Vevor rotary table troubles

[ChazzC]

That's great you got a refund, but with all the re-work it's going to take, that free table may still turn out to be pretty expensive in time.

But just in case it's not something you already know Wonk, if you try to use those division plates on another table, just be sure it also has the same worm and worm wheel ratio that your Vevor table has. 40-1 plates as an example could be used on something like a 90-1 table. But your actual division tables for whatever ratio that next R/T has would be useless unless you do the math. Even then, some divisions may not be possible.

Given the extremely poor build quality of that table I'm not sure I'd trust the hole count or even accuracy of there placement in those plates unless I double checked them first. Inaccuracy's in the actual hole placement are still divided by the worm - worm wheel ratio, so even an inaccurately done plate could be used to used to machine second generation plates that would be much more accurate. It just depends on what your using the R/T for and the actual level of accuracy you might need of course.

Might make a good project for someone else, and you could get a few more funds for your final purchase.

 

[Wonk]

I have disassembled the table and am working on de-burring everything (and everything needs it! ). I think for now I will fix the high center ring and the misfit dividing pin and not worry about the re-machining of the side of the base until another day or I find someone local with a surface grinder and bigger tooling than me that would be up for the challenge. I also bought a 3 jaw chuck for it when I purchased the table and like the dummy I am I ordered a 4" chuck for a 4" table so it's going to be a pain to mount it. I should have bought a 3" 4 jaw and may yet and just use the 3 jaw on my South Bend 9" lathe because the 3 jaw I have for it now weighs a ton. Just a couple more projects for me. Seems all I ever do is make tooling for the mill or lathe instead of trying my hand at building an IC engine I want to try.

 

[krypto]

You might be able to get the mounting bolts outside the scroll on the 4" chuck so you can use it on the table if you get that working. You need to disassemble the chuck anyway to remove all the grinding dust and sharp edges.

 

[awake]

A bit of an aside to the main topic, but ... has anyone else had some of the teeth strip on their RT? I've got a 6" Vertex, and was using it to mill a contour ... apparently it was too much for the RT.

 

[user 284]

I've not had any issues with my own Vertex R/T Awake, but it's now at least 35 yrs old. So I don't know about any of there recent R/T's. But a couple of years ago there was a thread on the Model Engineer magazine forums that mentioned the same issues with Yuasa R/T's and a few of the teeth stripping when used for rotary milling. I'm not sure if there was ever a solution or answer, but some thought the worm wheel might have been made by using sintered material. Maybe inspect yours under magnification where those teeth broke and see what the material looks like? I don't know what your Vertex uses, but mine has a steel worm and bronze worm wheel. What does yours have?

 

[L98fiero]

I've not had any issues with my own Vertex R/T Awake, but it's now at least 35 yrs old. So I don't know about any of there recent R/T's. But a couple of years ago there was a thread on the Model Engineer magazine forums that mentioned the same issues with Yuasa R/T's and a few of the teeth stripping when used for rotary milling. I'm not sure if there was ever a solution or answer, but some thought the worm wheel might have been made by using sintered material. Maybe inspect yours under magnification where those teeth broke and see what the material looks like? I don't know what your Vertex uses, but mine has a steel worm and bronze worm wheel. What does yours have?

Without knowing what Wonk's rt looks like internally, I can only go by a cheap one I brought that was only used for rotary positioning. Mine did need some TLC to be usable but it has a small diameter ferrous worm gear with a fairly fine pitch worm meaning they aren't suitable for heavy rotary milling, I can only assume the Vertex rts have a larger diameter worm gear that makes it capable of heavier milling.

 

[user 284]

Then best guess is yours very likely has a cast iron worm wheel L98. That might be ok if they used something like ductile iron, but with the cost cutting, then they probably didn't.

 

[L98fiero]

Then best guess is yours very likely has a cast iron worm wheel L98. That might be ok if they used something like ductile iron, but with the cost cutting, then they probably didn't.

I'm sure it's steel, but given the diameter and pitch, I don't think it's worth pushing it if I don't have to, I have a CNC for that kind of work.

 

[awake]

Mine looks to be cast iron, and it is a relatively fine pitch - more or less a module 1, based on the measurements. I've considered machining off the old gear, machining (or possibly purchasing) a new gear, and mating the two ... but I haven't had time to work on it. One of these days ...

 

[Richard Hed]

Mine looks to be cast iron, and it is a relatively fine pitch - more or less a module 1, based on the measurements. I've considered machining off the old gear, machining (or possibly purchasing) a new gear, and mating the two ... but I haven't had time to work on it. One of these days ...

I don't get why that would be necessary. Machine off the old gear and mating the two? Wky would you do that?

 

[awake]

Since there is a section of teeth stripped out of the old gear, it would seem necessary to replace it. Perhaps there is a better way to replace the gear? As I recall, it appears to be machined as part of the table, but perhaps I have missed something.

