Indicating Rough Cast Iron

[SteveHGraham]

Congratulations, Harold. I took them out of the package.

I have never used soft jaws before (obviously), so I am winging it. I figured I needed something to hold them in place while I bored out steps for the cast iron wheel. I cut a shoulder in a 2.5" piece of aluminum so it would fit in my chuck's hole and stay there, and I have tightened the jaws on it. Look more or less right? I would have preferred something a little bigger, so I wouldn't have to cut quite as much out of the jaws, but I think this will work.

[Glenn Brooks]

Steve, I went through a similar experience last winter, trying to find the center of a set of old - ancient really - 6" ore cart wheels. The axle and bearing surface ID was eccentric on each wheel, due to decades of corrosion, wear, lack of grease, etc. As a result, the outer diameter of the wheels were also rough and irregularly worn. Basically, They 'clunked' when they turned, rather than rolling.

I wanted them to turn concentric on new axles (for use on a miniature railroad turntable 12' long, 12" gauge).

Short answer, I finally decided to turn a reference surface on the OD. I just used a skin cut to establish a consistent measurement with my Dial indicator. (See the shinny surfaces on the wheel OD) Then when the wheel itself was reasonably proportioned and balanced in the lathe, I bored out the ID to be concentric with the OD reference surface. Then turned and pressed in new 2 5/8" shaft in each wheel, and turned that down to appropriate dimensions for the new axles/bearings.

And the finished wheel housing...

Now these wheels are larger than your handwheels and desired 3/4" ID shafting. However, same principle I think. Find or turn a reference surface- maybe the ID of the knob in your photo. Then move into center and drill/bore/ream your desired ID. This way, your working surfaces will be reasonally concentric to the shaft.

Good luck. These things are always fun to figure out!

Glenn

[Richard_W]

Lathe
Three jaw chuck
Spokes aligned with the chuck jaws
Face
Turn OD of hub if desired
Drill
Bore
Tap
Done

Do it this way.

[SteveHGraham]

I would do it that way, but these wheels are very hard and slippery, and they don't like staying put in the 3-jaw. They also like to find funny ways to arrange themselves in the notches in the jaws, so getting a wheel to run parallel to the plane of the chuck face is perilous.

I think Harold is finally going to get his way.

[Richard_W]

I would do it that way, but these wheels are very hard and slippery, and they don't like staying put in the 3-jaw. They also like to find funny ways to arrange themselves in the notches in the jaws, so getting a wheel to run parallel to the plane of the chuck face is perilous.

I think Harold is finally going to get his way.

If that is what it takes, go for it.

[Harold_V]

The nice part is that the wheels will relocate reliably, assuming you mark them so they go in the same position each time you mount them. If the OD is round and they are identical in diameter, you shouldn't have to mark them, however. That's the beauty of soft jaws. They'll locate and hold parts without effort, although one must make a good and proper setup first.

A spider used for setting jaws will permit a minimal removal of material when they are machined, so they will live a long and useful life. Drill and tap a large nut @ 120° intervals so you can use some 5/16" socket head cap screws. By choosing various lengths of screws, the spider will offer a huge range of sizes. Read my comments on soft jaws in The Resource Library.

H

[GlennW]

I would do it that way, but these wheels are very hard and slippery, and they don't like staying put in the 3-jaw. They also like to find funny ways to arrange themselves in the notches in the jaws, so getting a wheel to run parallel to the plane of the chuck face is perilous.

Aluminum or copper jaw pads.

[Atkinson_Railroad]

This thread is particularly interesting to me because a relatively simple job was made overly
complicated by choosing a method or approach that made it difficult right from its beginning.

Recalling the wisdom of, “… a job started ‘right’ is half finished” comes to mind.

But what’s the right way to begin this job?

In studying the initial photograph of the part rigidly clamped in a 4 jaw chuck on a milling table,there is nothing visibly noticeable
about the item that the part could not have been chucked in a lathe using a 4-jaw chuck.
The lathe would have been the first choice in handling this job. Not the mill.

And for sake of clarifying again… a 4-jaw chuck would best suit the job.

One of the first replies to the problem suggested indicating off the perimeter of the part.
This is sound advice number 1. The largest “machined surface” diameter of a part that can be indicated on… should always be used.
It provides the best “sampling rate” for lack of a better term.

The next suggestion was to flip the part over and grab it by the boss, or “hub”.
Another very good, (actually crucial) suggestion… number 2.

Gripping it by the boss to use the larger diameter to indicate on was suggested again.

And the key to “gripping” the part was hit home by suggesting the use of soft jaws. Suggestion number 3.

So one would think it should be as easy as 1, 2, and 3.

Let’s say you don’t have any soft jaws. And what is it about soft jaws that make a job like this easier?

A soft material padding the grip of the part being chucked, allows it to be more easily moved about while indicating it [in].
It also helps shield the surface of the part being chucked from jaw marks which can be
damaging to the item being held. (Gripping a bearing journal that needs to be protected for example.)

