Smithy 1324 & Taper ?

[JerryL]

I have a NEW Smithy 1324 and am still adjusting and testing it out .
I have noticed that I am picking up a taper when making a cut on the lathe . This is even on a very light finish cut ( 0.004 - 0.005 total stock off ) very slow feed . . It does not matter whether it's steel or aluminium.
I am using a 3 jaw chuck and I am picking up about 0.001 taper in 6 inches . The taper is kinda weird . It is running heavy from the tailstock end and smaller at the chuck . ( starting cut from tailstock end and feeding left toward the chuck ) ( That is the longest stock I have right now .) I tried using the tail stock with a dead center same results , tail stock and center are in alinement . The rod I was turning is about .850 or so diameter .

I have had the chuck off and cleaned and adjusted . I do have about .0035 Run out on the chuck .
I checked the spindle bore and the cam lock part and it is all running very close to 0.00025 Total run out . But when I put the chuck on I get the ..0035 Run out bu indicating a 1 in solid ground hardened dowl / locating pin , chucked up in the 3 jaw..

I have readjusted all the gibs etc .

Smithy said to take and adjust the head end / gear box and all of the lathe and it's mounted on the ways with ' V' and has gibs and adjusters .

Before I get into messing with the head etc. and possibly CREATING A NIGHTMARE ...does anyone have any idea's and or has experienced this ?.

As I said the head bearings are tight and running true so is the spindle bore and the chuck mounting cam lock . Gibs are tight and it does this with or without the tail stock .

Thanks all ....JerryL

[Jose Rivera]

You don't mention what diameter your are turning and how much overhang you are allowing.

A small diameter hanging long away from the chuck would cause the smaller diameter near the chuck as you describe, even with light shallow cuts.

Depends also in how sharp is you cutter, the type rake, the angle of cut and the size of the point on the tool and feed rate to name a few. (Not to mention the hardness of the material)

So one cannot give an accurate or approximate verdict about what your problem can be.

Wear on the ways maybe cause similar problems but if the machine is fairly new is not likely.

You mention 6 inches. Six inches is way excessive to have without support from the tailstock with either a dead or live center.

Something with a diameter of maybe .750 or bigger can be machined with such overhang.

If you're turning .500 or less then your part if flexing away from the tool thus causing a smaller diameter near the chuck.

Amen !

[tattoomike68]

A taper of 0.001" taper in 6 inches is nothing. That is super good, you should be thrilled.

My smithy's tailstock is set so I get <.0005" in 6 inches.

[JerryL]

Thanks... tattoomike68 & Jose

Hi Jose ...in my post The material is aluminium and also soft steel 12 L 14 . The diameter was approx. .830 to start and the finish final cut that I was taking off was only about 0.005 Total ( that would be about 0.0025 per side .) the size of the material at finish cut was about .800 . The feed rate was VERY SLOW and RPM was about 700 with lube. The total length of the material ( steel and aluminium ) was about 8 1/2 inches long and I was chucked up on about 2 1/2 inches leaving approx 6 inches out of the chuck to turn.
I tried center drilling and using a dead center with the tail stock and NOT USING A DEAD CENTER with the tail stock , the results where exactly the same .
I tried using lube and I varied my speeds and feeds , I used a cutter that I ground according to the manual HSS. I also tried carbide . I tried NOT using lube .
The 2 suggestion Smithy made was
1. Move the whole head of the machine 1/2 of my taper !!!! ( scary )

2. Put as long a piece as I can find that is about 1 inch in diameter , center drilled and use of a following center support , and a dead or live tail stock center . Take a small rough cut at slow feed. then take a very light finish cut .
Then check for taper if any with the indicator .
Whatever taper is take 1/2 that and move the tail stock that amount .
Retry whole procedure again .

As I said the taper is occurring in this manner .

The larger diameter is at the start of the cut ( tail stock end and feeding LEFT towards the chuck . The chuck end is smaller in diameter .

The machine is new and the ways / dove talis etc. feel / look OK . The Gibs are adjusted and there is oil / lube on everything .

JerryL

[Hyper]

The girls are adjusted and there is oil / lube on everything .

There's your problem, your mind isn't on machining !!

