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Royal Enfield General Discussion => Campfire Talk => Topic started by: gizzo on November 06, 2018, 02:09:17 pm

Title: Chinese Mini Lathes
Post by: gizzo on November 06, 2018, 02:09:17 pm
Anyone had any experience with these things?
Mini lathes are little metal lathes that fit on the benchtop. They come in a few different sizes between about 10-16 inches. I bought one a few months back. I'd have loved a more substantial machine but the cost and space made it not practical. Before I bought mine I did a load of research into them. It appears that they mostly come from the same factory in China and are sold under a bunch of different brands and are supplied in different levels of quality and finish. This depends on the price the brand wants to pay the factory. You can buy pretty much the same machine branded Grizzly, Harbour Freight, Seig and some unbranded one on eBay.  Probably others.

Anyway, I did the shopping and bought a Seig SC3. It's supposed to be at the higher quality end of the mini lathe spectrum. It's about 16" between centres, about 7" swing. So it's big enough for a lot of the jobs I'd want to do. It has a pretty powerful brushless motor with infinitely variable speed control and enough torque that it doesn't need a 2 speed gearbox, which is nice. There's a power feed for the carriage but not the cross slide or compound. There's a tailstock with a Morse taper. The tailstock is ok but is a bit sloppy so centre drilling is a bit of a PITA. The older versions with DC motor have a tailstock you need a spanner to adjust but the brushless version comes with a QR one. It comes with a set of screw cutting gears but I haven't tried that yet.

It worked OK out of the box but really needed some tuning to make it work right. I'm still working on that. It seems to get better with each bit if fettling. Sort of like the Royal Enfield of lathes I guess. Some of the tuning I've done:

Drill and tap tailstock for a bigger adjusting screw. Tightens up the feed screw and removes a bit of the slop
Drill leadscrew bushes for oil holes. Otherwise you need to dismantle half the machine to lube the plain bushes.
Lapped the saddle to the ways. It didn't move smoothly but lapping really improved it. the adjusting strips needed adjusting too.
Lapped cross slide and compound gibs. These are metal strips you can adjust to make the slides move smoothly. The gibs as supplied can be adjusted either too loose or too tight. Too loose the slide rocks around, too tight you cant screw it along. The cross slide screw backlash needed adjusting too. Lapping the gibs took hours but it's worth it. The slides are much smoother and the machine becomes more rigid.
The toolpost is pretty rubbishy and I've ordered a QR toolpost to make life easier.
Bought a drill chuck and live centre.
I'll also order a digital speed display some time. and maybe a bigger 3 or 4 jaw chuck.

So far I've done outside turning, facing, boring and parting off. It's hopeless at parting at least with the tool I have . Boring works well but you have to take it easy, small cuts only. Facing works a treat, as does regular turning. Some days I get a really nice surface finish, other days it's rotten. But I think that's to do with the material I used. Some steel just turns better than others. I wrecked a tool turning down a grade 8 bolt. But mild steel, aluminium and brass are fine, as is plastic.
I used the mini lathe to modify a steering tube to take different bearings, make various bungs and tubes from steel and brass, a water temp  gauge bucket from plastic and made kilos of swarf just for fun. I've tried brazed carbide tips and the indexed replaceable ones. So far the brazed ones seem to work better.

I reckon the Mini Lathe is pretty good value for money, if you buy the right one. It needs some love out of the box but is a pretty sweet running machine if you make the effort. It's a useful tool to have about the place. Machinist tradesmen will warn you away from buying one because they're "rubbish". Of course they are, compared to what they use to earn their living. But you know what? It's good enough for me.

What's your experience, opinion, tips?
Title: Re: Chinese Mini Lathes
Post by: Guaire on November 06, 2018, 05:38:50 pm
Here's review I saw on youtube:
Title: Re: Chinese Mini Lathes
Post by: Stanley on November 06, 2018, 05:50:37 pm
I have a 7 x 14 Sieg lathe and it's been a pleasure to use despite diminutive power and size. I opted for the mini-lathe to make bushings and fittings for repairs and mods. Your analogy to an Enfield is spot-on, since it takes skill and curiosity to make it shine.
I found the lathe a bit wobbly for the Taig vertical slide I adapted for milling but otherwise I'm very happy. After tuning it up and adding a A2Z toolpost, it's made parts for my ever-changing collection of bikes. The only issue was a galled dry gear bearing in the gear train that polishing and lubing put right. I also added a lead screw handwheel, saddle gear chip guard and some other improvements. A flexy LED lamp from Ikea lights the workpiece.

The first lathe I turned on was a big Logan professional job such as machinists are replacing with CNC gear. Craigslist is full of these wonders awaiting a forklift, truck or crane to fill someone else's garage. My brother has a garage full of machines including a Bridgeport mill. Sadly, it's in a hoarder's garage.
Title: Re: Chinese Mini Lathes
Post by: gizzo on November 07, 2018, 06:37:29 am
I like the handwheel. I might make one of those.