QCTP

[Metalistico]

Alright.

Most probably a vibration issue. If the parting blade chatters, the vibration can undo the locking bolt on top. Also, if there is play in the compound +/or cross slide, the parting tool vibrations are amplified and can result in the tool holder coming loose.

I would try with the TP turned 90* and use the other holding position to see if it does the same thing.

This style of TP requires a good amount of torque on the tool holder screw to cinch them tight. If one of the cams is not machined accurately, it may not rotate enough to give you enough grip on the tool holder pull-in and vibrations will cause it to back off.

Your not lying when you say they need torque to hold the holder, I can barely turn the top screw and that's all i can get. I'll have to have a good look at it tomorrow after work, Ide think I should be able to turn it a bit more than what I'm getting

 

[Tom Kitta]

I made my own holders for parting blades - this is not too hard to do. Blades use carbide inserts. You need to make sure they are square to work and the setup is very solid without much of a backlash.

 

[YYCHM]

Your not lying when you say they need torque to hold the holder, I can barely turn the top screw and that's all i can get. I'll have to have a good look at it tomorrow after work, Ide think I should be able to turn it a bit more than what I'm getting

May just need a washer to give you more thread to play with. On my 7X12 I would remove the compound and install the tool holder directly to cross slide and lock the saddle. That seemed to help a lot. You could make or buy a saddle lock from LMS. Also, your cutoff blade may need a little back rake, doesn't look like it has any.

 

[Metalistico]

I made my own holders for parting blades - this is not too hard to do. Blades use carbide inserts. You need to make sure they are square to work and the setup is

May just need a washer to give you more thread to play with. On my 7X12 I would remove the compound and install the tool holder directly to cross slide and lock the saddle. That seemed to help a lot. You could make or buy a saddle lock from LMS. Also, your cutoff blade may need a little back rake, doesn't look like it has any.

That's the other problem I'm having, besides the tool post loosening up when Parting off, the cut off tool digs into the piece I'm machining and stall's out the Lathe, witch in turn smoked my belt.

 

[YYCHM]

That's the other problem I'm having, besides the tool post loosening up when Parting off, the cut off tool digs into the piece I'm machining and stall's out the Lathe, witch in turn smoked my belt.

I never smoked a belt but I sure smoked my share of cutoff blades.

 

[Metalistico]

Lol, I'm sure I'll get there too

 

[Dusty]

I never smoked a belt but I sure smoked my share of cutoff blades.

Hey Craig, ain't that the truth you're not alone.

 

[RobinHood]

I can barely turn the top screw and that's all i can get.

Sounds like the cam is not allowing enough turning of the bolt head to properly lock the tool holder to the post. On my Dixons, the locking bolts turn through an angle of about 60* (one flat) to secure the tool holder.

Pictures show the unlocked and locked position. I’ve marked one flat for reference.

 

[6.5 Fan]

I hate cutoff/parting tools.

 

[Dusty]

I hate cutoff/parting tools.

Nothing to hate ensure you're spot on 90 degrees to the material, work slowly and use lubricant.

 

[RobinHood]

I hate cutoff/parting tools.

So did I.

Until I spent a good junk of $$s and bought an ISCAR parting blade (not affiliated; there are other brand name ones just as good) with inserts for SS, alloy steel and non ferrous materials. Problems essentially vanished. I even use power feed to part off now.

 

[6.5 Fan]

May have to look at those ISCAR ones. the cheap ones have given me much grief.

 

[RobinHood]

May have to look at those ISCAR ones. the cheap ones have given me much grief.

Yup, nothing but frustration for me as well. So it was time to upgrade.

Not specifically saying that offshore and more economical parting systems don’t work fundamentally. I think they do. It was just that when I was doing work for customers, I could not fiddle fart around to get them to perform properly.

The quality brand ones seem to be more forgiving to operator errors, we’ll call it.