 

[Richard Hed]

Since there is a section of teeth stripped out of the old gear, it would seem necessary to replace it. Perhaps there is a better way to replace the gear? As I recall, it appears to be machined as part of the table, but perhaps I have missed something.

oH, Sorry, forgot that you said that above. You have made gears before? Why not make one yourself, I'm assuming the teeth are slanted for the worm. You have a mill? Indexer?

 

[awake]

As I said: "machining (or possibly purchasing) a new gear" - machining is certainly an option, and yes, I have all of the tooling needed to cut spur gears, and I can cut them at an angle as well. What I don't have ATM is a way to hob the worm gear with a curvature to "wrap around" the worm screw. That said, if I recall correctly, the existing (partially stripped) gear does not have the curvature either ... which perhaps made it that much easier to strip - ? In any case, "one of these days" I'll get to it, probably when I next have a project that really needs the RT.

 

[Richard Hed]

As I said: "machining (or possibly purchasing) a new gear" - machining is certainly an option, and yes, I have all of the tooling needed to cut spur gears, and I can cut them at an angle as well. What I don't have ATM is a way to hob the worm gear with a curvature to "wrap around" the worm screw. That said, if I recall correctly, the existing (partially stripped) gear does not have the curvature either ... which perhaps made it that much easier to strip - ? In any case, "one of these days" I'll get to it, probably when I next have a project that really needs the RT.

That's very interesting. Can you post a foto of that gear. I can hardly believe they wouldn't put that necessary slant on the teeth. -- But . . . made in china

 

[awake]

It has the slant / angle. What it may not have is the curved shape on the sides that is found on higher-quality worm gears. It's too hot to go dig it up in the garage at the moment; I'll try to remember to take a picture next time I'm out there.

 

[user 284]

While it would be really questionable they did so for the methods used on that OEM gear, then high accuracy hobbing would certainly be the way the better tables have there worm wheels produced. That would also and automatically hob the correct helical tooth angle into the wheel to match the thread angle used on the worm. High precision thread and tooth grinding with possibly lapping to then average the lead / lag errors is probably done as well on the best industrial level tables. Something like a very low load thread dial indicator on a lathe could get away with using straight or spur gear type teeth. Even so, most of the better manual lathes still seem to copy how it's done on proper worm wheels. But that radius and those helical cut teeth on the worm wheel would be almost mandatory on an R/T. That increases the surface contact area between the worm and wheel and vastly strengthens each tooth's load capability. Exactly what you'd want during rotary milling. G. Thomas mentions in one of his books that the radius on the worm wheel should be to a depth of approximately 1/5th of the diameter of the worm. There's quite a bit more to why the price is so much higher for the better tables than what you can see.

In general, most dividing heads will use a 40-1 worm to wheel ratio. R/T's seem to use higher ratios although there are some fairly rare exceptions to that. But it's for that reason and sometimes what the material that worm wheel is machined from are why I believe it's usually recommended to not do rotary milling with the plain dividing heads. Both operate similar, but there are some logical and sound mechanical reasons for when to use either type. Of course there's also universal D/H's that are designed for both dividing and rotary or helical milling. For what most of us would be doing and our budgets, then an R/T with the optional set of dividing parts, plus a foot stock would I think be the better choice for what I'd buy first.

 

[L98fiero]

It has the slant / angle. What it may not have is the curved shape on the sides that is found on higher-quality worm gears. It's too hot to go dig it up in the garage at the moment; I'll try to remember to take a picture next time I'm out there.

If you can make an accurate copy of the screw, mill teeth in, and harden it to make a hob, you could gash the worm with a smaller form cutter and the 'free hob' it with the hob you've just made. It's not likely to qualify as a precision worm, but satisfactory for a lot of operations maybe even as good as the original.

 

[Richard Hed]

If you can make an accurate copy of the screw, mill teeth in, and harden it to make a hob, you could gash the worm with a smaller form cutter and the 'free hob' it with the hob you've just made. It's not likely to qualify as a precision worm, but satisfactory for a lot of operations maybe even as good as the original.

Frankly, I thimpfkd that that is probably the best solution, that is, making a hob from a screw. I am curious (yellow), as alluded to by one of the members, the teeth should NOT be of the straight surfaces, but the curved type that match the worm as it progresses.

 

[L98fiero]

Frankly, I thimpfkd that that is probably the best solution, that is, making a hob from a screw. I am curious (yellow), as alluded to by one of the members, the teeth should NOT be of the straight surfaces, but the curved type that match the worm as it progresses.

If you look at normal worm gears, they have concave faces that provide more contact surface with associated strength.

 

[timo_gross]

Frankly, I thimpfkd that that is probably the best solution, that is, making a hob from a screw. I am curious (yellow), as alluded to by one of the members, the teeth should NOT be of the straight surfaces, but the curved type that match the worm as it progresses.

I would think dedendum of the worm wheel is created by the addendum of the hob. If the worm and hob have the same addendum and dedendum, then there will be no clearance.
I think the hob needs to have a larger diameter than the corresponding worm.

p.s. contacting the manufacturer if they can provide a spare part was not an option?