Metal lathe options

[RobinHood]

That grind looks pretty good to me. Maybe it is just the camera angle, but the first picture shows almost a negative top rake. I would try neutral (flat) or slightly positive.
I would also go for a larger nose radius.
Honing the cutting edge might help as well (maybe you did, I just can’t tell).

 

[Chris Cramer]

I don't think @Chris Cramer has mentioned the diameter of his SS workpiece and the RPM he is spinning it at. Not all 7x lathes have tachs. And, the brush-type DC motors and controllers don't provide much torque at lower RPMs. So getting a tool to 'dig in and cut' with a reasonable DOC at lower RPM isn't easy. And at too-high RPM, a HSS tool won't last very long, even if ground at the correct angles.

That's a good point, this SS round stock is pretty heavy. The diameter is 1.25"/1', it was probably what first caused the belt to start slipping before I tightened it. My new tool had no trouble cutting the brass, leaving a very clean finish, and started cutting the SS fairly well at a lower RPM, only it didn't last long before the edge broke as I continued to feed it. I should try cutting the mild steel again after regrinding the tool.

 

[Susquatch]

I don't know you, but I think you don't have 'the right mindset' for a 7x, especially for most Vevor machines..

What is the right mindset?

Yes, as I said, that's what gets used. The same as on the Logan 200/210. Not like 'better' lathes which have two ways of moving the carriage with power, and folks don't put unnecessary wear on the threading leadscrew by using it for ordinary turning. I think I mentioned change gear options for ordinary turning in an earlier post?

OK, so it can do a controlled feed.

BTW: I may have missed it, but I don't think @Chris Cramer has mentioned the diameter of his SS workpiece and the RPM he is spinning it at. Not all 7x lathes have tachs. And, the brush-type DC motors and controllers don't provide much torque at lower RPMs. So getting a tool to 'dig in and cut' with a reasonable DOC at lower RPM isn't easy. And at too-high RPM, a HSS tool won't last very long, even if ground at the correct angles.

Yes, he has been asked for that kind of info. If it is available, I have not seen it or missed it.

 

[Susquatch]

Here are some photos of the next tool I just ginded.

Those look better although still too much IMHO. The tool looks low in the first photo. And the tool stick out should be reduced.

I confess I am dumbfounded by the rolled edge you are still getting. Something is still seriously wrong there. Edge not sharp enough, speed too high, too much tool pressure? Wrong angle, wrong height, tool holder bending, still rubbing someplace?

I agree with @RobinHood's comments - especially regarding too much speed. I never cut stainless very fast. Usually 70rpm which is as slow as my lathe will go. That being a big 1.25" bar only makes that worse.

That might also explain other comments about workhardening SS which does not jive with my experience. I can easily cut stainless with very shallow cuts (a few thou) at low rpm with a sharp HSS tool. Emphasis on slow and honed sharp. Also no more tool stick out than required to clear. Short & stubby = rigid.

I wish I could just drop by.

But thanks for the address. I'll try to get a tool out today before the weekend. I have some other stuff I need to mail anyway.

Should it be 3/8 or 1/4?

 

[thestelster]

I confess I am dumbfounded by the rolled edge you are still getting.

There is no way that a HSS bit will get a rolled edge. I'm thinking it might be BUE, built-up edge.

"This cutting tool wear type is caused by pressure welding of the chip to the insert. It is most common when machining sticky materials, such as low carbon steel, stainless steel and aluminium. Low cutting speed increases the formation of built-up edge."

 

[Susquatch]

There is no way that a HSS bit will get a rolled edge. I'm thinking it might be BUE, built-up edge.

I think you nailed it Stel. That fits with the other issues too.

@Chris Cramer - sometimes it can be difficult to identify BUE. It doesn't necessarily mean you are boogered. The key to addressing this issue is a sharp honed edge, high quality sulphur based cutting oil, and a nice formed chip curl to take any buildup away with it.

