Mini Lathe Unwanted Taper?

[WobblyHand]

Okay, I'll weigh in for what it's worth.

I have a Weiss made Amadeal branded 7x14. I've had this lathe apart so many times over the past year to adjust, fettle and improve it and I'm still not done.

Partly because of this, and because most of the things I've turned have been close to the chuck and absolutely not requiring of any kind of precision, and because my 3J is a cheap San Ou, a full job of checking for bed twist, checking headstock alignment and tailstock alignment has been delayed. Honestly, I've had stuff to sort out on this thing ahead of that.

Turning an unintended taper over the 12 odd inches the average 7x14 has? Yeah, they'll do that straight out of the box. Sure, you probably can get that taper down to sensible respectable amounts if you spend a fair bit of time (and potentially money).

However, you'll also be deburring and smoothing out all the sliding surfaces (apart from the main bed ways probably), sorting out the lacklustre torque at low speeds (even with the newer brushless motor models), trying to get the saddle interface with the bed, the cross slide interface with the saddle, and the top slide interface with the cross slide, all tight enough to avoid play and loss of rigidity without making things so stiff you can't move anything smoothly, fixing the tailstock quill's shakiness, replacing the rack with one that isn't shaped like a banana, putting a cover on the apron so it doesn't get rammed with chips, getting the leadscrew well adjusted enough to power feed smoothly, finding a solution for the lack of a fine enough power feed, adding thrust bearings to all the handwheels, and maybe extending the cross slide travel by milling out the saddle.

Frankly, if you gave has an 8x16, I can't imagine why you would buy a 7x. I promise you, you will not make a Chinese 7x as good as the 8x16 in any way. The possible ceiling of quality of Chinese machines goes up the bigger they are.

Honestly mate, save your money and spend it on something else. There are decent enough reasons to buy a mini lathe but I don't think any of them apply to you.

If you want a challenge, go on AliExpress and seek out one of their little benchtop surface grinders and try to turn one of those into a usable machine. It'll add to the diversity of capabilities in your shop, and if you really can't make it work as a mini surface grinder, you can probably mod it to become quite a reasonable tool and cutter grinder.

I'm not sure if you got a lemon, or all the Amadeal mini-lathes are that way. Yours is an example of what can go wrong in this class machine. Believe it or not, we've heard of worse here...

I bought the nicest 7x16 that Little Machine Shop (LMS) offered at the time. Whether that means I got a higher quality lathe or not, I honestly don't know. Mine had really low TIR at the spindle, less than 0.0001". It had a taper, but I don't remember how much, since I was able to adjust it fairly low, with some help from this forum. Was everything adjusted correctly on my lathe, no. But it wasn't terrible. Mostly I just tightened gibs and things, per the included instructions. Honestly as a beginning user, I wasn't quite sure what I should touch, knowing that I could make it worse! As I got more confidence, I made minor adjustments. There were no major problems with my lathe. I made a differential screw tail stock horizontal adjuster. Made it easier for me to get the horizontal adjustment. It sure was fun to design. Also made a straddle knurler that mounted to a plinth that was hard mounted to the cross slide. That was a fun little tool to make. I use the knurler to this day, as I don't have an equivalent for my larger 10x22 lathe.

 

[ShagDog]

Southern Chap, the reason I am inclined toward a 7x mini is the size and weight so that I could bring it into the heated basement, instead of the cold garage shop.

 

[WobblyHand]

I can just pick my 7350 mini-lathe up, which can be convenient at times! Think it is about 90 lbs. I have mine mounted on a tool chest so I have places to put tooling.

 

[SouthernChap]

I'm not sure if you got a lemon, or all the Amadeal mini-lathes are that way. Yours is an example of what can go wrong in this class machine. Believe it or not, we've heard of worse here...

