Metal lathe options

[Chris Cramer]

Have you tried a bit slower rpm with the carbide on that piece?

I did start at a lower rpm and tried cutting it at the lowest depth that it would actually cut. I had to feed the tool very slowly and apply enough force for the tool to cut very thin strings off of the part. By how thin those strings are and how much force was being applied to the stock, it makes good sense that sparks would come from the bright orange strings as they are cut from the part. The surface of the metal, and the debris was getting hot, but I didnt see the tool get very hot.

 

[VicHobbyGuy]

.The part you see in these pictures is a shank that was for my old drill press chuck that I am modifying to fit in the tail stock for drilling.

I have a lathe similar to yours and owned one identical to yours last year.
A few thoughts in no particular order:
That's a pretty ambitious project - turning a MT2 taper in hard material.
I agree with @Bandit - use a center in the tailstock. Most of the 7x lathes come with a 'dead' fixed center which will work fine at low RPM with a dab of grease or heavy oil; you probably should put a MT2 live center on your shopping list if you don't have one.
If your drill chuck uses a standard taper you can get a MT2 arbor pretty reasonably from AliExpress.
AliExpress is also a good spot to buy 'for alumium' carbide inserts which are a lot sharper and seem to work better on lower powered lathes - that's what I use on almost all materials, and I've seen the same recommendation from more experienced users here. I've also read posts here about 'touching up' carbide inserts to put a bit sharper edge on them - it would be worth a try since you have the wheel to grind carbide and the inserts are only $1 or so.
Talking about depth of cut (earlier posts in this discussion) really needs input about how quickly the tool is traversing. Power feed on a 7x with the stock gear setup is pretty fast; a lot of 7x owners get 'slow feed' gears for ordinary turning. It only takes a couple of minutes to change gears on a 7x (with some practice- most 7x gears need to be reamed to fit, and the stock setup on my Vevor had 'hammered-on' gears- I was amazed that they hadn't split) . You can get away with deeper cuts if you are hand feeding, but it's tough to keep the tool from rubbing instead of cutting cleanly....especially at the 'happy RPM range' for most 7x lathes.
Folks here are very helpful, but you may find more who 'share your pain' with the 7x lathe over at Facebook in the 7x group.

 

[Susquatch]

It is most likely made of very hard tool steel that is harder than the HSS of this tool, because the new tool could not cut it.

I agree with what Bandit says above.

A few other comments. The side relief on your new tool looks like it is insufficient. There should be a tapering gap there. It will work that way for a side cut, but poorly for the face cut you show. I cannot see if the relief is adequate on the chuck side of the cut. But I suspect not.



The color of the stub and chips does not suggest a problem with hardness. It suggests rubbing. See the comment above about clearance. Normally, you get coloured chips but the stub you are turning stays a normal metal colour. Ideally, the chips carry the heat away with them.

 

[whydontu]

Please don't get offended by this question - what are you using for cutting fluid?

 

[Bandit]

You can turn your tool post to get tool relief for some cutting operations. Carbide bits may have relief made into them, positive, neutral, or negative, or the bit holder has it built into it to set insert as "needed" for it.
What are the inserts you have for? Alumumin, cast iron, steel, hard steel, etc., the rake/relief angles are different. The carbide type/make up/coating are generally different too.
Generally I would get an idea of lathe ops and bits,machining, before working on hardened materials.
Please keep in mind that the materials heat up with metal removal and will change measurement when cool.
I am susbect of the metal colouring if it is happening/appears to be happening when machining the shank from the old drill press, was it coloured this way to start with or did it happen while machining? If it is happening while machining, tool bits are rubbing, and or, removed material is not carrying away heat fast enough.
" Chips" are controlled by depth of cut, and the speed of advancement of tool bit and rpm. This is not going into tool bit materials, coatings, rakes and reliefs, what can be a puzzleing mix.
Some of this is also above by others.

 

[VicHobbyGuy]

You can turn your tool post to get tool relief for some cutting operations.

Good point! Most of those '4-way' toolposts on the 7x lathes come with a detent on the underside which tries to 'lock' the toolpost at 90 degrees to the compound. Not very useful, so most folks remove that 'feature' fairly quickly. As you say, a few degrees of toolpost rotation can change that turning tool into a facing tool!

 

[Susquatch]

Hey @Chris Cramer . Some good points made by others above.

Get rid of any indexing under the toolpost if there is any.

I think Aluminium/Brass is too much of a crutch, and hard steel is too much of a cross. Get some cheap machinable steel barstock to practice on. You want to learn how to use your machine. Flogging and molycoddling are not the best environments to learn in. Not only that, but known quality steel provides more certainty when things don't go as expected. You will get better help from us too if we all know what the material is.

 

[Bandit]

As above 2 posts. Also try to point the tip of tool bits away from chuck for general turning, except when doing a face cut, turn towards the chuck. Remember, the tool bit will try to turn away from the work, if point of tool bit is in front of pivot point, it will cut deeper if anything moves. Behind or in line with pivot point, tool bit will move out of work. This can cause near instant grief, and how do I know? Yah, well, part of leaning!
There are different grades of high speed steel (HSS) tooling also. Some has a percentage of "cobalt" and or other materials in it, giving "more better" toughness and heat resistance. Might be hard to find around Calgary. Anyone know? The amount of cobalt will be marked on the bit blank.
The beauty of "HSS" is can be ground for different turning jobs and materials fairly easily.
Carbide inserts and bits, can be ground and modded with more difficulty. AND some known health issues. See some of the various post by RobinHood, Dabbler, and some others as to "tuning" carbide.

