly dimensioned,
perfectly finished...and perfectly started!! threads, will indeed locate and
perfectly center a chuck on a spindle without any aid from a register.

These people design parts and mechanisms as though the world were perfect..and
then wonder why it doesn't all come together and "work" perfectly!!

Others, a smaller group, envisage the parts or components as they "really
are" a "real" world..and how these "less than perfect" bits will REALLY
interact, fit, and move together. Their designs actually start out with a
genuine chance of "working"!!

First of all..ask yourselves...why lathes (of any quality, durability and
reputation) are, in fact, provided with a fitted register AND a threaded nose
piece.  SURELY so many different machine tool designers from so many companies,
so many countries and over so many years, can't possibly have continued to waste
their Company's manufacturing resources, and cut into Corporate Profit levels by
providing an (apparently) useless and expensive appendage, as a spindle nose
register, without SOMEONE yelling out "The Emperor has no clothes"!!..and
getting the whole lot of them fired on the spot

Why...would any Die, Fixture, Tooling or Machine Designer be laughed out of the
drawing office if..faced with the need for an ACCURATELY located pin or dowel,
he simple spec'ed a tapped hole and a pin with a thread to match?

Reason?  Because anyone who understands and can envisage the way REAL parts fit
and interact in the REAL world..would know and understand that, IN

Real World threads DON'T come perfectly formed, matched, dimensioned, centered
and located!!!

As a result..if you screw a couple of them together WITHOUT OTHER MEANS OF
RADIAL AND AXIAL LOCATION....They will do ANYTHING BUT self center and or

I could go on..but it is late, I am tired, and I am sure the ding dong "Battle"
this will start, will give me more than enough opportunities to fire a few more
shots from my "Ready Ammo" locker!!

Just remember Guys (And I Love and Respect all of you)..Don't bring knives to a
gun fight!!



> Robert Bastow <"teenut"@> wrote in article
> <kMnW4.3362$>...
> > It is (or should be) the register..both on diameter and on the rear
> > face..that do the location of thr chuck.  The thread is simply there
> > to hold the chuck to the register.  As such it can be a "Rattling good
> > fit" without detriment.
> > 
> > Indeed, a tight fit on the thread would be a definite way
> > can a vee thread act as a location or centering device to the accuracy
> > required by a chuck.  Even if it set out that way..lapped to fit
> > would soon wear and loose it.
> > 
> > Threads are HOLDING devices ..not LOCATING devices.  Yes..even
> > leadscrews are only good for AXIAL location.
> >
> > teenut
> >
> > wrote:
> > >
> > > I just bought a Chinese chuck, with a backplate.  The backplate rattles
> > > on the 1 1/2 X8 thread on my SB spindle.  The thread is at least 0.012
> > > oversize.  The straight parallel shank behind the thread on the spindle
> > > is 0.04 smaller than the bore on the backplate.  It seems to run fairly
> > > true though, so I am going to try it.  I am curious if anyone has any
> > > idea of what is reasonable tolerance for spindle/backplate fit. I have
> > > always made my own backplates, and I just made them fit, i.e. snug.

From: Robert Bastow <"teenut"@>
Newsgroups: rec.crafts.metalworking
Subject: Re: Chuck Threads Fit
Date: Sun, 28 May 2000 18:33:04 GMT

Whoa! Whoa ! WHOA!!!!!

First of all Bill..If you think I am a bit windy..Fine!!  I have no problem with
that..I am YES! Agreed!!  OK!

No you don't want to meet "Bob" one has, in the past thirteen one will ever again.  "Bob" Bastow was not a nice person..but he got
"Robert" Bastow through some awfully rough and dangerous places in his earlier
life.  He "lived" long enough for Robert Bastow to mature and start to develop
into a much nicer person who wanted to help people avoid some of the mistakes he
made and above pass on the benefit of years of experience, knowledge
and know-how in this fascinating Hobby/trade/Industry...much of it learned by
bitter experience some of it from people who took the time and effort to teach
and mentor him.  That persona is known as "teenut" round these parts

If I appear to you as an ALPHA male in this group..that certainly is not my
desire or intention.

If my responses to some of your posts has appeared to you to be demeaning..I
apologize!  It is not my intent!

Having said that!!

I stated, at the beginning of my response on the thread about chuck threads that
I was about to step on the toes of a lot of people I love and respect..I
did..and I will continue to do so..because they are (in this case) WRONG!!

Now the responses start to come in we start to see a trend.."So what if Locating
Collars etc. are theoretically..or even practically chuck screws on

Well fine!  Why didn't you say that in the first place..I don't have a problem
with that!

But it sure as hell ain't accurate enough for MY my home shop or in
my "Pro" shop!

My Home shop has taken me years to get to what I call an INTEGRATED level.  One
of the useful things I can do is to start out with a job in the lathe chuck,
machine it part way, transfer the CHUCK with its part to either mill table,
rotary table, dividing head, shaper, engraver, and back to the lathe for
It didn't take me a tenth of that time to introduce the same concept into my
"Pro Shop"

Sloppy fit of chuck to lathe spindle will not cut it for me..nor for anyone else
who wants to follow this same path, be it as a Proud Amateur or as a Competent

There are a whole host of applications..some of which I touched on, where a
thread, on its own, simply WILL NOT provide the accuracy required!


