diametar and taper incostistencies

hello i am Marko and i have a problem with my lathe . It is manual lathe Prvomajska ts 1 and i cant get constistant resaults ! its making a taper widouth any reason it is toward the chuck sometimes and sometimes toward talestock and it is betwen a 1 thou to 7 thou in any directio . do you expirients machinist have some solutions ?

If you have issues on short shafts and between centers I would think you have spindle bearing issues. I searched the internet and found this description that you can use to test your spindle. You do not say the size of your machine. The one shown is a small lathe and they are using hand power, but you can use a wood board to pry under the lathe chuck too. Test the up and down and left to right to test the PRE LOAD on the spindle bearings. The article shows a sleeve bearing but this same test can be used to ball, taper roller, angular contact, etc. Scroll past the words and you will see a drawing. http://www.wswells.com/data/howto/Spindle_Bearing_Adj_9_10k.pdf

Just measure lost motion. That is you push and let go, set indicator on zero, pull and let go and where the indicator settles is the lost motion. The extra movement before you let go is bend.

Also look at the bed and as if it is worn very bad then it could also cause this. Check how sharp your tool bits are, if your chuck jaws are loose or worn out, be a detective.

I also saw this Russian You Tuber that you might be able to ask. What better: modern Chinese lathe or old USSR lathe?(technical content) - YouTube

ok i will try that,my lathe iz 12 inch swing and 70 inch long and its on sleve bronze bearings not on roler bearings therefore i dont know if that have matters ? i will write my reasolts tomorow. thank you very much.

markoaleksic said:

hello i am Marko and i have a problem with my lathe . It is manual lathe Prvomajska ts 1 and i cant get constistant resaults ! its making a taper widouth any reason it is toward the chuck sometimes and sometimes toward talestock and it is betwen a 1 thou to 7 thou in any directio . do you expirients machinist have some solutions ?

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Larger, older, and very worn lathes are often victims of the cross-slide moving gradually while in the cut under the influence of EITHER.. a tool set low and being "pulled in", OR a tool set high or even set "OK" and being pushed back.

Before you go off to play at general-purpose detective, let's get the obvious and "usual suspects" out of the game for the specific issue at hand.

Go and turn your compound, if you are even using one, so its axis is parallel to the long axis of the lathe. Movement should no longer affect the turning diameter.

Set up for a test cut. MAKE SURE the tool-tip is NOT below center!

Find a large enough clamp and CLAMP the topslide of the cross so it cannot move.

Make test cuts. Both directions. Yes. The clamp is a b**y nuisance. Just deal with that for the duration of the test cuts.

Your mystery "either direction" taper will probably have vanished.

Report your results. There will be more "simple stuff" to do.

Sorting out what you have to do to NOT have to clamp it comes later and will take more work and more time.

thank you so much for helping me,in my country (Serbia) i dont have no one to ask obout my problem that is why i asked you,thank you .

My pleasure. As you can see some of us can help you better then others. Your welcome.

markoaleksic said:

thank you so much for helping me,in my country (Serbia) i dont have no one to ask obout my problem that is why i asked you,thank you .

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It's only fair. Many of the very skilled Serbian craftsmen are not there to ask because their Great Grandfathers moved to Pittsburgh, Pennsylvania, where I met them as Brother Steel Workers, USWA Union!

If your women are still as lovely - but extremely hard-headed - as ever, I'm not sure I understand why anyone STAYED home at all!



But there you have it... humans in all their astonishing variety, doing the best they can with whatever they have, not what they WISHED they had...

Richard can teach you how to fix your lathe to as good as new. When you have the time to take it out of service to do the work on it that is required.

I can teach you how to make good parts on it while it is still worn out and broken so you can earn the money to be able to AFFORD to take it out of service long enough to do that work. We - thousands of us - learned how to do that because we had no other option.

We did not own the machines. The companies we worked for did not PERMIT us to interrupt the flow of work to repair them. If you are working as an employee on a "company" lathe, welcome to that club. "Run what you got" was once MOST of the world of machining as a craft and trade, many countries.

Repair - if even it IS your own machine - needs planning, training, and practice.

Richard can do it fast. Most others need two to five - even TEN times as long. And they cannot do it it all properly if they have not paid attention to getting the BASICS right.

That sort of preparation does not happen overnight. Budget about a year to learn just the basics. Those "basics" can, however, do you a great deal of good. "Expert" comes very gradually, and only with longer years.

One hand washes the other, then both hands wash the face.

markoaleksic said:

thank you so much for helping me,in my country (Serbia) i dont have no one to ask obout my problem that is why i asked you,thank you .

