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Milling curves

Question on what kit I need

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Roy Garden20/03/2019 23:49:43
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Complete newbie, Have searched for an answer, not found one.
I want to mill a curve on the end of a piece of work (work is 6" long 2" wide)
Curve to be approx 1" Radius.
What gizmo do I need to get ?
Where should I look to learn about it?

I'm guessing a dividing head table, but asking as I don't know.
In future, I want to be able to cut gears too.

I'm using a Seig 2.7 mill.

duncan webster21/03/2019 00:09:45
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1953 forum posts
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several suggestions

  1. If you only want 'approx', file it
  2. work out the required co-ordinates and plunge the cutter through multiple times, then smooth it off with a file
  3. buy a rotary table
Roy Garden21/03/2019 00:14:39
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1) I'm lazy and fairly inept, so that's a non starter.
2) Better but see 1)
3) Which one ?

John Reese21/03/2019 00:25:51
697 forum posts

You didn't say in what plane you want the radius.

Roy Garden21/03/2019 00:29:46
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around the x and y axis (is that horizontal plane?)

duncan webster21/03/2019 00:33:57
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Posted by Roy Garden on 21/03/2019 00:14:39:

1) I'm lazy and fairly inept, so that's a non starter.
2) Better but see 1)
3) Which one ?

as you only want a 1" radius a small one will do, but might be restrictive for future jobs. I have 4" and 6" and use the 4" most, but anything you can do on a 4" you can do on a 6". However I'm not sure how a 6" fits on your milling machine, others will advise.

Roy Garden21/03/2019 00:46:42
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Which one tho?
As I want to cut gears and have the attention span of a housefly, is there a motorised table I can get (that costs less than I'll get by flogging one of the sprogs?)

Hopper21/03/2019 03:31:35
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3388 forum posts
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See this recent thread here for extensive discussion of a number of rotary tables, good, bad and toothless: LINK

You probably would not go wrong with a 4" rotary table from ArcEurotrade. 

Edited By Hopper on 21/03/2019 03:33:58

Paul Lousick21/03/2019 04:56:55
1003 forum posts
467 photos

If there is a hole at the centre of the radius, all you need is a pin in the hole and rotate the job in a vice. (see Youtube video).

Paul

**LINK**

Edited By Paul Lousick on 21/03/2019 04:59:42

JasonB21/03/2019 07:02:12
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Similar job on a SX2.7 with ARC 150mm table which gives you room for clamps

Plasma21/03/2019 07:36:19
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What is the material and how thick is it?

If you're abilities are not enough to file a workpiece into a curve I wonder at how you would go about setting up to mill the workpiece.

I'm not being rude but practical, as any apprentice will attest, you're expected to learn bench work first before being thrown near a 5 axis CNC machine. And a motorised table is kind of in that territory, you cant just bolt a lump.of metal to it, press a button and out pops the finished item. As with most things there is a hell of a lot more to do.

And the idea that machining a piece would be simpler and quicker is false, sometimes setting up takes a lot more work than actually doing the job.

Plus you can always apply Occams Razor, the principal that the simplest solution is usually the right one.

For me, a one off curve would be easiest done on a vertical belt machine or abrasive disc. By the time you have done setting up your mill and rotary table I would have shaped the piece, had a cuppa, painted it and gone in for lunch.

Brian G21/03/2019 08:15:35
455 forum posts
9 photos
Posted by Plasma on 21/03/2019 07:36:19:

What is the material and how thick is it?

If you're abilities are not enough to file a workpiece into a curve I wonder at how you would go about setting up to mill the workpiece.

...

Rather than buying a rotary table before you are certain which one you want (I made that mistake and haven't actually needed to use mine yet as for many jobs a file is quicker), you might be able to make filing it easier. After spending hundreds on machines, it was quite disheartening to realise that hand tools can be less work.

Perhaps take off most of the metal with a couple of angled cuts, either on the mill or more easily with a hacksaw (where you don't have to do mulitple set-ups or worse still reset a rotating vice to straight) and then file it between a couple of steel buttons. If you can't harden them put layout fluid or Sharpie on them and try not to file it off. If there is a hole, bolt them through (which would let you use cheap ballraces as buttons) otherwise clamp them.

Brian

EDIT:  If you do go down the motorised table route, take a look at Arduino Rotary Table for Dummies on HMEM.  The whole project costs less (much less if you use an Arduino clone) than a set of division disks for a rotary table, and assembling the electronics was a fun introduction to Arduinos.  I might even get around to fitting it to my rotary table one day should I need it... (EDIT2:  If I can find it that is, I have a horrible feeling I nicked all the components for other projects, Arduinos are seriously addictive).

Edited By Brian G on 21/03/2019 08:21:54

Edited By Brian G on 21/03/2019 08:24:20

Speedy Builder521/03/2019 08:45:30
1689 forum posts
114 photos

For a low cost solution, if your vice sits on swivel base, you could hold the piece in the vice, offset from the centre of the vice by the required radius. Mill a flat over the end of the component. move the vice around a few degrees and make another pass. You could do that for 180 degrees of rotation of the vice. Now turn the component upside down and repeat (if you can't achieve full depth on the first passes).

John Haine21/03/2019 09:02:43
2414 forum posts
132 photos

If there is going to be a central hole in the end of the material...

