Re: [Emc-users] Tell me if I did something right

2018-01-26 Thread Gene Heskett 
On Friday 26 January 2018 23:40:40 andy pugh wrote:

> On 27 January 2018 at 00:07, Gene Heskett  wrote:
> > > As a first measurement, try a dial indicator in the chuck around a
> > > good MT adaptor in the tailstock (assuming a set-over tailstock).
> >
> > That, even with the tailstock that close, is going to be off a good
> > 50 thou as I've yet to get shims (and shim stock enough) to get it
> > true, its off vertically, and I've also bought 2 more triple bearing
> > MT2 centers only to find their NT2's ground off center
>
> That is why I was suggesting an MT3 - to - 2 adaptor. (Or 2 to 1, if
> the tailstock is a 2)
> They would have to try very hard to make the outer surface of the same
> taper not concentric with itself.

OTOH, if the part such as a dead center, has to be reversed after 
grinding one end and the other end was done in a different jig or even 
machine, finding the tip of a dead center out of registration with the 
axis of the MT-2 is entirely up to the operator and how clean he kept 
the sockets.

Which is why I didn't take a lot of care making the MT-5 and the threads 
for the drawbar concentric with the piece of raw alu I started with. 
Verifying that the runout was as close to zero as I could get it in the 
spindles bore, I didn't care, because when I turned it around and put a 
few hundred lbs of pull into the spindle with it, it wasn't going 
anyplace. At that point I made a reversed 5C pattern on the other end of 
the alu rod and made sure it was a snug press fit, difficult to draw 
into place with a bolt and some washers in the end of the alu. The 
washers fit against the cut-away for the drawbar in the rear of the 
grizzly adapter, giving me free reign to grind and remove enough of it 
so it didn't hit the teeny ledge in the MT-5 taper in the spindle that 
the max reach (2.65") of the grinder left. That last was cut .625" a 
pass, with just a few sparks from the stone. Smoother than new once it 
was cleaned out after correcting the 5C taper wall to 10 degrees.

ATM, I think, useing what I brung, that pulling the tailstocks barrel, 
chucking it in the 4 jaw with very little projecting, adjusting the 
run-out of its bore with tension on the jaws, then inserting the worn 
center and giving it a few taps with a dead blow, and re-grinding the 60 
degree tip is the best way to get a center good enough to align the 
tailstock. As for the live centers, I guess I'll have to throw both what 
I have and bigger money out for a good one. These 2 $22 ones are sure 
junk. I wouldn't use them within 18" of the chuck, I've already had them 
make a well tightened workpiece walk in the chuck. At about 10" away.

Eventually I suppose I'll get to scraping the 70 years of wear out of the 
ways, or map it. I'll no doubt ask some questions about that because 
I'll be mapping the X error according to Z's absolute position. And that 
changes about half a thou depending on which way Z is moving. That I 
think might be an artifact of an apron thats about 50 lbs lighter than 
OEM monster apron holding it on the V. It lost a similar amount of 
weight on the rear with the removal of the taper assembly, and it may 
need some bearings to add some preload to the front of the saddle.  
We'll see...

Thanks Andy.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Tell me if I did something right

2018-01-26 Thread andy pugh 
On 27 January 2018 at 00:07, Gene Heskett  wrote:

>
> > As a first measurement, try a dial indicator in the chuck around a
> > good MT adaptor in the tailstock (assuming a set-over tailstock).
>
> That, even with the tailstock that close, is going to be off a good 50
> thou as I've yet to get shims (and shim stock enough) to get it true,
> its off vertically, and I've also bought 2 more triple bearing MT2
> centers only to find their NT2's ground off center


That is why I was suggesting an MT3 - to - 2 adaptor. (Or 2 to 1, if the
tailstock is a 2)
They would have to try very hard to make the outer surface of the same
taper not concentric with itself.


-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916
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Re: [Emc-users] Tell me if I did something right

2018-01-26 Thread Gene Heskett 
On Friday 26 January 2018 14:22:10 andy pugh wrote:

> On 26 January 2018 at 16:56, Gene Heskett  wrote:
> > Moving the dial with the carriage also tells me the head on this
> > thing isn't well trammed. The error, assuming the A2 isn't tapered,
> > is about a thou/inch.
> >
> > What sort of a measuring setup does it take to measure that?
>
> Comparing the results you get when turning work between centres and
> turning work in the chuck can probably indicate whether the head is
> set over or twisted (or both).
> As a first measurement, try a dial indicator in the chuck around a
> good MT adaptor in the tailstock (assuming a set-over tailstock).

That, even with the tailstock that close, is going to be off a good 50 
thou as I've yet to get shims (and shim stock enough) to get it true, 
its off vertically, and I've also bought 2 more triple bearing MT2 
centers only to find their NT2's ground off center.

