Investigating spindle runout on my Seneca Falls Star 30 Lathe.

PHPaul

PHPaul

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I've got about 3.5 to 4 thousandths runout at the spindle, measured as close to the bearing as I can get.

I realize that's not horrible for a 100+ year old lathe, but it's a rainy day and I felt like puttering, so I decided to have a look at it.

Popped the bearing cap off and see this:

spindle.jpg

Question 1: Is the ring next to the red arrow supposed to be in the groove on the spindle next to the green arrow? At the moment, it's just flopping around on the shaft. Pretty sure that isn't right.

Question 2: How should I check for play in the shaft? Just grabbing the chuck and trying to move it vertically or laterally doesn't indicate any perceptible play. There are shims under the cap that may well have been there since the lathe was built.

Question 3: What should I lube the spindle with when reassembling?
 
The ring next to the red arrow is exactly where it should be.....it's an oil slinger. It picks up oil from the reservoir and carries it up to the top of the spindle and it dissapates down to both ends and drains back into the reservoir.
The shims will control how much clearance the bearing has. As it wears, the shims need to be replaced with thinner versions to make up for wear. Torque on the bearing caps will also play a part. Knowing how tight they need to be for proper clearance is a function of friction, so the key is keeping the bearings and spindle from getting too hot. The basic rule of thumb is, run the spindle at top speed, and it should not get any hotter than what you could stand to touch (somewhere around 120 degrees). If it runs hotter, you need more clearance. You could either add a shim, or back off the torque, or a combination of both. It's kind of a trial and error operation. As far as oil, because this machine has no real bearings, it's just cast iron against cast iron, so I used a moly based chain oil in the reservoir. It's thin enough to flow good and it has the moly to protect it from galling.
 
Ah. I had considered the oil slinger thing, which is why I asked rather than assuming. Thank you.
 
Okay, so I've determined that the spindle bearings are in reasonable shape for their age.

Runout at the jaws of the chuck approaches 30 thousandths. Ungood. Also, I noticed when looking over the chuck that the internal threads on the chuck are seriously boogered up, chunks missing out of the first 2 or 3, and generally worn and tired. The spindle threads look good and are 1-7/16 by 12.

I'm seeing prices on new chucks range from a couple of hundred to a couple of thousand dollars. For a home machinist that would be ecstatic to do work within a couple of thousandths accuracy (and often considerably less than that) I don't see a high-end chuck, especially on an antique machine, being the answer.

I'm more than a bit bewildered by the various types, styles and prices of 3 jaw chucks. I'd greatly appreciate a little education on the topic or a pointer to a good tutorial or reference book.

One big question revolves around the mounting method. Does one buy a chuck that is designed to mount directly to the spindle, or must one purchase or machine an adapter to mount a new chuck on an old machine?
 
PHPaul said:
One big question revolves around the mounting method. Does one buy a chuck that is designed to mount directly to the spindle, or must one purchase or machine an adapter to mount a new chuck on an old machine?
Click to expand...

Usually you get a new chuck and machine an adapter to suit your lathe, but that depends. It is possible to find used chucks ready to go with the right thread or taper, and this saves effort if it's done right. I'd put a premium effort on finding a set-tru or adjust-tru type of scroll chuck that allows the runout to be dialed out of the picture. Typically this doubles the sale price of a used chuck. Reversible jaws are nice to have, usually configured as a top jaw on a scroll chuck. Other than going into a big conversation about wear, that's what I'd be looking for up front in a chuck.
 
If you have a useable 4 jaw chuck you can remove the backplate from your 3 jaw, bore it out and press in a bushing. Then thread the bushing. I have done this on my Seneca Falls #20 several times. In addition I have also made a few backplates from scratch. Given that the spindle thread is a 1 7/16-12 it's highly unlikely you'll find a premade backplate.

If you want to go the new backplate route you can buy an unthreaded blank from a number of machine tool suppliers like Zoro, Penn Tool, wholesale Tools, and others.

As for measuring the clearance on your headstock bearings I would go to an auto supply store and get some Plastigauge:

Plastigauge, Plastic Precision Clearance Gauges

Plastigauge is extremely effective for measuring the clearance of a wide variety of bearings which include automotive/machine bearings, marine drive shaft bearings, turbine housing bearings, pump and pressure system bearings, as well as shaft end-float dimensions, flatness and clearance in...
www.plastigaugeusa.com

It's used to measure the clearance between bearing clearances. It's available at almost any auto parts store, and comes in several different sizes. You cut a piece from the strip, place it on the spindle, & reinstall the cap. The cap will flatten the Plastigauge. Then use the paper sleeve to determine the clearance. I would get some from an auto store or the manufacturer, in that it becomes brittle with age. Someone selling it on eBay may be selling NOS that has crumbled in the sleeve

Once you determine the current clearance you can purchase rod bearing shims from either an auto parts store or engine restoration house. Older GM engines (pre 1950's) used babbited connecting rods and main bearings with a stack of shims between the rod or block and the bearing cap. As the babbiting wore the shims were removed to keep the proper clearance. Each standard shim is .002". They are usually available in sizes ranging from .0005" to .010", and are sold in packs of 10.

Here's what the shims look like:
www.ebay.com

Engine Crankshaft Main Bearing Shim Set Sealed Power FSM-104S for sale online | eBay

Find many great new & used options and get the best deals for Engine Crankshaft Main Bearing Shim Set Sealed Power FSM-104S at the best online prices at eBay! Free shipping for many products!
www.ebay.com

This vendor has both rod and crankshaft shims available
 
Is your current chuck mounted on a backing plate? You may be able to use it, or resize it to work.
 
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