gmane.linux.distributions.emc.user

Re: Can someone quote me a price on a simple(?) part?

Gregg Eshelman — 2013-05-22T10:23:26



Right hand thread.


The nut's not worn out, it's MISSING. Gone. Not there. Someone took things apart and lost some of the pieces. Also missing are the compound dial (anyone got any 2" diameter dial with a 0.5" bore and markings suitable for use with an 8 tpi screw? ANY dial, doesn't have to be off a LeBlond!), the bushing (which needs a 1" x 16 tpi thread - oh fun another oddball thread), and the handles for the compound and cross slides. The compound's two gib screws are also MIA and about 3/4 to 1" of the thin end of the tapered gib is broken off.

I've checked the thread width all along the screw with digital calipers and it's very consistent, very little wear or very even wear. The bed shows original patterning over most of its length. The worst wear is on the bottom of the tailstock.

So, if someone can machine one square profile threaded hole through a piece of brass, I can measure the screw every which way. I just need to get the lathe operational, and this nut is one step along that path.

If you

Re: Can someone quote me a price on a simple(?) part?

andy pugh — 2013-05-22T09:37:07

Is it a left hand thread?

This one is: http://www.ebay.co.uk/itm/190741007179
(And perhaps it is worth contacting that supplier)

It seems like a job best performed with the leadscrew available to compare to.

Alternatively, have you considered a new screw/nut pair? if the nut is
worn out then it is likely that the screw is past its best too.

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-22T05:39:24

On Wednesday 22 May 2013 01:30:27 Jon Elson did opine:

That speaks volumes Jon.


That is an extremely common problem. :(


Ultra fast, Si, or  Schotkey?  Si seems worthless but I have seen the amp 
or so rated Schotkey's make a difference.  Their Vf is only about 2/3rds of 
a germanium diode, and a very low impedance once conduction starts.
 


Cheers, Gene

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-22T05:29:11

On Wednesday 22 May 2013 01:11:07 Peter C. Wallace did opine:

So the problem isn't amenable to just delaying the on drive.  I take it 
that a hard and stiff off bias is simply swamped by the DvDt induced 
capacitance charge from drain to gate.

I also have to assume that tech writers 20 years ago didn't always 
understand the phenomenon they were writing about, because then the holy 
grail was just getting rid of any both on at the same time, eg they weren't 
sure of the causal mechanism.  So my knowledge expands a bit.

Now I wander into theory Peter, because it seems to me that with low enough 
impedance in the drive, if it getting turned back on for a microsec or so, 
that should be something that a better and lower resistance from the gate 
terminal to the gate area of the die ought to be able to absorb that.  
Perhaps the next generation of devices that may come out of the next shrink 
might find a better geometry to alleviate this?

Food for thought, thats for sure. And I expect the chip makers are st

Re: Superglue, or Loc-tite for that motors flywheel?

Jon Elson — 2013-05-22T03:53:15

4000-series can't handle large currents at the output.  I had an earlier 
servo amp
where I used a 4069 inverter, with 3 sections driving each side of a 
little charge pump
transformer.  It would blow up, run hot or just not work.  I finally 
figured out
inter-winding capacitance was driving a lot of current into the inverter
output pins.  I had to split the windings on the bobbin to make it work.

Anyway, the IR2113 and similar drivers can source or sink 2A to the FET
gates.  Can't do that with 4000 CMOS.  My first version of the brushless
servo amp used a triple half-bridge driver chip that was supposed to deliver
600 mA.  Turns out if you read the datasheet more closely, you really only
get 200 mA.  And, that caused the transistors to run hot due to slow
turn-on/turn-off.  The only fix was to go to 3 separate half-bridge
driver chips instead of the all--in-one part.  But, now it runs much
faster, without the partial shoot-through.

My brush servo amp is really old-school, uses 4000-series logic and
RC-dio

Re: Superglue, or Loc-tite for that motors flywheel?

Jon Elson — 2013-05-22T03:43:31

I went to a slightly larger transistor (moved up from the fast IRFB31N20D to
the slightly slower IRFB260N) and the problems disappeared.  The servo amp
runs cool at rated current, so losses are not a problem.  I've got about
as wide traces as the board can stand.  The boards is nearly all surface
mount, the IR drivers are right next to the transistors and the loop
area of the power section is very small.  But, the output conductors
run right under the logic on the bottom of the board.  I've sold 275 of
these, now, so they are a pretty mature design.
The big problem with this is the IR driver chips have a parasitic diode 
in them
that can't tolerate excessive negative voltage at the junction between the
high and low side transistors.  That was what I had to tame, that junction
going below ground.  The body diode in the low-side transistor takes
several MICROseconds to turn on with 12 V forward bias!  I put
ultra-fast power diodes across the low-side transistor to stop it from
going negative, but still wanted

Re: Superglue, or Loc-tite for that motors flywheel?

