Newbie questions on 10k spindle alignment

[Larry$]

Always use the same reference point when measuring end play, I.E. Don't rotate the shaft. Snug the nut on the thrust bearing (end of shaft) until you get no movement in the axial direction when pushing/pulling on shaft. A wee more tightness on the nut won't hurt and will provide some preload. I don't think those machines were built with tapered roller bearings on the chuck end. So, your only option there is how good the existing bearing is. Put a bar in the chuck, big enough not to have any bar flex when you pull up & down or side to side. W/O rotating the shaft put your test indicator on the side of the shaft and push on the shaft. The further away from the bearing the more movement you will see. Where that play is coming from depends. Is the fit of the shaft in the bearing snug, slight press fit? Ideally no movement. Is the fit of the bearing in the housing snug? Ideally no clearance but not a press fit. Is the chuck fully seated? Is the chuck so bell mouthed that the bar in it can be pushed side to side in it?

About ball bearings: As they run @ design speed they will reach design operating temperature and expand slightly taking up design clearances. Those aren't much and for your purpose on a slow rotating machine like a manual lathe the class of bearing fit should be fairly tight to start with. Bearings that are grease lubed should not be fully packed with grease as that will make them run hotter. High speed, heavily loaded bearings will have a looser initial fit until they reach design temperature. Tapered roller bearings eliminate most of these issues by using a set of two matched bearings arranged so they push against each other's cup sides by squeezing with some means of applying flexible loading. Commonly cupped fingered spring washers. Bearings used this way should always be kept as the matched sets, as sold by the factory. The design engineers of the machine will have determined the correct preload required and used the correct method of loading. Virtually no play will exist. Everything has some flex!

 

[palada]

Thanks to everyone for responses.

I did the lift test for clearance and it was in spec (I did this before too). I re-tightened the collet on the left, beyond what the manual said, but still allowing the spindle to turn relatively freely. I re-measured not using the flange and also using a spot inside the spindle and I'm at .0015, which I suspect is fine.

I chucked a small piece that I know to be round and it's off .004 now, so it's better. It's a 3-jaw chuck and I believe it's an import because there are no markings on it. Maybe that's a good number. I'll browse pages about truing chucks and see if I can make it better.

Obviously I'm not trying to make medical devices or aircraft parts, so precision isn't *actually* important. I'd just like to minimize variance so it doesn't end up frustrating me later when I'm turning something.

Thanks again.

 

[stupoty]

There’s still .0055 on a bar in the chuck. isn’t that still a lot?

Thats not tooo bad , not amazing but for a 3 jaw chuck not awful.

Have you had a good clean of chips / dirt from the chuck maybe cleaning the scroll on it if it feels gritty when opening and closing.

I get 0.003 quite repeatably with an older 3 jaw bison chuck.

Stu

 

[Larry$]

off .004 now, so it's better. It's a 3-jaw chuck

I think that's as good as you can expect from your 3 jaw. It may be different at different diameters of work. It won't matter when you turn something because it will turn round. You just won't be able to reverse the work in the chuck and get back to the same center. Almost never can with a 3 jaw. You have to put the 4 jaw on at that point and center the work. Use the tailstock when work has over a 4 times length to diameter.

Always try to do all the turning from one setup. After you part the work off it should be done. If there is a little nub left, clean that up by hand or put it back in the chuck and face it off W/O doing anything to the diameter, just the end. If the part is too big in diameter to part go far enough to make a good reference and then band saw or hack saw it off. Then put it back in the chuck and do the final facing to length using the parting line as your reference.

Working close to the chuck, on small work can get feeling risky if you want to do any hand polishing or the like. Never reach over top of the chuck! I've got a 5C collet chuck that I feel much more comfortable using on small diameter work. The smooth nose won't beat your hands up if you happen to make contact. ER chucks are almost as safe feeling and require fewer collets. A collet chuck with a run true back plate and high quality collets will allow you to revers work accurately. Also great for gripping threads w/o damaging them. Sorry, I'm taking you down the rabbit hole. Only buy stuff as you need it.

Best bet is to watch videos by Joe Pie or the That Lazy Machinist site has a great series to learn from. Be safe! Plan ahead.

 

[rwdenney]

Hi all,

I'm completely new to machining, so keep that in mind when I ask silly questions or make false assumptions please.

I bought a 1950s SB 10k at an estate sale this year. Because the previous owner was deceased and I couldn't get history on it, I picked up a guide to renovation on eBay and disassembled it to clean it and replace felts. I followed the manual closely for disassembly and reassembly. It's back together now and everything works.

The problem is that I think the spindle is too far out of true. With a dial test indicator on the flange, I get a variance of .0085 when I turn the spindle. When I put a piece of small round stock in the chuck, I get .0055. As mentioned, I'm no expert, but this seems like a lot to me, even for hobby stuff.

Some questions: this is too much variance, right? Anyone know the cause/solution? Seems like the spindle would have to be egg shaped to measure that way. If it is egg shaped, can it be remediated? Thanks in advance for educating me.

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You were measuring on a press-on dirt control ring, which is just pressed on and not intended to be true, as you found out.

Your dial test indicator can track the inside surface of the taper, and that track should be round if the DTI is rigidly mounted in a good holder. I get a couple of tenths at most on mine measured that way.

Once I put in a 4C collet holder and chuck up a bore gauge, I get more like a thou and a half. That could be any dirt or any imperfection at all in the taper of the collet adapter—I haven’t seriously cleaned the inside of the spindle yet on my lathe or clues up that adapter to check it. And even though the collet I used is a good Hardinge, it could be off a bit, too. All this stuff is ancient and subject to who knows what abuse in the past.

4 thou for a scroll chuck isn’t abnormal, especially for a screw-on chuck. Have you stoned the seating surface of the Chuck threaded mount? Mine was all nicked up. My scroll chuck is a first-quality Rohm and measures about there, even after I addressed the nicks and marks on the seating surface. The threads are never tight enough to ensure complete concentricity.

That’s why people also have four-jaw chucks that can be indicated in.

Measuring is hard

Rick “study a Monarch 10EE’s construction to see what it takes to get trueness in the sub-tenth range” Denney