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Ја сам стваран, а не сви разговори и никакве акције. Ја сам машински мајстор, а не верујем машинисту
Ja sam stvaran, a ne svi razgovori i nikakve akcije. Ja sam mašinski majstor, a ne verujem mašinistu

Мој пријатељ на њемачком говори руски и он зна многе машинске ребуилдере у Русији док ради са Биак Германи. Можете га послати е-поштом и рећи му пријатељу и треба вам савјет о поравнању и поправци машине. Ф.Пацхомов@биак.де
Moj prijatelj na njemačkom govori ruski i on zna mnoge mašinske rebuildere u Rusiji dok radi sa Biak Germani. Možete ga poslati e-poštom i reći mu prijatelju i treba vam savjet o poravnanju i popravci mašine. [email protected]

English: My friend in German speaks Russian and he knows many machine rebuilders in Russia as he works with Biax Germany. You can email him and tell him your a friend and need some advice on machine alignment and repair. [email protected]

Also you can email me directly. [email protected]]

I will be teaching a Machine Rebuilding class in Austria next month. I wish you could attend, but unfortunately it is full. This will be my 8 TH class I have taught to new machine builders, used machine rebuilders, and hobbyists in Germany and now in Austria. I have also taught several classes in Scandinavia, You can see several You Tube shows my students have made.
richard king scraping - YouTube
8th Scraping Class with Richard King - BIAX

sorry mr Richard i didnt completly understud what you wanted to say ?

and i am so sorry for my bad english i am a bit rusty with writing words .

markoaleksic said:

and i am so sorry for my bad english i am a bit rusty with writing words .

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Your English is fine. write me at [email protected] and I will contact some people in Europe who will be able to help you.

markoaleksic said:

sorry mr Richard i didnt completly understud what you wanted to say ?

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It will become clear later.

Let's just get some usable parts coming off that lathe so you don't starve first.
It will show us what it needs.

Do you own it? Or does it belong to an employer?

its my lathe , i am not a professional machinist by no means i am a river saleor but i enjoy working with metal especially with lathe and milling machine . my lathe is not extremly worn but something iz wrong with it .
I have checked spindle movment and i have fixed it to one thou maxim ,what to do next ?

I am happy I was able to help with information links and just not HOT AIR.

Take some test cuts now after you do the following shown in the links below.. There are several links to pages on past Practical Machinist forum articles.
https://www.youtube.com/watch?v=GErhXyUb2Go

practical machinist testing a lathe between centers - Google Search

i will do that and i i will post resault here.

Be sure to lubricate or oil the spindle and run it at about 1/2 speed for approx. 30 minutes, checking every 5 minutes to be sure it that you can not hold your hand on the casting it is to tight. If it gets hotter or over 60 degree's C - Centigrade or 140 F loosen the spindle a very small amount say 1 or 2 degree's. Then once you know the spindle is OK take some test cuts. Do you own or can borrow a precision level?
8" Master Precision Level Graduation .5 Bar Level Measurement Leveler - - Amazon.com

You will need to test the bed alignment with one of these. Or if you do not take some test cut like OXTool and other You Tubers show. Then tell us what happens. :-) Rich

markoaleksic said:

its my lathe , i am not a professional machinist by no means i am a river saleor but i enjoy working with metal especially with lathe and milling machine . my lathe is not extremly worn but something iz wrong with it .
I have checked spindle movment and i have fixed it to one thou maxim ,what to do next ?

Click to expand...

I think you will be able to master this one. They were reasonably decent lathes.

You don't need to go buying any extra tools just yet! A modest tightening up and a change to the way you set up and tool for the cut may be all you need for now.



We first need to see if that top slide is moving while IN the cut.

Besides the trick of clamping the top slide, another is to grasp the top of the toolpost and lean back, ever so slightly. This puts a constant force against the near flank of the topslide's leadscrew.

Your bi-directional taper may go away just that cheaply. It needs a more permanent fix, but at least you will know right away what it is that needs to be fixed, no money spent.

top slide is not moving at all!it is in very good condition and i made a fiew cuts with bar in chuck just to check if spindle
is hot and it is not just sligthly worm.

markoaleksic said:

top slide is not moving at all!it is in very good condition and i made a fiew cuts with bar in chuck just to check if spindle
is hot and it is not just sligthly worm.

Click to expand...

OK. Now we look for rotation of the cutting tool and for TILT of the tool-tip while in the cut.

All "hang out" is leverage. If the toolpost, the compound itself under it, the mountup of the compound to cross CAN move, they will move and they DO move.

If cutting forces increase to the point they can twist the tool and post, they will do. Depending on how you have done the setup, the tool can swing AWAY from the cut, resulting in an increased diameter when OD turning. If it is going to move AT ALL, then this is what you want. It is "fail safe".

If the tool has been positioned such that twisting on axis pushes it deeper into the work, a reduced diameter is produced, possibly ruining the work. This can also lead to a crash. You want to avoid that sort of setup if it can possibly BE avoided.

These things always move. The only question is by how much.

The other source of movement is in the bar being turned itself. It can flex away from the tool. It can even climb atop the tool and led to a crash.

We have not asked how large a diameter, nor if being worked single-ended held in collet or chuck, or if a center is stabilizing the TS end, or if fully between centers. We need to know all of that now.

A photo of the work in-progress and the surface finish being produced would be useful, too.

You may email me one if you are not yet familiar with posting a photo here on PM or linking to a photo on a hosting service that will permit us to see it. Not all photo hosting services are open to non-members.