 

[YYCHM]

Mini Lathe Tool Post

Got 2.5' of 2" X 2" square in the recent Group Buy and realized it's the perfect size for a tool post on my mini lathe. It's going to replace this two piece version. For some reason MSM couldn't supply me with a 1.5" X 2" X 2" piece, so we went with a 1" and 1/2" piece? This style tool post...

canadianhobbymetalworkers.com

 

[Dusty]

May just need a washer to give you more thread to play with. On my 7X12 I would remove the compound and install the tool holder directly to cross slide and lock the saddle. That seemed to help a lot. You could make or buy a saddle lock from LMS. Also, your cutoff blade may need a little back rake, doesn't look like it has any.

@Metalistico, I use a wedge style QCTP with (three 3) different kind of blade holders. First photo, my go to carbide tipped (T 102 264F Super carbide) blade made in the US, expensive. Second photo, my cut off (3/32x1/2x4) blade normally used on aluminum. Please note both holders are angled at 7 degrees nose high. Third photo, my mystery metal cut off (3/32x5/8x5) blade, if I don't know the kind of material I'm cutting then I use this one. From my second and third photo you can see a slight finger tip back rake that is ground out this is what @YYCHM is speaking to.

Bottom line it took me several years of messing around to come up with this cut off blade formula which works for me.

 

[Susquatch]

I hate cutoff/parting tools.

Me too. I hate parting. I never know if it's gunna work or not.

Right up until I discovered upside down parting.

Basically, flip the blade so it's pointing down and then run the lathe in reverse. Because the blade has nothing to react against, it can't dig in anymore. The part just turns until the blade cuts. No chatter, no failures, no ruined blades, no stalls. It just works.

It's not the way it is supposed to work, but it works - every time all the time.

That's the other problem I'm having, besides the tool post loosening up when Parting off, the cut off tool digs into the piece I'm machining and stall's out the Lathe, witch in turn smoked my belt.

See above. You will never smoke another belt because the cutting tool cannot dig in if it is upside down.

 

[Susquatch]

Just because it's new doesn't mean it's sharp. Did the cutoff blade come with the QCTP?

Yup. Spot on. I have yet to see a brand new cutoff blade that was sharp. In my experience THEY ALL NEED SHARPENING.

Edit - Well, not the insert kind.

 

[PeterT]

So far so good on my AliExpress specials. I really didn't have high expectations but they are performing fine. The shanks fit the standard toolholders. I use the coated ones for steel & uncoated for aluminum. I don't think the coating makes any difference but just trying to preserve the edge for aluminum. I think I may have fiddled the center height setting a bit, not much. by much. Possibly the tuna can 4140 is deflecting a bit under load LOL. A way to check center is take part cut on the end of stock & examine what remains. A bit of nub remaining means the cutter is low. Usually I aim for dead center & go from there. I also have a dedicated holder for HSS type blades, it works fine too & allows a bit deeper DOC. HSS is useful to profile the end for curved grooves etc.

You might want to check if your toolholder and/or blade is twisting or deflecting. A longer stick out + angle on the cutting edge and/or the top bevel can 'steer' the tool into the side of the groove. I know many people prefer a slight bevel so that the nub comes off a preferential side clean, but I grind mine square. I don't really consider parting a finishing operation usually, so just lop it off with the least stress.

 

[YYCHM]

9" SM Utilathe Restoration

Looks like the runout on the face plate chuck registration boss is 0.0016"

canadianhobbymetalworkers.com

9" SM Utilathe Restoration

Things are not going very well at all...…… Geepers, I'm only trying to part off 1/4" wall 1 3/4" pipe here. This is what's left after breaking the blade 3 times now. I don't think I have managed to make a single pass with out some disaster happening. Things seem to be going really well...

canadianhobbymetalworkers.com

 

[Ian Moss]

I agree with RobinHood. The cam lock function is probably not working properly. Three things are involved, the rotating cam, the T piece it fits through and the toolholder T slot location. If all the other holders lock properly in that location, it is probably the T slot location in the toolholder. If that is the case, one would not want to change the cam stroke or the T piece as that would upset the locking of the other holders. Some careful measurements and comparisons could be made to find the deviation and remedy it.