Metal Planer

Thanks lyn,

Belt sander was my first thought too. The blade tips are only 8" wide i just have to mind the slight radius. Lots of work but I can keep the cast aluminum cool that way. Fine emery cloth with a scribed edge will do it. I just do not want the liability of doing it. You would think that when you order a Axial Prop to a specific dimension and wait 4 months for it, the prop maker would deliver the right size.

Hugh, that's just me expecting other people can do their job though.

Thanks for the thoughts

WOW! 45 inches?

That screams scribe a line on each blade and use a band saw and belt sander to finish.

Good luck with this one.

Additionally, use a pivot point as before to rotate the blade into the band saw. It shouldn't be very hard to set up.

The belt sander should work but use coarse grit belts until you approach the desired diameter. You asked for a prop diameter of 44.094 inches at 1800 rpm, if you are going to trim the prop you might ask the mfr what the radial growth of the prop would be at 1800rpm. You could also ask the mfg for their field fitting instructions. Do you trim the prop until it can just be installed & then trim the diameter down by a amount tabulated somewhere to provide the proper clearance at your rpm of 1800? The mfr should also be able to tell you how close you will have to balance the prop so as to avoid fatigue issues. If you trim the prop then the safety of future operation is yours. Please check all mfr documents for disclaimers concerning non factory work on there products.

Hi Lyn

Set your prop up on a drill stand table so that it turns horizontally. Mount it so it is tight on a verticle shaft and won't move when you feed it into the cutter.

Why not feed it into an acid bath? Dip the ends until they dissolve, next one, yes please. It would be a bit time consuming but in the end very accurate. No noise no burrs. Final polishing and Bob's part of the extended family.

Would I do this at home? Only under lock and key!

Tough to do.

The edge is not straight, so the blade would have to be masked to get the proper radius on the end.

That brings a whole new problem of "etchback" of the metal. More metal will be removed from the center/core of the blade, than the edges.

But, it could be done.

Good points. My suggestion was really off the top of my head.

My suggestion was made before I knew that the blade was 45 inches in diameter.

Top of the head sometime gives the best results. I use mine a lot, when I'm not shooting from the hip, or pulling it out of my a*s.

Cheers.

would have to be masked to get the proper radius on the end.

If the tip of the blade would be directed through the acid, back and forth, it would create a very slight curve, actually the perfect outline of the circle from the pivot.

To save time the bath and blade could be charged by DC current and make it a electrolysis process.

With the original cat not at hand it is hard to say. I'll leave this one half skinned

I figured you might think of that, and I can't find any fault with your logic.

Imagine a 45 inch diameter fan spinning through a chemical bath, fast enough to not let the solution run "down" the prop, but slow enough to not throw acid everywhere.

It could be done, but would ya want to?

Only if the problem would be at my doorstep every day and precision would be paramount, which it would be at those dimensions.

Stedou73ish will know whats best for him. Not to introduce a wobble is the name of the game. Even heating the ends will create some kind of torsion of the blade. Would be good to see a picture.

Like AH said, Lastly, I assume you considered modifying the assembly that the fan fits into? It would be a good idea to see if the 'frame' could not be made to fit. Hope the guys don't have to work the weekend.

Are you certain the blades are solid?

I'm not really getting a warm and fuzzy feeling about this.

Definitely no warm and fuzzy at ALL. They are cast solid and the MFT will not take the behemoth back.

The claim is that all of these blades are made a bit long to be field fit to the housing. I have never, ever had to "field fit" and Axial fan.

Thanks for your thoughts, its nice to know I am not alone in the same thought's.

A roughly equivalent process would be fly-cutting.

http://www.youtube.com/watch?v=koYGLVGkRsI

But I think the sanding/grinding method would work better for what you describe.

You need to trim 3/16" off the end of the blades ? I would construct a jig....If you need to curve the end of the blades, I would make a template....It depends on what tools you have to work with....Personally I would return the blade and contact a manufacturer for one made to specs....Liability issue...

Exactly my thoughts to return the blade. They claim the blade is made to be field fit and they want us to trim the edge. I asked that they send out their rep to do the trimming since the blade was made wrong.

In the end I am still wrestling with modifying the blade due to needing to get the building on line the send back is 4 months for return, but loss of life if a blade breaks free is forever.

I will probably send the blade back and let the projects time line go to hell due to the liability factors if they do not come out to fix the blade.

