Hard turning, finishing the part.

Had to do some parts today using my second least favorite lathe operation.

Knurling.

3 1/8 Dia. steel tubes, the knurl is 22 5/8" long and 12 TPI. X .015" depth.

Did use a clamp knurling tool. Eaglerock.
Did not skim the OD to achieve some multiple of 12 TPI circumference as many youtube videos recommend.
Did use about as much coolant as I could throw at it, one nozzle per wheel, this is important.
80 Rpm's, .008" feed per revolution.

I used their (Eaglerock) recommended methods for a manual lathe.
Set tool X axis, center of the wheels at the center of the spindle.
Run the tool to center with the spindle stopped, turn the adjustment until the wheels touch the part then crank in the wheels to full depth.
Engage feed then start spindle.
This is not a full depth knurl, the top has a flat per the drawing/sample.
They get hard chromed afterwards.

Worked a charm for the most part, had to do a bit of fussy adjusting on the first part but the following ones ran rather well. 3 more to run tomorrow.


 
Had to do some parts today using my second least favorite lathe operation.

I appreciate seeing your posts about "a day in the life of a working machinist" keep them coming ! :)
 
Thank you
It is not fast however, 80 Rpm's X .008" feed is .64" per minute, 22.625" / .64 IPM is 35+ minutes per part just for the spindle time.

I have ran knurls much faster in the past but common knurling tools are HSS wheels running on hardened tool steel pins, I have had them seize together in the past when used to fast, this does not work well as you can imagine.
 
Dovetail O-ring groove. A nasty job on a large part in a manual machine.
The dovetail keeps the O-ring from falling out of the groove when the part is inverted. I can understand the rational behind this but they can be a bugger to produce. 11 3/4 OD X .120 deep plunge in 304 SS then decrease the diameter in the groove by about .050" per side to produce the dovetail with a large radius.

How easy do you think this carbide insert would be to break? If your guess is very easy you win.


It looks like this on the drawing minus the radii,depth, width and tolerance dimensions, these are all on a second tabulated data sheet for each O-ring cross section.
I am doing this on a 24" X 100" manual lathe by very gently bumping the carriage wheel for infeed in Z to produce the initial groove to depth, the carriage, compound and toolpost weigh well more then 500 Lbs on this machine including it's own 3 phase motor that will rapid each axis close to where you want it, this is an excellent feature as one will quickly grow weary of hand cranking a large carriage 50 or 60" up and down the bed (-:
 
Long small diameter parts today, 125 parts in total.
3/8" 1018 CRS round bars.
They finish at 33.75" length with a reduced diameter and a retaining ring groove on each end, the tolerances are rather loose.
+- .030" on the length, +- .005" on the diameters and the groove width is .039" +.000 -.005" with a minor diameter of +-.005"

This was done in a CNC Bridgeport lathe, the parts were a few inches longer then the spindle stop so I made an extension for it that is extremely simple.


The stock was cut about .200" long so I faced one end then turned and grooved, turned with a VCMT insert and grooved with a Kennametal Topnotch .029" wide grooving insert tool. The finish was excellent considering the material.
A very conservative 1000 Rpm's with .020" DOC and .012" feed for roughing, .004" DOC and .004" feed for finishing.
Short end

Long end


Part
 
Cold rolled 1045 steel, 6 1/2" nominal stock diameter 36 1/4" long.
The part finishes at 36 1/8" +- .030"

We do not have a lathe that is 6 1/2" through the spindle so the steady is employed.
Place part in chuck and push a flat center drilled plate against the end and push it against the chuck with the tail stock, indicate this end and knock in as close as needed.
Turn a band as wide as required for the steady rollers/fingers, set the steady and face the first end and drill a center in it.

Put a live center in the end and turn the OD as close to the steady as possible, in this photo the first half is finished and I am facing and center drilling the other end using the band for the steady, the finish OD is 6.437 +.000 -.005.


I have flipped the part and will now turn the second 1/2, this will require a cats head for the steady because running the rollers on the finished surface will damage it, I have also placed aluminum flats between the chuck jaws and finished surface. Steel banding is used under the set screws inside the catshead to protect the surface. This requires much set up time.
The finish is excellent considering the material, turned the OD at 400 sfm at .008" IPR feedrate using a TPG 321 triangular TIN coated insert.
6 7/16" diameter cut at 400 SFM is 237 RPMs.
The C-Clamps and sheetmetal are a movable guard to keep the chips away from the rollers on the steady, nothing will ruin your day faster then rolling a large chip in a steady, a steady with non rolling elements does not have this problem, score 1 for 1850 era technology
 
Indicate the part after flipping it, I use 2 indicators for this 1 for the axial runout of the cats head and one for the radial runout of the part.
This is a very time consuming process.


The finish turning looks like so. This method will not likely work for many hobbyists because it will leave a visible line at the center when turning from both ends, in this case it is well within the +.000 -.005" on the drawing.
A 1 tenth difference in diameter will leave a visible artifact on the part.

I am beginning to like this enormous noga indicator holder that I bought several months ago.
 
Just made it, 25" diameter X 1" thick disk in 304 SS, the ID and OD were first milled to size because the 25 1/2" diameter rough burnout would not clear the ways with the gap in place. Removing the gap causes all manner of tooling problems on this machine.
It cleared by a healthy 1/4"

I believe that way oil stained this machine (-:

Now to face it to 3/4" thick with a 250 surface finish on both sides then cut an extremely annoying dovetail O-ring groove at 13 3/16" minor diameter in one face, for anyone that has never done a face dovetail groove in a large machine it is tedious at best, it looks like so. Feeding such a small carbide insert form tool with a 500+ Lb carriage machine is difficult, I have broken many inserts doing this operation, fortunately the inserts are so easily broken that they do not ruin the part.

Using one of these toolshttp://www.thinbit.com/products/face-grooving/index.php
 
those face-grooving bits do look fragile. out of curiosity. to get the underhang, I guess you plunge into the face to the required depth then move in to create the underhang?
 
those face-grooving bits do look fragile. out of curiosity. to get the underhang, I guess you plunge into the face to the required depth then move in to create the underhang?
Exactly.
This is my least favorite lathe operation on a large machine using a very small tool. I will take some pictures tomorrow morning.
If the first part goes well of course, if not no pictures means that it did not happen.
Successfully
 
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