[JerryL]

Hi Hyper
I don't know how I missed that , other than it was the middle of the night when I wrote that post.
Not sure what's happening , I write something out and then use a spell checker on it and at times even if I have a word spelled right spellchecker will CONVERT that word to something else it thinks it should be !!!!!!. I do proof read my posts after using the spell check but this must have slipped by me . IT WAS SUPPOSED TO SAY GIBS .

I have had a few very embarrassing things like this happen in posts that i didn't catch it.

Thank you ............JerryL

[Hyper]

I figured it was something like that, Jerry. Just that, I couldn't resist adding that reply.

A litttle Freudian slip now & then shows a healthy mind !!
From Google definitions.....

Freudian slip: a slip-up that (according to Sigmund Freud) results from the operation of unconscious wishes or conflicts and can reveal unconscious processes in normal healthy individuals

[JerryL]

OK Guys

I went and hit the rear end bearings where Smithy said to . Did that once more again today .

I made a cut and the taper is now down to about .0005 ( 5/10 ) 10,000
in a 6 inch cut .

Talked to Smithy Techs again and they said if I could find or get a bar / rod that is about 12 inches to 15 inches long and that is known to be straight and has a smooth finish . Also that is has center holes in both ends and to get it between dead centers from head stock spindle to tail stock and run an indicator along the length and that would show where the taper is coming from ??

Soooo where do I find a drill rod or whatever that is about .750 round and 12 - 15 inches long with centers in both ends that are spot on ???
AND THAT IT WON'T COST ME $$$$$$$$$$$$

Oh well I guess I am getting close and Maybe I am expecting tooooo much out of a 3 in 1. I used to work years ago on a Devlieg Jig Borer / Mill and worked in .00002 - + location as well as .00002 bore size with micro finishes . I know a Smithy Will not EVER even get close to that , and I'm not expecting that . But .0005 limits and NO taper would be nice .

JerryL

[b151]

I would put the longest truest piece of round stock you can fit between dead centers. Put your indicator base on the carriage and indicate where the tool would be (machine off). Indicate the length of the bar. Near the chuck, near the tail stock and any where you have a variation rotate the bar by hand to see if it is bent and record variation on the bar with a sharpie (B+ or B-). Check the diameter with a micrometer at that exact place and for several other positions (90° Min.) at that place. Write any variation on the bar (+ or -). Now indicate the top (TDC) of the bar for the length in the same manner Your readings should agree with what you marked. If not you have some info to figure out what’s wrong.
After you have checked between centers you could repeat the above procedure with the same bar in your chuck using the tail stock. This might help isolate a chuck problem.
Like Jose suggested consider that the path the tool travels may not be parallel to the center line of the part with respect to height. What ever small distance the tool position changes up or down will be magnified in the part diameter. In any case if it were my machine I would use it for a while before I made any radical adjustments. Your problem may correct itself after break-in.

[JerryL]

Thanks b151
I am going to try and take down the 3 jaw chuck TOATALY and clean / hone whatever , maybe try switching the jaws around and see if that helps .
I am going just use it for a period of time ..... As you say I don't want to start making some RADICAL adjustments and create a night mare that won't go away ....hahahhahah
I have gotten some GREAT ideas and tips on what to adjust and where and how .....

It's kind of a PIA doing all this adjusting and checking , but I would be doing the same no matter what make / style / type / brand machine I would have bought. In one way it is fun and gratifying knowing that whatever I do and can adjust will be right and I am leaning the quirks of this machine .

Sure can Pee Away the hours !!! just fiddling with it though.

JerryL

[hgporter]

I'm getting in late here. Is the taper concentric, or is the runout at one end different from the runout at the other?

[JerryL]

Hi Hgporter
The run out is same at the chuck face as it is about 6 out from the face .
As for the taper its concentric along the whole cut ( 6 inches ) but is larger at the start and smaller at the end of cut . ( cut starting at tail stock end and cutting to left ,towards chuck.

I haven't had time over the weekend to do any further adjusting , cleaning , testing .

I'm waiting for some longer material to take a cut on . I want to check and test with something that's 12 inches long .

Thanks ....JerryL