Need Help In Choosing Mini Lathe - 7x14 Vs 8x16

[dakopian]

Hi Dear enthusiasts/professionals!

I need your help in choosing a right lathe for my needs.

First of all, shortly about me: firmware engineer. I got some machinist experience in my childhood, that knowledge is 14 years old, so I'm considering myself as a newbie. My hobbies include RC models, model rockets. After reaching some point in that, I realized that my ideas are limited by capabilities of my tools. To go to the next level I need a bench top lathe.
It's unlikely I will process things larger than, say, 4" x 5", so, seems to, 7x14 lathe would have enough size. What I really need is accuracy - 0.0005" is pretty desirable. I understand it's unlikely I get that accuracy right out the box, but I'm very ok with doing some adjustments/improvements by myself (as long as heavy machinery is not needed). Most used materials are aluminum and delrin. The budget is something about $1000 (there is no way to get approval from my wife for any higher ). And, yes - I'm going to operate the lathe in my apartment, so noise level matters.

 

[dakopian]

After doing some research, I'm considering next candidates:

1) Grizzly G0765 (7 x 14) - seems to be a classic Chinese lathe from the same factory as Big Dog lathe. A lot of positive reviews on YouTube and price you cannot beat - $674 with delivery. If I go with this lathe, I would spend almost $400 on accessories/mods and finally, I would get a decent lathe (probably).

2) Grizzly G0768 (8 x 16) - heavier and cooler lathe made of metal, no plastic gears. If I go with that, it will take a long time to get an approval from my Boss for any additional spendings on accessories. Main questions: is this lathe more rigid than previous one? Is it more accurate? Does it worth extra bucks?

3) Sieg C3 (7 x 14) from LMS. Very similar to option #1, but weaker (350W vs 550W). Maybe it's much better quality?

4) HiTorque 5100 (7 x 16) from LMS. Seems to be one of the best 7x lathes. Cost about the same as #2, but it's still 7x lathe with the same origin as #1 and #3. Only one difference is BLDC motor. As I understand, all the machines listed above have some electronic control circuit which maintains RPM under various load. It's unlikely I will be processing large diameter stock very often and I'm not lazy to switch the Lo-Hi lever. But if this lathe gives me the best accuracy, I will opt it out.

All the internet forums are carefully studied, mini-lathe.com is being my homepage for a month

My mind is about to blow up, so I really hope for any help/suggestions - that would be much appreciated!

Thank you,

Dmitrii

 

[wrmiller]

Had a 7x16 from Micro Mark that is basically the same machine as the LMS. The BLDC motors are better at maintaining a constant speed than the brushed DC motors.

Given your description of what you intend the machine for, you are not going to stress any of the lathes you describe. You will however, have to basically take the thing apart and clean, measure, deburr, stone, possibly file, make new gibs, etc. to get the accuracy you are looking for. The small Chinese machines (even my LMS mini-mill) are basically kits that you tweak to get the accuracy and functionality you want. Not much help, sorry.

 

[kd4gij]

I usually say get the biggest lathe you can afford and have room for. But it sounds like you are cramped for space. And tooling is as important as the lathe. You just need to find a way to get the better half to thing it is here idea. One thing you need to look at is what is the swing over the cross slide. A 7" lathe will swing 7" over bed but you can't turn the od. I haven't run a 7" or 8" lathe so I can't help there.

 

[dakopian]

wrmiller19, kd4gij - thank you guys for participation!

Currently, I feel like these are 2 border cases:
1) Buy the cheapest one 7x14 and invest time and bucks in improvements.
Pros:
- Lots of online materials/reviews. Well known machines.
- Less noise (because plastic gears and power feed disengagement system).
- Due to low initial price, lots of extra money to invest in accessories which are right for the work I intended to do.
Cons:
- Number of major modifications needed (tapered bearings, lapping) to achieve desired level of accuracy.
- Limited rigidity which is difficult to overcome.

2) Invest the whole budget in a larger 8x16 machine.
Pros:
- Looks sturdier, more operational space (which is not significant factor for me, but who knows).
- All the gears are made of metal.
- Tapered bearings from the factory.
- 4 jaw independent chuck in the box.
- At the first glance and from the single existing YouTube review, good overall finish and quality.
Cons:
- Potentially more noise due to metal gears and power feed design (all the gears seem to be engaged at all the times).
- Very limited number of reviews/feedback.
- Belt manipulations needed to switch between Lo-Hi spindle range (although, 'Lo' configuration will be used 99% of the time).

