My slager 12x36 lathe

[Trion]

Here's my second attempt of checking for taper. 19mm mm brass bar


A razor sharp hss tool (so sharp that I actually cut myself on it), gave this silly amount of chatter. I tried speeds from 200-800rpm and allways using the lowest feed and very small cuts, nothing helped.


Tool ground almost like a hook, as I heard this would be best for gummy materials


Top view, there is a slight radius on the tip.


Then I decided to try a uncoated carbide tool at some higher speed. Initially it was chattering just like the HSS one, but with a bit of WD40 it instantly improved


The finish near the chuck was very good, but you can already see the starting chatter to the right in the picture


Chatter is starting about 30mm out from the chuck


Here's the starting end


After making two passes back and forth with the slowest feed and locked cross slide and compound slide, I measured the bar.


Results:
0mm   -   17,465
20mm -   17,48
40mm -   17,50
60mm -   17,52
80mm -   17,535
100mm - 17,56

I am thinking there is some issue with rigidity in the machine. When turning you can see long chips laying on the chip pan bounce to the frequency of the lathe. I have tightened the gibs for saddle, cross slide and compound slide, and two of them were also locked during the test. This has me thinking in the direction of spindle bearings, but I'm really not sure.

[Swarfing]

I would suggest that the work piece may need to be supported really. The other option would be to use a straight cut angle bit of tool steel? worth a go anyway.

[Trion]

I thought the whole point of the exercise was to turn the shaft while it is only supported by the chuck, in order to check spindle alignment.
I am not sure what you are meaning when speaking of a straight cut angle bit of tool steel.

[Swarfing]

Sorry Trion a state of 'you should have read the whole post' crept in with me and i see your point 

Using the slightly round ended cutter will give some deflection hence the chatter marks. With a square ended cutter with slight rake back to the side will pull into the material more whilst cutting. The finish will not be so good though and sorry for the mix up.

Paul

[SemiSkilled]

 A bit on the dumbell test,










Lee

[Trion]

Swarfing: Haha, now I see the misunderstanding! I was beginning to think I had gotten it all wrong
I think I get your point regarding the cutter. I´ll try to grind one without nose radius, I still have a lot to learn on tool grinding

SemiSkilled: Thanks for the pictures. Seems like a very interesting book!

[Bogstandard]

Trion,

That really looks like a speed induced chatter, running too fast, and setting up resonating vibrations,

Try say a 0.05mm cut, slow feed and speed. If your cutter is razor sharp, as it should be, and close in to the toolpost, and you have lubed up the machine, then that should cut perfectly from about 75 to 100mm out from the chuck, using say 15mm stock brass.

If that doesn't do it, then you are into real guesstimations, as without actually being there, anything else would be pure guesswork.


Bogs

[Thomas]

Hello Trion!

A fellow Norwegian guy here who just signed up to the Mad Modder forum.
Happy to see there are other guys from Norway here, yay!
It seems like you got a nice lathe there.
Where in Norway are you btw?

Regarding your lathe alignment test, you say you're using a brass bar, but it looks more like red bronze or something much gummier than brass (you said yourself it was gummy).
This is your picture of the test bar, look how red the metal is, and how it curls up where the cut ends:



Get some "real" brass, it should be yellow/golden, and it's definitely not gummy.
And with brass you should use a hss tool with no top rake, it should be flat on top (no hook).

Plus for the alignment test at least, grind it with no/little radius. That will lessen the chance of chattering.


Hilsen Thomas
Fra Asker, Norge

[toolman]

Hi Trion,
Sorry about the delay in getting back to you,things have been a bit busy here, the torrential rain we have had in Melbourne flooded my workshop, fortunately no serious damage but a good excuse to have a serious cleanup
R.E. Toolposts : the 12 inch lathe seems to be the crossover point between the AXA and the BXA toolpost. I chose the AXA as its smaller size makes it more maneuverable in tight tooling setups and to date it has been rigid enough for everything I have required it to do, but then I only use sharp positive rake tooling, negative rake tooling might be a different story.

R.E.: Gearbox lubrication: Fig 1 shows what I mean by removing the front cover, it may seem like overkill to remove the cover once a week but with a 5mm Hex key in a cordless drill it takes about  3 minutes   
and I know I'm not in for nasty surprises in years to come (been there, done that).

R.E. Tumbler Gears: Fig 2 shows the 22 and 28 tooth gears I'm talking about (the term tumbler gears is generic description and probably shows my age).

