Bridgeport operators, help a novice please

Fritz Maurer · Mar 22, 2017

I need to bore the ends of a 2" x 48" bar to insert axle stubs. I have a right-angle milling attachment, but I am concerned about finding the center accurately. I have tried the center square/center punch method and have not been happy with the results. I would like to keep it within .005 TIR if possible. I have heard of these things called edge finders. Is this the thing I need? Thanks, Fritz

Butch(OH) · Mar 22, 2017

There are many ways ways to do it. If you have DROs you can find the center of a shaft quickly with an edge finder but if your using the dials that method has it's own set if issues. By far the easiest to learn for the accuracy you are needing is called a "coax indicator" The real ones are made by Blake and a bit spendy but China/India Clones are about $50 last time I checked. Rather than explaining how they work just google "Blake indicator" Or watch a vid on You Tube. They are simple and reasonably accurate.

Janicholson · Mar 22, 2017

Set the vice at 90 to the chuck so the axle points directly at it. support the far end accurately to level. Position a small center drill in the chuck. Loosen the axle such that you can just barely turn it by hand. Paint the end with die to see a scratch. Turn the axle against the center drill while moving the x and Z axis wheels to make a clear tiny circle or spott on the die. Lock the X/Z axis. Center drill that end, then the other. then with no changes, drill and bore the desired holes. Jim

Steve@Advance · Mar 22, 2017

Trying to find center with an edge finder is going to be difficult. Even with a digital readout, you will be trying to jockey the knee up and down with slack in the lead screw, not going to be easy or accurate.

Sweeping it in with an indicator will be the easiest and most accurate. If you don't have an indicator, going to be impossible to hold any true tolerance.

You will also need this to indicate the vice, the angle head, and the part itself to get it parallel with the table.
Indicator set

Steve@Advance · Mar 22, 2017

One other thing, trying to run a boring head in a right angle attachment is probably not going to give good results.

The quill, the part the angle head clamps to, will have a little bit of radial movement. Nothing you can do about that other than tighten the lock. With the length of the boring head, and the bar, chances are the quill will rock back and forth from the force of the extended cutter. That will result in an out of round hole, other problems.

This job will be much better suited for a lathe.

Butch(OH) · Mar 22, 2017

Beg to differ with you on that Steve. The scales for the DRO measure actual moment of the axis thus the lead screw slack is out of the picture. My DRO is pretty basic but with an edge finder I can locate one side, hit zero, then locate the opposite side, hit "center" then do the same for the other axis. Then turn the cranks until the DRO reads .000 and I am in the center within .002 if done quickly, maybe half that when I take my time. There isnt any middle road with Blakes as you probably know. People either love them or hate them but for most general shop work they are quick and plenty accurate enough,,,in my opinion. When needed I break out the test indicators but they gather a lot of dust between uses, LOL

Eric in IL · Mar 22, 2017

It would be ok to lay out the center and pick up that center with a pointer in the spindle. It doesn't matter if you are not perfect at this point. Go ahead and rough out the hole undersize enough for a couple test cuts when you start the boring operation. Measure the position of the test bored hole compared to the outside of the bar at 9, 12, and 3 o'clock then adjust the position of the bar to put it dead nuts.

Now, IF the 90 degree head is not perfectly aligned ( which they rarely are ) you will be boring a slight ellipse, so checking at 9,12, and 3 may not get it perfect but it should be mighty stinking close.

tom stalker · Mar 22, 2017

I'm [b:a22e663fd9]guessing[/b:a22e663fd9] by the poster's question and no edge finder / last word indicator that he doesn't have a read out....so he must know about backlash

Assuming he has a 0-1" indicator to get the shaft parallel to the table

If using an edge finder, he could set a 1-2-3 block against the shaft and touch off in the y axis. Move to the center and set the Z height using the knee

I would sweep the OD with an indicator

Jiles · Mar 22, 2017

(quoted from post at 14:47:34 03/22/17) I need to bore the ends of a 2" x 48" bar to insert axle stubs. I have a right-angle milling attachment, but I am concerned about finding the center accurately. I have tried the center square/center punch method and have not been happy with the results. I would like to keep it within .005 TIR if possible. I have heard of these things called edge finders. Is this the thing I need? Thanks, Fritz

I am a retired Tool&Die Maker.
I would use a dial indicator- (Last Word works well) with proper holder and indicate the circumference of shaft while rotating spindle.

Steve@Advance · Mar 22, 2017

Butch, yes, DRO will work on X and Y, (if he has DRO), but he's running an angle head, will be trying to locate center with the knee...

Never seen a DRO on the knee, guess it's possible, but doubtful he has that option.

Butch(OH) · Mar 22, 2017

Really, no DRO in the knee? Guess I understand where you were coming from now. The knee DRO is invaluable for my work, never seen much use for one on the quill of a kneee mill but that's where a lot of them get installed first.

Mike(NEOhio) · Mar 22, 2017

I'm a retired T&D man, too. Can you mount the shaft vertically over the side of the table? Then swing and extend the head to the end of the shaft. You'll need a V-block and angle plate or V-block in the vice. Indicate for center. Edge finders are handy but not for a curved surface.

tom stalker · Mar 22, 2017

Not enough height clearance..... unless he had a big riser block on his machine

Would be easy hanging it off the side as suggested if the shaft was shorter

Easiest way would be a lathe with a 2 1/4" spindle bore or larger

As with most things, several ways to do it

Paul in MN · Mar 22, 2017

I think that solid bar 48" long is the wrong piece of iron for an axle. Quality axle manufacturers use a hollow tube to reduce weight and yet have plenty of strength. Even with the tube less than .250 wall thickness, the stub will bend before the tube bends. A friend borrowed my tandem axle trailer and proved the stubs will bend before the tube bends (if the spring pads are close to the brake flanges). Purchase some appropriate ID tubing for the axle stubs you already have, set up a careful alignment jig and weld the stubs in place. That is how most (maybe all?) commercial axles are built. The axle is then bent with a rise in the center to give the wheels and tires a bit of camber.

If you are cheap and lucky, you might find a trailer home or RV axle that you can cut the tube section from. Because of the camber already bent into it, mark the center of the tube and then cut 24" to either side of center. You may get lucky enough to avoid any lathe or mill work. I did get that lucky with some used axle tubes, so careful welding was all that was needed for 6000# capacity axles.

Good Luck

Paul in MN

Bridgeport operators, help a novice please

Fritz Maurer

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Butch(OH)

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Janicholson

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Steve@Advance

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Steve@Advance

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Butch(OH)

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Eric in IL

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tom stalker

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Jiles

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Steve@Advance

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Butch(OH)

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Mike(NEOhio)

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tom stalker

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Paul in MN

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