Swarf build-up

[gerry maddenParticipant @gerrymadden53711]

I enjoy boring, generally, but today was doing this to a workpiece approx. 50mm deep. I had to enlarge the hole in it from a drilled 16mm, out to 45mm. I use a 12mm bar fitted with the 6mm CCMT tips and the material was 6028 aluminium.

The cut always starts beautifully, but by the time I’m halfway in, the swarf gets wrapped around the bar and you have to repeatedly extract the tool, clean it and re-enter. The problem is that progress is just SO slow and with a lot of material to remove, the job can get very tedious.

I have tried boring in a series of wide diameter steps on the entry side, to help the swarf make an easier escape but that’s of limited help. I have also tried angling the bar when the hole gets to a diameter that allows me to do this. But again, this is only partially successful.

High speeds and low speeds change the texture of the swarf, but don’t stop the wrapping-around-the-bar tendency. I was hoping that the highest speed of 2600RPM might produce chips instead of wire, but it doesn’t.

One real frustration is that even when making a final very light finishing pass, I don’t seem to be able to do this in one go to avoid getting a ‘stop line’. If I try to, by pushing on ignoring the squeals and vibration, the finish is damaged by the swarf instead.

Anyone have any thoughts ideas or suggestions as to how to minimise this swarf buildup issue?

Gerry

 

 

[Ian PParticipant @ianp]

My suggestion would be to use a say 12mm diameter endmill (a long series might be best) to rough out the bulk of material and use your boring bar for the final finishing. Clamp endmill just like the boring bar, rotate/adjust endmill to get the best ‘tip’ position.

Ian P

[FulmenParticipant @fulmen]

Coolant?

[David SeniorParticipant @davidsenior29320]

Try a more aggressive feed to see whether you can get it to chip.

If you are feeding by hand then feed in short bursts. At least the swarf is shorter, and the interrupted cut won’t matter until you need to do the finishing cuts.

6026 can be better at chipping. You say you are using 6028 which I am not familiar with. I know 6082 is bad for this.

It is a recognised problem in industry, especially where machines are running unmanned. The swarf build-up can mean that running overnight is a problem.

Dave

[Mark RandParticipant @markrand96270]

High speeds and low feeds mean the swarf is thin and flexible. it’ll be stringy because it’s to flexible to snap and the insert’s chip breaker groove isn’t fully engaged.

Lower speeds (if absolutely needed by available hp and/or reaction time) and (much) heavier feed rate and depth of feed will allow the insert to break the swarf into chips.

Yes. It is quite scary! but once you get an insert into making chips instead of strings in aluminium you’ll be amazed.

[EmgeeParticipant @emgee]

A ccgt insert may give better results or even one of the diamond inserts although those I have used don’t have a chip breaker.

Emgee

[Brian WoodParticipant @brianwood45127]

I might have tried a holesaw to hog out the plug to start with, then clear up with the boring bar. Two cuts of 25 mm deep to meet in the middle and allow plenty of bites at it to avoid chip choking in the teeth gullers.

Brian

[Tony Pratt 1Participant @tonypratt1]

My immediate thought was you need to up the feed rate.

Tony

[Pete RimmerParticipant @peterimmer30576]

Use the biggest bar you have that can fit in the hole and push it harder. Take deep enough cuts so that the material chips. Measure the bore after each cut and set the final pass to hit the finished size, still chipping the swarf.

[FulmenParticipant @fulmen]

When you say the cut starts beautifully, do you mean you get chips or just that the swarf doesn’t pack? If it’s the latter it’s just how long swarf behaves in deep holes. if it’s the former it suggests heat buildup. Aluminium softens quite fast when heated, so cooling quickly becomes a necessity. Especially in deep holes which trap both heat and swarf.

 

[old martParticipant @oldmart]

As already mentioned, aluminium needs some type of lubricant, stop and start rather then continuous feed, as large a boring as will fit in the hole as it gets bigger, and trying out different inserts or regrinding if using HSS tools.

I often have exactly the same problems with swarf, and deeper cuts would help if you are confident of the work not coming out of the chuck. I would always use a four jaw independent chuck if greater workholding security was important.

[Martin KyteParticipant @martinkyte99762]

You could always try boring from the bottom of the hole outwards

[JasonBModerator @jasonb]

6082 is stringy.

You could try a bar for DCGT inserts as they have more clearance between the wall and the shank of the holder, likewise a piece of HSS in a holder will have more clearance. Won’t stop the strings but it will stop it getting between the insert and ID and pushing the tool off the surface.

[Dave SParticipant @daves59043]

Doesn’t look like you have much depth of cut on?
In aluminium I’d probably have about 3mm doc or more per pass, then remember to let it cool down when you are getting near diameter for measurement and final pass.

16 ->45mm is 29mm, so about 4 passes at 3mm doc, (24mm) then cool and take probably 2 passes to size.

[gerry maddenParticipant @gerrymadden53711]

Gentlemen, thanks for all your useful thoughts.

Apologies firstly for my metallic dyslexia. As some correctly worked out I was using 6082, and not 6028, and this may be the key issue.

Next on the list is the cut depth. I tried light and fast and slow and deep. However my ‘deep’ probably wasn’t ‘deep’ enough. I was worried about pulling the workpiece from the jaws. As is not clear in the pics, I was holding using the ‘outside jaws’ with a spacer to give clearance for the tool to pass all the way through the workpiece. This meant a limited grip which I didn’t want to test with a seriously heavy cut. For the sake of learning, I will do some trials on the outside diameter with progressively deeper cuts to see if I can form chips in this horrible lump of 6082. I’ll let you know what happens.

Jason’s suggestion of an alternative bar is a good one. This will give an extra 1mm of clearance. Doesn’t sound much but it’s an increase of 50%. Infact these tips will have other uses for me so I have already got one on order.

I’m not yet ready for coolants. I already spend too much time cleaning up instead of making things. I might try that in my next life!

Gerry

 

[old martParticipant @oldmart]

You don’t have to use coolants, but a little squirt of WD40 or similar used every few passes will prevent aluminium sticking to the tip of the tool.

[David George 1Participant @davidgeorge1]

Use paraffin as a lubricant cheeper than WD40 and it works better. you can pick up a gallon from B & Q £12.00 .

David

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