Two issues.... took video footage

[Pcmaker]

yeah, it's rotating CCW

 

[TerryH]

LMS carriage lock is worth the money in my book. Works perfectly on my G8688. I would have just made one if had a mill when I bought the lathe but did not.

https://littlemachineshop.com/products/product_view.php?ProductID=2977&category=



Tweek the spring in the collar a little. Had to do the same on mine. Also, make sure there is no oil/lube in that area where the spring is located.

 

[royesses]

To find out if the carriage is your problem put the back gears in neutral so the lead screw won't turn and lock the half nut. This way you are using the lead screw as a carriage lock. Not the best lock but it should be good enough to get a straight cut. That's what I did before I got the carriage lock from LMS. Also you may need to adjust the carriage gibs a bit tighter. You don't need a mill to make a carriage lock. You could duplicate the LMS lock by welding flat bar and drilling for a center bolt and nut.

Don't get discouraged. We all have gone through this kind of stuff with our mini lathes and mills. It is kind of fun to debug these kits and you learn a lot from all the little problems that you discover. Before long you'll have that lathe running like a dream.

Roy

 

[markba633csi]

Could the lock be put on the other side of the cross slide? It looks like an awkward location in the photo above
Pcmaker: do you have any high speed steel tool bits you can try? They act differently than carbide and can be easier to use- they can be sharpened easily and ground into custom shapes
Mark

 

[Hawkeye]

Referring to Terry's photo, take note of the HSS cutter in the toolpost. You'll find that HSS is generally sharper than carbide, when properly sharpened. It's easy to learn to sharpen lathe tools - plenty of videos on line. Quite a few of us recommend starting with HSS tooling when you're learning.

If you're going to use Roy's suggestion of using the leadscrew as a carriage lock, have the compound (upper) feed set to 0 degrees so that you can feed in between cuts with out having to turn the feedscrew by hand.

I can't tell from the video, but have you checked the tool height? It needs to be right on the centre-line of the spindle.

As far as cutting speeds go, this is the single biggest factor for new operators getting good or bad results. We were all there at one point. The attached file is a set of charts that I made up when I learned about cutting speeds. It was for a different lathe, but most of it, other than the last one, should help you. It helps to have an optical tachometer to check the actual speed.

 

[Richard King 2]

On those tiny machines it doesn't take much to have issues. On the facing issue. The saddle might be convex and as it cuts it rocks back and forth like Grannies rocking chair. Take a mag base and put a thin sheet of paper (used to protect the ways from getting scratched) and set it under the mag base. Then reach out and put your .0005" or .001" indicator on the operators side of the saddle as close to the chuck side. Then with your thumbs only put one on the same side as the indicator and one as far to the right and press and release each thump pressing say with 10 psi and see if the saddle rocks on the bed. I have seen this several times on lathes that are Asian or worn. many times they are never scraped correctly and the leave the middle high on the bottom of the saddle. And no matter what you do you get movement.

You can do that same test on the cross slide and compound ends. Have to mount the indicator on the matching member so you don't get multiple errors Keith Rucker has a you tube show showing how to set up the table gib in hid knee mill. Same principal but on a much smaller scale. Rich

 

[TerryH]

Could the lock be put on the other side of the cross slide? It looks like an awkward location in the photo above
Pcmaker: do you have any high speed steel tool bits you can try? They act differently than carbide and can be easier to use- they can be sharpened easily and ground into custom shapes
Mark

The carriage lock is designed to mount in 2 existing tapped holes for mounting the steady rest. Everything on a mini lathe is in an awkward position.

 

[Pcmaker]

To find out if the carriage is your problem put the back gears in neutral so the lead screw won't turn and lock the half nut. This way you are using the lead screw as a carriage lock. Not the best lock but it should be good enough to get a straight cut. That's what I did before I got the carriage lock from LMS. Also you may need to adjust the carriage gibs a bit tighter. You don't need a mill to make a carriage lock. You could duplicate the LMS lock by welding flat bar and drilling for a center bolt and nut.

Don't get discouraged. We all have gone through this kind of stuff with our mini lathes and mills. It is kind of fun to debug these kits and you learn a lot from all the little problems that you discover. Before long you'll have that lathe running like a dream.

Roy

Thanks. Yeah, I admit I'm getting a little discouraged since I bough this lathe, but hopefully I get all this figured out.

 

[Richard King 2]

It looks as if you did not tighten the cap screw on the feed screw to handle. Page 15 and 24
http://cdn2.grizzly.com/manuals/g8688_m.pdf

Most machine have a woodruff key on handle to feed screw. That uses a friction fit it seems. Either the shoulder on the feed screw is to long or you didn't tighten it tight enough. I would also turn my compound more so your riding on the top more. I would also try a HSS toolbit as sometimes the geometry on inserts and bad geometry on mini lathes are not the same. .

You may see if you can track down a mentor or say school instructor who lives near you to help you. Call around to some local machine shops and see if they have a retired lathe operator who you could call and see if he can help you.

 

[SamI]

Thanks. Yeah, I admit I'm getting a little discouraged since I bough this lathe, but hopefully I get all this figured out.

Keep at it - you'll get there. The mini lathes do come with their limitations but then their price and compact size make machining accessible to those who don't have the money or the space for larger machines. I had mine for about two years and there was a steep learning curve. But after a while you adapt to your machine and can create some fantastic parts with it! You will probably also find that when you do move onto a bigger machine you have a much better understanding of how the thing works which makes troubleshooting much easier. I think the general rule of machining is that no matter what size of machine you buy you always want bigger! The first few weeks of owning my 13 x 30 lathe I thought it was the best thing ever but soon I realised that given the machines increased rigidity I can take much deeper cuts. This led me to realise that the machine is under powered to take said cuts! Oh well, I had best start saving for a more powerful motor!

I suspect the facing issue is due to the carriage moving back under the force of cutting. As you cut the work piece there will be a force pushing back against the tool. Without a carriage lock this force will push the carriage back slightly (i.e. moving the tool away from the workpiece) which will be giving you a convex face.

As has been mentioned before, try disconnecting the feed screw gears and engage the half nuts. This will prevent the carriage from moving back. It's not perfect but it'll be a huge improvement on what you're doing currently. Alternatively you can make a very primitive carriage lock as shown here: http://www.mini-lathe.org.uk/images/lathe_carriage_lock_3.jpg It looks to be a piece of flat bar that's been cut to the appropriate length and drilled and tapped to accept an M5 screw so you could knock something like this up with very little effort assuming you have some scrap flat bar lying around.

Have a look at your machine. On mine there is a drilled hole on the tailstock end of the carriage which is designed for the carriage lock. This makes it a bit more accessible than one at the headstock end.