Bushing material question

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John Evans
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Re: Bushing material question

Post by John Evans »

Heel of insert rubbing? Raise bar and rotate tip downward. If that is a double sided insert ,thats the prob ,no clearence .
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Bill Shields
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Re: Bushing material question

Post by Bill Shields »

Agreed...you are below minimum bore for that tool.

Grind one or purchase a one piece boring bar
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seal killer
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Re: Bushing material question

Post by seal killer »

John and Bill--

Thanks. I'll look around and see what else I've got. I MIGHT have something that will work without spending money. In any case, I'll report back!

Thank you for the help.
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Harold_V
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Re: Bushing material question

Post by Harold_V »

When you have proper clearance and cutting geometry, this material should bore with an exceptional finish, without a hint of roughness, although it will reflect the feed rate, depending on how much radius you have on the cutting edge.

Any time you see metal extruded, as you see on the inside corner, pretty good chance that the tool is either exceedingly dull, or it is dragging where it should not. The roughness of the cut and the extruded metal pretty much indicate that the bar is making contact where it should not. You should be able to see where it is touching because the material will have left tell-tale deposits at the contact point.

It's pretty easy to grind a small boring bar, which will most likely out-perform a carbide insert unless you have inserts that are specifically ground for finish cuts. They'd have distinct positive rake and a small tip radius.

H
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NP317
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Re: Bushing material question

Post by NP317 »

I would set that cutter slightly above the center line. And look at the bar bottom to make sure it is not scraping anywhere.

I suspect the top relief of the cutter is excessive, and raising it will decrease that a bit. Copper alloys like to be "scraped" and not cut like steel.
But phosphor bronze??? Perhaps another matter. Someone else needs to step in here with knowledge.

OR: Leave the bore rough so it will hold grease forever!
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seal killer
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Re: Bushing material question

Post by seal killer »

John and Harold and RussN and All--

Harold, I rebored the piece with a 1/64" radius carbide insert, which, following John's guidance, I tilted a few degrees down. The results are much better. Next, I will raise the bar as John suggested and see what happens. (I am at 0.491"d on the way to 0.50x"d.)

RussN, if I can't manage a good finish I will say I wanted it that way to retain grease. That is such a great CYA idea and good engineering, too! (Maybe.) :)
Better bore result.jpg
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GlennW
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Re: Bushing material question

Post by GlennW »

seal killer wrote: Tue Jul 12, 2022 3:41 pm I grabbed one of my Borite bars for the mill and clamped it's round shank in my tool post.
seal killer wrote: Wed Jul 13, 2022 6:58 pm(I am at 0.491"d on the way to 0.50x"d.)
A .500" Borite boring bar is geometrically set up to bore a clean .500" hole. You are presently below that diameter, so there are clearance issues. It may clear up when you reach .500", but using a boring bar that is made to rotate on it's axis to bore a .500" minimum bore may not cut properly when set up in a lathe with the cutting edge on center. The geometry of the bar may not like that!

I try to bore a piece of aluminum as a test when I am setting up to be sure what the minimum bore will be for a nice finish. I learned the hard way! Usually, it works better with a size smaller bore so you have some room for chip clearance as well If there is little to no clearance between the bottom of the bar and the bore, chips get pinched in there as the part rotates and that makes the cutting edge move around as the chips are bumped over. It can also lead to a tapered bore.
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Bill Shields
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Re: Bushing material question

Post by Bill Shields »

Ever consider just shoving a .5 diameter end mill right up the center?

Granted...getting it exactly on center takes a while..

To get around that my favorite trick is to put the part on a milling table, indicate the hole and push the milling cutter through with the quill.

I know...I have a strange solution for most every challenge...been thinking outside the box ever since I first asked the question "what box?'

Lathe .. mill -> not much different anymore .
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SteveM
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Re: Bushing material question

Post by SteveM »

Bill Shields wrote: Wed Jul 13, 2022 9:54 pm Lathe .. mill -> not much different anymore .
Lathe is mill spelled sideways..
sort of.

Steve
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Bill Shields
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Re: Bushing material question

Post by Bill Shields »

I write a lot of software for vertical lathes that have adjustable angle milling heads -> as well as horizontal mill-turn centers that trequently have more milling tools than turning tools..so the term sideways is a very nebulous concept in today's world

One of the first attachments I purchased 50+ years ago was a boring head and set of HSS boring bars that would let be bore holes from .100" diameter on up to ?

It used to be that a lathe is a machine the uses square tools to make round parts -> and a mill is a machine that uses round tools to make square parts.
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seal killer
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Re: Bushing material question

Post by seal killer »

RussN and All--

I took Russ's advice and raised the bar as much as I could and still have clearance between the top of the bar and the hole I am boring. That produced a nice--acceptable to me, anyway--bored finish.

The axle has a nice, no slop fit. Sliding a 0.500"+ plug gage into the hole produces pneumatic pressure on the way in and a vacuum on the way out. The axle stock fits about the same. Is that too tight for my low load, 0.almost-nothing feet per year wheels?

I plan to use my power saw to lop the workpiece off. I do not know what phosphor bronze will do to my saw blade. I use it to cut everything from hard steel to aluminum. Can you tell me about cutting the 1" diameter phosphor bronze workpiece? (I will stick with my Rustlick coolant.)

After I cut the two bearing pieces off the stock, I will face them. I do not like the finish of the face you see, although it would certainly work. I want it to look better. I'll try that same insert I used to bore the hole to face it and see what happens.

Here's the piece . . .
bored to size.jpg
Thanks!
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Harold_V
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Re: Bushing material question

Post by Harold_V »

Because phosphor bronze is an excellent bearing material, the qualities that make it so will also make it difficult to saw with a blade that is not pristine. Once a saw blade has seen use in cutting steel, it will generally struggle with cutting copper alloys, even free machining brass. A new saw blade will likely cut perfectly well. Phosphor bronze is not hard---it's tough. There's a huge difference.

If you try your well used blade, one of the things you can expect is a crooked cut, whereby the set on one side is worn worse than the opposite side, causing the sharper side to cut easier. The blade will favor that side.

The typical response to sawing bearing material with a dull blade is for the blade to simply stop cutting as surface area (in the cut) increases. You may find that the blade simply floats in the cut, assuming there's enough area.

You may find the blade works just fine, but don't count on it.

H

Edit:

I suspect that you'd get a much nicer finish if you didn't rely on inserts. A well honed HSS tool of proper geometry should yield an excellent finish in this material. Were it leaded, the finish would most likely be the best you've ever created. That's the nature of that alloy.
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