If you don’t have any soft jaws, they can be replicated by using a soft material inserted between
the chuck jaw and the work. Copper is an excellent soft pad. It allows the part being chucked to easily slide/move about while being indicated. And it compresses as the jaws are slowly tighten or gripped to their final resting place. Depending on the size of work, the copper material can be as thin as “thin needed” up to a ¼” and thicker for very large work.

Knowing photos of an example are always helpful in explaining something, I searched through my extensive library of repair photographs taken over the last too many years and found only one picture to illustrate the practice.
(It’s obviously a less than glamorous subject that’s never been a highlight to photograph.)

http://www.pbase.com/visual_first/image ... 4/original

It’s a blurry photo taken using a camera phone, but if you look to the extreme left at the lathe chuck,
you’ll see flat strips of copper are inserted between the chuck jaws and the work.

I could have shown a 36” diameter cast iron motor end bracket or a pump volute chucked in the same manner,
but the chuck jaws would have been hidden from view by the part(s).

In the original post, it was noted the wheel part was too slippery or difficult to hold in place to chuck up.
That problem could have been remedied by nudging the lathe tail-stock up against the wheel for an additional “third hand”.
Of course large items would be held by a crane hoist.

And one other observation: The original photo shows the wheel hub tucked all the way back into the chuck.
When a part is crammed all the way up against the face of a chuck, the part cannot be adequately moved about to indicate the face portion.
A little bit of space between the item and the chuck face and jaw face(s) is necessary.

As for indicators, some machinists utilize the luxury of two dial indicators at the same time with one indicator measuring the face surface,
while the other indicates on the diameter during the chucking process.

This is a long reply to something that was as easy as 1, 2 and 3, but couldn’t resist jumping into the fray.

John

[SteveHGraham]

This thread is particularly interesting to me because a relatively simple job was made overly
complicated by choosing a method or approach that made it difficult right from its beginning.

Recalling the wisdom of, “… a job started ‘right’ is half finished” comes to mind.

But what’s the right way to begin this job?

In studying the initial photograph of the part rigidly clamped in a 4 jaw chuck on a milling table,there is nothing visibly noticeable
about the item that the part could not have been chucked in a lathe using a 4-jaw chuck.

Respectfully, this is a good example of judging a problem without reading previous comments thoroughly or understanding the mechanics of it.

This is a hard part to mount vertically in a 4-jaw chuck, for reasons already gone into. The rotary table is a relatively simple solution that will work just fine, but it involves a lot of indicating which can be eliminated using the 3-jaw and soft jaws or shims. The use of shims or similar materials introduces more difficulties, such as keeping the shims in place.

[SteveHGraham]

I should also add that last night it occurred to me that machining the soft jaws may be a waste of time.

Part of the difficulty of holding the wheel comes from the fact that hard cast iron skates on hard jaws. With soft jaws installed (fresh from the box), I have three soft surfaces to hold the hard wheel, and I can rest the wheel on the face of the chuck, which will locate it pretty well in the vertical plane. I'm going to see if I can hold it that way while I drill it. If I can drill it, then boring and tapping will be just as easy. If it slips while I'm drilling it, no harm done, and I can machine the jaws to hold it better.

This would mean Harold would only get a partial victory in his quest to get me to use soft jaws.

[Harold_V]

And for sake of clarifying again… a 4-jaw chuck would best suit the job.

No, it wouldn't. If the periphery of the hand wheel has been machined properly, and there's more than one to do, soft jaws will beat, hands down, a four jaw. Parts can be inserted in the proper attitude in a second, held rigidly, and can be removed and replaced for other operations, when necessary. It can all be accomplished with a level of precision that rivals a four jaw, and is likely to be more precise if one is not comfortable with dialing in items in a four jaw, where perpendicularity is an issue (which it would be in this case).

Again, assuming the periphery has been properly machined, the part can be gripped for machining both sides and can be expected to be parallel and perpendicular, as well as concentric, all without effort. How is it that a four jaw, which offers none of these features, would be superior?

H

[Harold_V]

I should also add that last night it occurred to me that machining the soft jaws may be a waste of time.

You're overlooking the one feature where soft jaws win. When you machine them to fit (exactly) the radius of the part to be held, they grip without damage. If you use soft jaws that are harder than the item being held, you can expect indentations where they make contact.

The disadvantage of using the chuck body as a register is that you may not be able to access the entire face for machining, assuming it would be necessary. Properly machined soft jaws will allow you to do so.

Bottom line: If you have no need to machine anything but the bore, you may enjoy success using the chuck face as a register. Still, ensure that the diameter machined to grip the periphery is machined to the correct radius, and that you use the same socket (in the chuck) for tightening the chuck. Because the scroll has a tendency to move slightly, using random holes will introduce concentricity issues.

H