# Turning Steel



## Chip Monkey (Jan 7, 2022)

I know mini lathes _can_ cut steel. I don't have a lot of experience doing it, but have been able to hold decent size and finish on stuff of varying lengths and diameters. But, seems like more often than not that every steel session has to be followed up with a carriage adjustment. Light cuts, good tooling, proper speeds/feeds, etc., but so far I'm not impressed with its ability to stand up to 12L14.

What might I be doing wrong/what should I check? I'm all ears and would love to find out that I'm the problem and not the other way around. I think it's me, but at the same time I really think I'm doing things properly. I consider myself a novice on a lathe, but all my time has been on larger, domestic machines.

My machine is a LMS 7350 which I am not singling out. Talking generically about these Sieg based lathes. What's your experience?

PS

Not to gush, but I'm a new guy here and have _REALLY _appreciated the knowledgeable feedback I've received from other posts. *Thank you all very much.*


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## Flyinfool (Jan 7, 2022)

When you say you are "using proper speeds and feeds", what is your source for "proper"?

Many small machines can not handle the speeds and feeds that are published, You might just be trying to cut more than a small machine can handle.


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## SLK001 (Jan 7, 2022)

A sharp HSS tool with the correct geometry should cut 12L14 like butter.


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## WobblyHand (Jan 7, 2022)

Chip Monkey said:


> I know mini lathes _can_ cut steel. I don't have a lot of experience doing it, but have been able to hold decent size and finish on stuff of varying lengths and diameters. But, seems like more often than not that every steel session has to be followed up with a carriage adjustment. Light cuts, good tooling, proper speeds/feeds, etc., but so far I'm not impressed with its ability to stand up to 12L14.
> 
> What might I be doing wrong/what should I check? I'm all ears and would love to find out that I'm the problem and not the other way around. I think it's me, but at the same time I really think I'm doing things properly. I consider myself a novice on a lathe, but all my time has been on larger, domestic machines.
> 
> ...


I have a 7350 from LMS.  It is fairly capable.  I have found the saddle retainer needs to be tightened more often than I like.  They simply cannot be done while on the ways.  That being said, it was fairly easy to slide off the apron and tighten the retainers once there is easy access.  I have found a mod that can be done that allows the retainers to be adjusted from the top.

That being said, if you haven't adjusted your gibs and saddle retainer, you should do that according to the instructions.  A 7350 will have no problem cutting 12L14 at all.  (Or 1144)  But your tool needs to be on center, it has to be sharp, and all the slop in the lathe adjusted out. Adjusting the gibs and retainer doesn't take long at all.  Once you do that, it's pretty good for it's size.


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## Chip Monkey (Jan 7, 2022)

Flyinfool said:


> When you say you are "using proper speeds and feeds", what is your source for "proper"?
> 
> Many small machines can not handle the speeds and feeds that are published, You might just be trying to cut more than a small machine can handle.


Below 80 sfpm, not more than .015 per pass


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## DavidR8 (Jan 7, 2022)

Chip Monkey said:


> I know mini lathes _can_ cut steel. I don't have a lot of experience doing it, but have been able to hold decent size and finish on stuff of varying lengths and diameters. But, seems like more often than not that every steel session has to be followed up with a carriage adjustment. Light cuts, good tooling, proper speeds/feeds, etc., but so far I'm not impressed with its ability to stand up to 12L14.
> 
> What might I be doing wrong/what should I check? I'm all ears and would love to find out that I'm the problem and not the other way around. I think it's me, but at the same time I really think I'm doing things properly. I consider myself a novice on a lathe, but all my time has been on larger, domestic machines.
> 
> ...


What kind of tooling are you using? 
As @SLK001 mentioned sharp HSS with the right geometry should cut 12L14 like butter. 
Cheap import carbide will probably not do a great job.


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## WobblyHand (Jan 7, 2022)

Chip Monkey said:


> Below 80 sfpm, not more than .015 per pass


Carbide insert, brazed carbide, or high speed steel tooling?  CCGT carbide inserts work well, or sharp HSS, or sharp brazed carbide are ok.  If not sharp, not so good.  I can easily cut 12L14 with your settings.

By sharp, I mean the tool is sharp enough to slice your thumb.


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## Watchwatch (Jan 7, 2022)

SLK001 said:


> A sharp HSS tool with the correct geometry should cut 12L14 like butter.



This. The geometry doesn’t even have to be that great. HSS, 500 rpm, a couple thou per rev feed rate, and .02ish max DOC.

I bet the OP is using the wrong carbide inserts for the size of lathe. 


Sent from my iPhone using Tapatalk


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## Chip Monkey (Jan 7, 2022)

I know gibbs/ways are routine maintenance, I meant that by "carriage adjustment". I can get things nice and snug from the ways to the tool post, I was just expecting them to stay that way longer.

BTW, using home ground hss and will absolutely brush up on geometry. I never really thought carbide would be much good. Should I try?


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## WobblyHand (Jan 7, 2022)

Chip Monkey said:


> I know gibbs/ways are routine maintenance, I meant that by "carriage adjustment". I can get things nice and snug from the ways to the tool post, I was just expecting them to stay that way longer.


