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13th Dec 2013, 01:57 AM #1Senior Member
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Dialling in long shaft on fixed steady
Dear all
how do I dial in a long shaft on the fixed steady when no room to use tailstock as a reference? I found no rhyme or reason when I twiddled the screws on the steady. The error on the DTI moved all over the place noting that twiddling the screws pushes the shaft both back and forth AND up and down!
Dave
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13th Dec 2013, 02:10 AM #2Most Valued Member
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set the steady up on a shorter piece of stock closer to the chuck
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13th Dec 2013, 02:18 AM #3Senior Member
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Dialing in on fixed steady - clarification
Re my previous post, I have read previous posts on this. I am aware that when three fingers of steady are snugged against shaft, DTI will show no movement when placed right next to steady. But when placed further away from steady, DTI will show up wobble on any shaft that is not coaxial.
So my question restated is, how to get shaft coaxial with lathe bed by adjusting finger screws when steady is at far end of lathe bed?
Best idea in previous posts seemed to be to set the steady fingers on a centred piece of same OD right next to headstock and then slide the steady to the far end. The shaft in question is already machined to 50mm OD. I just need to turn true the last 40mm of it.
Dave
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13th Dec 2013, 02:23 AM #4Senior Member
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Thanks
Thanks Stu. You were too quick for me. I think is probably best I can do. I was hoping to turn a fairly accurate concentric groove in the shaft at its right hand extremity.
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13th Dec 2013, 02:47 AM #5Most Valued Member
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Go gently, the steady is effectively your spindle bearing.
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13th Dec 2013, 03:22 AM #6Senior Member
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Too true
Yes. I think that at the end of the day, cannot turn REALLY accurately at the extreme end of lathe bed on fixed steady alone. I think answer is to transfer to a larger lathe and turn between centres, if accuracy is important.
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13th Dec 2013, 06:46 AM #7Philomath in training
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You should be able to. The thing to remember is that the steady is using the outer surface of the material as a guide. This means that you can adjust a steady up so that it runs smoothly but the centre position can still be out. Within limits this won't matter if you are only trying to do something to the outside surface. As soon as you try using a drill you could be in trouble.
Stuart's suggestion is the standard one, but another would be to make up a centre that you can secure in your tool post, true that up so it is concentric with a centre in the headstock and then wind it down the bed to use to secure the bar stock while adjusting the steady.
A third option is to use the steady on the non working end - true it up as close as but do your machining at the headstock end.
Remember to grease the fingers. I've also been told that running a strip of paper between the fingers and bar stock can reduce marking.
Michael
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13th Dec 2013, 06:53 AM #8Senior Member
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How big a grove and how thick / long a shaft are we talking? I also disagree with the idea that you cant turn such things accurately, it might just take a big of time to get the rest set right.
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13th Dec 2013, 08:45 AM #9Most Valued Member
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13th Dec 2013, 01:11 PM #10Most Valued Member
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Yeah I cant see why you cant turn accurately. You just have to remeber you've gone from a using the headstock casting with its bearings to your steady casting with its two points of contact(I wonder if using your traveling steady as well would inprove things? never tried that one).
If the bar is moving outboard of the steady that would to me its not running true at the chuck end to begin with(or its walking).
One thing to watch for, if you dont get the steady close enough, it may well flex the work piece so it all looks fine but will try and "walk" out of the chuck.*
Being that your workpiece is machined all over by the sound of it. For lining it up in place with DTI's. Get the steady close. put it where you want it. leave the top open. get the work running true in the chuck(but not super tight). On the carraige at the chuck, set one DTI on TDC and another on center height. move carriage to the other end and using the two lower steady fingers 0 your DTI's. repeat until you are happy. tighten chuck. check and you're good to go.(do I need to say close tge steady and adjust the top finger?)
Stuart
p.s. Like so many things it depends on a lot of factors, how big the lathe is, how far the work goes into the chuck, whether or not rollies dad has been twisting the thing to get it to cut parallel at the chuck etc etc
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13th Dec 2013, 02:12 PM #11Most Valued Member
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center hole
use a boring bar to make the center hole. use soft jaws in the 4 jaw or even better a brass ring between the the job and 4 jaws.
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13th Dec 2013, 04:48 PM #12Most Valued Member
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If the job was at the limits of the machines capabilities it would probably be better suited to a more substantial machine.
That said was a 3 or 4 jaw chuck being used for set up.
Your best/safest bet in my opinion would be to use a 4 jaw chuck.
Was a cat head used or were you mounting your stock just in the steady.
Was the stock machined or ground or just bright?
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13th Dec 2013, 11:14 PM #13Senior Member
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Thanks again
Thanks to all for useful ideas/advice. Have done job now by setting up steady next to headstock. The comments about job "walking" out of chuck useful as I had to watch job in chuck closely. Worked out fairly ok in the end.
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