Hi Stuart

I wouldn't worry too much about backlash as long as you always approach from the same direction i.e. wind back further than required then back in again to add more cut.

Removing twist, or 'levelling' the lathe, has been the subject of many postings and a few disagreements so try entering the word "levelling" in the box at the top of the posting.

Rob

So it would seem you do not have the compound set square to the chuck face. Lots of vids on you tube showing this being done. Blondiehacks has done a few.

So with your questions do we assume you ended up buying the used model from ebay.

If so, hope you are happy with it.

Steve.

Stuart you could make it a project to build a powered screw feed.

Steve.

Without backlash it would be impossible to move one part relative to another, so must allow for the backlash.

So if you put on a cut of 0.02 mm but overshoot to 0.025, all is not lost.

Withdraw the tool by 1.00 mm. Advance to Zero. Having taken out backlash, you wind in a further 0.02 to where you want to be.

Without taking out the backlash, accurate, or consistent results are impossible.

As a newbie you will learn a lot from books on model engineering.

"The Amateur's Lathe" by L H Sparey..

Neil Wyatt and Dave Fenner have each written books on the mini lathe.

Ian Bradley's "The Amateur's Workshop" covers general techniques

A set of Zeus charts is useful, for many things, plus Tubal Cain's "Model Engineers Handbook " a frequently consulted reference book, on many things.

The mini lathe is a hobby machine designed and built to balance cost versus accuracy and durability.

It lacks the power, accuracy or features of an Industrial Tool Room lathe, or costs as much!

Similar, if not identical machines are available from suppliers specific to the model engineering trade, such as Arc EuroTrade, Chester, Warco, Amadeal, or SPG – to name a few. These are more likely to be able give advice, as well as many on here, than Machine Mart, where knowledge may well vary from branch to branch.

The above suppliers may provide advice and help even if they did not supply the machine.

Where are you located?

Find a model engineering club local to you, and join. Again, advice, help and, Covid permitting, even face to face demonstration, may be possible.

Within its limitations, the mini lathe is capable of good work. Careful adjustment and skill can produce outstanding results.

Do not expect a 3 jaw chuck to hold anything without some run out (eccentricity ) There are very few 3 jaw chucks without run out, Many in good condition ( even brand new &nbsp may yet show run out of the order of 0.10 mm A worn or damaged chuck may be even worse, I know of one very old chuck showing nearly 1 mm run out.

Diameters that will,be concentric to each other, as long as they are cut without disturbing anything between cuts.

The taper that you found could be from a variety of things.

1 ) How far was the material into the chuck jaws? For what you are checking, it needs to be gripped by the full length of the jaws. This assumes that the jaws are clean, both where they grip the workpiece, and where they touch the scroll inside the chuck.

2 ) Is the chuck clamped accurately to the flange on the mandrel? The flange and the register on the back of the chuck must be clean, and free from any burrs. If the chuck is misaligned, you will have problems.

3 ) Are the bearings in the Headstock worn or lost their preload? If YES to either of these questions, as a newbie, this is not work that you should undertake without finding out the correct way to check and then rectify the problem.

For this you really need expert attention.

4 ) Were you trying to reduce from 25 to 20 mm in one cut? 2.5 mm in one cut is heavy work. (My handbook says that 0.010" – 0.0025 mm is a roughing cut, although many take far deeper cuts without damage) Lacking the handbook, get one.

For your checks, a cut of 0.05 mm might be more suitable, since it will cause smaller deflections in the machine. Also, your feed rate needs to be slow. Forcing the tool will cause deflections.

Using changewheels and Leadscrew for the feed, a 20:80/20:80 train should produce a feed rate of 0.0937 mm per rev.

5 ) Is the cutting tool sharp? Don't expect good results from blunt / chipped tools.

6 ) Is the tool mounted with the cutting edge is on the centre line of the Headstock?

Quick check; face across the end of a short piece held firmly in the chuck. Off centre the tool will leave a pip near the centre of the work.

A tool above centre will rub rather than cutting properly. A tool, below centre will have the wrong effective angles to cut properly.

Both will need extra pressure to cut, if at all..

7 ) The gibs on the Cross Slide may be slack, allowing movement. Until this is minimised, consistent results are unlikely. The saddle should be located by the Vee bedway, but if there is vertical movement accuracy will be impaired, so that is another adjustment to optimise.

With a second hand machine, you cannot be certain what use / abuse / misadjustment has taken place.

(I bought a secondhand lawnmower. Worked far better once the blade had been fitted the right way up! )

Hence the machine needs to checked over, and excess play removed.

8 ) If you were turning between centres, one of the centres could be "out" and need cleaning up, or the Tailstock could be misaligned.

Easy to rectify, but needs measuring equipment to do as accurately as possible,.

9&nbsp Disaster scenario, AFTER you have checked all the foregoing, it is possible, but unlikely that the Headstock is out of line with the bed. Again extra knowledge and measuring equipment is needed to confirm and correct it.

Sorry to ramble on on such length, trying to cover as many options as possible.

Howard

Stuart post a picture of the adjuster you mentioned on the QCTP. I have one & the adjustment is quite easy to do, to get the cutter to be central to the workpiece.

Steve.

Hi Stuart , you sound just like i did some months ago when i 1st got my lathe. You'll get there no problem.

So on the lathe bed is a carriage which traverses left & right with the main feedscrew you mention.

On top of the carriage is mounted the cross slide which pans across the carriage.

On top of the cross slide is mounted your compound. Or anything else you care to fit on there.

Don't fret over parting off. I am pretty useless at it myself. Getting better slowly. Lots of youtube video's of people who have done mods to them. Just saw one guy who made the gear holder longer, for doing more varied threads. I had to stop watching it , as his camera was so wobbly i started to feel woozy. Good luck with you new venture.

Steve.

Edited By Steviegtr on 27/12/2020 14:40:53