Compound slide not good.

[lesrhorer]

On my Vevor Lathe, the compound slide has both its travel and rigidity severely limited by the fact the dovetails and / or ways are not properly parallel. If I move the slide to its middle position and properly set the gib screws so the slide moves easily but is still acceptably rigid, then the rear 1/3 of its travel is incredibly sloppy, with more than 0.020" slack. If /I set the gibs at the rear 1/3 of the travel, the slide siezes by the time it is in the center of its travel. Even if I loosen the gib screws entirely, the slide siezes before it reaches its farthest excursion forward. Even a lathe this small (200 x 750 mm) should have a practical compound slide travel of more than 12mm, but this one does not. The gib is far from perfect, but I don't see how it could be responsible for the evident taper, at least not by itself.

The dovetails are not ground. It seems to me they, or at least the ways, should be ground and then lapped and /or scraped. The milling marks are not very fine, at all. I think I can help significantly by merely re-milling the dovetails. It may not be worth it, but I think the dovetails and the ways should at least be ground, as well. Is there someone out there with a surface grinder who could grind the dovetails, or at the very least the ways and the gib?

 

[Winegrower]

I agree with re-milling the dovetails. I had this problem when I first got my Logan 10". It was an easy and very successful fix. Obviously only the lightest touch is needed. Didn't surface grind, didn't need to. Now that I have a surface grinder, I still probably wouldn't. I'm still at the point I can do a lot of damage with the grinder.

 

[jwmay]

Welcome to new H-M Commercial member P&B Grinding!

Please take a moment to welcome new member Bill aka @P&B GRINDING! Bill operates P&B Grinding and Machine out of Garrettsville, Ohio and is excited to be a commercial sponsor of Hobby Machinist. We are excited to have a shop sponsor on the forum and looking forward to having his expertise here...

www.hobby-machinist.com

Maybe call this company.

 

[woodchucker]

I agree with re-milling the dovetails. I had this problem when I first got my Logan 10". It was an easy and very successful fix. Obviously only the lightest touch is needed. Didn't surface grind, didn't need to. Now that I have a surface grinder, I still probably wouldn't. I'm still at the point I can do a lot of damage with the grinder.

wait... you can do a lot of damage with a grinder but not a mill?

for me it takes way longer to grind than mill. At any rate... I don't know of dovetails being lapped.. scraped yes.
do you have any idea how much you are out by?

do you have a machinery's handbook? in it it explains how to use pins to measure inside and outside the dovetails. You may want to read that and check so you know how much you are out by. Once you have done that you can determine what the next step is.

You may even be able to stone it by hand to bring it in close. Richard King is the man to talk to once you have your measurements.

 

[lesrhorer]

Yes, I know how to measure dovetails, but I do not have any roller pins. No, I don't have a Machinery's Handbook.

 

[Winegrower]

wait... you can do a lot of damage with a grinder but not a mill?

You do not know me, apparently.

 

[Janderso]

The dovetails are not ground. It seems to me they, or at least the ways, should be ground and then lapped and /or scraped

Takes too much time, costs too much money.

We see this all the time on the Asian imports.
Like so many have said before, you are buying a kit that has to be finished.
Keep us along for the ride.
Love to see how it works out.

How to measure dovetails>>>

 

[lesrhorer]

Thanks. As I said before, I already know how to measure the dovetails, I just don't have any dowel pins.

 

[lesrhorer]

The gib was pretty messed up. The divots for the gib screws were incredibly sloppy. All three were way off axis. One was so far off the gib screw did not even touch it. They were doing a terribly poor job of keeping the gib in place, and there was a great deal of anomalous vertical force when the screws were tightened. I machined an Aluminum bar flat and glued the front of the gib to the bar. I took a 6mm end mill and cleaned up the divots. Now the force vectors shoud be uniform. Below you can see how far off and non-uniform the divots were. The bar is slightly banana shaped, and the thickness varies by about 15 tenths. 'Not great, but the front of the bar seems flatter than the back. OTOH, it is concave on the front of the bar, which is less preferred to my way of thinking. I don't have any good way to actually measure flatness. I am just going by the fact the bar spins on its center when pllaced on its back on a reasonably flat surface, and one can see light between the surface and the bar. I did hand lap the front of the bar a little bit, but I don't have any good means to do much more than that.

 

[lesrhorer]

I have ordered a set of dowel pins. They should be here this week or early next week at the latest.