Subject: Why instant reversing?

From: [email-masked] (Chris Kantarjiev)
Date: 10 Jun 1996 21:52:44 GMT

In "How to Run a Lathe", South Bend has this to say about choosing a motor:

"Capacitor Motors for single phase alternating current are made in
instant reversing, and start-stop reversing types. The instant reversing
type is preferable but the start-stop reversing type is less expensive
and may be used satisfactorily on certain classes of lathe work. This
type of motor has a fairly high starting toque and constant speed. It has
a starting switch but has no commutator to cause radio interference."

Can someone tell me what class of lathe work *needs* an instant
reversing motor? I'm not completely inexperienced in this area, and I
have yet to come up with a situation where I needed to turn the motor
around *RIGHT NOW* instead of, say, disengaging the feed, stopping the
motor and reversing it.

(Besides, just how instant can instant be?)

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From: [email-masked] (Jim Shockey)
Date: 11 Jun 1996 20:17:01 -0700

In article <[email-masked]> [email-masked] (Chris Kantarjiev) writes:
>From: [email-masked] (Chris Kantarjiev)
>Subject: Re: Why instant reversing?
>Date: 11 Jun 1996 19:54:36 GMT

>Ah, but wait ... won't the backlash in the drive train
>completely alter the tool's position? That's what I didn't understand
>the first time through. Backlash.

With any luck, it'll all get gathered up and come together at 
the same time both coming and going. Tapped a lot of holes, 
both blind and otherwise, and tons of slack and lash have never 
broken a tap, yet. I have managed to figger out plenty of other 
ways to break taps, thank you. 

I haven't had the pleasure of running a Hardinge Chucker; but, 
if Ed would like me to come on down to So. Calif., I can show 
him how to break taps on it, too. <g> 

--jim			<[email-masked]>
"Outside of a dog, a book is man's best friend. 
Inside of a dog, it's too dark to read anyway."	
		--Groucho Marx

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From: [email-masked] (Peter Drumm)
Date: 11 Jun 1996 11:05:40 GMT

In message <[email-masked]> -
[email-masked] (Chris Kantarjiev)10 Jun 1996 21:52:44 GMT
writes:
:->Can someone tell me what class of lathe work *needs* an instant
:->reversing motor? I'm not completely inexperienced in this area, and I
:->have yet to come up with a situation where I needed to turn the motor
:->around *RIGHT NOW* instead of, say, disengaging the feed, stopping the
:->motor and reversing it.
:->

Possibly threading, with either a die or a tap held by the tailstock.

:->(Besides, just how instant can instant be?)

I don't have any exact figures, but it's darn fast, less than 1 second
I'd say.  The garage I used to work at had a carwash with 3' dia x 4'
high side brushes, run by 5HP instant reverse gearmotors. When they
changed direction, the 'snap' of the brush would throw water about 100
feet!

[email-masked]
Using Warp/Neologic News/PMMail/iLink2/WebEx
Wausau, WI. 44d 58m 00s N x 89d 36m 45s W
All opinions are my own, even if they are wrong!

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From: [email-masked] (Scott Logan)
Date: 11 Jun 1996 11:45:31 GMT

[email-masked] (Chris Kantarjiev), the following was
written:
> reversing motor?

Tapping or chasing threads with a Die.

--
>From  Scott Logan,
http://ourworld.compuserve.com/homepages/LoganAct
Reply to [email-masked]

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From: [email-masked] (Edward Haas)
Date: 10 Jun 1996 22:26:45 -0700

Chris Kantarjiev ([email-masked]) wrote:
: Can someone tell me what class of lathe work *needs* an instant
: reversing motor? I'm not completely inexperienced in this area, and I
	(SNIP)
	--Well, my Hardinge Chucker has that feature and it's damned 
handy when I have to tap a whole bunch of identical parts. I just put on 
the flood lubricant, put it in a low speed range, feed in with the right 
hand and reverse direction instantly at the correct moment with the left 
hand on the reversing lever. Cost-effective, it is...
-- 
	"Steamboat Ed" Haas	:	Another proud member of 	
	COMING SOON		:	The Anti-Virus Vigilanties
	http://www.west.net/~steamer  	
		---Decks a-wash in a sea of words---

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From: [email-masked] (Chris Kantarjiev)
Date: 11 Jun 1996 17:26:36 GMT

Aha. I am enlightened. Thanks, all.

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From: [email-masked] (Bill Wyant)
Date: Tue, 11 Jun 1996 04:40:49 GMT

>(Besides, just how instant can instant be?)

When you turn a screw thread that is an oddball thread, i.e. 11.5
threads per inch, you cannot use the screw thread gauge on the lathe
to mark where to engage the threading lever for sucessive cuts. In
this case, the only thing you can do is back up the threading tool by
putting the lathe into reverse and backing the tool out of the cut.
That is why you reverse the motor without disengaging the thread feed.

