Mega modifications for a mini lathe

[homebrewed]

Welcome to H-M!

The saddle slide plates (some folks refer to them as gibs) definitely are one of the weaker design point of these lathes. It's pretty easy to improve that by getting rid of the OEM jack screws and using shims to get the running fit you need. That mod was one of the best and easiest I've done to my mini lathe. You don't need to get all fancy and do the tapered gib thing, and it really improves the overall rigidity.

If you replace the compound with a riser block, don't throw or trade the compound away. You still will need it for cutting threads or short tapers.

 

[deadwat3r]

Pay particular attention to this one:

It deals with the most frustrating aspect of these lathes. I mounted mine to a wooden base and then filled it with concrete, but might bump that up to a rigid metal plate if I can get some of the other flaws fixed.

Speaking of which: pay attention to the gibs on the saddle. Slop in the saddle is probably the biggest weakness of these lathes, even more than bed twist. And you do yourself no favors if you lock the carriage and use only the compound to feed. You're gonna need a fix for those gibs.

I'm considering making a Gibraltar-style toolpost to use in place of the compound and that crap (non-OXA) QTCP supplied by Micromark: just a big hunk of metal (likely machined from that 2" cast iron round that Hobby Metal Kits provides) with maybe 5/8" for tool shanks, using shims or sleeves to get tools to height.

That was the first one i checked! Any suggestions for those gibs? Anyone? Keep me in the loop of that tool post. The very little info i could find is very interesting.

 

[deadwat3r]

Welcome to H-M!

The saddle slide plates (some folks refer to them as gibs) definitely are one of the weaker design point of these lathes. It's pretty easy to improve that by getting rid of the OEM jack screws and using shims to get the running fit you need. That mod was one of the best and easiest I've done to my mini lathe. You don't need to get all fancy and do the tapered gib thing, and it really improves the overall rigidity.

If you replace the compound with a riser block, don't throw or trade the compound away. You still will need it for cutting threads or short tapers.

Removing the screws and shimming it doesn’t sit right in my head. Could you explain more? And i wont throw it out. Unless i just all together make a new one.

 

[ThinWoodsman]

Removing the screws and shimming it doesn’t sit right in my head. Could you explain more? And i wont throw it out. Unless i just all together make a new one.

As shipped, the gibs under the saddle attach with 3 screws that go through the gib and attach to the saddle, and two screws that go into threaded holes on the gib. These two screws are jack screws: they work by going through the gib and pushing it away from the saddle. The other screws pull the gib towards the saddle. It is very fiddly, to say the least.

There is a photo on mini-lathe.com that hopefully clears things up.

I agree with getting rid of the jack screws and just using shims: put shim stock between the gib and the saddle until it is just right.

When I spend more time with my 7x16 (and to be honest, I somewhat hate the thing but do view improving it as a challenge), I will probably mill a part that is put in place of the gib/side plate, and have it house a proper gib, perhaps bolted in from the side instead of from the bottom so gravity isn't fighting you during adjustment. Still just an idea though. There any many ideas out there on how to fix the gib problem. There's a chapter in David Fenner's book Mini-Lathe Tools and Projects that covers the three most popular approaches.

 

[RJSakowski]

If possible with your setup, position the lathe so there is free space to the left of the lathe. This is so you can insert long bars through the spindle. You will also want space to be able to change gears, belts, etc. The tailstock will only extend past the bed by a few inches at most.

 

[savarin]

This gentleman has a heap of improvement mods for the chinese mini lathe

Steve Jordan

I have worked in the Aerospace Industry for 27 years in these skills...CNC & centre lathe setting and machining, assembling & testing hydraulic, pneumatic an...

www.youtube.com

 

[deadwat3r]

If possible with your setup, position the lathe so there is free space to the left of the lathe. This is so you can insert long bars through the spindle. You will also want space to be able to change gears, belts, etc. The tailstock will only extend past the bed by a few inches at most.

thanks for the advise. that was my plan. I do have a good bit of experience on large lathes at work.

 

[deadwat3r]

As shipped, the gibs under the saddle attach with 3 screws that go through the gib and attach to the saddle, and two screws that go into threaded holes on the gib. These two screws are jack screws: they work by going through the gib and pushing it away from the saddle. The other screws pull the gib towards the saddle. It is very fiddly, to say the least.

There is a photo on mini-lathe.com that hopefully clears things up.

I agree with getting rid of the jack screws and just using shims: put shim stock between the gib and the saddle until it is just right.

When I spend more time with my 7x16 (and to be honest, I somewhat hate the thing but do view improving it as a challenge), I will probably mill a part that is put in place of the gib/side plate, and have it house a proper gib, perhaps bolted in from the side instead of from the bottom so gravity isn't fighting you during adjustment. Still just an idea though. There any many ideas out there on how to fix the gib problem. There's a chapter in David Fenner's book Mini-Lathe Tools and Projects that covers the three most popular approaches.

ok thank you. I will keep that in mind and add it to my list of books to buy.

 

[deadwat3r]

This gentleman has a heap of improvement mods for the chinese mini lathe

Steve Jordan

I have worked in the Aerospace Industry for 27 years in these skills...CNC & centre lathe setting and machining, assembling & testing hydraulic, pneumatic an...

www.youtube.com

I have watched a few of his videos. to be honest I find he gives me a headache. but I will try to suffer through if I run into major problems.

 

[homebrewed]

Make sure to spend some time and effort on the tailstock, too. On this class of machine they are notorious for being problematic -- not aligned properly, unstable base (causing wide variations in position) and so on. I found it most expedient to do some mill work to address the issues mine had, but a lot can be done with shims if you don't have the luxury of a mill sitting next to the lathe. Once aligned, I'm damned if I'm going to set the TS over to cut a taper, but that's just me.....

One alternative (and one I also have done) is to mount a drill chuck on your toolpost. I did it with a chuck that is mounted using a 1/2" thread. I had a boring bar holder that accepts 1/2" diameter shanks so it was -- almost -- a no-brainer. It can be real nice if you start with a small-diameter drill and work your way up, because the tailstock usually has to be moved back partway through the operation to accommodate longer drills. Not the case with a TP mounted chuck. However, that also is when I discovered my problem with the saddle gibs AKA slide plates -- the whole saddle would tip up and back when I applied pressure to the drill. One things leads to another.

BTW, if you're enlarging holes in brass, beware -- conventional drill bits will self-feed, or, worse, try to and then break. This problem is most apparent when using the toolpost-mounted chuck because there's nothing to prevent it from happening. Trust me: I know this for a fact. It's scary to see your drill bit sort of "unwind" when it catches, because you know it's THAT close to just snapping apart from the stress. And since a chuck mounted in the tailstock is just using the taper to hold it in place, it could be pulled out of the tailstock......so the fact that the TS has a feed screw isn't much comfort, either.