Attempting to make an L-00 mount spider chuck, trouble boring the proper taper

M

mofugly13

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I am attemting to make a spider chuck to attach to the L-00 spindle on my Sheldon lathe. When I began planning this project, I assumed that boring the taper just right would be the most difficult part. It turns out I was right. I began with a 4" round chunk of steel, 3 1/2" long. I faced both ends of it in the three-jaw, driled a 5/8" hole all the way through, and then bored a 2.25" hole, 2.10" deep. At this point, I removed the chuck with the workpiece still chucked, and mounted a .0001 indicator on my toolpost. I was able to adjust the compund slide while indicating off the far side of the spindle nose taper to less than a tenth. With the compound properly adjusted, I re-mouunted the three-jaw with the workpiece in it and bored the taper by hand cranking the compound (with the cairrage locked) until there was about 1" of tapered surface. I have a spare L-00 spindle that I picked up on ebay, and I put that into my tapered bore. With the taper seated, I was able to rock it a bit, telling me that my compound was not quite right. So, I removed the chuck again, and re-indicated off he taper nose, and I was still at less than a tenth. I put the chuck back on and made a few more passes with the boring tool. After every pass, I am putting my spare spindle nose into the bore, checking for it to seat without any rocking. I have not been able to get it perfect. I make 4 pases of the tool at the same setting each time, to make sure tool flex is not an issue. I can not get the angle perfect, the spare spindle 'guage' still rocks.

How do I determine if I have my indicator tip set perfectly on the spindle centerline when I indicate the taper?

How would you go about setting up to bore the taper perfectly?

I have a lot more passes until I am at my full depth, so I have a lot more tries to get it right, but so far no luck. My adjustment method now has been determining whether my 'guage' is pivoting on the inboard (spindle side) of the bored taper, or the outboard end, loosening the compound nuts very slightly and tapping the compound in the apprpriate direction with light taps from a dead blow hammer. I have gotten the fit extremely close, but not perfect. At this point I am dancing on either side of 'perfect', but not quite there. I notice that all of my L00 chucks have the middle part of the taper relieved so that the spindle nose seats on the front and back of the taper. Could the fact that my bored hole does not have this relief yet be an issue?

I am making my own tooling to rebarrel a Model 7 to 7mm-08. Once I get this chuck finished, I will only need to make a loating reamer holder (I am going to copy Butch Lambert's design) and I will be able to get started with that. But, this tapered hole is proving a whole lot more difficult to get just right than I originally thought.

I appreciate any advice you guys can give.
 
It's likely your compound swings in an arc. Just cause it doesn't do it with an indicator in it doesn't mean it won't when there's tool pressure. Try with it's gibs locked up more, at least decent locking pressure. Somehow you need to get that compound moving in a straight line.

Could the fact that my bored hole does not have this relief yet be an issue?
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Certainly could be a part of it. They relieve them in order to cheat a bit on getting the taper perfect. Ideally, you should be grinding that taper on. I'm gonna assume you don't have a grinder capable of that so in lieu of that, I suggest a sharper tool, (smaller tool radius), more pressure on those gibs... If your compound has travel more than you need, use a different spot in that travel. More centered if possible. Try anywhere else.

Bottom line is, after you've indicated, the angle you set isn't what you get. I think yer lookin in the wrong places to fix it.
 
NOt only does your boring tool have to be on center, when you indicated in the taper was it on the same center? Both tool and idicator need to be in the same plane. And yes, it should be ground,

You might want to try some prussina blue to see where your error is.
 
Mo,
What you have to do is get your bore within a few thou of size. Aquire some hi-spot blue and a soft bristled brush. Apply the blue to the male gauge. A thin coat....not globbed on. Carefully put the gauge in the tapered bore, seated with light to medium pressure & turn the gauge fore & aft by hand. Remove the gauge carefully & then polish the bore with emery where the blue is. Repeat this process, cleaning the bore after each polish using alcohol, until you have 85-90% contact.
The other thing you can do once your compound is close, is to put your indicator on the compound when you tap it around to see exactly how much you are moving it.
 
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Why make it so complicated? I have a L00 set up on my Clausing lathe. I bought a L00 backplate and machined it to 5" OD and machined the face plate with a .250 hub about 3" in diameter. I took a piece of .750 aluminum and bored the center hole to about 2 1/8" to match the ID of the through hole of my backing plate. I machined a counter bore 3" in diameter .250 deep. I drilled 4 holes in it at 4" hole centers to bolt the new hub to the backplate. I did a cleanup bore on the ID and the OD. I put it in an indexing head and drill and tap 4-7/16 fine thread holes. The centerline of my 4 cat head screws are 2.750 from the very back of my L00 adapter. That is approx 1.375 from the end of the nose of the spindle of my headstock.
I don't see how you could do much better making it from scratch.
 
I've looked at my L00 spindle nose many times and given up the idea of making one. You may be able to spot yours in but how are you going to cut the key way in a blind tapered hole? Butch's method of building one up by adding onto a store bought back plate is the way to go IMO.
 
You should be able to dial the compound in on the taper. If the indicator is not showing much variation then the compound should be at least tracking straight . I am not sure dialing in on one taper and then checking with another spindle is a good idea . You need to make sure both tapers are the same.
However how I do all my short tapers now is by using a sine bar setting gauge on the compound .
I first get the taper specs . LOO 2.75 large end . Length 2 .00 . Taper half angle 8.2972 ( 3.5" per foot) . This calculates to a small end diameter of 2.1667 .
Entering this in the sine bar program with a roll distance of 3.4845 gives me a stack height of .502841 (.503) .
Then I attach my gauge to the compound unlock the compound then apply the .503 block between one roll diameter and the tailstock shaft surface and push the other roll diameter hard up against the tailstock shaft at the same time then lock the compound in place . That way the compound is set very precisely at the correct taper angle and can be reset quickly anytime you want.
http://benchrest.com/showthread.php?81335-setting-up-to-taper-bore&p=663966&highlight=#post663966
Don't run back and forth with no cut pressure as backlash may be getting you. Don't turn the compound in a jerky motion use both hands on the compound wheel in a double turning motion that keeps it turning slowly without stopping .
Make a final cut with a few thou cut and smooth turning and test that. Don't turn with the compound overhanging too much , try and stay in the center part of it's travel. Test the compound for sideways slop in the gib.
Dial in on the taper after you lock the carriage . Try a higher spindle speed and slower feed for a light test cut as you may just be getting rough finnish upsetting the fit.
 
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