  • tee bolt in table slot clamped down with nut, same diameter as hole
  • big washer on top,
  • then your workpiece
  • another big washer
  • another nut to clamp down firmly
  • cutter adjusted so its OD is distance the radius from centre hole
  • Take a facing cut across the end
  • loosen clamp nut and turn material around a few degrees, tighten
  • take another cut
  • repeat until most of the material has gone and you're left with a polygonal approximation to your curve
  • file smooth.
Michael Gilligan21/03/2019 10:19:13
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Posted by Brian G on 21/03/2019 08:15:35:

EDIT: If you do go down the motorised table route, take a look at Arduino Rotary Table for Dummies on HMEM. The whole project costs less (much less if you use an Arduino clone) than a set of division disks for a rotary table, and assembling the electronics was a fun introduction to Arduinos.

.

Thanks for posting that excellent link, Brian yes

... It's sure to be useful sometime

MichaelG.

[the proud owner of one of Tony Jeffree's original DivisionMaster units]

Howard Lewis21/03/2019 12:11:36
1798 forum posts
2 photos

Cannot see that a motorised Table would be much help, when you want to cut gears, other than to save time, when indexing. (But you would possibly spend more time programming it! )

FWIW, I use a HV6 Rotary Table, with Division Plates, to cut gears. So far, seemingly, with success.

Do check that the Table has the Ratio claimed (Elsewhere, on the here we read of 48:1 tables with 47T gears! )

There have been instances of the chart supplied with the Table and Division Plates, containing errors, so if in ANY doubt, do the calculations and check!i

When you are milling your radius; a) make sure that the work is clamped securely b) Do NOT "climb" mill. The work must approach the cutter blades, head on, (from the opposite direction). Without backlash correction, climb milling is likely to pull the work into the cutter with possible ruin for both.

Howard

SillyOldDuffer21/03/2019 12:46:00
3977 forum posts
808 photos

Variation of advice already offered by others. Make a pillar that can be clamped into the mill's vice, tapped to allow a carrier and/or workpiece to be rotated against the side of a milling cutter. dsc05959.jpg

Take care - the thick washer in the photo was damaged by a grab. Beware of fingers - take it gently, don't climb mill or use large diameter cutters that might allow a small job to be pulled inside the helix.

Not tried it myself, but a more elaborate version of the pillar fitted with length of hacksaw blade bent in a circle, can be used to index a gear-wheel.

Nice thing about owning a mill and a lathe is you can make things to make things. I often make jigs or fixtures to hold or support work during awkward cutting operations. For example, this aluminium block was made to put a filleted half-flat on a long brass pin.

dsc05960.jpg

dsc05964.jpg

Dave

John Reese21/03/2019 16:50:50
697 forum posts

A lot of the import DROs will allow cutting a radius by providing a series of x and y coordinates for points on the circle. I suppose one could use the bolt circle function on most DROs if a huge number of holes were specified. Of course, it would be necessary to compensate for tool radius.

Here is a link to a way to do it that does not require any special equipment: https://www.youtube.com/watch?v=hTj6LC6agrg

That method may not work for longer parts.

AdrianR21/03/2019 17:38:48
98 forum posts

If you want a useful tool too, you could make a face plate balancing spindle. Then use it with a long leaver as a rotary table.

Two tools for the price of one.

Roy Garden21/03/2019 23:38:16
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17 forum posts
3 photos

Gents, I'm profoundly grateful for the advice, thank you all.
Through some budding bodgineering (which is what I aspire to) and using hints and tips from this thread, I've kind of got close to what I was after.

20190321_230323.jpg

The "nail it to the table, and spin it round" advice kind of covers most of the equipment I currently have.
The "File it, it's faster and easier" Well, I have a car, driving to get a bacon buttie is fast and easy, flying there is a pain in the butt, slow, unreliable, fraught with wasted effort, but good fun ! (99 times out of 100, I'll take the easy option, but when it's new . . I'll go with the wasted effort just for the experience)
Can I file? Yes.
Do I want to file? No, that's why I bought a belt sander.
(Tho, having said that, I've never heard of using bearings whilst filing, Can I get a link for how that works? )


I went with the "Pin through a hole and rotate in the vice" method, Sadly, a long (ish) piece of work and a low vice meant I managed very little of the curve that way, but enough to get a "feel" for the shape, 5 minutes on the belt sander and, from a distance, with yer glasses off, in low light, it kind of, looks ok.

Probably 4 hours time playing with the mill today, I think the finish looks good (it's what I wanted to see)
I'm discovering that "machining" is probably best done by fairly accurate sawing, finished off by machining the bits the saw can't do and providing a surface texture.
An hour spent cleaning (that's new to me too, I'm sure I'll get faster) and the garage has a shiny, uncompleted "bit" in it, a clean shiny mill, and a happy bunny who is now waiting for more "essential tools" to arrive.
In the meantime, I can pick the swarf out of my socks . . .
(and try to hide the battery Dyson from the wife, it looks a bit sad for having eaten lots of aluminium swarf and WD40)

Thanks again, I shall be asking more questions as I blunder along the learning curve.

Edited By Roy Garden on 21/03/2019 23:42:20

Edited to remove oil rig language.

Edited By JasonB on 22/03/2019 10:03:55

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