Lathework for Beginners

Thanks Neil

My CJ18 looks identical to Warco,s super mini lathe. The tailstock does have quick release and there are 2 x M6 grubs, one low down towards the rear of the front face and the other repeated on the back face. I am guessing that these must be for the adjustment but there is also a pair of M4 grubs about 30mm apart low down underneath the handwheel. I am thinking these may be locking screws once adjusted but I,m not certain.

Ron

I adjusted the carriage rack as per Hoppers instruction and it worked a treat (thank you Hopper), the handwheel feels much smoother now. I should mention that before I made any adjustment I removed the rack as I could see evidence of paint in the rack teeth. It would seem that the factory paint the lathe bed with the rack attached but mine was poorly masked and had paint in between the teeth, some of which was quite thick. It was easily removed with a wire brush, plus the rack was very dry so I lubricated it.

Having removed the 3 jaws from the chuck I found no burrs or any other visible problems. I did try the set of jaws in the other two positions and one of them made the chuck feel a little easier so have gone with that. Winding the chuck key is still a bit stiffer than I would like but its not too bad and I hope it will ease with use.

I have also removed the spring loaded plunger from under the tool post as it only allows the post to rotate in one direction which I think is a bit of a pain.

Ron

probably worth taking it off the lathe and separating the top and bottom to better understand what each of the screws does.

Removed the bottom plate and as suspected the 2 x M6 screws act on block which is part of the plate, these adjust the tailstock across the bed and the 2 x M4 screws act on the back face of the block locking it in position. Glad I removed the plate as there was quite a bit of swarf in there and it was bone dry. Cleaned it all out and lubricated the cams and cam gears for the quick release.

Its only aligned by eye at the moment but will turn up a centre in the chuck to set the tail centre against.

Ron

Edited By Ron Laden on 23/06/2018 17:41:41

Sounds like the arrangement on my old mini-lathe. May not be quite as simple as the two rear screws being locking screws, which is exactly what I thought until I tried adjusting them!

Whether by design or crude manufacture, on mine the four screws worked in concert. As expected the side screws control the major right/left angle. But tightening the rear screws also moved the centre slightly, not only right/left but up/down as well. The effect was to make the tailstock describe a small figure of eight movement as the 4 screws were tightened. I found it a fiddle to get spot on. One of those, nearly right, better, better, better, bugger start again jobs!

Possible that the 8 movement was due to poor finish of the rear block, rather than a deliberate fine adjustment feature. However, as the tailstock was spot on from the factory, they knew how to adjust it in China, as did I after 10 minutes of industrial language. Decided in the end that the tailstock adjustment is a basic cost-saving design that substitutes operator time for ease of use.

Interested to know if you get the same result.

Dave

Edited By SillyOldDuffer on 23/06/2018 18:26:30

Hi Dave,

Thanks for the advice, it did cross my mind that the rear screws could be for something other than locking screws. I found it odd that the two screws are not equi spaced off the tailstock centre but the pair are offset to one side.

I will wait until I turn a centre in the chuck and have a good play then. I can see how the rear screw nearest the tailstock edge could pivot the tailstock around the underside fixing screw.

Will let you know how I get on.

Ron

I milled out more space and fitted a brass gib to my tailstock.And replaced the adjustment grub screws with cap heads.

BTW the sprung plunger on the toolpost is a stop to allow you to change tools and return to a position with accuracy. It's reasonably effective.

Neil

A question I have been meaning to ask: The gear set I have with the lathe are plastic (nylon I think) should these be lubricated with anything in particular or just general lubricants.

Ron

I have both read and been told that the 3 jaw chuck supplied with minilathes is something of a gamble. Some are very good whilst others are not with them well out of true.

Well I must have been lucky or the gods were smiling on me or something. The dial gauge arrived yesterday so I checked the chuck this morning. I first checked the spindle face plate and that had 0.0004" run out so I was very pleased with that figure. I then checked the chuck main body expecting it to worse but it wasnt, it gave the same reading. I then looked for something that would be quite true to check the reading at the jaws, dont have a lot to choose from just yet but used a new medium size centre drill and a new good quality 1/2" tap. I measured both of them on the ground body/shank. To my amazement the run out was 0.0004" for the centre drill and 0.0005" for the tap. To be honest I couldnt believe it would be that good so I put one or two other not so good items up to check the dial gauge was ok and that I wasnt seeing things...lol.

So I am obviously really pleased, I wouldnt imagine you would get much better on a minilathe.

Ron

Ignor this post, I'm just testing something for Ketan.

J

I can't say I'm hugely surprised Ron, but be aware that to keep those figures you need to be careful not to overtighten and strain the chuck and to keep it clean!

Test post for Jason, please ignore.

Hi Neil,

I must admit I was very surprised, I have watched a lot of minilathe videos on youtube and some I have seen have had 5-6 thou run out. I thought that if I get half that I would be reasonably happy but to have less than half a thou I,m just delighted.

I will look after it Neil, in fact I,m going to strip the chuck and make sure its clean and well lubricated.

Ron

With the chuck checked this afternoon I also set up the tailstock for centre, I have it as true as I can get it.

I then set up the dial gauge on the barrel running from fully in to all the way out both vertically and in the horizontal looking for any deviation off centre but it appears to be spot on through all its travel.

Ron

.

Stripped down the 3 jaw and found it to be clean but a little dry, gave it a good lube and made sure it went back to the same position on the spindle face plate. Double checked it with the dial gauge and it is still showing .0004" run out.

Well thats about it for now, all is checked/setup and with the HSS tool set having arrived, time for some serious practice.

Ron

That's an impressive figure for runout Ron, especially if it holds over a range of diameters. Personally I don't worry too much about runout but I am interested in whether the face of the chuck and the face of the steps are true as they are references for facing work that you would like to be parallel.

Mike

Just a heads up about the power feed handle for the saddle and cross slide feed. It is VERY EASY to go straight through the neutral position and straight into the cross slide power feed position when disengaging the saddle power feed as I have found out AGAIN. This happened even though I had practised the gentle movement required and knew the possibilities !!! Fortunately it didn't cause too much damage to the work piece as the lathe stalled as the tool dug in and I was able to get the E. Stop hit.

I was looking at setting the Sieg lathe up to cut a 12 tpi thread and decided to use the method I was taught at school and to angle the compound slide to half the included angle of the thread and wind on all the cuts from there. As this is a Whitworth form thread that gives and angle of 27.5 degrees. To achieve that the compound slide has to be rotated clockwise (looking down on it) 62.5 degrees.

Two problems immediately arose. One- The slide would only rotate about 45 degrees and then something was stopping it. On investigation I found that the head of the backlash adjustment screw under the compound was catching on one of the bolts seen in the photo below.

The answer was to remove the screw and gently file about 1.5 mm from the thread. This leaves ample thread for further adjustment and gets the screw to just clear the bolt head. Below the offending backlash adjusting screw.

Problem Two- Once you rotate the compound round to about 45 degrees you can no longer see the witness mark against which the angle is usually set as it is now hidden under the compound! What is needed is a second witness mark round to the left of the compound against which the angel can be set. Question is what is the best way of making the new mark, maybe a centre punch mark or a scribed line of some sort, if that how please ?

Edited By Nige on 30/06/2018 19:59:40

How does the face plate fit onto the SC4 Please? Does it bolt on the same as the chucks ?

I think its the same as the chucks, 3 or 4 bolts depending on how many holes in the back of the faceplate.

You could scribe a mark on the cross slide or just put a bit of masking tape on and mark where say 40 deg is then just move until 22.5deg lines up with your mark.