Until Stel mentioned BUE, we had not discussed cutting oil. I use Vipers Venom. It's hard to find. But I'm sure you can get a good alternative there. You can brush it on or drop it on. I prefer to drop it on. With a good oil, it will stick to the work and last for two passes. It will help reduce heat, lubricate the cut, and improve finish. I rarely cut stainless without it.

Please don't use the tool bit I'm sending you without it. No sense ruining it right out of the box.

 

[Susquatch]

You won't hear anybody saying that over at the 7x groups.
CHMW is a 'Bridgeport and big lathe, or working up to it' sort of place.

My 'other lathe' is also a small lathe (by CHMW standards),

That's twice that you suggested CHMW is a big machine group. Frankly, this hurts a bit. Your experience is yours so I won't defend the contrary view. Instead, I'll just accept that your view is valid to you. Especially since you are a very active member.

Suffice to say that I think the majority of our members are someplace between the big stuff and the little stuff - sort of in your "other lathe" family. But I confess that I don't know that for certain.

I confess that my own machines are probably on the bigger side. So it is entirely possible that I might be guilty as charged. However, no matter how guilty I might be, I can assure you that it isn't intentional. I try hard to help everyone who needs it and I try not to tell them that the answer is bigger equipment. This particular thread is a good case in point. Just picking on two other members, I know that @RobinHood and @thestelster, are also here trying to help and they are both bigger machine members too. None of us has mentioned upsizing as a solution. The worst we have done is to say we don't have that issue, but I think that's just honesty or perhaps even an excuse for not knowing the exact solution.

I think our forum wants to be a place where all metal workers can get and give help to each other no matter what the size of their machines are. But we may be failing on that goal.

Nonetheless that's your impression. Your impressions are just as valid as anyone's. So I'd like to try and address it. I think the first step is to identify our active member makeup.

I'll start that process with a survey sometime over the weekend. I'll also raise it as a topic for our next admin meeting.

Any suggestions you might have would be very welcome.

 

[Bandit]

Hmm, I have not seen the "bigger" machine side in the group. I would tend to say there are likely a good number of members with mini lathes and some mini mills, some in the "middle" ground with 9 inch to 14 inch swings by 20 to 40 inch beds and mill drills up to small knee type mills, and "small type bridgeports? Some members have a "bit larger equipment",not many have over 16 inch swing by more then 48 inch beds or mills with 12 inch by 72 inch or bigger tables. Sorry even this isn't the large stuff.
I was lucky enough to see one member's equipment in the spring, some very fine gear! Yes, it was larger then a watch makers gear, equipment that size wise would be in a general machine shop.
Your equipment is what you can afford, want, can get, and have the space for. Topped by how big your projects are.
So, for the survey, I have, 1-- 6 x12 mini lathe, high/ low range. running
1--9inch utilathe x36? bed. running
1-- 13x40 lathe. running
8 inch shaper. running.
10 inch drill press. running
12 inch bench drill press. running
16? Inch floor drill press. running
2 mig welders. Running
1 stick welder. Running
Smaller oxy/ac torch
Smaller plasma cutter, not set up yet.
A mess of hand tools of various disciplines, and some things that are not running/useable.
Ya, I have more then some, and less then others, but that applies to brains too.
I don't have a problem with them that has the big stuff or the small stuff, it's about seeing how others do things and trying to learn or pass on a bit of learning.
If I came across on the hard side, sorry, but there are others things in life that I find worrisome, but not here.

 

[CWret]

I think our forum wants to be a place where all metal workers can get and give help to each other no matter what the size of their machines are.

I’ve been following this thread as a learning experience - as you know- i don’t have a lathe (yet). I can see myself in Chris’s ( @Chris Cramer ) shoes and similarly looking for help. I appreciate the advice that Forum members offer and their willingness to do so. It comes from members with many years of experience and it also comes from beginners who are trying to help other beginners. They are ‘giving back’ or ‘paying forward’ or whatever you want to call it. IMO their: size of shop; number of machines; size of machines; technical training; years (or weeks) of experience; or their ability- has no influence on their willingness to help beginners (or each other for that matter).

