Furrows on a milled edge

[Former MemberParticipant @formermember19781]

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[Former MemberParticipant @formermember19781]

[DMBParticipant @dmb]

Try sharpening the flutes.

John

[JasonBModerator @jasonb]

Are you cutting the full 5mm in one depth or several? 4-flute is OK.

What material, what material & dia is the cutter, speed, feed, what machine.????

Edited By JasonB on 05/08/2019 11:45:20

[EmgeeParticipant @emgee]

Hi Bill

You don't say what material, you could try speeding up the spindle and/or reducing the feed rate. If that doesn't help as John said check the flutes are sharp.

Emgee

[Mick B1Participant @mickb1]

Check the cutter's running true within a thou or so.

Increase the rpm if you can within recommended surface speed, consider slowing the feed.

Lubricate if not already.

Reduce depth of cut to a few thou for finishing.

If the depth of cut's already small, consider climb milling a final spring cut, but don't do that for more than a couple of thou.

[Former MemberParticipant @formermember19781]

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[Former MemberParticipant @formermember32069]

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[JasonBModerator @jasonb]

Up the speed to 2500 or even 4000

You don't say how far you are cutting in on each pass but with a small 4mm cutter take say 0.25mm per pass, definately don't try to go full depth and full width. Swarf should be fine 5mm long needles not dust or chips.

Also are the furrows vertical across or horizontal along the edge

Edited By JasonB on 05/08/2019 12:04:21

[Former MemberParticipant @formermember19781]

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[Former MemberParticipant @formermember19781]

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[David Standing 1Participant @davidstanding1]

Posted by 34046 on 05/08/2019 12:11:52:

Jason

Bit small the reply

Vertical along a 75mm length

When quoting, start your text below the left hand vertical line on the quoted part, you will then get full size text – as here

Re the lines on the work, do you have a larger diameter cutter you can use?

Also, are you winding in the feed evenly? If manually feeding, there is a tendency to speed up and slow down the hand wheel rotation if not careful, which can leave marks.

[Former MemberParticipant @formermember32069]

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[JasonBModerator @jasonb]

I'll also see if I can rig mine up later if I still have some intact drive belts.

Are you using the milling attachment?

[Former MemberParticipant @formermember19781]

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[DMBParticipant @dmb]

Yeah, OK, so follow others advice above but after you have exhausted their recommendations, try using a brand new cutter. Lack of info to start with, didn't know it was brass. Dont use a cutter (any type, including files) on brass that you previously used on steel or any other ferrous / stainless metals. Why such a small cutter?any special reason? I nearly always use a biggie – 1/2 or 5/8" for general metal removal, seems to work OK. Self taught using a mill and using large dia endmills, failed to bust em! Sharp cutters = better finish, but correct speed and feed also very important. Many years ago I worked in a factory that was divided by a chain link fence! One side was called "clean conditions" and the other side was the rest where Ali and steel were machined.

Hope all the advice works 4u ok

John

[SillyOldDufferModerator @sillyoldduffer]

Are you climb milling Bill? Try cutting from the other end. Front to back rather than back to front or vice versa depending on which side of the cutter the plate is.

Climb milling will produce a better finish provided the machine and set-up are rigid enough to take the strain. Being on the weedy side small machines and cutters are might bend enough for the cutter to bounce along the edge creating a chopped cut. If you can't stiffen up the set-up, cure is to change the direction and take conventional cuts. On a much bigger machine than an EMCO I only climb mill on light finishing cuts.

Small diameter cutters tend to bend, so high speed and light cuts are the order of the day. The amount of flute in contact might be contributing too. My 4mm cutter has a flute depth of about 8mm and pushing it on a 5mm edge would working it hard. (Jason's point about width and depth.) Next size up might do better.

Brass likes a sharp cutter and steel tends to blunt them enough to make a difference.

Dave

[JasonBModerator @jasonb]

So I dusted off the milling attachment which has not seen the light of day for at least 20yrs and had a go.

I don't have a collet chuck for mine so used the 3-jaw. And used 1/4" material as no 5mm or 3/16 small enough.

Only 4-flute 4mm cutter I had was a coated carbide one with quite along shank which meant it stuck out far more than I would really like. First cut on the video is this cutter at 2500, 0.2mm DOC, some chatter and deflection which is due to the stick out and a worn machine an resulted in a fair amout coming off on the return cut.

Second cut is a 3-flute HSS FC-3 cutter at 2500rpm, 0.2mm DOC, less spring on the return cut due to lower stick out.

Final cut is the same cutter at 4000rpm, 0.1mm DOC which gave about the best finish.

Looking at the surface in a raking light there are some vertical lines but they can't be felt with a finger nail and would come out with a couple of draw file passes of fine emery or wet and dry wrapped around the file. I could probably play around and get a better finish with a bit more time, a tweak of the machine and say a 6mm cutter.

 

Edited By JasonB on 05/08/2019 18:53:21

[David Standing 1Participant @davidstanding1]

Jason

Thinking of your poor old fingers, please use a brush to clean the swarf off before before poking your fingers in brass milling swarf

[Former MemberParticipant @formermember19781]

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[DC31kParticipant @dc31k]

You could try vacuuming up or blowing away the chips as they are produced so there is no recutting of chips happening. This can lead to an uneven finish.

[Former MemberParticipant @formermember19781]

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[Mick B1Participant @mickb1]

Posted by David Standing 1 on 05/08/2019 19:33:47:

Jason

Thinking of your poor old fingers, please use a brush to clean the swarf off before before poking your fingers in brass milling swarf

… and when despite this you still get tiny brass splinters stuck in your skin, an illuminated magnifier helps, and your Vernier or digital caliper excellently fulfils a secondary purpose of pulling the bu99ers out…

[Former MemberParticipant @formermember32069]

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[Kiwi BlokeParticipant @kiwibloke62605]

Emco dropped the ball when they designed the milling attachment for the Unimat 3. It uses sleeve bearings, which can't be adjusted. The spindle end-float also can't be adjusted properly. The pulley is pressed onto the spindle – its position determines the end-float. It can be 'adjusted' by judicious use of press or more brutal techniques.

I have two milling attachments (don't ask…), both bought barely-used, but both have unacceptable play in the sleeve bearings, making the attachment effectively useless for milling. I would imagine that they have been like that since new and have not worn excessively. The result is as you have shown. I suggest you check your spindle for radial play.

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