R.E. Feed Rates: I would not suggest for a moment that all turning be done at fine feed rates,  most of my general turning is done at rates of anywhere between .005" and .025"/rev depending on material, diameter and tooling, but for certain jobs such as machine tool accessories or specialized hand tools where surface finish is important I use the finest feed available. Fig 3 shows a 200mm length of 30mm Mild Steel finish turned  at .0014"/rev, yes it is a slow process but on items that I  intend to use for years  I feel it is worth the effort.

Regarding your concerns about Headstock alignment, is it possible to hire a test bar bar from a machine tool dealer in your area ? they are available for purchase but here in Australia they cost about $ 150 AUD a lot of money for some thing you will only use a few times.
Regards,
Martin

[Trion]

Thanks for the reply guys! 

Bogs: I did take fine cuts like 5/100mm as slow as 200rpm, but this far out from the chuck there was no hope. Actually, when the machine wasn't running I could see the bar bend as i touched up on it with the tool. I had a thought fly through my mind, that it was like trying to turn a rubber bar

Thomas: Yay, another Norwegian! I´m from a town outside of Stavanger. You might have caught me here, that might very well be something else than brass. That should explain why it made those long curly chips
Thanks for the tips on tool grinding, will keep that in mind when I get hold of some real brass

Toolman: No worries, just glad to hear your shop is undamaged. 
Ok, I still think I´m going for the BXA as I rarely fiddle around with the smaller stuff, but it is nice to know ones options. I see what you mean regarding oiling, I have squirted in a bit of oil underneath the cover but I guess it is about time to take it of and oil the parts properly. Your eccentric gear bushings look nice, another project I´d like to take on some day!
I don´t either turn at the slowest federate all the time, I meant to say when finishing I have always thought it to be more than slow enough. Though the finish on the bar in your picture is like nothing I´ve ever made!

I do not know of any machine dealers in the area, but i will check it out. The most recent dumbbell illustration showed using a 1" bar, so I should be ok with my micrometer. Just need some more shop time to finish my current project and get along with the alignment again.

[Trion]

The checking of the lathe is currently on hold as it still is a bit intimidating. The machine is working for what i need it to do so I have used it a bit lately. A while ago I made a splash cover, after having been sprayed with coolant as the coolant reached the chuck..


It is not very nice. I'll make a better (and transparent) one someday!



A long time ago I started on somethign resembling a ball turner. Those plans were not thought through enough and have been discarded. In the meanwhile I have seen loads of good solutions to make ball turners. With a new lathe on the way, I wanted to make something rigid that would fit both lathes without problems. Therefore I have decided upon a horizontal shaft perpendicular to the lathe axis, holding something like a boring head. By altering the tool height or adjusting the boring head I can make concave and convex radiuses. When removing the boring head I have a ball bearing spindle perpendicular to the lathe axis, add a jacobs chuck and a power drill and it becomes a lathe cross-drill - i hope..

So I started by making a C-o-c


Found a suiting piece


Cut it to length on my beloved bandsaw


It just fitted through the chuck bore


Centre drilled the tip and brought out the live centre


I needed to remove about 12mm of the diameter, so I tried different speeds, feeds and depth of cuts to find the most efficient solution. I was always pushing it close to the point of resonance, but as I got closer to the chuck I could gradually increase the depth of cut


Roughing out the basic shape


When I began some light semi-finishing passes I measured the chuck and tailstock diameter. The difference was 0,12mm, so I moved the tailstock 0,06mm towards me. A few iterations and the diameter was within what I can measure accurately with my digital vernier


Here's how I left it today. Two bearing surfaces turned to 30,03mm, while the bearing has an ID of 30,01 (digital vernier measurements mind you). The black region is where I plan on making a M30x1,0 thread, used for tightening of the angular contact ball bearings that are going to support the shaft. I think it's going to be beefy enough!
I still have a lot to learn on getting beautiful surface finish!

[Trion]

Yesterday I cut the thread, M30x1,0


Then it was time for the bearing housing. I found a suiting piece of mystery steel


And cleaned it up a bit


Before i could make a proper c-o-c


I want it to be a one-piece construction. To allow for mounting of the shaft, it must be eccentric, so out came the 4-jaw


Before I started turning, I was thinking about the feed gearbox oil issue mentioned by toolman, and decided to resolve this first.


A hole was drilled, and there you have the extra gear oiling hole.
I used a lot of WD 40 when drilling so that all the swarf became wet and got stuck to the cloth, trying to minimize the dust in the gears


Eccentric turning sure takes a while!