Peter C. Wallace — 2013-05-22T03:33:08



Unfortunately its not a delay issue but how fast the MOSFET that is switching 
on turns on. At some point the rate of rise of voltage (dVdT) at the drain of 
the off MOSFET caused by the other MOSFET turning on will cause the off MOSFET 
to turn on (due to the drain-gate capacitance of the off MOSFET) Having a gate 
driver with assymetrical drive (slow on fast 
off) helps


Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.


------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that delivers powerful full stack analytics. Optimize and monitor your
browser, app, & servers with just a few lines of code. Try New Relic
and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may

Re: Can someone quote me a price on a simple(?) part?

Gregg Eshelman — 2013-05-22T03:23:18


West Idaho, which is a bit of a drive from East Tennessee.

------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that delivers powerful full stack analytics. Optimize and monitor your
browser, app, & servers with just a few lines of code. Try New Relic
and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-22T03:18:28

On Tuesday 21 May 2013 23:09:36 Peter C. Wallace did opine:


Very true Peter, but would not this sort of problem be better treated with 
some logic to use the gate delay to delay the on swing?  I'm thinking cmos, 
old style 4000 series because I personally used some of that sort of 
trickery to put colored outlines around a character in a character 
generator that didn't have that capability originally.  Running on 28 
volts, that 4028 ran detectably warm, but in 2 years, never failed.  Of 
coarse in those days we thought 200 ns was a short time.  Now, 25ns is 
economy grade utility stuff.  But the idea should be just as valid.
 


Cheers, Gene

Can someone quote me a price on a simple(?) part?

Cecil Thomas — 2013-05-22T02:44:18

Gregg,
Where do you live?
I don't quote prices since I mostly work for fun but I have an iron 
clad business model.....

If you bring me something to work on:

1. You must be present throughout the process either doing the work, 
helping or standing around waiting.
(This eliminates most requests because most of the friends needing 
work done value their time much more highly than they value mine.)

2. Since I work mostly for free my guarantee is that I will give you 
back ALL the pieces of the thing you brought....even if they won't 
fit together anymore.

Seriously, If you are anywhere in East Tennessee I would be happy to 
have you come by and use my machines (which are fully capable to do 
the job) or I would make the the part if you brought the stock and 
the screw for test fitting.

Cecil


------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that deli

Re: Superglue, or Loc-tite for that motors flywheel?

Peter C. Wallace — 2013-05-22T02:14:46



In practical Hbridges, gate resistors for assymetrical gate drive (fast off 
slow on) are often needed to prevent dVdT turn-on of the high side by the low 
side switches or vice versa. If your choice is a little bit of switching loss 
vs shoot-through, its easy to choose...




Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.


------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that delivers powerful full stack analytics. Optimize and monitor your
browser, app, & servers with just a few lines of code. Try New Relic
and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-22T02:04:34

On Tuesday 21 May 2013 21:53:39 Jon Elson did opine:


Those are problems you should like Jon, they are telling you that your 
ground & power planes need to be wider, and need more bypassing.  Both of 
those translate to reduced switching losses & cooler devices.  Often you 
will need both a .05 ceramic on very short leads or better yet, surface 
mount, AND a 10uf in order to get enough bypassing.

Of course I'm far enough away its not worth getting in the car to come and 
beat some manners into me.  :)  I think.

FWIW, resistors in the gate to slow the rise & fall times will raise the 
switching losses, in some cases enough to destroy the device long before 
your finger says its even getting warm.

But you knew all that.



Cheers, Gene

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-22T01:49:56

On Tuesday 21 May 2013 21:17:53 Peter C. Wallace did opine:


Correct.  Very little, and prices are top secret, need to know stuff.  Some 
things never change at Fairchild I guess.


That 80 mOhm is now $16.67 from the Cree dealers (digi-key et all) here in 
the states.  And it looks great, till you look at the gate voltage swings 
it needs. -10 to +25?  Who makes a driver for that?

And/or/but I just got another wakeup call, I've been studying the spindle 
controllers available including the C41 I am going to re-use, and not a 
single one of them can exert the reverse relay without the PWM.  So I 
either have to preface any active sink loads with a big honking full wave 
bridge, or use a resistor only lashup.  Or buy a separate relay board & 
make a PSU for it.

Why the hell do I have to be the only one on the planet that wants 
separate, independent, reverse controls?  I just recently found, by 
watching the ammeter in series with my mills motor, that regardless of how 
much time I add in the .hal file to

Re: Superglue, or Loc-tite for that motors flywheel?

Jon Elson — 2013-05-22T01:49:31

I use the IR2113 and similar chips to drive FETs.  You'd need some op amps
and/or comparators to generate the PWM.  Lack of speed?  The IRFB31N20D was
so fast it caused problems with the dV/dT (and dI/dT) affecting the rest 
of the
circuitry.  Easily 100 ns turn-on/turn-off times, even with resistors in the
gate circuit.