I measured and ordered 44.094" dia it was sent 45.00" dia. The manufacturer of the fan said they make them big so they can fit into the housing with an "in the field trimming". The comment is that everybody field trims axial fans, I never have. Guess I could take it to a local aeronautics machine shop. They will not take the $18,410 blade back and trim it them self's.

Yes I told our rep for them to order another fan and in the mean time here is your paper weight, but the building is ready to go and we are being pushed to resolve. All the proper lawyer paper work has been filed by our legal "if we modify we are not liable.......

It only takes them 4 months to make the wrong blade, I wonder how long it will take them to make the right blade.

With a blade that large you will likely have to consider balancing the assembly, too.

What did the manufacture suggest as far as methods and procedures to trim the fan blade?

Is there a clear paper trail that demonstrates that the manufactured failed to make it to spec?

If so, can you enlist the manufacture to modify the fan for you in a timely fashion? They may have a shop local to you that they could recommend. Remember, you catch more flies with honey than vinegar. You goal is resolution in a timely and hopefully inexpensive means.

Lastly, I assume you considered modifying the assembly that the fan fits into?

Google ""planer for metal".

Scribing the line for the correct dimension is the trick on a fan blade. If there were a way to rotate the blade I would look for a way to mount a hand power planer to gradually remove the tips. Then sand and balance.

To scribe the line, mount the blade above a precision flat table so the blade can rotate. Set a scribe to the correct dimension from the center, and mark the blade.

A good fabricator could grind to the scribed line. Going to be a noisy job.

That is the easy part!

1. Get a set of dial calipers, open to the desired thickness that you want to remove, and lock the thumb screw at that distance.

2. Use the calipers as a scribe by running one of the jaws along the outside edge of each blade and using the other jaw as a scribe on the fan blade.

You can spray the blades with Machinist Marking Blue paint to make the scribe marks more visible.

I would still belt sand or grind the bulk of the material away close to the line and finish with a German Mill (hand file).

You still need to spin balance the assembly.

"Use the calipers as a scribe by running one of the jaws along the outside edge of each blade and using the other jaw as a scribe on the fan blade."

Now, that's not a nice way to treat a precision instrument.

But it does work well, I've done it too.

I do it all the time. Aluminum is not hard enough to be a problem for good calipers.

Well, color me paranoid! But; if the MFR can''t supply the right diameter, did they bother to at least balance the blades? I think the first thing you need to do is mount the blade assembly on a pivot and check the static balance. If they can't at least do a static balance, you might just have a slightly oversized paperweight.Of course if it's that bad, just tie it to the MFR's feet and toss him overboard.

Using coolant, heat won't be a problem This type of job appears to be a special setup using a jig to position the fan, probably on a horizontal rotary table and using a band saw or vertical mill to do the cutting.

Just for your information, a planer used for metal, is a machine that has a flat bed that travels on an X axis. The work is clamped to the bed and that travels under a fixed cutting tool. It is use for large work. An example would be to plane material off the top of a a slab measuring 35 feet in length. http://en.wikipedia.org/wiki/Planer_(metalworking)

In my high school, we had numerous war surplus tools and machines donated by General Motors. One of them was a metal planer. I don't remember all the dimensions, but it did have a moving table about 35 feet long. It traveled through a central gantry that held the cutting/grinding tool. The gantry had vertical tracks on which rode a trolley about 6 feet long, giving an adjustable Z axis. The trolly carried a movable tool post which could be moved in the Y axis. We were told that GM used the planer to bore and hone the cylinder holes on Sherman tank engines. Following that, the tool would be exchanged for a fly cutter to mill the block surface perpendicular to the cylinder bore. The next step was to install a tool post grinder and grind the milled surface to o.ooo1" flat. Since it was a production machine, the did eight engines at a time because of the war and all. All of my classmates and I got to run the planer to flatten the tops of all of the shop anvils. All of the axes could be set to automatically increment after each pass. A fascinating experience I will never forget!

GH

The owner of the machine shop I worked in liked to collect machines. He got a planer with a six foot travel, a shaper with a three foot travel, it was HUGE. The machines didn't get much work, but when they did, it was a marvel to watch them go.

Sorry I think it was KY that asked for a picture. This is the prop before the trimming.

Thanks

Now the field fit becomes even more absurd.