 

[Chris Cramer]

As above 2 posts. Also try to point the tip of tool bits away from chuck for general turning, except when doing a face cut, turn towards the chuck.

That makes good sense. The tip of the tool would need enough relief to pierce the side of the round stock if it doesn't start at the end the stock; and if the tool is put on an angle away from the chuck then the edge will cut into the side of the stock instead of the thin layer of the face that it is fed into. I worked with the pivot of the tool post when I did a bit of tapered turning and boring in some brass round stock. After the brass I did try turning some hot rolled mild steel; but that was before I made the new tools so I'm thinking thenew tool could cleanly cut the mild steel now that it's centered.

 

[Susquatch]

Very good cobalt HSS blanks can be had from Amazon and BusyBee. I've never tried HSS from Ali but they do offer it.

 

[VicHobbyGuy]

I've never tried HSS from Ali but they do offer it.

And cheaper too, though you need to wait a few weeks for delivery. Square 8mm or 10mm, for the 7x lathe. I may have been unlucky, but I've found the eBay Indian HSS not as good as the AliExpress Chinese stuff...very very small smple size in my research, though!

 

[VicHobbyGuy]

The beauty of "HSS" is can be ground for different turning jobs and materials fairly easily.

I agree. And it's easier to get HSS sharp, and to change the tip radius easily. However, HSS needs slower turning speeds than carbide and most 7x lathes don't excel at lower RPMs. So there are several different factors to consider.

 

[VicHobbyGuy]

Also try to point the tip of tool bits away from chuck for general turning, except when doing a face cut, turn towards the chuck. Remember, the tool bit will try to turn away from the work, if point of tool bit is in front of pivot point, it will cut deeper if anything moves. Behind or in line with pivot point, tool bit will move out of work.

The location of the hypothetical pivot point can be a bit of a mystery - 7x lathes can be 'loose' in a multitude of areas! One thing I can guarantee - side flexing of the tool itself is not an issue with a 7x.

 

[Chris Cramer]

I purchased 2 3/8 Accusize cobalt HSS blanks from Amazon the 3/8 x 6" blanks are only $16, and delivered the next day.
I agree that HSS is much easier to work, but it is far less wear resistant than corbide. I don't know what type of HSS these blanks are made of or if they come fully hardened/ heat treated. Maybe I can find that out and improve the hardness with my kiln.

 

[Susquatch]

I may have been unlucky, but I've found the eBay Indian HSS not as good as the AliExpress Chinese stuff...very very small smple size in my research, though!

I have ordered a fair number of things from India over the last 5 years but especially recently. I have NEVER been happy. Assuming it even arrives, it has all been very disappointing junk.

It's a little hard to believe given that so much of my recent China experiences have been so good.

I now avoid India. I don't actively avoid China. But I do prefer a middleman like Vevor or Accusize that I can call or email and get a decent English reply. Accusize has had a few quality problems, but they have always made good on them and NEVER let me down.

 

[Chris Cramer]

The accusize HSS is M35 HSS. M35 is an older HSS with some cobalt added to it. M4 is a newer steel with more wear resistance and it's not all that hard to get as a foot of 1/4 1" flat bar which would be enough for four tools. I'm thinking of making some tools out of 1/4 M4 in its annealed state and heat treat it to its top hardness.

 

[Chris Cramer]

I ran into a problem with the machine itself now. The drive belt continues to bounce on the drive pulley. The teeth on the pulley are in good shape, but the belt feels and looks loose. Is there any way to tighten the drive belt or just the drive pulley, or do I need to replace the belt?

 

[VicHobbyGuy]

I ran into a problem with the machine itself now. The drive belt continues to bounce on the drive pulley. The teeth on the pulley are in good shape, but the belt feels and looks loose. Is there any way to tighten the drive belt or just the drive pulley, or do I need to replace the belt?

Take the back cover off the motor and you will be able to figure out how the motor mount is set up. You adjust the belt tension - it should be pretty tight to make sure the 'lugs' on the belt don't skip on the pulley- by adjusting the motor position. I forget how the Vevor is set up. Some of the 7x lathes have a motor bolt whose head bears against the underside of the lathe ways. Others have a pair of bolts from the front of the lathe frame into the motor shell to hold the motor in position. You may have to loosen the control box to get a good view of the front.

Also, make sure the motor pulley is tight on the shaft and fix it if it isn't.
Don't assume it was put together properly at the factory.

Go to aliexpress and order spare belts. If you don't have a Hi-Lo transmission you need a 90T belt, as I recall.

https://www.aliexpress.us/item/3256804489543763.html?

https://www.aliexpress.us/item/3256803420751050.html?

 

[VicHobbyGuy]

Make sure the motor pulley and the spindle pulley are aligned. The motor (and its pulley) have some limited adjustment in the Z direction.

A spare motor pulley might come in handy, too. Order one from AliExpress or LittleMachineShop - check the motor shaft diameter- or find a 3D print file for one (there's at least one on Thingiverse).

While you have the end off the machine, check that the leadscrew and change gears are moving freely. My Vevor leadscrew support blocks were mis-aligned and the leadscrew was binding.

I guess you get the general 'drift' of my recommendations.. You will get to know every part of your 7x lathe; might as well get started!

 

[Chris Cramer]

I found the motor mount behind the control box. The two bolts that hold the motor were not tight and were sitting in the middle of the mount. I pulled the motor to the bottom of the mount and made sure the nuts were tight. It actually isn't necessary to remove the back plate that covers the gears, the motor mount is easily accessible by removing the control box.