Jon

------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that delivers powerful full stack analytics. Optimize and monitor your
browser, app, & servers with just a few lines of code. Try New Relic
and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may

Can someone quote me a price on a simple(?) part?

Gregg Eshelman — 2013-05-22T01:28:06

I need a nut for the compound slide on a 17X78" LeBlond Regal. Ain't none to be found anywhere, new or used in any condition.

What I need is a 5/8" x 8 tpi square thread* hole put through a piece of brass bar stock, leaving sufficient thickness to the end for strength. I can measure the thread and groove width etc. accurately.
The rest of it I can turn to diameter and cut to length.

There's plenty of room inside the bottom of the slide, the lower end of the nut simply slips into a 0.999" diameter hole.

*Yup SQUARE, not ACME. The lathe was made in 1944.

The only currently operational lathe I have is my 1940 Montgomery Ward, which has no gearbox and just the change gears that were on it when I got it. (Possible CNC conversion candidate, or at least e-leadscrew.) Currently rehabbing Wade 8A #403 and the forementioned large Regal.

------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application perf

Re: Small & Easy To Install Embedded PC Power Supply

andy pugh — 2013-05-21T21:38:47


I watched some short films made by a young film-maker at the
electromagnetic wave event. They are about various folk from the
Society of Model and Expeimental Engineers. I can't recall if it was
in one of the films, or in her personal commentry, that there had been
a round of applause when someone who was only 37 was elected to the
society.

 I can't find the films online yet, but here is something very similar
by the same film-maker
http://vimeo.com/37467868

Re: Superglue, or Loc-tite for that motors flywheel?

Peter C. Wallace — 2013-05-21T21:24:59


Asking for both is a bit optimistic :-)

http://www.fairchildsemi.com/products/sic-bjts/

has a little info on upcoming products and

Cree has been shipping SIC MOSFETs for a while
(80 mOhm 1200V ~$30 each 160 mOhm 1200V ~$15 each)
These MOSFETS have characteristics that are simply unobtainable with Si



Peter Wallace
Mesa Electronics

(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.


------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based application performance monitoring service 
that delivers powerful full stack analytics. Optimize and monitor your
browser, app, & servers with just a few lines of code. Try New Relic
and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may

Re: Small & Easy To Install Embedded PC Power Supply

John Stewart — 2013-05-21T21:18:09

Hi Bruce -

(I really like Sherline lathes - and was looking at getting a Sherline like
yours before this Unimat came along)

My blog (cnc-for-model-engineers.blogspot.com) is meant to help those who,
like myself, are computer-savvy, and are not career-machinists. I was at
the Harrogate show (UK) a week or so ago, and, probably 90% of who I saw
wandering around were older than I am.

So, in order to keep the metal bashing side of model engineering alive,
people a generation younger than I am need to get interested. I know one or
two of the suppliers there understand this, and are working to modify their
wares...

Taking a little unimat/sherline lathe around, and actively showing it off,
and answering questions can only help.

I know Cecil on this list has a really good little one, and there are
probably others...

John Alexander Stewart.
------------------------------------------------------------------------------
Try New Relic Now & We'll Send You this Cool Shirt
New Relic is the only SaaS-based applicatio

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-21T21:14:23

On Tuesday 21 May 2013 17:12:44 Peter C. Wallace did opine:

Si Carbide?  I wasn't aware that anyone was using those for more than lab 
curiosity.

In production AND affordable?



Cheers, Gene

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-21T21:11:43

On Tuesday 21 May 2013 17:11:09 Jon Elson did opine:

I'll see about those when I return from dinner Jon. thanks.



Cheers, Gene

Re: Superglue, or Loc-tite for that motors flywheel?

Gene Heskett — 2013-05-21T21:09:54

On Tuesday 21 May 2013 16:54:40 Peter C. Wallace did opine:

Humm, is there an IC that will function as the switch driver, and whose 
output could be controlled with a PWM mode?  Something that would start at 
15% duty and taper to 100% when the applied voltage had dropped to say 20 
volts.  Then the Q is how fast can these be switched, I get the impression 
I'm still looking at hexfets I can steal out of dead computer PSU's.  These 
things speed (lack thereof) will cause their own SOA self destruction I 
expect.


See my question above.  Something that could be powered by a 8 pack of fwd 
biased 1n914 type diodes?  For this of course, the load R would go in the 
collector.

A good google search term would probably help.
 

I did the same thing in a 275 volt bias supply.  600 volt hexfets slowly 
faded to pure resistance, which rather played hell with the operation point 
of an 85kw water cooled triode final in our old NTSC transmitter.  I liked 
how it worked, making definite improvements in the video linea