Hood
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@Lewis_RX8 just wondering if you are using the power feed when you are getting these marks or just feeding by hand?
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Screwdriver
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Why do I bother....
Lewis_RX8
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Power feed was engaged away from work piece at 5 Thou Per Rev and let it feed itself in.
Maybe hand feeding could be worth a shot to see if maybe the power feed is causing it but that seems unlikely in my unknowledgeable opinion
Hood
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Power feed is usually a lot easier for getting a better finish than hand feed as it should be a constant feed which would be hard to get by hand. It is certainly worth trying a hand feed to see and if it is better then you will have to start looking at the feed shaft. It might also be worth trying it in a fine thread and engaging the leadscrew to see what it looks like.
Pete.
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Looking at the vid your finish is perfect off the tool but it's getting torn up by the curling chip about 1-2mm behind the cutting edge.
Change your tool angle so that the shank is parallel to the chuck face. That's the angle it is intended to be used at. Look at the DOC and feed specs for the insert if you know the manufacturer. Set the machine to those settings and take another pass. If you can't find the speed and feed specs try increasing the feed and reducing the DOC, and try a bit of lubricant.
Change your tool angle so that the shank is parallel to the chuck face. That's the angle it is intended to be used at. Look at the DOC and feed specs for the insert if you know the manufacturer. Set the machine to those settings and take another pass. If you can't find the speed and feed specs try increasing the feed and reducing the DOC, and try a bit of lubricant.
I'm far from being an expert but IME powerfeed gives a better (or at least more consistent) finish.
The other issue with aluminium particularly is it has a tendency to build up on the tool which can cause issues.
I've found the sharper CCGT inserts make quite a difference as well as ensuring plenty of lube. It's quite noticeable if you're cutting dry that a squirt of WD40 will leave a smoother section.
Lewis_RX8
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I worded my post slightly wrong , I know power feed gets a nice finish or should do but I was mentioning hand feeding to rule out if power feed was causing any lines
The cut in the video was mild steel forgot to say
Good idea on the feedscrew hood again can rule out the power feed and see if that's causing it
Think their kennemetal at a guess TNMG 160404 would need to have a look online for the spec sheets never easy to find.
Cheers
Munkul
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Why, indeed.
In the work, the tool/saddle. isn't going to float forward because it takes the path of least resistance. The resistance is huge when thread cutting, putting pressure on everything. If the tool/saddle floated forward in the lash, it would be doing more cutting - helically. This, plus the friction in the entire assembly, means it simply wouldn't happen, unless large vibrations overcame all the resistance. Now for vibration or chatter to make the saddle float forward in the lash, it would have to be bad enough chatter that you'd have a horrible surface finish, and you'd be far more worried about that than any threading inaccuracy.
But your question itself was worded badly. I answered your question honestly.
No, because the tool is engaged in the workpiece....
Obviously if the tool isn't engaged and you closed the half nuts, you can move the saddle back and forth within the lash... I mean, that's absolutely obvious...
Lewis_RX8
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Thanks to @Pete. for the call on tool angle , Rewatched the video not sure how you could tel with the chip better eyes for this than me but there I might see it breaking the chips off further to the left out the way of the nice surface finish breaking them really nice making lovely small yellow chips. Still not dead on 100% mirror and getting some lines but getting really close
Gets sad when a good lathe finish is this big a deal
Looks better in this pic than in person IMO , the small line to far left of cut is due to the DOC changing
I was 1200RPM , 5 TPR and at about a 0.8mm DOC on the dial on 25mm approx - Fizzy you should try this if you have any 0.4 radius tooling as could be handy to use along with the alu cutting tips
More realistic finish shot
This macro shot under light on the desk shows the slight groove finish and this pic makes it look worse than it is lol the grooves seem to be really shallow well atleast alot shallower than they where and just picking up on finger nail
Some of the chips which I think look quite good in terms of heat and chip breaking
And a video
@Munkul Had a quick look at the rack seems to be relatively uncrusty but will get the boroscope in on the pinion and see what it looks like , Worth a try at some point if that caused issues on your lathe and also could do with a clean anyway I think.
Thanks chaps
Gets sad when a good lathe finish is this big a deal
Looks better in this pic than in person IMO , the small line to far left of cut is due to the DOC changing
I was 1200RPM , 5 TPR and at about a 0.8mm DOC on the dial on 25mm approx - Fizzy you should try this if you have any 0.4 radius tooling as could be handy to use along with the alu cutting tips
More realistic finish shot
This macro shot under light on the desk shows the slight groove finish and this pic makes it look worse than it is lol the grooves seem to be really shallow well atleast alot shallower than they where and just picking up on finger nail
Some of the chips which I think look quite good in terms of heat and chip breaking
And a video
@Munkul Had a quick look at the rack seems to be relatively uncrusty but will get the boroscope in on the pinion and see what it looks like , Worth a try at some point if that caused issues on your lathe and also could do with a clean anyway I think.
Thanks chaps
Lewis_RX8
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Yup especially on this crappy mild steel bar , now got it sorted on that will be even better on proper free machining steelsNo ridges in that finish, anyway
Lewis_RX8
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Yea the motor can power through way more than that sort of cut and make serious chips proper hot and mm's of cut but was just looking for a finishing cut , will try get a few vids of heavy cuts the later
Max RPM is 1200 could push it further with vfd but would say maybe not any further than 1500 if that alot of weight spinning that fast on old lathe
Also that's 1.6mm off the diameter which can get confusing to DOC
Kram
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Yes I'd expect yours to improve finish with a deeper cut. 1mm-2mm dia is the sort of cut I take on better steels with ~1.2mm giving best finish and limited by rigidity.
On mild, I cant say. My bars often have a pure, low carbon bits all over, which change a smooth nice finish, to rough tearing. I change to 0.2-0.4mm dia finish cuts to reduce the tear but still needs to be sanded/polished - I dont do that on anything else.
Seeing your results I think I will need to try power feed again with your settings, as 0.005mm/rev is painfully slow. I only remember using powerfeed once, and the lowest is 0.1mm/r.
On mild, I cant say. My bars often have a pure, low carbon bits all over, which change a smooth nice finish, to rough tearing. I change to 0.2-0.4mm dia finish cuts to reduce the tear but still needs to be sanded/polished - I dont do that on anything else.
Seeing your results I think I will need to try power feed again with your settings, as 0.005mm/rev is painfully slow. I only remember using powerfeed once, and the lowest is 0.1mm/r.
Hood
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You being serious, 0.005mm/rev?
Fnish cuts on the CNC I do at 0.15mm/rev, roughing dependant on material etc but somewhere between 0.2 and 0.3mm/rev. Fook knows what I use on the manual, just shift levers until it looks right. Will have to have a look one of these days
daedalusminos
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So you do know relationship between tool radius and DOC and maintaining cutting forces axial to workpiece?
Hood
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daedalusminos
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It will if you swing the compound the wrong way, advancing the tool away from the feed direction, as I did it the other week cutting an internal thread.
First couple of passes went fine, but then instead of cutting properly, the tool would luch forward in the backlash, wait for the leadscrew to catch up with the nut and then chew a really nasty thread into the rest of the part, eventually getting to the point that it cut the crest off the partially formed thread and I gave up. Took me a couple of days to realise what I'd done wrong.
Pete.
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It will if you swing the compound the wrong way, advancing the tool away from the feed direction, as I did it the other week cutting an internal thread.
That's a lesson you only need to learn once
