Subject: Re: The Bloop maker, a shaggy dog story

From: [email-masked] (John W. Hall)
Date: Thu, 12 Sep 96 13:35:45 GMT

In article <[email-masked]>,
   Mike Rehmus <[email-masked]> wrote:

>Jones immediately threw the metal overboard where, when it hit the 
water,
>made a sound like BLOOP and promptly sank.
>
>That, my friends, is a Bloop.
>
We mustn't miss the historic perspective here. When I was doing 
archeology in Pennsylvania thirty years ago, we would find and bag up 
inummerable stones on our sites that we instructed the innocent high 
schoolers who worked for us were "Iroquois bloop stones". Obviously 
the concept of bloop predates the machine age. 
John

---

From: [email-masked] (Ian R. Howcroft)
Date: Thu, 12 Sep 1996 11:39:35 GMT

[email-masked] (Jens) wrote:

>I would like to know what peoples secrets are to getting a real smooth
>lathe turned finish. No matter what, if I use mild steel (yes I know
>it's crappy stuff for finish) I get a surface finish that shows tear
>marks. Yes, if I use a real sharp cutter with a large radius point and
>slow feeds I get a nice looking finish but when you take a magnifying
>glass to it ,it still shows tear marks. Even using brand new carbide
>inserts at high (or low) RPM gives this kind of finish.
>So, am I living in dream land or is it possible to get a finish that
>is 'as ground' ?
>I have got water soluble cutting oil on order as this is pretty much
>the only thing I haven't tried yet but I have my doubts about this
>having any major surface finish effect.

You will find that it will make a tremendous difference, as the oil in
the coolant will reduce any tearing.  That is it's purpose.  Many
years ago, I had to turn bearing journals on mild steel, and a  good
finish was essential - obviously.  The way I achieved this, was to
grind a tool with an angle about that used on h/s parting tools, which
ensured that the back of the parted off unit was clean with no pimple.
Now, if you have a tool ground like that - about three sixteenths
wide, instead of parting off with it, you use it to turn the diameter
on which you want your finish.  Keep revs to a minimum - it's not a
quick procedure - take a very light finishing cut and keep heaps of
coolant on it.  I must confess I have not examined the finish I
achieved with a magnifying glass because it was entirely satisfactory.
However, it was  finish that was very pleasing to the eye.  The tool
by the way was made from high speed steel.  If you have any difficulty
in understanding what I have said (and that wouldn't surprise me -
it's not the best bit of descriptive writing I have ever seen) please
feel free to contact me - [email-masked] and I'll try to help you
further.
                              Best wishes.
                                                IRH.

>This whole issue came about when I was trying to produce a threaded
>rod on the lathe and got very ()*(&^ finish. I managed to improve the
>finish quite a bit but when you run your fingers over the threads it
>still feels rough/pointy because of the tearing. I realize the
>commercial screws are rolled and not cut but it would be nice to
>achieve that kind of finish.
>By the way, rigidity in my setup is not an issue !

>Jens

>By the way, on my previous question on modulus of elasticity I
>received a number of replies but none that explained the reasoning at
>a 'gut' level. In other words, I know how deflection is calculated etc
>but it just doesn't feel right at gut level (although I can certainly
>figure out deflection at the 'brain' level)
>Thank you to all the people that tried to sort out my gut. I guess I
>have to use my brains on this issue instead of my gut .....

>If any of this jibberish makes no sense than my apologies :)

---

From: Mike Rehmus <[email-masked]>
Date: 12 Sep 1996 13:32:18 GMT

Another bit to the smooth finish story.

I'm reviewing a video tape made in the Lawrence Livermore Laboratory's Machine Shops 
regarding machine accuracy.  There is much more to it than we could imagine.

However, regarding the issues of surface finish (they have a lathe that will make
aluminum mirrors for their fusion experiments in a single pass), they have quite a bit 
to say.  I'll be starting on a serialization of the information for our local engine 
modeler's club newwletter, The Crank Calls, Real Soon Now.

Some of the main points they make are:

1.  If you have a lot of vibration present, you cannot expect a good surface finish.
2.  In single-point cutting, workpiece imbalance will not degrade the surface finish.
3.  Diamond cutting tools, because of their sharpness, will cut sub-0.001" passes and
    not rub the surface of workpiece.
4.  Diamond cutting tools will not experience a build-up on their cutting edges that
    destroy (good) surface finish.
5.  Gear train noise in most lathes causes lots of problems in surface finish.

One has to remember that these guys are talking about mirror-like single-pass finishes 
in many cases.

They do show an old flat belt driven lathe with an overhead motor that was modified in 
a high school industrial arts class to cut a mirror finish.  The budget was $100.  The 
methods used were simple.

