Milling machine question: How would you mill in a cicle?

[Deuce Rails]

Hi guys.

I'm as excited as a kid on Christmas. I bought a mini milling machine from http://www.micromark.com/. I thought that their prices were reasonable, and I liked the fact that their slides measured in 0.050", as opposed to 1 mm, which comes out to 0.040 minus 2%. (Travel an inch by the wheel, and you'll be way off.)

I'm also going to have to tear the whole thing apart and rebuild it in order to make it accurate and reduce the backlash in all the gearing. But that's nomal for these Asian cheepies.

And so I'm learning a lot. In particular, I'm learning what I don't know about machine work. Here's one example.

If you wanted the mill end to follow a circle, how would you figure that out? Is there any rule of of thumb in order to convert X-Y co-ordinates into a constant curve?

Thanks in advance,

Matt

[36-3window]

i'm not an expert machinist , but when i want to mill in a cricle , i use a rotary table on my mill , like this:

[Unkl Ian]

Depends on what your trying to make. http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

Rotary Table is one way.
Boring head is another way.

Trigonometry comes in handy some times.
Or just scribe a line and work to the line,then blend with a file or grinder.

[disastron13]

Old fashioned fly cutters are easy to make and can have the tool bit ground to any shape- keep a phone book under your shirt when you are using it...if you don't have total trust in your work...
See if there is a community college machinists course by you, they are reall good value for money
Have fun

[Shaggy]

Yea I built myself a flycutter at school on a lathe i Might even have some drawings left. I can find them if anyone is interested.

[Morrisman]

If you actually want to mill a circle, using a slot drill for instance, you need either CNC capabilty, or a rotary milling table.

You could try it freehand, cranking the wheels in order to make your slot drill follow a marked circle, but it takes a lot of practise and will always look awful if you are after accuracy.

[Phil1934]

I've cut some odd sizes in up to 1/16" with a cheap adjustable hole cutter from General! You have to sharpen the cutter after each job, but it works and saves a trip to the hardware. My boring bar was painfully slow as I could not take more than a whisker off each pass. I've got an Enco mill.

[fab32]

Trying to mill any kind of a curve freehand is a challenge, it's usually 'GET CLOSE AND HAND FINISH'. That's why CNC is so popular. I've only known one person who could could work the X/Y axis handles and free hand curves really accurately and fast. It only took, acording to him, about 10 years of operating a Bridgeport to get really good. How much time do you have?

Frank

[oldchevyseller]

if you want a circle out of stock i have just used a straddle milling set up and sitting on a rotary tabl you just make multiple passes,turn the piece into a octagon then turn the table and cut em again , there is no fast way to get that done the diameter of the cirle is measured by the space between the cutters, as far as making cursive cuts freehand ,aproach it the same way cut a straight line and then mill out to the cuvre line ,straight line is easiest to index and follow, cut kerf cuts into the curve and then just clean up the rest,then finish shaping the curve with a drum sander head

[C9]

Depending on the thickness of the stock and size you may be able to cut a circle, but not mill a slot via the following.

Scribe a circle on the workpiece.
Bandsaw it to approximate shape.
Make a mandrel from an appropriately sized bolt, couple o' nuts & washers. (Cut the hex head off the bolt and clean up the cut.)
Clamp the center drilled workpiece in the mandrel between two flat washers and the nuts.
Install the mandrel/workpiece in the chuck of the mill.
Round the workpiece by applying files to the spinning workpiece.
This method works well if most of the material is cut away prior.
It can be fairly accurate as well.

Along with the rotary table mentioned you can also mill circles with a dividing head.

[Phil1934]

Sounds like another good time to wear a phone book in your shirt. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[stealthcruiser]

i'm guessing,the phone book is to intercept the flying tool piece or work piece?

[Morrisman]

[ QUOTE ]
"Install the mandrel/workpiece in the chuck of the mill.
Round the workpiece by applying files to the spinning workpiece.
This method works well if most of the material is cut away prior.
It can be fairly accurate as well.


