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View Full Version : Centering Tips / Steady Rest



elbryant
02-27-2005, 09:23 PM
I have a project that I need to turn between centers. Using a drill press, I marked, punched, and center-drilled both ends. One end was very close, about .003" of runout when on the tailstock center, while the other end was in my 3-jaw.
I worked on that end, and turned it around to put it between centers, and I find that my center-drill on this end is way off, maybe .08".
There is enough material to face it off and drill again, but I need to find a better way. Usually, I just chuck it up and turn it, but I don't have much material to spare on the diameter, so I have to get the center drill in the center.
What about the steady rest? By definition, there is no runout according to the dial indicator, so long as the work is round (right????). But how do I make sure it is on-axis witht he lathe, so I can center drill it in the middle?
I am guessing that if it isn't on axis, something like the tailstock center would scribe a circle on the end of the newly faced-off work. Do I adjust the steady rest to get the smallest possible circle (point) and then drill?
Thanks for your help.


Ed

toolsrul
02-27-2005, 09:35 PM
Always indicate your part in. Whether it's in a chuck, collet or a steady rest. You'll be safe doing it this way rather then marking & drilling on a drill press. It'll be more reliable.

elbryant
02-27-2005, 09:51 PM
How do I indicate it in to mark/drill the center?

precisionworks
02-27-2005, 09:53 PM
Ed,

Had exactly the same situation on a 4' long implement shaft. Couldn't get the shaft through the chuck (too large OD) so I set the steady as close as possible and touched my tailstock live center lightly, inscribing a circle as you said. Helps if you use Dykem. Readjust the steady until the circle is a dot, then center drill as normal.

------------------
Barry Milton

Yankee1
02-27-2005, 10:26 PM
Hi Ed
What I do is put a piece of round stock in the chuck and slide the steady up to the
chuck and adjust the steady to the round stock, then slide the steady out to where I'm going to use it. Works for me.

Yankee1
02-27-2005, 10:30 PM
Forgot to say that I then drill it with a center drill held in a chuck held in the tail stock.

kap pullen
02-27-2005, 10:57 PM
elbryant,

I would first set the stock in the 3 jaw and indicate the tail end in. A brass hammer will tap the end true.

If the chuck won't support the shaft, you'll have to rest it on the steady, scratch a circle as mentioned re-adjust to center, then centerdrill.

http://img.photobucket.com/albums/v206/kappullen/steady1.gif
Note the rest pads are not touching the shaft.

Than I would move the rest pads to have .001 pressure on the part, grease the pads up and center drill the part.

http://img.photobucket.com/albums/v206/kappullen/steady3.jpg

If you are working a piece of hot rolled, a machined spot for the rest is in order.

http://img.photobucket.com/albums/v206/kappullen/steady4.jpg

Run on the center and cut a good spot.

Finish whatever you have to do with that end.

http://img.photobucket.com/albums/v206/kappullen/steady5.jpg

Reset the center, remove the rest, skim a spot on the other end while running between centers.

http://img.photobucket.com/albums/v206/kappullen/steady9.jpg

The steady can usually be removed and reset
without disturbing the shaft.

http://img.photobucket.com/albums/v206/kappullen/steady6.jpg

Re-set the steady to the new spot. just machined


Turn the shaft around, slide the rest out, and set the new spot on the rest.

http://img.photobucket.com/albums/v206/kappullen/steady7.jpg

Re-center and finish the other end.

Better idea is make the second spot the same diameter as the first and avoid some fooling around with setting the rest again.

The work you actually have to achive may vary this procedure somewhat.

Accurate work requires certain steps, without shortcuts.

http://img.photobucket.com/albums/v206/kappullen/steady10.jpg

When doing shaft work, I will frequently machine a "positive stop" to chuck on.
This prevents the material slipping back into the chuck from cutting pressure.

kap

[This message has been edited by kap pullen (edited 02-27-2005).]

[This message has been edited by kap pullen (edited 02-28-2005).]

J Tiers
02-28-2005, 01:33 AM
I was told that if the stock is round enough to run OK in the steady, the best way was to cut a center with a tool, and then run on that. Wouldn't matter if the original setting of the steady was any closer than "about right".

Tried it with the arbor project, and it appeared to work well. I had basiclly no runout

Can you comment on the method?

kap pullen
02-28-2005, 07:15 AM
J tiers,

You're right about skimming the center with a tool.

The best way is to set the compound on 30 degrees and bore the center with a weany boring bar.