1.  They removed the overhead motor and isolated it from the lathe.
2.  The gear train was removed and a variable-speed motor was used to drive the
    leadscrew.  The connection from the motor to the leadscrew was a piece of rubber
    garden hose.

So, if you want to turn mirror finished salt and pepper shakers for your Aunt Rose,
those are some of the methods to use.

Look for more in the Metal Working WEb site.  YOu are contributing, aren't you?

Best regards,

MIke Rehmus

---

From: Roger M Weppelman <[email-masked]>
Date: 12 Sep 1996 14:25:33 GMT

[email-masked] (Rrice2) wrote:
>In article <[email-masked]>, [email-masked] (Chris
>Heapy) writes:
>
>> hence the advantage of setting the topslide over to half
>>thread angle and just using one cutting edge on the tool, this way you
>>can add top-rake to the cutting edge greatly improving the finish.
*********>
>This is the first time that I have heard of setting the tool to half the
>thread angle in threading. Is the tool ground differently other than the
>top rake? If not, I don't see how you get the 60 degree thread angle.
>Please give us more information on this technique.

The current issue of HSM (September/October) contains a letter to the editor 
entitled "Where's the Tangent" by Jim Canner, who, like the original respondent, is 
also from the UK. (Is this method unique to the UK?) Canner explains this technique 
in some detail. As I understand it, the included angle of the tool can be anything 
just so that it is less than the included angle of the thread. Canner notes that a 
tool with a 45 degree included angle can be used to cut 47.5, 55 and 60 degree 
threads. By this technique, the tool's leading edge does all the work and the 
trailing edge does nothing so you give the leading edge all the rake and clearance. 
The set up is as follows: the compound is set at the half angle of the tread (only 
the compound is used feed the tool) and the leading edge of the tool is then set at 
the correct angle to the work piece with the usual thread gage (the trailing edge of 
the tool does nothing so ignore it). The thread is then cut in the usual fashion.  
Canner claims this method leaves a finish so good that it "has to be seen to be 
appreciated". Canner also notes that threads cut in this fashion are V-form rather 
than radiused, but for most applications this is of no consequence. 

Sounds like a good technique to me and I intend to try it the next time I cut a 
thread.

Roger Weppelman

---

From: [email-masked] (Chris Heapy)
Date: Thu, 12 Sep 1996 15:40:35 GMT

Very briefly it's simply a matter of setting the the topslide to 30
deg (for a 60 deg. inc. angle thread), with the tool still set at
right angles to the work of course, and using the topslide to feed the
tool into the work. The tool will follow the angle of the right-hand
land of the thread whilst just cutting on the left hand side (for
normal threads). There are many variations and modifications on this
theme and most are covered in Geo. H. Thomas' book "The Model
Engineers Workshop Manual" ISBN 1-85761-000-8 from TEE publishing,
which I highly reccommend.

Chris

---

From: [email-masked] (Mike Clayton)
Date: Fri, 13 Sep 1996 08:54:13 +1300

In article <[email-masked]>, [email-masked]
(Bruce Holder) wrote:

> Peter O'Leary ([email-masked]) wrote:
> : [email-masked] (Jens) wrote:
> 
> : >I would like to know what peoples secrets are to getting a real smooth
> : >lathe turned finish. No matter what, if I use mild steel (yes I know
> : >it's crappy stuff for finish) I get a surface finish that shows tear
> : [clip]
> 
> : Believe it or not, for mild steel (crs,hrs) a sharp corner on your
> : tool bit (no radius) will give a better finish.
> 
>   Doesn't that depend on the feed? When I've used a sharp tool, even the
> slowest power feed on my lathe isn't slow enough to keep the tool mark
> from looking like a real fine thread.
> 
> Bruce

My opinion/experience:

I use the late great LBSC's technique, viz get a piece of quarter inch
diameter round high speed steel tool. Grind the end to a 20 degree rake
angle. Grind a V into the top of tool on the corner of the grindstone so
that there is a straight cutting edge the full diameter of the tool
formed. Ensure the edge so formed is as sharp as you can make it.

Put the tool into the holder so that the cutting edge is at 45 degrees to
the logtitudinal axis of the work (I have the top corner of the tool
inclined towards the tailstock) and the centre of the edge is at centre
height of the lathe. Use slowest feed, high rotational speed. Take no more
than 2 thou cut. Flood with coolant. Swarf will stream off in long fine
hairs which will rip your hands to pieces - use protective gloves and your
safety glasses. The finish is usually very good, but as usual be prepared
to play about with things to get the best result. The cut is partly
rubbing, which I believe is the secret.

