I disagree thoroughly, and here's why:Having watched a video by ox tool Co their conclusion was fiddling with the levelling feet didn't make much difference on a 1 piece cabinet.
A 1 thou cut is too small with a carbide insert tool - they’re basically blunt and will just push the work away. Try a razor sharp hss tool instead.
Well yes, it is possible to get sharp inserts, but they aren’t the norm, especially if you buy from Banggood or any of the usual hobby suppliers. And most people can’t decipher the code to see exactly what their insert is like!I disagree thoroughly, and here's why:
I managed to induce twist in my short bed M400 (short, extremely stout, and extremely well built one-piece cabinet) to the tune of half a thou over 10 inches on the test piece cut. This tells me that at the opposite pair of feet, the twist will have been around 2-3 thou.
It's amazing how you can look at something and think, THAT will not twist. How can it? But it does.
I personally don't think levelling is all that important, and I know two machine shops that prefer to have a slope on their lathes. But making sure there is no twist, certainly is important... or at least, sat as well as it can be...
You can get razor sharp positive carbide I have some Taegutec CCGT inserts for aluminium/light cuts in steel - that will draw blood, literally. They'll shave peach fuzz swarf off mild steel.
Thats good to know - I spend days on itI disagree thoroughly, and here's why:
I managed to induce twist in my short bed M400 (short, extremely stout, and extremely well built one-piece cabinet) to the tune of half a thou over 10 inches on the test piece cut. This tells me that at the opposite pair of feet, the twist will have been around 2-3 thou.
It's amazing how you can look at something and think, THAT will not twist. How can it? But it does.
I personally don't think levelling is all that important, and I know two machine shops that prefer to have a slope on their lathes. But making sure there is no twist, certainly is important... or at least, sat as well as it can be...
You can get razor sharp positive rake carbide I have some Taegutec CCGT inserts for aluminium/light cuts in steel - that will draw blood, literally. They'll shave peach fuzz swarf off mild steel.
I agree though - a negative rake roughing insert is totally the wrong choice... depends what @fizzy is using... Doesn't look too bad going off the finish...
Well I'll go with Tom!Having watched a video by ox tool Co their conclusion was fiddling with the levelling feet didn't make much difference on a 1 piece cabinet.
This is nonsenseThere are many ways in which an error like that can creep in, the most likely is a warp or twist in the bed. If the bed is not leveled it can be difficult to detect (for those who correctly point out the lathe does not really need to be "level" per se, it just needs to be not twisted!). The other issue is that as often as not, any error in alignment in any part of the lathe is going to be random so one error can (and often will) counteract or compensate for another "opposite" error. Unless you start the entire process from scratch, you can't know for certain if you are creating an offset in one part of the setup to mitigate the error in another.
A less likely cause could be a misalignment in the headstock to the bed. Clearly if the headstock is "off axis" it can also introduce an error. Easy way to test for that is to measure along the top of the test bar and compare that to the measurement from the side (i.e. measure the "height" of the test bar relative to the bed ways).
The only way to be sure exactly what you are measuring is to start from scratch and take all of the twist out of the bed and the easiest way to do that is to level it. I did that a couple of times on mine and it is a right faff! Using a precision level, adjust the feet until every part of the bed is "perfectly" level. Takes ages because every time you adjust one thing, it moves another and the more accurate your level is, the longer it takes to settle. Even the foot adjustment doesn't necessarily update in real time either. A big heavy cast iron base takes time to settle but the surprising thing is just how much changing the bed levelling adjusters changes your cut.
Don't take these numbers at face value but you could easily introduce a 2 thou taper just by badly adjusting one of the feet (on my old Colchester). Oh and you can easily spend a day trying to dial it in too!
I know you can get super sharp negative rake inserts, but i don't have any experience or knowledge of them. I'm learning on the flyThats good to know - I spend days on it
I used a sharp tip but negative rake as you say. I do have some razor sharp positive rake tips for aluminium - shaped like a diamond almost. Will try one of those next in case it is deflection.
Skip to 24 minutes in on the 2nd video where he shows the measurements he gets from messing around with levelling.
Tiny difference.
My CNC lathe will twist due to the concrete floor in my workshop moving, it is way more rigid than a Triumph so anyone saying a Triumph sized lathe will not twist is... well I better not say.
if hes not tool dealing welll..... i best not sayMy CNC lathe will twist due to the concrete floor in my workshop moving, it is way more rigid than a Triumph so anyone saying a Triumph sized lathe will not twist is... well I better not say.
Talking of dealing with tools, are you wanting that Carbtuneif hes not tool dealing welll..... i best not say
for the record i agree
Just a random interjection.
but on your saddle, could it be the tool post is a fraction off a 90° setting ?
Just throwing an idea out there.
Sure you guys know better than me
Sorry, just a thought. I'll be quiet in the corner.No. As has been said a few times now, the tool will cut a path with whatever twist, bend or offset. But if you then run a DTI in the toolpost, along the exact same axis you cut with, all things being equal you should see zero deflection (even if the part ends up looking like a banana).
The tip of the DTI must follow the exact path of the tool tip, even if it is the "wrong" path.
I’ve got twoYup like rocking horse poo
Well at least one thing about you is normalI’ve got two