It is hard to convince even experienced machine operators to take that extra step.

Making long heavy precision shafting, that is a requirement, but most get by on small parts with the center drill.

A heavy shaft running on center will transfer any inaccuracies in the center hole to the machined surface.

A small job will transfer as well but that can be un-maesurable with the micrometer.

Many toolrooms have center hole grinders
to prepare precision work for the cylindrical grinder.

The center hole is a mirror of the condition of the shaft od.

On heavy shafting, spots are best machined at the headstock end where they will come out closer to round because of the proximity to the headstock bearings.

The shafts may have to be re-set,and re-skimmed several times to minimise the errors produced from the origional condition of the material.

Machine operators will frequently omit this extra step, and end up with out of round, out of tolerance surfaces, transfered from the out of round center hole, or steady rest spot, back and forth from spot to hole etc.

Resetting a large shaft with a crane is a pita, but required at times. The operators are, like the rest of us, basically lazy.

Cold rolled steel, the favorite of many here, has roundness and straightness tolerances that allow the steel mill to send you any junk they have.

It is best to develop the skills to make a rough as a corn cob piece of material into a precision work of art.

I used to work in a shop that made spindle drive shafting for atomic submarines.

They had many problems with out of round work before I dictated the shafts be spotted at the headstock.

These shafts were in fact made fron cylndrically cast steel tube and rough as a corn cob.

This extra spotting operation saved days of production per shaft and improved quality.

In the perfect world, this is what you do;
set the ground material in the collet,

http://img.photobucket.com/albums/v206/kappullen/steady1a.jpg

Set the steady up near the chuck.
Than slide the steady out to the working point and do what you have to do;

If you loosen the steady rest clamp bolt, oil the ways and shaft, the steady will slide out with the part revolving slowly.

http://img.photobucket.com/albums/v206/kappullen/steady2a.jpg

That's not where I live.

The steady has to be set RIGHT ON CENTER or the shaft will work out of the chuck.

Each time the shaft revolves, it will work (slip) in the chuck and soon get you in the head.

That is where those steadies on ebay come from with the top, or bottom brazed back togather.

kap

ps;
I try not to feed any more information than people are willing, or able to grasp at a time.

[This message has been edited by kap pullen (edited 02-28-2005).]

[This message has been edited by kap pullen (edited 02-28-2005).]

elbryant
02-28-2005, 09:30 AM
Kap,

I am in your debt. I am printing out this whole thread with your careful instruction. Wish I had a book as good.

Ed

DennisB
02-28-2005, 12:40 PM
Ed,
An old trick I read somewhere goes as follows.
Machine a "cap" that is a light press fit on the stock you want to center drill. Without removing this from your chuck, drill thru the rest of the piece with a drill just a thou or two under the size of your combined drill/countersink major diameter. This hole must be long enough to capture the major diameter of the drill/countersink before the drill tip starts to drill. Use this "cap" pressed on the end of your stock to guide the drill/countersink. Should get you within 3 or 4 thou if you do it carefully.

The other replies you've received are far more accurate than this one.

Dennis

ricksplace
02-28-2005, 02:49 PM
Thanks Kap.

I echo the comment. I wish I had a book this good.

Rick.

burnlast
02-28-2005, 05:06 PM
When I started out in machining,one of the first jobs I had to run was a lathe job that required the use of a steady rest.After I got it set up(or so I thought),one of the old lathe hands come by and told me where I was about to mess up.He showed me 2 different ways to set up a steady rest so that the work will not pull out and will be running true to the axis of the spindle.On shorter,smaller work,take a magnetic indicator base and put it on the OD of shaft.Set your indicator tip on something 90 deg. from the spindle axis(ex. the face of the chuck).Rotate chuck 180 from were you set your indicator.Adjust steady rest until you achieve zero readings top and bottom and side to side.Usually you can get away with .002 to.003 runout.Just remember when using this method the further you are away from the chuck when indicating it in the more accurate the alignment will be.
The other way is to bring your tail stock up to your chuck and indicate the spindle of your tail stock.Either mark down the run out or adjust the tail stock to run true.Position steady rest where you want it.Once your shaft is in, clamp your indicator on the shaft and adjust steady until it is trued up with the tail stock spindle.I have used both of these methods more times than I care to count and can't recall of ever having problems with pulling or having a part out of line with the spindle axis.
It's been a long day and I hope this makes sense and helps you out.


BURNLAST!!!!!