[/ QUOTE ]

C9, you can also clamp a lathe tool in the mills vice, or straight to the mill bed, and use it like a lathe.

I've done milling in a lathe too. Fit a fly cutter or slot drill in the chuck, clamp your job to an angle bracket bolted to the crossslide and mill away at leisure.

I've also done rotary grinding, on a hardened steel shaft, with an angle grinder clamped to the toolpost http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

"Imagination is more important than knowledge"

[oldchevyseller]

[ QUOTE ]
i'm guessing,the phone book is to intercept the flying tool piece or work piece?

[/ QUOTE ] no i have my next of kin and the surgeons numbers highlighted so when i am laying there people can just look it up faster

[Flexicoker]

hahaha, thats hilarious

[Deuce Rails]

Thanks for the responses, guys.

Morrisman and Fab32, you guys were answering my question.
Maybe I should have added, "You know, like making a circle on an Etch-a-Sketch."

--Matt

[Unkl Ian]

[ QUOTE ]
You know, like making a circle on an Etch-a-Sketch."


[/ QUOTE ]

It would probably look just like it was done on an Etch-A-Sketch. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

That's fine for rough machining,but the are other methods for finish maching.

[Kool Kat]

Like this

3" circle 1" deep

No ramping or helix angle shit. Easier to jump around in the program. 3/4 pilot hole then circle interpolate. Easy. http://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif
( CIRCLE )
( FORMAT: DAEWOO MILL [RI] NRMU99.20.1.PST )
( 8/10/04 AT 9:54 AM )
( OUTPUT IN ABSOLUTE INCHES )
( PARTS PROGRAMMED: 1 )
( FIRST TOOL NOT IN SPINDLE )
( TOOL 1- 1/2 ENDMILL )
( TOOL 2- )
N2
( OPERATION 1: HOLES )
( TOOL 2: .75 DRILL )
N10G20
N20G17
N30G94
N40G91G30Z0.
N50G30X0.Y0.
N60G90
N70M1
N80T2 ( )
N90M6
N100G54
N110S178M3
N120G90G0X0.Y0.
N130G43Z.1H2M8T1
N140G73G99X0.Y0.Z-1.1R.1Q.25F1.25
N150G80G0Z.1
N160M9
N170G91G30Z0.
N180M5
N190G90X3.Y0.
N200M1
N1
( OPERATION 2: CONTOUR )
( TOOL 1: .5 FINISH ENDMILL )
( 1/2 ENDMILL )
N210T1 ( 1/2 ENDMILL )
N220M6
N230G54
N240S306M3
N250G90G0X0.Y.2
N260G43Z.1H1M8T2
( CYCLE START )
N270G1Z-.25F1.22
N280G41Y.25D1
N290G3J-.25
N300G40G1Y.2
( CYCLE START )
N310Z-.5
N320G41Y.25
N330G3J-.25
N340G40G1Y.2
( CYCLE START )
N350Z-.75
N360G41Y.25
N370G3J-.25
N380G40G1Y.2
( CYCLE START )
N390Z-1.
N400G41Y.25
N410G3J-.25
N420G40G1Y.2
N430G0Z.1
( OPERATION 3: CONTOUR )
( TOOL 1: .5 FINISH ENDMILL )
( 1/2 ENDMILL )
N440G90G0X0.Y.6
( CYCLE START )
N450G1Z-.25
N460G41Y.65D1
N470G3J-.65
N480G40G1Y.6
( CYCLE START )
N490Z-.5
N500G41Y.65
N510G3J-.65
N520G40G1Y.6
( CYCLE START )
N530Z-.75
N540G41Y.65
N550G3J-.65
N560G40G1Y.6
( CYCLE START )
N570Z-1.
N580G41Y.65
N590G3J-.65
N600G40G1Y.6
N610G0Z.1
( OPERATION 4: CONTOUR )
( TOOL 1: .5 FINISH ENDMILL )
( 1/2 ENDMILL )
N620G90G0X0.Y1.
( CYCLE START )
N630G1Z-.25
N640G41Y1.05D1
N650G3J-1.05
N660G40G1Y1.
( CYCLE START )
N670Z-.5
N680G41Y1.05
N690G3J-1.05
N700G40G1Y1.
( CYCLE START )
N710Z-.75
N720G41Y1.05
N730G3J-1.05
N740G40G1Y1.
( CYCLE START )
N750Z-1.
N760G41Y1.05
N770G3J-1.05
N780G40G1Y1.
N790G0Z.1
( OPERATION 5: CONTOUR )
( TOOL 1: .5 FINISH ENDMILL )
( 1/2 ENDMILL )
N800G90G0X0.Y1.19
( CYCLE START )
N810G1Z-.25
N820G41Y1.24D1
N830G3J-1.24
N840G40G1Y1.19
( CYCLE START )
N850Z-.5
N860G41Y1.24
N870G3J-1.24
N880G40G1Y1.19
( CYCLE START )
N890Z-.75
N900G41Y1.24
N910G3J-1.24
N920G40G1Y1.19
( CYCLE START )
N930Z-1.
N940G41Y1.24
N950G3J-1.24
N960G40G1Y1.19
N970G0Z.1
( OPERATION 6: CONTOUR )
( TOOL 1: .5 FINISH ENDMILL )
( 1/2 ENDMILL )
N980G90G0X0.Y1.2
( CYCLE START )
N990G1Z-.25
N1000G41Y1.25D1
N1010G3J-1.25
N1020G40G1Y1.2
( CYCLE START )
N1030Z-.5
N1040G41Y1.25
N1050G3J-1.25
N1060G40G1Y1.2
( CYCLE START )
N1070Z-.75
N1080G41Y1.25
N1090G3J-1.25
N1100G40G1Y1.2
( CYCLE START )
N1110Z-1.
N1120G41Y1.25
N1130G3J-1.25
N1140G40G1Y1.2
N1150G0Z.1
N1160M9
N1170G91G30Z0.
N1180M5
N1190G90X3.Y0.
N1200M30
%

