VEVOR 7X14 Lathe converted to a dedicated horizontal mill.

[homebrewed]

Well I have had a few days to play with this thing and after shiming the vertical slide in both directions I couldn't get it any better than using no shims at all. The surface profile after shims only got worse. But I did get good results when I worked on cross slide. I tighten up the Gibbs and got (to me) exceptable results.
.0005 horizontal difference and .0008 vertical
difference BUT this thing is NO fun to crank!
I guess a total rebuild and refit of the cross slide is in order.
I have a extra cross slide that I dissected today
And found two obvious issues one being way to much back lash as stated by HomeBrew and the other issue was poor fitting gibbs.
They looked to me like they were at least 1/8" to narrow. As it stands now I don't know if fixing this one or buying a upgraded cross slide would be better?

The fact that the gib is pretty narrow might affect its rigidity, since the force from the gib screws won't be distributed quite as well. Before buying a cross slide I'd recommend buying or making a replacement gib. It will be a lot cheaper than a cross slide.

My theory could be totally off, as well -- I have read of folks making gib strips out of plastic, which would be a lot more flexible than steel, with no problem. Still, it would be a less-expensive experiment.

 

[steelcat]

The fact that the gib is pretty narrow might affect its rigidity, since the force from the gib screws won't be distributed quite as well. Before buying a cross slide I'd recommend buying or making a replacement gib. It will be a lot cheaper than a cross slide.

My theory could be totally off, as well -- I have read of folks making gib strips out of plastic, which would be a lot more flexible than steel, with no problem. Still, it would be a less-expensive experiment.

Humm.....I could 3d print some good fitting Gibbs from nylon.
Nylon being naturally slippery and tuff may just work
Hell its worth a try. I think I have my project for tomorrow.
Thanks!

 

[homebrewed]

Humm.....I could 3d print some good fitting Gibbs from nylon.
Nylon being naturally slippery and tuff may just work
Hell its worth a try. I think I have my project for tomorrow.
Thanks!

It will be interesting to see how that works out. Please let us know!

 

[steelcat]

This experiment was a good lesson on rigidity. The nylon gibb did kinda work but was no were near rigid enough in my opinion.
The depth of cut and feed speed was severely hampered.
Maybe nylon wasn't the best choice of material to try but I am done with it.
I will stick to brass.

 

[homebrewed]

This experiment was a good lesson on rigidity. The nylon gibb did kinda work but was no were near rigid enough in my opinion.
The depth of cut and feed speed was severely hampered.
Maybe nylon wasn't the best choice of material to try but I am done with it.
I will stick to brass.

Still, it was worth trying. Thanks for reporting back on your experiment.

 

[steelcat]

Yep! Nothing ventured nothing gained.
Adding the additional gibb adjusters made a lot of difference with the metal gibb. I think a proper sized gibb will be the ticket but what do I know.
After looking at the gibb when installed it looks like the height is OK but the thickness may be the issue.
As it stands now when adjusted the gibb is cocked at a angle. It seems to me that the gibb should stay square to get full contact?

 

[homebrewed]

Yep! Nothing ventured nothing gained.
Adding the additional gibb adjusters made a lot of difference with the metal gibb. I think a proper sized gibb will be the ticket but what do I know.
After looking at the gibb when installed it looks like the height is OK but the thickness may be the issue.
As it stands now when adjusted the gibb is cocked at a angle. It seems to me that the gibb should stay square to get full contact?

Unfortunately what you're observing isn't all that unusual. The gibs on this class of machine are problematic. To address this some folks have inserted bearing balls between the gib and gib screw, on the theory that the ball will permit the gib to rotate so it is in full contact with the dovetail. A smooth gib (one without the dimples to accomodate the gib screws) might not work because the ball won't keep the gib in a fixed horizontal position. So another option would be to machine small plugs with a sloped end whose angle matches the dovetail angle. I'm using the latter approach on my mini mill but see no reason it wouldn't work on a lathe as well. Easy to make with a mill, perhaps not so easy with your setup.

If you see a thin wear line on the dovetail that's an indication that the contact area between your gib and dovetail is very small. That definitely would affect the rigidity of your cross slide.

If your gib is too thin you may not be able to use a bearing ball, another reason to replace the gib.

 

[steelcat]

I ordered some brass and I will take a stab at making the Gibbs. I have a few ideas how to size them. It will take quite a bit of time and patience.

 

[homebrewed]

I ordered some brass and I will take a stab at making the Gibbs. I have a few ideas how to size them. It will take quite a bit of time and patience.

I made some brass gibs for my mini mill using this holder. However, you still have to figure out some way to machine the slot at the desired angle.

A dovetail cutter would simplify things. If you don't have one or don't want to spend the money it also is possible to make your own using a "T" style carbide insert. Most of it can be made on your lathe. If interested, you can take a look here. It would be slow going to use it because it just has one cutting edge. To reduce the cutting load you'd need to take light cuts. Assuming you're going to use your Frankenmill to cut the gibs

 

[steelcat]

Well its been awhile since last post.
I did manage to fix/make the cross slide Gibbs. I ordered the brass Gibbs from LMS and to my surprise they fit pretty close. The height was perfect. I only had to cut them to length and adjust the thickness. They were 1/32" to thick.
I accomplished this on my belt grinder that is made for cutting/ polishing knife blades. Its like a thickness plane for steel. The Gibbs not being magnetic created a problem but a custom jig fixed that.
I cut the Gibbs adjuster pockets with a ball end mill ( I think that is what they are called) the adjuster screws were cut convexed and polished on a lapidary wheel.
All this work took a ungodly amount of time but the results were amazing. I often wonder how much of this was overkill?
After installing and adjusting the cross slide I checked the slop with a dial indicator and came up with (nearest I can figure)about one ten thousand of a inch. The cross feed is silky-smooth and effortless now. I have used it for a few milling jobs and the surface finish and accuracy is definitely improved.
I am now doing the same process to all the slides on my lathe. Fingers crossed.