If you are like me, those saddle retainers don't get looked at often enough.  Tightening them really helps with lathe rigidity.  Last time I looked at them (last week) all the retainer screws were loose.  I've had the middle screw fall out before.  The middle screw is totally inaccessible when the apron is on the lathe.


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## Chip Monkey (Jan 7, 2022)

WobblyHand said:


> If you are like me, those saddle retainers don't get looked at often enough.  Tightening them really helps with lathe rigidity.  Last time I looked at them (last week) all the retainer screws were loose.  I've had the middle screw fall out before.  The middle screw is totally inaccessible when the apron is on the lathe.


I look at them more often than I wish I had to. Someone above mentioned top down mod? Have to check that. To me, it would be a big part of the answer. I'd much rather be on top.....


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## addertooth (Jan 7, 2022)

There are multiple people who have come up with a better way to maintain saddle retainers which are more solid, and effective.   I would suggest you look into it.  The mod is a simple one.  I have not done it yet. But it is on my to-do list the next time I have a reason to remove the saddle.

The lathe is essentially a Sieg SC2, so the mods you find for this model will largely apply to a LMS 7350.

The Saddle Retainer, as it is designed tilts in at an angle, and only the edges of it make contact.  The better design uses a flat to flat mating surface, which more surface area and rigidity.  It makes for a more reliable (and less wear-prone) assembly.

I saw a really nice design on MadModder, where he made adjustable tapered brass gibs for his.  The adjustments are made within easy reach. 

By the way, I have an LMS 7350 too, and am rather happy with it.  Out of curiosity, I tried to "wiggle" my apron, and it was rather secure.  I have done a fair bit of steel with mine.


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## mikey (Jan 7, 2022)

Chip Monkey said:


> BTW, using home ground hss and will absolutely brush up on geometry.





Chip Monkey said:


> Below 80 sfpm, not more than .015 per pass



Haven't used a Seig lathe before but from the looks of it, you should be able to take a heck of a lot bigger cuts in 12L14. I agree with the other guys that you might want to work on the geometry of your tool. If you care to show us some pics of the tool, maybe we can give you some idea of how to make it better.


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## Watchwatch (Jan 7, 2022)

Chip Monkey said:


> I know gibbs/ways are routine maintenance, I meant that by "carriage adjustment". I can get things nice and snug from the ways to the tool post, I was just expecting them to stay that way longer.
> 
> BTW, using home ground hss and will absolutely brush up on geometry. I never really thought carbide would be much good. Should I try?




CCGT inserts for aluminum will work.

Post a pic of your cutter. The king of HSS for the small lathe, Mikey, is posting in your thread and will let you know.


Sent from my iPhone using Tapatalk


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## mikey (Jan 7, 2022)

Watchwatch said:


> The king of HSS for the small lathe, Mikey, is posting in your thread and will let you know.



Hardly, but I will try to help if I can.


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## homebrewed (Jan 8, 2022)

The saddle retainer plates (A.K.A. slide plates) _are_ a weak point of these lathes.  But it isn't necessary to go to the extreme of making the oft-mentioned "tapered gib" modification.  I dumped the OEM jack-screw approach and went with a much simpler method, basically using flat slide plates and shims to get the right spacing between the plates and lathe bed.  I did that a few years back and haven't found it necessary to do any adjustments yet.  In contrast to some of the other approaches, this one doesn't require any mods to the saddle, either.

I didn't even use metal for the slide plates.  I used cast MDS-filled nylon, which is filled with molybdenum disulfide for lubrication.  McMaster-Carr has it for not a whole lot of money.  It WAS convenient to have a benchtop mill to shape the pieces but it's been done with a lathe and a milling attachment.  Acetal would probably work just about as well for this kind of application, and, if your lathe is in a humid environment, won't absorb moisture and expand like nylon will.  I haven't experienced that, but YMMV.


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## Chip Monkey (Jan 8, 2022)

homebrewed said:


> The saddle retainer plates (A.K.A. slide plates) _are_ a weak point of these lathes.  But it isn't necessary to go to the extreme of making the oft-mentioned "tapered gib" modification.  I dumped the OEM jack-screw approach and went with a much simpler method, basically using flat slide plates and shims to get the right spacing between the plates and lathe bed.  I did that a few years back and haven't found it necessary to do any adjustments yet.  In contrast to some of the other approaches, this one doesn't require any mods to the saddle, either.
> 
> I didn't even use metal for the slide plates.  I used cast MDS-filled nylon, which is filled with molybdenum disulfide for lubrication.  McMaster-Carr has it for not a whole lot of money.  It WAS convenient to have a benchtop mill to shape the pieces but it's been done with a lathe and a milling attachment.  Acetal would probably work just about as well for this kind of application, and, if your lathe is in a humid environment, won't absorb moisture and expand like nylon will.  I haven't experienced that, but YMMV.


Your suggestion is what I started with a few weeks back and I have things getting pretty close. I ditched the jack screws, made a pair of tool steel side plates, and I'm sneaking up on zero slop by adding a shim or shims every time I have reason to disassemble the carriage.

Your plastic side plate idea interesting. Thanks!


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## Chip Monkey (Jan 8, 2022)

mikey said:


> Hardly, but I will try to help if I can.


Mikey,

Appreciate it. I'll get some pictures if I don't get this sorted out.


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