Next operation was to start boring out the bearing and shaft bore. This is probably overkill, but I wanted to use my steady rest. Unfortunately it wasn't big enough!


So the boring commenced without the steady. The hole is 100mm long, I don't have so long small drills, so I drilled as far as i could get with a 6mm drill. The rest was left to a long 10mm one, which had to suffer through lengths of steel


That's about where it stands today. The hole is going to be drilled out to 30mm, then I'll use a boring bar to open it to 31mm and make it concentric for alignment when I flip it over in the chuck. I'll also bore out for the bearing in the same setup.

[Trion]

I continued some more on the project today 
I drilled the hole to 30mm, and prepared for boring


I had to use coolant because chips were getting captured between the boring bar and the hole wall. This made a large spray of coolant around the entire machine, so I had to adapt some covers to avoid getting wet


A while later the 31mm bore and 62mm bearing seat was finished. Not superb surface finish, but it is smooth to the touch

[Trion]

Yesterday I finished the reliefs around the bearing surface, to allow for tightening of the bearing and letting grease get in. The bearing is 16mm wide while the seat is 28,5mm deep, so I bored 11,5mm to a slight oversize so the bearing slides nicely in until it reaches the "press fit"


Then I flipped the part over, indicated it by the hole i had bored through until it was within 0,005mm. Then I got cutting and have now finished the second bearing seat. This also needs relief cuts.

[Trion]

And it goes on.. Turning the bearing seat on the opposite end


Yesterday I rediscovered HSS!
While roughing out the outside diameter in interrupted cuts I stalled the machine several times and was allways struggling with chatter unless i made 0,4mm deep cuts or smaller. When I drilled the 30mm hole I was using a HSS drill and had a massive metal removal rate, so I figured I'd give a bit of HSS tooling a go at a lower speed. And wouldn't you know, It took up to 2,4mm deep cuts (that is 4,8mm off the diameter) at a feed the carbide tools never would have managed!
Ofcourse, the carbide would probably be able to remove more metal on a sturdier machine, but for my little lathe HSS was just fine


And here we have the bearing housing finished turning


Bearing housing and shaft meet. I will not press in the bearings before I have finished machining all parts.


I have not decided on how I am going to make the mounting flange on the bearing housing. I am tempted to make it a dovetail to suit a BXA QCTP that I am planning to buy. But I could also just mill out a flat on it and call it a day.. I also need to decide how I want to mount the boring head to the shaft, as it would be very nice to be able to replace the boring head for a jacobs drill chuck for drilling operations.

[rvt]

Brilliant documentation, thanks for sharing it all! I'm very jealous

[Miner]

Trion,
Due to my time away from home I just read this. I haven't read every single post. so some, Or all of this may have already been pointed out.

Your first pictures show a tool tip that's obviously not set at the lathes centerline.

Your tool chatter problem while checking the headstock alignment? If? you were using free maching material, An ultra sharp tool, And all slides adjusted properly, The standards for part projection from a lathe chuck for unsupported material at the free end are around 2-3 times the materials diameter. And that's MAXIMUM.

Lathe leveling, And the need for a machinist's level? I've got enough trys at this that a dead level lathe is just an easy way to get you to a starting point. A dead level lathe is just a static condition. Aligning a lathe to turn parts to the same dimension end to end requires as you've done, Testing under cutting conditions. Due to tollerances required for the lathes parts to even move while cutting, Inacuracys while machining and grinding the parts for your lathe, Ect. Further adjustments away from dead level would be expected. Probably by now you realise this already.

I like your lathe, For it's age and what I can see in the pictures it looks to be in great shape.

Pete

[Rob.Wilson]

Hi Trion


Wow thats a great  lathe you have there    good to see you have it up and running 

Rob


I must get round to making a chuck guard for my lathe 

[Trion]

Thanks lads!

Miner, when checking headstock alignment I was clearly using the wrong material, too long protrusion and the wrong cutting tool. How much more could i get wrong? Maybe run the lathe in reverse 
I did think though, that it would be possible to use a longer protrusion than 4xmaterial diameter if one was only taking very, very light cuts.
As you point out, proper lathe leveling should also have been done before any attempts were made to tweak the machine. One of the reasons why I'm fooling around with other stuff at the moment.

I must say I begin to appreciate the lathe more every time I stumble across a worn beaten old machine which requires a wrench to move the handles. Hell I recently even had to clean of dragon fat from the underside of the bed, where the tailstock clamp sits. That is, some 22 years after the machine left the factory!!

Rob, looking forward to your chuck guard. I'm expecting it to be better and nicer than mine in many ways!