I'll start that process with a survey sometime over the weekend.

Your taking the time to get this study started emphasizes my point. As does your idea to bring up the issue with the Forum admin.

A survey may shed some light on this issue. If it is an issue?
You can’t fix a problem you don’t know you have!

I’m glad you ( @VicHobbyGuy ) expressed your viewpoint. Thanks.

 

[VicHobbyGuy]

What is the right mindset?
(for using a Vevor 7x)

Think of homesteading on a new property, doing your farming with a 4-wheeler (ATV) instead of your tractor.

 

[VicHobbyGuy]

That's twice that you suggested CHMW is a big machine group. Frankly, this hurts a bit.

I don't know why that would hurt, actually. I probably need to adjust my ideas about 'hobby metal work' (I think of Elmer Verberg in his basement or the Brit guys making their railway engines) and 'big' metalworking machines. @Bandit has clarified that even a 16" swing lathe is not big.

I think our forum wants to be a place where all metal workers can get and give help to each other no matter what the size of their machines are. But we may be failing on that goal.

Nonetheless that's your impression.

As far as I can recall, I have never suggested that people here weren't helpful. If I ever did that, it was incorrect.
It isn't easy to give appropriate suggestions without some knowledge of, or better yet, experience with the machine being discussed.
No fault with that, when people are trying to help.

I wouldn't recommend going to the Sieg 2X mini-mill group on FB for hints about fixing your knee mill, or going to the 7x mini-lathe group for advice on 14" chucks for your 'mid size' lathe.
More than once, I have recommended here that people with problems with their 7x lathes and mini-mills go to those places. The fact that they don't do so, proves to me that they are getting the advice they need right here from the helpful folks who built this forum, and sustain it.

I didn't intend to pull @Chris Cramer's thread off-topic; my apologies if I have done so.

 

[Susquatch]

Think of homesteading on a new property, doing your farming with a 4-wheeler (ATV) instead of your tractor.

Maybe that's a good analogy, maybe it isn't.

My great grandfather and my grandfather (his son) homesteaded the home farm I was born on in Saskatchewan with an Ox. A few years later, they upgraded to a pair of Belgian work horses. I went to school riding one of those horses. From their perspective, I think that ATV might have been an upgrade.

Also, I do some spraying and cover crop seeding with an ATV. It isn't like my big row crop tractor but it has its place.

But I think I understand your point. My personal attitude about such things can be summed up with a few quotes:

1. Never let what you can't do get in the way of doing what you can.

2. Many an impossible thing has been done by someone who didn't know it was impossible.

3. The little engine who could. It's a great feeling to own such a machine. That's what I call my little tractor. She has a can do attitude and I am very proud of her. Much more so than my big row crop tractor.

If I had a small lathe, I would use it for the things that it can do and only because I do have a bigger lathe I wouldn't push it. If I didn't have the bigger lathe I prolly would push it. At the same time there is something to be said for what a small lathe can do better than a bigger one. I think I would enjoy that enough to dedicate some basement space to one at the right price.

 

[VicHobbyGuy]

I would also go for a larger nose radius.

Most 7x lathes don't have enough torque- especially at low RPM- to cut with a very large nose radius. So, I agree that the radius should be larger (a point won't be as tough) but moderation is the key IMO. A few swipes on a diamond hone to round the point a bit, are all that it takes for me.

 

[VicHobbyGuy]

I never cut stainless very fast. Usually 70rpm which is as slow as my lathe will go. That being a big 1.25" bar only makes that worse.

