Why did you use a thrust bearing and a ball bearing in your vise instead of a tapered roller bearing? Does a thrust bearing really give that maxial torque under high force that its worth the added manufacturing cost of
Does a thrust bearing roll more smoothly under high loads of axial torque compared to a tapered roller bearing?
so it is worth adding the cost of a second bearing to the manufacturing for added smoothness?
What did you find out when you crunched the numbers and ran your experiments?
I’m asking because I’ve managed to save a ball
screw and it’s three ball bearings from being thrown in the dumpster
I have inherited/found all the tube steel I need for a vise similar in size to your hard tail vise so I was planning on making one of my own. I either need to buy a tapered roller bearing or a thrust bearing. I was planning on posting updates on this forum as I work on it.
A tapered roller bearing would be useful if a significant portion of the load it sees is radial, but in the vise it’s basically all thrust because it’s pulling the jaw straight back towards the rear of the vise and the handle never spins fast, or under much of any radial load. That’s why @Fireball_Jason said the thrust bearing is stronger.
Thrust bearings are often used with ball bearings to give extra radial alignment. Tapered roller bearings give the best of both worlds, so would be my preference for the extra radial alignment.
Just a hunch since I don’t know what exact bearings are in the vise, but by separating the load and having the ball bearing handle the radial load and alignment, and the thrust bearing handle the thrust load, each is likely stronger in its given roll than a single taper roller bearing doing both roles would be.
It’s also possible it’s cheaper depending on the exact bearings that were specified. Sometimes you can get bearings for a smoking good deal because they are a super common bearing, so that may be a factor. The common and cheap tapered roller bearings often have a shallow taper angle, so they’re mainly for radial loads, and a little thrust load, not a lot of thrust load and a little radial load (as it would see in the vise). That could mean an expensive low volume tapered roller bearing VS 2 inexpensive high volume thrust and ball bearings.
Again, just speculation on my part based on experience and the shock I’ve gotten in the past for the cost of some bearings. I doubt @Fireball_Jason chose the bearing setup on a whim, so there’s got to be a reason, maybe even the two I suggested.
I assumed there were no radial bearings.
If I were to use tapered roller bearings. I would use a pair with the tapers opposed, preloaded to remove backlash.
So you’re still using 2 bearings, but why opposed? They only see load in 1 direction, so you’d be better off using them the same direction to double their thrust load.
Again, I go back to a cheap ball bearing for radial loads and thrust bearing for thrust loads may be the better design choice for a vise. For the end of a ballscrew on a CNC mill or something like that, your opposed tapered roller bearings would be the right choice, since it will see about the same load in 2 directions, and spin quickly.
I’ve looked at one of the fireball drawings & it looks like there are only 2 thrust bearings with the backlash taken out with a spring, there are no radial bearings.
Traditionally, tapered roller bearings are mounted with their tapers opposed. This allows them to be tightened together to preload them, eliminating backlash. It may not be the preferred solution but I would use this tested method for a personal vise to gain radial alignment & eliminate the spring.
For smooth running it may be prudent not to over constrain the far end of the nut.
Given the leadscrew nut and boxed ways control the up/down and side/side slop of all the important bits, and there isn’t much radial load to speak of, I suppose that would work just fine.
Just throwing this out as well, I’m familiar with why to used tapered roller bearings opposed, I had to convert my IH CNC mill from using ball bearings with preload spacers (stupid design) to opposed tapered roller bearings to get rid of some backlash issues on the X and Y. Stupid expensive little bearings those were indeed.
But that doesn’t mean tapered roller bearings can ONLY be used opposed. The main advantages of opposed tapered bearings is that it makes it easy to remove backlash from the system and it’ll have the same thrust rating in both directions.
If I wanted to use tapered roller bearings for a vise, unless they were huge or had a steep angle (putting a lot of their strength into the thrust direction) I’d use them the same direction with a different way to control backlash; or be extra cautious about knowing for sure what their thrust load rating is, and that I wouldn’t be exceeding it.
This is part of the fun though, ask 10 guys to design something, and there’s a good chance you’ll have 10 difference designs in your hand at the end of it, you just have to decide what design you’re most comfortable with.
It was very strict yet still a huge priveledge to have acess to such an intense & thorough structured program. The ethos of a tradesman was as important as the technical stuff. I was extremely lucky to have been selected. Thankfully, it has kept me in Engineering work for almost 50 years.
Nice. I wish there were still more places that helped developed talent like that. I’m not sure if it’s that there are too many other things to be interested in, but it seems like passion for manufacturing or related skills really dropped off, and is just starting to make a comeback.
I’ve looked into the capacity of tapered roller bearings & their thrust loads are much lower for a similar size thrust bearing. As you advised, they are not an option for such high forces.
Another option is to mount two thrust bearings in a headed sleeve. This allows the bearings to be preloaded onto the leadscrew and this assembly simply slid in from the front. The new headed sleeve assembly can be fixed with a set screw from underneath & easily changed for maintenance.
There is a large hole at the base of the fixed jaw for access to set the original spring assembly after loading the leadscrew & bearings. This hole can now be completely closed off. Preventing grit from entering the inner thrust bearing, leadscrew & nut while also greatly improving the strength of the casting.
Here is a link to a sketch to demonstrate the overall idea with some fillets added to eliminate several stress risers. fireball2-Model.pdf - Google Drive
We’re getting deep into the weeds here, I’m printing off your drawing so I can read your description and visualize the original and the what you’re talking about without going back and forth on my phone screen. I’ll get back with my thoughts (for whatever they’re worth).