-- 
Mike Clayton
Language Labs
University of Canterbury
[email-masked]

---

From: [email-masked] (Chris Heapy)
Date: Thu, 12 Sep 1996 23:09:10 GMT

Guess I forgot to answer the obvious question in my last post "how do
you gauge the depth of cut if feeding in at an angle?". The answer is
either to add 1/8 to the cut (rough estimate) or do it properly and
use a table. There is one on my web page at:
http://easyweb.easynet.co.uk?~chrish/threadz2.htm
This lists the amount of infeed for a variety of threads.

Chris

---

From: [email-masked] (Chris Heapy)
Date: Sat, 14 Sep 1996 09:07:31 GMT

>> By this technique, the tool's leading edge does all the work and the
>At the trade school in Huntsville, Ala.  I was taught to set the compound
>to 29 degrees, so that the trailing edge made a very slight cut.
>Otherwise you might have a slight trace of the various cuts on that
>surface.  Seemed to work well.

>Was also taught how to use a surface grinder to sharpen HSS for cutting
>threads.
>				Cheers,

You're right, that is the best way. To add a little more description
to the method the steps are as follows:

1. Setover the topslide to half thread angle (or slightly under - 1
deg or so).
2. Run the tool point in to just touch the work, zero the cross-slide
dial.
3. Move the tool to the right of the work and use the top-slide to
move the tool inwards  to the previously calculated cutting depth.
4. Zero both the topslide dial and the cross-slide dial.
5. Now, backout the tool using the top-slide only until it's again
just touching the work (move the the toolpoint to left)
6. Put the cut on using the top-slide only, traverse for the first
cut.
7. Pull the tool out of the cut using the cross-slide and wind the
carriage back to the beginning, wind the cross-slide back in to it's
zero setting.
8. Add to the cut using top-slide again, and repeat. When the
top-slide reads zero you know you've reached full depth.

Note: if you used exactly half thread angle (and I do) add the last
thou using the cross-slide to clean up the trailing thread face.

Hope that wasn't too patronising or boring to the many expert
machininsts here :) just thought it was worth being clear about it.

			oOo

To sharpen tools to the correct angles initially I use my vertical
miller, a universal vice, a protractor head, and a 4" grinding disk
(from an angle grinder) mounted on a special arbour turning at about
2500 rpm  - that's as fast as it will go. Those disks are tough and
won't shatter easily. I actually TURNED the disk hollow so it cuts at
the outside edge with a carbide tool (run in back-gear, sharpen
often!). Messy job, but I've only needed to do it once - and you don't
need to take much off. Cover up the lathe and clean up well after.
This gives a flat, smooth surface , with accurate angles, and needs
very little touching up with a hone.
One day I'll make a tool and cutter grinder...

Chris

---

From: Jeffrey Prothero <[email-masked]>
Date: Thu, 12 Sep 1996 17:29:54 -0700

---

From: [email-masked] (Felice Luftschein & Nicholas Carter)
Date: Fri, 13 Sep 1996 23:42:25 GMT

This happened to me with the Sherline mill. I enede up machining a #10 square 
nut down on my lathe. You should go to the hardware store and buy a square nut
for whatever bolt/stud fits the slot, then alter it so that it is fits the 
slot. It helps to have clamping hardware to do this, so unless you use a file 
or your lathe, it's a catch-22. peen the bottom of the nut threads so the stud 
cannot go all the way through and mar the table!

In article <[email-masked]> Eduardo 
Haddad Filho <[email-masked]> writes:>From: Eduardo Haddad Filho 
<[email-masked]>>Subject: Standard Slots?
>Date: Thu, 12 Sep 1996 18:34:52 -0300

>I've just received my first milling machine - a Prazi.
>I'm not sure but I think its slots are not standard. I went through 
>Machinery's Handbook and found some standards for slots, bolts and slot 
>nuts but Prazi's dimensions are different.
>I've done a "drawing" for the slot.
>As many mail order catalogs simply mention 3/8" slots, without giving its 
>profile, could you tell me if I should by hardware for a 3/8" or 5/16" 
>profile?

>Here is the "drawing"(Argh!)

>Thanks!

> ________    A     ________
>|        |        |        |
>|        |        |        |
>|        |        | D      |
>|        |        |        |
>|   _____|        |_____   |
>|  |                    |  |
>|  |                 C  |  |
>|  |          B         |  |
>|  |____________________|  |
>|__________________________|

>A(throat) =  0.387"    9.8mm
>B(width)  =  0.620"   15.7mm
>C(height) =  0.310"    7.9mm
>D(height) =  0.307"    7.8mm

>Eduardo Haddad Filho
>[email-masked]

---

From: [email-masked] (Paul Pierce)
Date: 15 Sep 1996 18:55:50 GMT

Nicely done.  

