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Need a way to round corners

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Stan

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#1
My first project after purchasing a 6x26 mill. I needed a way to round the corners on this motor mount and this is what I came up with. 2-1" bearings, short piece of 1" shaft with a 3/8" threaded hole in the end and 2-3/8"x1"x3" pieces of stock. Used 2 bearings because they were floaters. Mounted the bearings back to back with the 3/8"x1" stock in between to be held in my vice and the shaft is held in place by 4 set screws. I used a counter sink machine bolt to hold the piece that I am rounding in place. This makes sure that the hole will be centered. The corners turned out as nice as the straight cuts. You can see pictures at http://www.flickr.com/photos/stanleygill/sets/72157632458663968/. Please advise me of other methods since I am new at this. Any help will be appreciated.
 
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Tom Griffin

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#2
Those look pretty good. Just be careful to conventional mill as climb milling can grab and get you into trouble.

Other methods to produce arcs like that are the rotary table or just scribe an arc with a pair of dividers and belt sand them.

Tom
 

DMS

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#3
Other ways to do that are with a file (hehe), with a rotary table (which you kind of made a simple version of), or on a CNC machine with circular interpolation. Very fine work on that motor mount BTW, looks great.
 

pburns

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#4
Very Nice. I like your ingenuity.
 

Winegrower

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#5
This is an old thread, but a constant problem for me. Especially I would like to know some good ways (or any way) of rounding a corner radius where you cannot accept a through hole at the center of the radius. Yes, I have a rotary table, but it weighs a ton, takes a long time to set up, and generally is only practical for major jobs. This would be more of an impulse kind of thing to do when considering the almost completed project.

Help anyone?
 

JimDawson

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#6
12 inch disc sander. ;)

 

Winegrower

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#7
Jim, that is definitely practical. I was hoping for something a bit more elegant! :)
 

Nogoingback

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#8
I use a belt sander. It's possible to get very good results if you're careful and mark the steel with a scriber before you go to work. I clean
up the edges with file and emory paper. It does take time though.
Works best on thin stuff or aluminum of course.
 

P. Waller

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#9
If the radius requires a high degree of accuracy, for instance if it is a feature on a cam that translates motion than the rotary table is your best bet with a manual machine, if for appearance or clearance only grind it and finish by hand.
 

Winegrower

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#10
Thanks for your comments, No and P. I can only think that there is no good way to do this short of a full boat rotary table setup and that grinding is a time tested solution. Sad, but that's life I guess.

I wish some creative Hobby Machinist would come up with something though.

For example, for woodworking I have a set of corner rounding gizmos that fit over a corner and guide a router or router table around. Makes perfectly smooth corners in seconds.

Maybe if I knew faster ways to set up the rotary table...takes me forever, now. And the thing is just plumb heavy. Ah, me. :)
 

Nogoingback

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#11
I use a router when rounding over the edges of aluminum. If you have a jig that allows the use of the router on wood, you might be able
to use it that way on aluminum as well. I always take very light cuts, and have never had a problem. but of course you would have to
experiment carefully.
 

GrayTech

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#12
Would corner rounding endmills work? They come in many radius sizes.

Sent from my H3123 using Tapatalk
 

Winegrower

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#13
Interesting thought, Greytech. I guess you could use a large radius tool, and move perpendicular to the plane of the rounded corner. By Jove, I think you have it! Will try this and report!
 

Winegrower

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So the only roundover bit I had was a 5/8" radius, tried it on an aluminum plate...see below. I'm very satisfied with this, in that it's very easy and fast, and precise, compared to either a rotary table or sanding or grinding. You could set up a mill stop and knock these out like crazy.

My thanks to Graytech! Maybe everybody but me knew about this, but I just never thought of using the tool this way.

Weird, the picture looked right when I downloaded, oriented and saved it. I pasted it, and it looked good while I typed, then turned around by itself. Will never understand why it's so hard to get them oriented right.


Roundover bit.jpg
 
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SCLead

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#15
@Winegrower - please don't take this the wrong way, honest question here...What else do you use them for? haha

The only thing I've ever used them for is that, and cutting radii in the lathe, is there another use I'm not thinking of?
 

P. Waller

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#16
If adding a radius to the corners of different parts everyday there is really only one way that will do so easily without a good deal of setup.
You will not like this method however.
 

Eddyde

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#17
I usually grind them on the belt sander, first nipping off the corner on the bandsaw saves time and sanding belts.
 

Winegrower

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#18
SClead, I just thought of them as rounding edges along the long side of a part. Duh, never considered working crosswise. As I say, everybody but me knew this, i guess. Well, that's the value of this site. Thanks, all.
 

GrayTech

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#19
Don't sell yourself short winegrower, I've never seen anyone use them quite like this, and it wasn't mentioned in any other replies. I came up with it to round corners on 1/8 plate rather than set up my rotary table. It's fast, it's simple and it's far more elegant than a grinder or sander, just what you ordered. Bet you will be looking to complete your set of corner rounding endmills now.
Gray

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Winegrower

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#20
Yep, already on order, GrayTech.
 

Cadillac

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#21
A radius cutter is used to put a radius anywhere or position you can think of. I used a radius cutter to knock the corners off my lathe height gauge. It makes the chunk of metal nicer to pick up and gives character to a part. Very easy to set up actually. I setup to cut along the fixed jaw of vice so once your depths are set you can keep flipping the part and not have to set up each cut. Very repeatable. Here’s a example
451DBCDC-F032-460C-B316-9EBF635C5892.jpeg

Can be used in tool post on lathe to cut radius on parts if you don’t have a radius attachment. Mount in tool post use one flute of cutter mounted center of lathe axis.
 

P. Waller

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#22
This is 2018 not 1958.
I machine a radius like so, this is a lathe made in 1996, a simple wire rope sheave with a .200 radius. It was a home part so don't tell my employer that I made 4 of these in 15 Minutes (-:
 
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