I bought the nicest 7x16 that Little Machine Shop (LMS) offered at the time. Whether that means I got a higher quality lathe or not, I honestly don't know. Mine had really low TIR at the spindle, less than 0.0001". It had a taper, but I don't remember how much, since I was able to adjust it fairly low, with some help from this forum. Was everything adjusted correctly on my lathe, no. But it wasn't terrible. Mostly I just tightened gibs and things, per the included instructions. Honestly as a beginning user, I wasn't quite sure what I should touch, knowing that I could make it worse! As I got more confidence, I made minor adjustments. There were no major problems with my lathe. I made a differential screw tail stock horizontal adjuster. Made it easier for me to get the horizontal adjustment. It sure was fun to design. Also made a straddle knurler that mounted to a plinth that was hard mounted to the cross slide. That was a fun little tool to make. I use the knurler to this day, as I don't have an equivalent for my larger 10x22 lathe.

Oh, mine had a spindle runout of about a tenth. The headstock assembly wasn't much of a problem although there was a teensy bit of axial.play; it went away after I replaced them with angular contact bearings.

The point I was making really was that to get the best out of a cheapish 7x14 (and I don't imagine the OP was planning on spending the extra on an LMS Hi Torque model, which seems to be from a better QC bucket), it takes a lot of time and effort.

I just think, given his existing kit, a mini lathe is a waste of money.

 

[mac1911]

Yes. As close to zero as possible. About .0003" max over 3" length on 1" diameter for example, so about .0001" per inch. Am I asking too much? Is anyone getting close to this number?
As to mini lathe, 7x to 9x.

I have been think about this,
Are these 7x mini lathes even sturdy enough not to have .0001” flex
IDK the proper term by can these small 7x lathes be adjusted well enough that you dont get .0001” of carriage/craddle walk

I have yet to measure it but i fought with my smithy 1220 just to eliminate it visually and by feel …. Crab walking down the ded ways?

 

[WobblyHand]

I have been think about this,
Are these 7x mini lathes even sturdy enough not to have .0001” flex
IDK the proper term by can these small 7x lathes be adjusted well enough that you dont get .0001” of carriage/craddle walk

I have yet to measure it but i fought with my smithy 1220 just to eliminate it visually and by feel …. Crab walking down the ded ways?

Depends on DOC and finesse, I'd suppose. And some luck, if you got a decently made example. If you go for a heavy DOC, forget it. But with minimal stickout of both tooling and stock and sharp HSS for minimum push, and some patience, it's possible to do a lot. If you are in a hurry, or in production, look elsewhere.

 

[SouthernChap]

I have been think about this,
Are these 7x mini lathes even sturdy enough not to have .0001” flex
IDK the proper term by can these small 7x lathes be adjusted well enough that you dont get .0001” of carriage/craddle walk

I have yet to measure it but i fought with my smithy 1220 just to eliminate it visually and by feel …. Crab walking down the ded ways?

There are things you can do to allow for more rigidity around the saddle, cross slide and top slides.

You can add a carriage lock, you can add a central shear plate (it's a bit like a large long T nut that's attached under the centre of the saddle and rides on the underside of the ways in the middle of the bed; mind those undersides are barely machined if at all so they need sorting; that's the most onerous part of that improvement), you can add extra gib adjustment screws and add cross slide and top slide locks.

And as Wobblyhand says, be sensible with DOC and it's fine.

If you want a small pick up-able lathe. I"d keep an eye out for something like a Unimat or Prazimat. Or if you don't mind spending a fair bit more, a Sherline maybe.

If you really want a 7x then I reckon LMS are probably your best bet to reduce the amount work you need to do.

 

[WobblyHand]

I only can speak to a circa 2019 LMS 7x16 (Sieg) lathe, but it's ok. LMS was pretty helpful to me when I made a beginner's screw up early on, and actually gave me some parts free. They certainly didn't have to do that, nor did I ask for any favors. Yes, it was a minor crash, and yes, a gearshaft bent. They got me what I needed to get going again with minimal fuss.

 

[homebrewed]

I think a well-fettled mini lathe + machining practices that are appropriate given its rigidity limitations will get you a long way toward your goal. But "well-fettled" could cover a lot of territory!

 

[ShagDog]

I think a well-fettled mini lathe + machining practices that are appropriate given its rigidity limitations will get you a long way toward your goal. But "well-fettled" could cover a lot of territory!

That is an interesting term .