If someone knows all this, they should just agree with you as I'm sure 
there are plenty that welcome such information.  That is what I sort of 
thought the Newsgroups were for, to help others.

Information like this may or maynot be in the FAQ, but apparently some 
folks are not aware of its' existance.  Jim K posts the FAQ in its 
entirety every month, God Bless Him...

Paul in AJ AZ
[email-masked]

---

From: [email-masked] (Rrice2)
Date: 13 Sep 1996 09:21:17 -0400

In article <[email-masked]>, [email-masked]
(Chris Heapy) writes:

>normal threads).

Gosh! In my original reading of the comment on setting the top slide to
half the thread angle, I got in my mind that the writer meant 15 degrees,
or half the "usual" angle of 30 degrees. That's what happens when I try to
think, I guess! Sorry to have cluttered the thread with a stupid question.

RR

---

From: Eduardo Haddad Filho <[email-masked]>
Date: Thu, 12 Sep 1996 18:34:52 -0300

Thanks!

 ________    A     ________
|        |        |        |
|        |        |        |
|        |        | D      |
|        |        |        |
|   _____|        |_____   |
|  |                    |  |
|  |                 C  |  |
|  |          B         |  |

A(throat) =  0.387"    9.8mm
B(width)  =  0.620"   15.7mm
C(height) =  0.310"    7.9mm
D(height) =  0.307"    7.8mm

Eduardo Haddad Filho
[email-masked]

---

From: Pat Kelley <[email-masked]>
Date: Sun, 15 Sep 1996 04:06:55 -0500

> 5.  Gear train noise in most lathes causes lots of problems in surface finish.

	Sounds reasonable. I used to run what was possibly the first CNC
contact 
lens lathe, and the cutting tool was a single, rather large diamond. The
spindle
turned on air bearings, and was powered by a high-frequency three-phase
convertor,
which wound it up to 20,000 or so RPM. When everything was perfectly
adjusted,
which was an incredibly tedious chore, it produced an amazing finish
which looked
like it didn't even need polishing, though that was just a naked-eye
impression.
The material was not steel, of course, but usually polymethyl
methacrylate - and
sometimes brass, when the machine went crazy and started cutting the
lens mount.
To give some idea of the antiquity of this setup, it was controlled by a
DEC LSI-11
speaking Fortran. Those were the days. Rather unpleasant days, actually,
but it
was a fun machine to work with.

-- 
///////////////////////////////////////////////////////////////
               Pat Kelley ([email-masked])
    "I think, therefore you are. Don't make me regret it."
              http://www.flash.net/~manaret/
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\

---

From: [email-masked] (Honor� de Gronckel)
Date: Mon, 16 Sep 1996 21:19:03 GMT

Soluble oil makes a difference! In turning mild steel I get a surface
finish comparable to what I get with sandpaper 1000. This is the same
as the 'roughness' of my (honed) cutter. Without the soluble oil it's
worse.
I use the standard cutting angles for mild steel (clearances 10
degrees, top rake 20 degrees if I remember correctly) but  ground a
small land on the tip. The biggest problem I had was to get rid of the
damage of the turned surface caused by the chips just created. Since I
don't have a flood system for cooling I played around with the side
rake angle and the back clearance angle. Currently I use a side rake
of approximately 3 degrees and a back clearance angle of 20 degrees.
Works fine for me. A chipbreaker edge may do the same. Never tried
that though.

In turning threads I have the topslide parellel to the bed. When I
feed the cross slide in, I feed in the topslide half the amount.
Enables one to perfectly work to depth with the extra advantage that
it's very easy to clean up the flanks (leading and trailing) with
light cuts afterwards. The only problem I experience is that of burrs
on top of the crests. If necessary I file them off between the cuts.
For cutting threads on a lathe I can really recommend the book of
Matrin Cleeve, 'Srewcutting on the lathe' (or something like it)
published as no. 3 of the WPS (Workshop Practice Series) by Argus
books. 100 + pages about screwcutting by a guy who ran a machine shop
himself. I guess, if it isn't in there it's not worth knowing.

Hope this helps, Honoré.

---

From: Steve Austin <[email-masked]>
Date: Fri, 13 Sep 1996 22:41:23 -0400

The Machinerys Handbook has a nice section on grinding thread
tools.  It gives all the formulas for culculating the helix of
the tread and effective relief angles.  This is a good
introduction to setting up compound angles.  If the top of the
treading tool is not flat and the trailing edge makes any cut,
then the geometry of the tread will not be correct.  A tread has
a V form parallel with the axis.  The form of the thread at the
intersection of a helix and an inclined plane off center is a
very complex curve.  A top raked tool gives a nice finish on the
leading edge but guess which edge takes the load 90% of the time?

Steve A.