Rotated in the barrel, the major diameter of the dead ones cone can be 
seen to have a pronounced wobble at the major diameter. So I am still 
looking for a center claiming .0005" or better accuracy before I fight 
any more trying to align the tailstock in any direction. The marketplace 
at ebay is loaded with junk. But I expect you knew that too...

The only choice I may have is to make another MT5-MT2 adapter which at 
the size for boreing, will be a major project in itself, and regrind the 
badly worn/scored dead center I got with it. The live centers I've 
bought, look "purty" but the MT2 on the rear isn't even close to being 
concentric with the tip. 2 brand new ones are at least 20 thou out. But 
for a $20 and change, I guess I got what I paid for. :(

What I just thought of, is to pull the barrel out, put it in the 4 jaw 
and make it run concentric at its ID, then put the worn dead center in 
it and grind it true.  Does that sound like it would work well enough 
for this?

Seems like it ought to. Then I can worry about sourceing some shim stock 
to jack it up. Mostly at the rear IIRC.

Thanks Andy.

-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Tell me if I did something right

2018-01-26 Thread andy pugh 
On 26 January 2018 at 16:56, Gene Heskett  wrote:

>
> Moving the dial with the carriage also tells me the head on this thing
> isn't well trammed. The error, assuming the A2 isn't tapered, is about a
> thou/inch.
>
> What sort of a measuring setup does it take to measure that?


Comparing the results you get when turning work between centres and turning
work in the chuck can probably indicate whether the head is set over or
twisted (or both).
As a first measurement, try a dial indicator in the chuck around a good MT
adaptor in the tailstock (assuming a set-over tailstock).

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is designed
for the especial use of mechanical geniuses, daredevils and lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1916
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[Emc-users] Tell me if I did something right

2018-01-26 Thread Gene Heskett 
Greetings everybody;

I just came in from putting the finishing touches on that MT5-5C adapter 
I bought from Grizzly, finding it wasn't the MT5 my sheldon wanted as 
its called a short MT5 in the spindle description.

First. I had to regrind the MT5 in the spindle as the spindle was bent, 
around 7 thou at the mouth, I assume from the sudden stop with a chuck 
mounted in the same fallover that demolished the compound. Got that 
fixed but then tried to clean up the adapter I got with the lathe, which 
was obviously a shop made part that was never compared to a 5C drawing. 
The inner bore was all over for size, the taper seat angle was maybe 8 
degrees. So I bought another from Grizzly. 

I took around 2.25" off the small end. then bought some 1.75" alu rod and 
made a short MT5 on one end, but threaded for the drawbar tubes threads 
on the end.  Then I turned it around and pulled it solidly into the 
spindle and carved a 5C profile on the other end, overshooting the small 
end cut by about 2 thou, shloppy fit.  Cleaned it up, cleaned up a 
knurling tool and gave it a crosshatch about 5 thou tall. filled 
crosshatch with permatex liquid metal. Gave that a day to harden and cut 
it back to the right size. Grizzly part, turned end for end, seated 
well, so I set the grinder back up and ground it to an MT5 taper whose 
big end was about a thou bigger than the mouth of my now slightly larger 
spindle. Measured how deep the short MT5 was, and shortened it to about 
1/8" less.

Then on putting it into the spindle and starting the spindle and from the 
contact pattern on the ER-40 adapter telling me it wasn't ground to a 10 
degree angle, but it was obvious, you could see it from 6 feet away, 
that the tapered section the ER-40 was supposed to seat in, was 
eccentric by a measured 16 thou!

So I cleaned it and the spindle, seated it in the spindle, drove it in 
with a dead blow, set up the grinder and made that both concentric and 
10 degrees. Mouth of ER-40 adapter run-out now about .00012". Unwrapped 
the new nut, (the one that came with the adapter had 20+ thou wobble in 
its seating cone) a ball bearing type, cleaned it up, unwrapped a 1/2" 
collet, and stuck a 2' piece of A2 in it. Drew it down with the wrench I 
bought with it, then gave the wrench a couple whacks with a deadblow. 
Dial says .0001" on the A2 at the collet, and .0004" an inch from the 
collet.

I think that calls for a minor celebration.  Makes for a VBWGrin anyway.

Moving the dial with the carriage also tells me the head on this thing 
isn't well trammed. The error, assuming the A2 isn't tapered, is about a 
thou/inch.

What sort of a measuring setup does it take to measure that?

But so far my work to correct the bent spindle has I think been 
successfull. I not touched the outside of it. but I have the new 4 jaw 
chuck running within .0006" of true, and some of that may be warpage 
from tight mounting bolts, its a very noisy .0006".

And I will do the same backplate cleanup on the 3 jaw.

I'll make a real lathe outta this $2000, 1500 lb pile of scrap yet! ;-)

Thanks for reading guys, comment if you like.
-- 
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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