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From: [email-masked] (Chris Kantarjiev)
Date: 11 Jun 1996 19:54:36 GMT

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From: [email-masked] (Edward Haas)
Date: 12 Jun 1996 08:32:45 -0700

Jim Shockey ([email-masked]) wrote:
: >Ah, but wait ... won't the backlash in the drive train
: >completely alter the tool's position? That's what I didn't understand
: >the first time through. Backlash.
	--Not a problem because the tool is being fed by hand (a light touch: a 
tap  will mostly feed itself), not being driven by a leadscrew... Just turn the
 feed-handle the other way at the right moment; the reversing chuck will let 
you "feel" what's needed.
: I haven't had the pleasure of running a Hardinge Chucker; but, 
: if Ed would like me to come on down to So. Calif., I can show 
: him how to break taps on it, too. <g> 
	--Hey, I'm *in* So. Cal. Come on up! 
-- 
	"Steamboat Ed" Haas	:	Another proud member of 	
	COMING SOON		:	The Anti-Virus Vigilanties
	http://www.west.net/~steamer  	
		---Decks a-wash in a sea of words---

---

From: Charles Lamont <[email-masked]>
Date: Fri, 14 Jun 1996 00:08:27 +0100

Chris Kantarjiev writes
>the first time through. Backlash.

Back the tool out for running back.  Wind it in again before next cut.

You still don't *need* instant reverse for this, it just may be a bit
quicker.
-- 
Charles

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From: Steve Wellcome <[email-masked]>
Date: 13 Jun 1996 12:12:40 GMT

With a 3-phase motor, "instant" can be pretty instantaneous.

For industry (with real 3-phase power), people quite often
push reverse/off to stop the motor, so the machine will stop
quickly.  After all, time is money and all that.

In a home shop...who cares?

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From: PPIERCE <[email-masked]>
Date: Thu, 13 Jun 1996 11:24:23 -0700

Chris Kantarjiev wrote:
> 
> In article <[email-masked]>, Steve Wellcome <[email-masked]> writes:
> Well, that's what I'm trying to figure out. Given that the use of instant
> reversing feature is to stop tapping, it might matter a lot!
> 
> The real question is whether I need to spring the extra money for
> an instant reversing motor (which I'll likely have to buy new) or
> will be happy with a good used cap-start motor.

With a threaded spindle and a large workpiece I don't think an instant
reverse is smart.  I heard of a fellow who almost lost a foot when a
large workpiece and chuck fell on him.  What's a few seconds?  
I'm sure a camlock would not present that problem however.

Paul in AJ AZ

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From: [email-masked] (Chris Kantarjiev)
Date: 13 Jun 1996 17:41:16 GMT

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From: Mike Rehmus <[email-masked]>
Date: 13 Jun 1996 22:15:29 GMT

I use instant reversing when I am tapping holes 
in the lathe under power.  Or in the mill.

I think there are classes of tools/toolholders
designed for turrets where reversing the rotation
of the workpiece triggers another type of cutting
action.  I am not too clear on this.

Of course instant reversing is always great when
you get your tie caught in the chuck!

Also can unwind a thread-on chuck very nicely.

Best regards,

Mike Rehmus

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From: Charlie Greenman <[email-masked]>
Date: 14 Jun 1996 11:50:09 GMT

RE: the "oddball" threads and having to keep the half-nuts
locked.... I'm pretty sure you only have to do that with
metric threads and an inch leadscrew. With any "threads
per inch" and an inch leadscrew, the thread will repeat
for all threads if you use the same point on the indicator.
So for any thread if you always pickup on say "2", you'll
be fine. (Obviously you wouldn't want to do this unless it
was necessary!)

This information came with the User Guide for my Logan 920
lathe (right Scott? :-)...  which I got from Logan.

/Charlie

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From: [email-masked] (Scott Logan)
Date: 17 Jun 1996 12:26:12 GMT

In article <[email-masked] m>, From Charlie Greenman 
<[email-masked]>, the following was written:
> be fine.

Actually, it's not even that complicated.  There are some tricks that
are not often known about threading.

#1    If you have an 8TPI lead screw and are cutting any multiple of
8TPI (ie 8, 16, 24, 32, 40 etc.), you don't need ANY thread dial.  You
can pick up the thread anywhere.

#2    This applies to Logan Lathes (and should work with any other lathe
where the thread dial makes 1 revolutions per 2 inches of carriage
travel):  When cutting ODD number threads (5, 7, 9, 11 etc.), engage the
half nut on one of the 2 numbered marks an the dial.  When cutting EVEN
number threads, engage the half nut at any of the 4 marks on the dial. 
When cutting half-numbered threads (4½, 5½, 11½ etc.) engage the half
nut at the SAME mark on the dial.

#3    For other pitches (metric, ¼ pitch, special etc.) you will
probably have to keep the half nut engaged, and reverse the spindle to
bring the tool back to the starting point.

#4    MEASURE TWICE - CUT ONCE!  And start with a piece of scrap
material if you not too sure.

--