[Deuce Rails]

[ QUOTE ]
It would probably look just like it was done on an Etch-A-Sketch. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[/ QUOTE ]

Except I can't measure thousands of an inch on my Etch-A-Sketch!
I was really hoping for some geometric solution...

[Deuce Rails]

[ QUOTE ]
Like this

3" circle 1" deep

No ramping or helix angle shit. Easier to jump around in the program. 3/4 pilot hole then circle interpolate. Easy. http://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif

[/ QUOTE ]

What the hell is that?
Over 150 lines of code in order to mill a 3" circle 1" deep?

[fatassbuick]

He also drilled a hole.

[Deuce Rails]

Hee hee!!!

[Kool Kat]

2.54 kb in size not that big.
using a 1/2" endmill in carbon steel. 4 passes at 1/4" a pass.If you wanna hog iron let me know.

I could program a canned cycle and make it smaller but ifin ya rerun it, cuts alot of air.

[Deuce Rails]

Any way you slice it, you Tejas guys cut a lot of air!

[Unkl Ian]

[ QUOTE ]
No ramping or helix angle shit. Easier to jump around in the program.
3/4 pilot hole then circle interpolate. Easy.

[/ QUOTE ]



A looping Macro,with cutter offset changes,would do the same thing with alot less code.

[Unkl Ian]

[ QUOTE ]
I was really hoping for some geometric solution...

[/ QUOTE ]

Trigonometry will allow you to calculate the correct position anywhere along a circle.
Enough time with a calculator would give you the necessary co-ordinates.

If you do it in small enough steps,you can get reasonable results.

But it will take a LONG time.

Hope you got the optional digital readout too.