# Logan 820 Lathe With Potential Runout



## Whizbang (Apr 3, 2016)

Hey all,

So I have a 820 series Logan Lathe. I believe I am only the second owner and it looks nearly brand new (got lucky and bought it from an older gentleman who worshiped his machinery). Its always ran great for me and I can honestly say that I have never really crashed anything hard enough to fear having done damage, however just recently when I was using a center in the tailstock I noticed I might have some runout. After taking apart my 3 jaw chuck and cleaning it I tried again and saw the same thing. I finally got dial indicators out and started to measure it. I used ground drill rod in the chuck to measure along with a few other tools to make sure it wasn’t the part that was the issue. When about 2 inches away from the chuck I see about .010” radial runout. Both before and after cleaning the 3 jaw was measuring .002” radial runout right at the jaw and about .010” 2in away from chuck. I removed the chuck and measured the nose of the spindle for runout and see virtually nothing. I have the version with collet draw system, I put that on and checked the same part and saw the same runout. This in my mind says I have an issue with my spindle or bearing but when I try to actually take a reading directly at the nose of the spindle I don't see anything. Below is a link to some videos/photos to show what I did and what I see. I checked the spindle axially as well and it looks good but at soon as I get a part in the machine the runout is very apparent. I put my old Buck Tool 4 jaw chuck on and tried to dial the part in. In the attached photo you will see a ruler next to a part. Where the ruler starts I dialed the 4 jaw chuck in to see .000” runout, but when I moved to check the runout at the 1” mark I was still seeing .010” runout. I double checked myself with another dial indicator. I have made sure in all cases my dial indicator was in contact and not maxed out.


Any  ideas?


Thanks,

Whizbang


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## Whizbang (Apr 3, 2016)

Sorry, site won't let me post link until there are 3 posts due to spam I guess


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## Steve Shannon (Apr 4, 2016)

Three jaw chucks usually have some runout. An independent 4 jaw chuck can be adjusted to eliminate runout.  If it shows no runout at one place along the bar, but runout elsewhere on the bar then the bar is not straight, or isn't held straight by the jaws.
That your spindle nose showed no runout detectable by your dial indicator makes me think it's just your chuck. If you chuck some metal and then turn it, how much runout does it have?


 Steve Shannon, P.E.


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## atlas ten (Apr 4, 2016)

I recommend check lathe for level and turning a test bar using 2 collar method. Likely the chucks or just the jaws need trued up. I had a very badly bell mouthed 3 jaw. Dremel tool as grining post did wonders to hold material.  I will not check it beyond that knowing it will runout forever. 
Jack

Sent from my SGH-I337M using Tapatalk


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## wa5cab (Apr 4, 2016)

One possibility is that the left spindle bearing has radial runout.  I'm not familiar with the 820 but is there a surface on the spindle near or to the left of the left bearing on which you can put the indicator?


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## MBfrontier (Apr 4, 2016)

It would seem to me if your test bar is true that having the same runout with your collet setup would rule out an issue with your chucks.

I agree with Robert D. on checking the runout at the rear of the spindle. You can search for posts on how to check for spindle bearing wear with dial indicators and putting side pressure on the spindle to measure runout.

I have a Logan 200 made in 1943 and a Logan 1957 made in 1953. I ended up replacing the spindle bearings in both machines. The Logan 200 bearings were questionable from a smoothness standpoint and the Logan 1957 had a grinding sound with the spindle belts removed and spinning the spindle by hand. I did not have the same issue you are describing. In both cases the old bearings were manufactured by New Departure and were probably original. I've read other Logan owners have had good luck with the original spindle bearings in their machines but that has not been the case for me. I'm not saying that spindle bearings are your issue. The bearings are expensive but eliminate any concern of bad bearings going forward.

Good luck on resolving your issue.


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## Chipper5783 (Apr 5, 2016)

It maybe that what you are observing is pretty normal.  No chuck is going to be perfect.  If you pay a lot it is going to be pretty good.  The two common issues with any chuck (there are probably other issues as well -but let's keep it simple): radial run out and angular alignment.  It is pretty well a given that a 3jaw will have a little run out.  If your 3jaw is at 0.002", I'd say that is pretty good.  Of course with a 4jaw you can get the run out down pretty good in a single plane.  However, neither chuck is likely to have the axis of the jaws perfectly in line with the axis of the lathe bed.

You can, and should tune the mounting of your chucks (to start with ensure everything is clean).  There have been numerous posts on this.  It starts with making sure the back plate is properly mounted to the spindle, then skim the chuck mounting surface of the mounting plate.  You'll need to decide if you want the chuck register to be snug, or loose.  I prefer to make it a snug fit, but I know others like to leave it loose, then dial it in and rely on the bolting (sort of a poor man's set true).  Then you grip a good piece of bar in another chuck, take a skim cut on the bar (do not remove the bar - you have just made it nice and true) and mount up the chuck you are tuning - skim the mounting face of the chuck.

If you think the above through carefully, and take your time to tune up your equipment, you can even cheap'o chucks to perform quite well.  If you are after a more precise method, then a chuck is not you best bet.  Hold your work between centers.  If the job is such that you must use a chuck, then grip near the end of the jaws on top of a piece of wire - with the outboard end held by a center or a steady.  Go easy and be aware that the work may try to walk out of the chuck!

Let us know how you make out.  David


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## wa5cab (Apr 7, 2016)

David,

All that you say is true.  But Whizbang does appear to have an issue where the measured runout is essentially zero on the spindle, very near (or set to) zero right at the chuck, and gets worse as he moves towards the tail stock.  Re-read his initial post.


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