BillDarby wrote:

> I don't know what you want.  I said nothing in ths post that I haven't
> said to you privately as witnessed by this, my last post to you:
> "Hello again John!
> Welllllll,, Robert is given to be a little windy at times. <VBG> Both he
> [and you] (and all the men who have made machining a career) have the
> others in the group at quite a disadvantage in the sense that they are
> playing in their own sandbox. If this were rec.crafts.heartsurgery then
> the doctors in the group would be in the position of "playing on home
> turf" I just tend to get annoyed at hearing an amateur berated by a pro
> as if he were an apprentice,,,, when in fact the "amateur" is a grown
> man perhaps of some station in life and possibly the ultimate
> professional in his chosen field and who comes to the group for the love
> of machining in a quest to learn.
> That is not to say that all or even a very few "lord it over" others,
> but I see it now and then and it does grate. I do also notice that
> people defer to the Alpha male, which, I guess is no big deal,,,, it's
> so natural!
> I think both you and Robert are Alpha males (in the trade, of course)
> and are both recognized as such.  I like the way you conduct yourself,,,
> by contrast, lets just say Robert is a little windy. I think him to be a
> good soul though.
> That's my bit of insightful thought for the evening.
> Bill   "
> Now, if you think I am a little intimidated in trying to argue machining
> concepts with the likes of Bob, your right!  He spent 35 plus years
> working "in the trade" while I was digging slit trenches in Germany.
> So, yes, he does have a decided edge but you know from his writing that
> he is not mean.
> Which brings me to your post.  I do not know what you want. I know it's
> not about machining concepts.
> Bill Darby
> John Stevenson wrote:
> > On Sat, 27 May 2000 12:36:28 GMT, BillDarby <> wrote:
> >
> > >Well, here I go into the "Jaws of death"
> > >
> > >When it comes to machining knowledge and experience, I'm so far down
> > >the food chain that I don't exist and maybe I am full of S**T but I
> > >have not lost the ability to think for myself.  I both like, and
> > >admire you.  I envy your experience in machining and I respect your
> > >words, but if you stop quick, you won't find my nose up your butt.
> >
> > My God Bill I have to give you credit you've certainly got balls.
> > Have you taken legal advise before you posted this ?
> > After all you don't want to meet Bob Bastow.
> > Would you mind terribly emailing me your full name, date of birth and
> > address.
> > I would like to take some life insurance out on you if you don't mind.
> > I might just get enough to buy a new chuck and spindle so I don't have to
> > risk somebodies wrath.
> > --
> >
> > Regards,
> > John Stevenson
> > Special Purpose Machines
> > Nottingham, England

From: Robert Bastow <"teenut"@>
Newsgroups: rec.crafts.metalworking
Subject: Re: Chuck Threads Fit
Date: Mon, 29 May 2000 15:12:52 GMT

> Mike Rehmus wrote:
> > My chuck backing plates already don't touch the register.  Never did, even
> > straight from the factory.  Neither did yours or Bob' or anyone else's.  If
> > they touched, they'd jam on.  And if they touched the first time, they'd
> > rapidly wear until they didn't.  Understand?
> >
> > You want to volunteer, go make yourself a backing plate and try it.  On your
> > lathe.  I already know it works.

The "Correct Specification"...If there is such a thing!! for a parallel chuck
nose register and its backing plate, is that the male register should be ground
true and parallel to the lathe axis, to VERY close limits.  The Female register
should be sized "dead on size" in other words between a few tenths over size to
a tenth or so under other words a very close "push" fit to a VERY
slight "Interference fit"

Both should be kept spotlessly clean and lightly greased before screwing
together. This will make the last few turns quite stiff..but far less likely to
unscrew at an inopportune cutting threads in reverse.

Yes! They WILL eventually wear..which is why they are not my favorites for
spindle noses..nor are they used much on "High Class" lathes..except the very
smallest ones.  They are used there, because there really isn't room for a
"better" spindle nose an L0 taper or a D1 type..without
massively increasing the spindle diameter..which requires either lower speed
limits..or VERY much more expensive bearings...A kinda "Catch-22" situation.

In actual fact, the wear on such an arrangement is not as rapid as one might
expect...given proper cleanliness and lubrication that the spindle is
(or should be) hardened steel and the backplate is (or should be) close grained
cast iron..An almost perfect, slow wearing, non-galling, "bearing" combination.

I have only ever owned two lathes with parallel thread/register spindle noses.
One a Myford Super7 the other a Smart and Brown Toolroom lathe.

In both cases I had to have the spindles Hard Chrome plated, and ground back to
original spec's..and either make new backing plates or bush and bore existing
plates to the above mentioned "tight clearance" spec's.

In both cases they then gave many years of sterling service, during which the
chucks and fixtures were completely and accurately interchangeable between lathe
and other workshop equipment.


From: Robert Bastow <"teenut"@>
Newsgroups: rec.crafts.metalworking
Subject: Re: Chuck Threads Fit
Date: Mon, 29 May 2000 15:28:51 GMT

Mike Rehmus wrote:

> Guys,  I hear what you are saying.
> So, those of you who have tried it, seem to believe me.  Practical proof.
> Those of you that don't.  It's OK with me.  We'll all probably be able to
> turn out good work no matter which way we go.

> Pax

Pax indeed Mike!..It really is a grey area..and I tend to become a little "Anal"
in grey areas!!

On the other hand I am trying to guide people who, right now..or some time in
the future, for whatever reason, need to "Chase Tenths"

Remember that if you CONSISTANTLY want to work to "thous" your equipment and set
ups must be repeatable to "tenths"  For those that need or want to work
consistantly to "tenths"  The margin of machine and set-up repeatability becomes
very tight indeed.

Having said that..My weapon of choice in the shop, is still, a two pound, ball
pein hammer!!  A judicious tap..or even placing it in close proximity to a wonders!!


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