Hard turning, finishing the part.

[P. Waller]

Excellent finish on the part aside from the threads,

this is what often happens when the threading tool crests when the PD is too small, it creates a sharp edge at the crest of the V, this often leaves a nasty burr, do not do this with a single point threading tool.
A full form insert will reduce this but it is unlikely that many hobbyists will buy or grind a full form tool.
The thread PD on this one is way too small, the following part threads look excellent, almost like I know what I am doing.

 

[P. Waller]

Bloody hell, I just bought a new mag base indicator holder, I was looking for a long reach holder with a very strong magnet base as I will use it on a 24 X 100 lathe.

It arrived today, it is WAY larger then I had anticipated. This is with a 3" dial drop indicator. I bought the arm and base without an indicator as I have several.
This is a commonly available sized base in the foreground as a size reference.
It looked way smaller in the pictures, one of the advantages of an actual physical store is that one may see it in scale. It is reasonably well made so I am keeping it.

 

[Boswell]

It looked way smaller in the pictures, one of the advantages

I have struggled with learning this lesson of online purchasing. "Don't trust pictures for scale, always check the measurements" One of these days, I'll get it. (I hope sooner than later).

 

[P. Waller]

I have struggled with learning this lesson of online purchasing. "Don't trust pictures for scale, always check the measurements" One of these days, I'll get it. (I hope sooner than later).

Fortunately it is exactly what I was looking for but far more robust then I was expecting for $170.00 https://www.amazon.com/gp/product/B002NEPEXO/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
We shall see how it holds up after a year of use in a busy job shop, it appears very well made however. The fussy little indicator holder on the end is not likely to live through the next year I suspect, there are indicator holders that I prefer over this type that are easily added via a threaded hole on the end.

 

[P. Waller]

Interesting problem that had me scratching the old head for a few hours on this part.

The first order of operations was leave just enough out of the chuck in order to turn the large diameter past the un-threaded end, face then turn the OD's including the thread undercut.

Thread 9/16-32 then drill 15/32" (.469") from the nominal .420" ID of 3/8 NPT pipe. I measured the thread PD over wires.
Finished part, the wall thickness is .025" under the thread.




This worked well for 40 parts or so then the PD began to grow, this was caused by the drill becoming dull and deforming the tube. Normally I will do every roughing operation before any finish operations but figured that drilling .024" per side is almost finishing, but I was wrong.

Drilled first then did everything else and the next 65 parts ran flawlessly, live and learn.

 

[P. Waller]

My venerable Mitutoyo indicator failed after 23 years of use, I bought a new B&S Interapid last week.
This will last beyond my limited life span I suspect.

 

[P. Waller]

One easy job today, 6061 aluminum ring water jet cut from 1 3/8" plate stock, the flange OD is 14 1/2" X 1/4" long, the smaller OD is 13 1/2" X 1" long, the bore is 13" leaving a 1/4" wall.

This became a problem once the part became thin, the part was held in a 3-Jaw chuck with soft jaws, there is considerable unsupported distance between the jaws, it began to chatter in the area between the jaws. I suspect that a few here have experienced this with thin parts.

Until it became a game of cat and mouse between speed and chatter I could have at it.
14"+ diameter, 450 SFM cut speed (125 RPM's), .008 IPR feed and a .050" DOC using a CCMT negative rake insert with a positive rake chip breaker geometry.

Roughing aluminum with stable work holding should look like this, chips not coils, springy coiled chips will drive you mad over time.
This is a manual lathe.



I did produce some annoying stringy chips when finishing due the reduced speed and feeds required to stop the chatter.
Turned out well however, with set up included about 5 hours.

 

[P. Waller]

Tomorrow morning I have to do something that I have never done before.
Pick up an existing 1 1/4-7 thread on a CNC lathe, have not the faintest clue how to do so on this machine.
Anyone with hints (-:
Jim Dawson?

 

[e189552]

We would use the tool offsets.
Back the tool up in X a comfortable amount and run the thread routine.
We would carefully “eyeball” the Z position relative to the thread flank and adjust the Z tool offset.
Apply dykem layout fluid or even a permanent marker when you get really close to see which thread flank you contact first.

 

[P. Waller]

It went very well adjusting the Z offset and eyeballing the tool when it got close but it kept moving to the right. I then remembered that this control has an approach angle parameter in the thread cycle and someone had set the default value to 29 Deg. Once I set it to 0 it was quite easy to pick up the thread, it just scraped off some of the dykem then finished the additional 1/2" of thread on gauge.

I use a 0 Deg. approach angle when threading on a manual lathe so didn't consider this until doing a bit of head scratching.