249 forum posts
Asking as a noob, would it be worth moving the compound back so the parting tool is on the centreline on the cross slide, and that the cross slide gibs are very well adjusted? I assume so.
|Ron Laden||29/11/2019 14:05:48|
2063 forum posts
Ian, that probably would help a bit but I think the bottom line is that the cross/compound slides and tool post are just not rigid enough. They are fine for general turning though so dont let it put anyone off the mini they are good machines but parting really does test the mini lathe at least it did mine.
Having said that I have read on a number of occasions people saying that their mini-lathe is fine with parting and they regularly part 50 - 60mm steel bar with no issues..? That is not my experience with the mini and it was only after I made the heavier cross slide and rear post that I could tackle that size of job.
|COLIN MARTIN 2||05/12/2019 11:50:41|
|11 forum posts|
Right, as promised, here is the run-down on changing the spindle to a later type with the mounting for a 100mm chuck.
It is pretty simple; I removed the chuck, took off the cover at the gear end and unscrewed two allen screws that hold on a cast aluminium plate, giving access to the two ring nuts on the end of the shaft. By holding the chuck flange these can be uscrewed using a 'c' spanner and the drive gear and plastic spacer removed. A simple puller has to be devised, using a flat piece of bar with a centre hold drilled; with this held off the end of the chuck flange by two lengths of tubing against the headstock, a long bolt can be passed through the spindle and the nut on the end tightened, drawing out the spindle and end bearing. The remaining bearing is tapped out of its housing.
The top picture shows the new angular thrust bearing on the left, old ball race on right. The lower picture shows old spindle at the top, new at the bottom.
Fitting was simple - press new bearing onto shaft and then feed shaft through the plastic drive gears - although this presents the problem of how to get the bearing into its housing - I managed to tap it in by inserting a small rod through the chuck mounting holes and working around the bearing until it was snug. The bearings are a really tight fit upon the shaft, but because the angular thrust bearings need to be adjusted to remove any end-float, ideally the bearing at the other end should be a tight sliding fit upon the shaft, but after much use of emery cloth, I still was not able to get it as loose as I would have liked. I had to resort to tapping the bearing into the housing, while gently tapping the inner race onto the shaft. finally I tightened the end nuts to remove any end-float and all was well. one small problem is that the tiny parallel key in the end of the shaft is shorter on the new one, so I had to make one to fit. If anyone is ordering the new shaft, be sure to include a new small key.
The new chuck is supplied with mounting bolts that will not fit behind the flange, so I made up some studs and screwed these into the back of the chuck mounting holes. I stripped and cleaned the chuck before use to remove swarf, which other internet videos have shown to be necessary. The chuck is pretty impressive for something so cheap and I only have runout on a length of ground rod in the jaws of half a thou, so all in all I am very pleased.
|COLIN MARTIN 2||24/12/2019 12:42:37|
|11 forum posts|
I've been busy doing a few more jobs on the lathe to try and improve it. A few days ago some play developed on the cross-slide area, which I traced to the saddle; on closer inspection one of the saddle shear plates had fractured where the grub screws are fitted. Those who have fiddled with this abomination will know, and those who have yet to do so will find out, what a stupid bit of design this is.
I found that the rear plate was very close to being right without the grub screws, so used pieces of 15thou shim to take out the play, but the front shear plate needed a lot of shimming, which was going to be very difficult to get right, so I found that a small spring washer sandwiched between the plate and the saddle was a perfect fit, so replaced the three Allen screws with small studs, fitted spring washers over each stud, replaced the plate, and fastened it with nylock nuts. Then using feeler gauges, was able to tighten the nuts evenly until the saddle was a good fit over the bed. While the lathe was apart, I also made a cover to go over the handwheel gear housing.
Lastly, I have made a swarf tray that fixes to the saddle, to keep chips away from the leadscrew and lathe bed. You are never bored when you have a mini lathe.
|2677 forum posts|
I have an 8 1/2” x 14” lathe and don’t have too much trouble parting since switching to the HSS T shape blades. Kept sharp they work very well. Like others I don’t find my lathe is particularly rigid and as a result I’ve stuck with a four way toolpost. I bought the T blades from Chronos. **LINK** So far I’ve used them on stainless steel, mild steel, brass, aluminium alloy, plastic and even wood. I screwed a spacer on the bottom of the tool holder so it’s permanently on centre height.
|Niels Abildgaard||29/11/2020 19:50:07|
|367 forum posts|
Parting need less overhang and stiffer spindle.The picture shows a mini lathe upgrade where spindle (ca 15 $ among chineesemanufactures ,bearings (less than 2$) and drive system (30$) has changed.The spindle belt drive disc cannot sit between bearing and has to come out in free air..
The gearing to leadscrew is unchanged and the 125mm four jaw is bored to 50mm.Front end of new spindle is 30mm bore.
Enjoy or improve
|KEITH BEAUMONT||29/11/2020 20:19:52|
|110 forum posts|
I have been using my Clarke 300 mini-lathe regulaly for 14 years. I have changed the bearings some years ago, but in all that time I can say I have not had any problems with parting off or deep grooving. I always run the lathe in reverse with the tool upside down. My usual tool is mounted in a quick set post and is 0.060" wide. The big advantage of having a bolt on chuck and being able to reverse the motor,seems to be ignored by a lot of users.
Edited By KEITH BEAUMONT on 29/11/2020 20:22:09
|old mart||29/11/2020 20:48:27|
|2462 forum posts|
I bought a couple of new chucks for my Warco 7 X 12 mini lathe, an 80mm three jaw scroll which was a direct replacement, and a 100mm four jaw indipendent, which was rear mount and required modification to fit directly on the spindle. They are Sanou, Chinese and better made than the original pair. It was not difficult to turn a suitable register and drill front mount holes in the 100mm body.
|Niels Abildgaard||30/11/2020 05:33:19|
|367 forum posts|
It will also be no big deal to fit a 125mm big hole fourjaw on a 80mm mini spindle
Edited By Niels Abildgaard on 30/11/2020 05:33:53
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.