Any machinist out there?

[sasjzl]

Hi all,

I have an elderly Vega 24 bowl lathe that I am trying to revive and I have a question about how I can change the spindle size from it's current oddball keyed size of 3/4" to what my faceplate and chuck uses with is 1" x 8 tpi. I could not find a 3/4" adapter but already had a Shopsmith style 5/8" to 1" x8tpi. I thought I'd be clever and drill the 5/8" out to fity the 3/4" spindle that you see in the photo below. I don't think it worked out that well because I definitely have 'runout' when I use that adapter. I think it is called 'runout'. I am afraid that I did not drill the hole absolutely centered because I get alot of chatter and if I lay a straight edge on top of the spindle adapter I can hear and see a very small, but obvious bounce. If I could find a 3/4" to 1" adapter I could probably use that but my ideal situation would be to either get a new bearing and spindle that would be the correct 1" size so that I do not have to hang an adapter out there. I would be more than willing to replace the entire assembly from the pulley on down to the threads. Would it be possible to having a threaded piece of metal permanently welded on my current assembly?

Thanks very much,
Jim Lee

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[Gotcha6]

First of all, I am not a machinist, but I have done things like this. It would be difficult to weld an adapter to your current shaft that would end up true enough. The heat from welding will distort the metal and it would end up off center. You'd be better off making an adapter as you've tried but getting the hole bored perfectly true. You may even be able to salvage the one you have if it could be bored oversize and a bushing pressed in & then re-bored. Either way, it'll be about 1-2 hours' work for a machinist.

 

[striker]

Jim,

I think your problem started with drilling the adapter out. You can expect runout if the fit between adapter and shaft is not on the money. A drilled hole typically runs oversize. If you want a hole to be on size, generally you drill undersize then ream to size. In this case, the adapter would have faired better if it was carefully bored out on a lathe. Boring keeps the ID & OD concentric while allowing for better control of the bore diameter.

That being said, I think your options are to have a new, one piece shaft made or boring your adapter oversize, installing a bushing then boring the bushing back to size (lite press fit on shaft). Once the adapter is put in place, you can add a crosspin to the assembly to avoid any welding being necessary.

Thanks for the opportunity to run my mouth. Good luck with it.

 

[bob vaughan]

Looks like you've got a mess to deal with.

The bearing is an integral shaft bearing, commonly known as a water pump bearing. Examples below.

Whatever the solution, it'll have to be executed on a metal lathe for satisfactory results. A new water pump bearing looks needed. A keyway will have to be cut into it. Most of those bearings have a 5/8" shaft (as pictured), but they can be had in 3/4 size (.7465). Likely a new adapter will have to be made. That should take a couple hours of lathe time once the geometry has been put down on paper.

Welding will ruin the bearing. Heat from gas welding will ruin the lubricant and electric welding will arc pit the balls.

Not good news, I know, but I'm afraid that's the way its going to have to be. Maybe Vega will be able to help, but that's not been my experience with older products made by that company.

 

[Glennbear]

Have you checked Grizzly ? I was able to find an adaptor in their catalog for an ancient Sears lathe so that I could use more contemporary attachments on the headstock. :wsmile:

 

[sasjzl]

Thread a straight shaft?

That was exactly my experience with Vega. Disappointing. I called them and they acted like it was made before the internal combustion engine and more of the dead sea scrolls would have to be found to even get a parts list. No owners manual was ever produced as this was made way back in the early 90's of the last century. Which is fine. I take full responsibility for buying a used piece of machinery but was kind of surprised they were not more interested, at least in selling me something in the future. Not a very large user base as far as I can tell either. After posting on three woodturning user groups I have only found one person with the same style/vintage lathe and he is dealing with the same issue. Not many lathes with a 3/4" non threaded spindle out there.

Sounds like it might not be too difficult to get a replacement water pump bearing for what I have. My latest possibly hare(sp?) brained idea is to bring what I have to a machine shop and see if they can turn a typical 10tpi external thread on my spindle and then I can use the widely available 3/4" x 10tpi to 1" x 8tpi adapter. Is it possible to turn the thread with the key way slot? The other possibility is to get another 5/8" adapter and bring it straight to a machine shop and have them drill a true hole instead of messing it up myself. The adapters are reasonably priced (~$16) so I don't mind buying a new one. I was pretty well aware that I might be ruining the one that I drilled. I know that I have seen spindle adapters at Grizzly but for the life of me I could not find any just now. I think that I have checked them before though and the only 3/4" adapters they have are for threaded spindles. Now that I think of it I am not aware of any other wood lathes with a non threaded spindle. That must have been a passing fad of the last century.

Thanks for the info on the hazards of welding. Fortunately I am not yet that dangerous with a welder as I do not have one....yet.

Thanks all,

Jim Lee

 

[bob vaughan]

The problem with water pump bearings is that the indexing surface for adapters is the nose of the center shaft. There's no precision ground bearing inner race to bump against, and its the axial compression load that makes the difference. Making a new nose piece will require the bottom of the hole be precision flattened, not just drilled, and the end of the bearing's shaft will also have be squared off nicely.

Doing things sloppily will give results that may work to a certain level of make-do satisfaction. As long as things don't move on the shaft, once a piece is started, its trued to the lathe anyway regardless of how floppy the chuck is orbiting around the center line.

 

[Mike Davis]

If it was my lathe...

I would take the whole head to my machine shop and ask them to make a new spindle with tapered roller bearings to fit in the head. They would bore the casting and use standard easily replaceable tapered roller bearings and make the shaft to fit with what ever screw end I want on it.

I would expect to pay around $300 to $500 for this work. But, it would be dead right and probably never have to touch it again.

 

[bob vaughan]

Boring the casting is good if there is a casting. Some I've seen were sheet metal weldments. As for tapered roller bearings, most commonly used wood lathes today use Conrad or standard bearings. Commonly available tapered roller bearings usually require oil or grease fittings.

One thing's for sure, that tapered roller bearings will hold a much greater load at lower speeds as long as there's a lot of cast iron there to sustain such a potential load. Lighter weight modern lathes from the Powermatic 3420 on down usually use the lighter sealed bearings. I think the big Oneways also use standard bearings.