I've seen some feedback from the people who own 7x series, like "If I could make that choice again, I'd better start from, at least, 8x series".

Also, I found the next note in G0768 manual: "Reducing backlash to less than 0.002" is impractical and can lead to accelerated wear in leadscrew and other components. Avoid temptation to overtighten leadscrew nut or set screw while adjusting. ".
Does that mean the accuracy better than 0.002" is not achievable?

Sorry for too many letters

 

[brav65]

wrmiller19, kd4gij - thank you guys for participation!

Currently, I feel like these are 2 border cases:
1) Buy the cheapest one 7x14 and invest time and bucks in improvements.
Pros:
- Lots of online materials/reviews. Well known machines.
- Less noise (because plastic gears and power feed disengagement system).
- Due to low initial price, lots of extra money to invest in accessories which are right for the work I intended to do.
Cons:
- Number of major modifications needed (tapered bearings, lapping) to achieve desired level of accuracy.
- Limited rigidity which is difficult to overcome.

2) Invest the whole budget in a larger 8x16 machine.
Pros:
- Looks sturdier, more operational space (which is not significant factor for me, but who knows).
- All the gears are made of metal.
- Tapered bearings from the factory.
- 4 jaw independent chuck in the box.
- At the first glance and from the single existing YouTube review, good overall finish and quality.
Cons:
- Potentially more noise due to metal gears and power feed design (all the gears seem to be engaged at all the times).
- Very limited number of reviews/feedback.
- Belt manipulations needed to switch between Lo-Hi spindle range (although, 'Lo' configuration will be used 99% of the time).

I've seen some feedback from the people who own 7x series, like "If I could make that choice again, I'd better start from, at least, 8x series".

Also, I found the next note in G0768 manual: "Reducing backlash to less than 0.002" is impractical and can lead to accelerated wear in leadscrew and other components. Avoid temptation to overtighten leadscrew nut or set screw while adjusting. ".
Does that mean the accuracy better than 0.002" is not achievable?

Sorry for too many letters

I think the tendency as new guys (myself included) is to chase perfection, i.e. extreme accuracy. In reality the accuracy needed for each project is a function of its intended use. I struggle to try and keep the obsession with perfection within reason, in all areas of my life. There are thousands of guys producing unbelievable projects on these mini lathes.

 

[JimDawson]

Does that mean the accuracy better than 0.002" is not achievable?

Not at all. I think what they are talking about is backlash in the leadscrews. Once you get down to the 0.002 range, the accuracy is dependent more on the operator skill than the machine.

 

[T Bredehoft]

That .002 possible error would be in length, not diameter. Is it critical? Only you know.

 

[wrmiller]

As Jim said, backlash isn't machine error it's a description of the amount of free rotational movement of a leadscrew within it's mating nut. You WANT some backlash on all of your screws or you will suffer premature wear on the screw and/or nut. I prefer about 5 thou or more on my leadscrews. When moving a cutter or work piece (lathe vs mill) you want to do your movements so that the screw and nut are always loaded. This is where practice and skill have much more impact on a part's final dimensions than the overall tolerance of the machine will. I have built competition guns on aluminum Sherline machines in my past. I cut a titanium compensator on my 7x machine (won't do that again...). I wouldn't recommend these types of work to a beginner, but things like this can be accomplished on these smaller machines.

If you need quiet, I would stay away from the steel gears. Plastic gears and belt drives are SO much quieter.

 

[stupoty]

I had a 9x20 (cm) lathe as my second lathe, i liked a lot about it and a few things i don't so much.

I didn't have a quick change gear box on mine so changeing Feed speeds means fidling with change gear for a few minuits(at least) this causes a user to find sets of speeds that work well and not change so much where as with a feed gear box you can try different feeds very quickly and easily.

Rigidity was always a little bit of an issue, parting off could be problematic. I realised that the frount gib is only a half gib on mine.

The one i had had a flange mount chuck which was a bit problematic as it had 3 bolts to fit and remove a chuck but the nuts were rediculusly dificult and fidly to use. A cam lock one would be much easier or a thread mount is also quick.

I got into using centers a lot.

Good hunting

Stuart