I don't know how slowly @Chris Cramer can get his lathe to turn effectively. My Vevor 7x14 0-2500 RPM lathe (without the Hi-Lo transmission the Sieg lathes have) wouldn't turn steadily at low RPM. I found this 'feeds and speeds' chart from Tom's Techniques really useful. https://tomstechniques.com/wp-content/uploads/2014/12/CuttingSpeeds.pdf Once I started using that chart, I realized a couple of things:
1- I'd been turning aluminum and brass too slowly
2- My lathe couldn't turn slowly enough to use HSS tools on larger steel workpieces. The right side of the chart was mostly 'terra incognita' for my 7x machine. So I switched to using mostly (sharp, for Al) carbide tooling and the higher RPMs it could handle, for 'larger' steel workpieces.
Some folks here may remember my struggles trepanning a recess in a 3" steel model engine flywheel, using a HSS tool. RPM was probably 250-500...

 

[Susquatch]

I don't know why that would hurt, actually.

It's ok. It is my nature to always question myself and strive to improve.

I didn't take offense. It's just that our mission is not segmented to big and little. We want to serve all segments. It's part of my volunteer activity to be mindful and sensitive.

And no, you didn't criticise the help that has been given. I was just pointing out that the guys with bigger machines do care about the guys with smaller ones.

Survey coming up soon.

 

[Susquatch]

@Chris Cramer - A Custom ground HSS hit the mail today. I used minimum but adequate relief. I figured the extra strength and heat sink would help.

I used a 5/16 Cobalt blank. I figured it was better than 1/4 and less than 3/8 and a better chance of fitting. I also ground a bit off the top just in case. Make sure the top is level with the center of your spindle.

This blank is for turning not facing. But you will be able to see the angles and duplicate them on a facing tool. That or turn your compound a bit so that the shank clears.

You can also see that I put a very small radius on the tip as well as honed all the edges. I also marked the top as Up.

Lastly, I did a test cut on 1" stainless here. It cut just fine.

Let me know when it gets there.

 

[VicHobbyGuy]

I didn't take offense. It's just that our mission is not segmented to big and little. We want to serve all segments. I

That's a pretty tall order; you guys are making a good attempt at it already.
The other forum that's not bad in the 'all segments' area is the Hobby-Machinist in the US. Some of the leading participants here are also helpful on that forum.
The 'general' groups on Facebook- places like the 'Benchtop Metal Lathes and Mills' group are absolutely toxic.
Any post or question about a 7x lathe or mini-mill quickly gets posts about "effin Chinese junk boat anchor toy POS, get a real machine, boy etc etc..."
So people migrate to where they will find 'like minded' individuals.
Really, that was the great benefit of the internet when it was young and not yet fully 'monetized' - no matter how unusual your hobby you could find other like-minded individuals from around the world. So I really don't think there's anything wrong with 'specialized' forums and groups.
Your survey results will be interesting. Unless there are a lot of 'read-only' folks, I'd be surprised if you turn up many 7x lathe and mini-mill owners, judging from the paucity of posts about those classes of machine. Which is OK! No need to be offended.

 

[Susquatch]

That's a pretty tall order; you guys are making a good attempt at it already.
The other forum that's not bad in the 'all segments' area is the Hobby-Machinist in the US. Some of the leading participants here are also helpful on that forum.

We try.

As you noted, many of our own members are active there too. @David_R8 & @Dabbler are even volunteer moderators there. No surprise you think we are similar.

Personally, I don't think much of Facebook groups. I am only there for marketplace.

We don't generally approve of members knocking other members wives, dogs, or machines here. That ugly guy in the mirror is fair game. So are his tractors.

Time will tell how the survey ends up.

 

[DavidR8]

We try.

As you noted, many of our own members are active there too. @David_R8 & @Dabbler are even volunteer moderators there. No surprise you think we are similar.

Personally, I don't think much of Facebook groups. I am only there for marketplace.

We don't generally approve of members knocking other members wives, dogs, or machines here. That ugly guy in the mirror is fair game. So are his tractors.

Time will tell how the survey ends up.

The motto on HM is it's the friendliest machinist forum. "We're here to help, not to flame, criticize or judge each other."

 

[VicHobbyGuy]

We don't generally approve of members knocking other members wives, dogs, or machines here.

And, sometimes "Get a bigger lathe" is the correct answer, too.