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Parting tool too high up

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Pcmaker

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#1
I have an 0XA QCTP. My parting blade sits too high up. I have a few things in mind to remedy this issue, but I was wondering if there's a better way.

The tool holder is already at the bottom and can't go any lower.

I can't mill off much off the bottom of the tool holder. Maybe a 1/16 of an inch is all I can shave off.

20180719_134830.jpg
 

RWanke

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#2
Take a pic of your setup from the other side so we can see better what you have going on.
 

benmychree

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#3
Machining off the top of the compound to bring the tool down to center may be a cure, or machine/grind off the bottom of the parting tool holder.
 

ddickey

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#4
Flip your blade upside down. Raise the blade to get on center and run your lathe in reverse for parting. If it's a screw on chuck that's probably not a good idea.
 

T Bredehoft

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#5
Take some material off that square block between the QCTB and the compound.
 

Chuck K

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#6
Your could grind some height off the top off the cut-off blade.
 

dcsleep

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#7
There are a couple of cutoff tool holders that fit the OXA QCTP - one that holds the tool horizontal and one that holds the tool angled up. I can't tell from the picture which one you're using but if you have the second type that could be your problem.
 

markba633csi

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#8
Can you mount the parting tool upside down in the back, without reversing the spindle and feed the tool toward you instead of away from you?
I've heard that sometimes works better- don't know if it will solve the height issue
mark
 

Pcmaker

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#9
There are a couple of cutoff tool holders that fit the OXA QCTP - one that holds the tool horizontal and one that holds the tool angled up. I can't tell from the picture which one you're using but if you have the second type that could be your problem.
yeah, it holds the cutting tool angled upwards

I've already thought of several ways to fix this issue, including a milling a regular tool holder
 

benmychree

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#10
Flip your blade upside down. Raise the blade to get on center and run your lathe in reverse for parting. If it's a screw on chuck that's probably not a good idea.
Also, not so good is that it would put the parting blade at a negative rake to the cut.
 

Pcmaker

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#11
This is my parting tool

 

dcsleep

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#12
This is the one I use on my small lathe. Got it from Little Machine Shop. I also have one like you have but can't use it due to the same problems you're having.

 

royesses

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#13
This is my parting tool

You ordered the wrong 0XA kit. The one you need is the 3117 which is true horizontal. The one you have is the 3774 which angles up 4° and is listed for up to 9" lathes. LMS may exchange it for you if you call them.

Roy
 

savarin

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#14

Pcmaker

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ddickey

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#16
You can do it. I've made a couple.
 

Pcmaker

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#17
Managed to use the same angled holder and milled some to get it to work. Still having problems parting, though. So far, I've had the most problems doing this than any other procedure with my lathe. Not sure what I'm doing wrong.

 

Hawkeye

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#18
Hands up, everyone who has had more trouble parting off than any other operation.

To summarize, cutting edge right on centre (you know that one), make sure the blade is exactly at right angles to the X-axis of the lathe, slow the spindle down, use lots of cutting oil, feed in fairly smartly, but you can back off quickly as well. You just don't want to take too light a cut, if it leaves the tool rubbing on the work.
 

markba633csi

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#19
Parting is hard on smaller lathes, you are not alone, I try to avoid it on my 6" (in fact I never have)
I'm waiting till I get my 12x36 set up- major delayed parting gratification
mark
 

higgite

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#20
I can’t say for sure since my parting tool holder is the horizontal model, but I’ll throw this out as food for thought. I have seen it said that mini lathes aren’t rigid enough to handle a positive angled parting tool. It tends to dig in to the work piece and the smaller lathes get mucho chatter. Is that what you’re experiencing?

Tom
 

WarrenP

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#21
I had lots of troubles parting on my 10 x 22 lathe until I got one of those "T" blades... They seems to work a lot better for me. I used a feeler gage right below the T section in my tool holder to keep it straight. Now I can part. :oops:
 

MarkM

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#22
Add some angle to the leading edge and grind some off the top with some rake to hit centre will make it much easier to machine. Top rake is a good thing for smaller lathes. Much easier to machine. Don t hesitate be aggressive!
 

royesses

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#23
Managed to use the same angled holder and milled some to get it to work. Still having problems parting, though. So far, I've had the most problems doing this than any other procedure with my lathe. Not sure what I'm doing wrong.

Parting on the mini lathe is difficult. For your first tries at it use aluminum that is 1" diameter or less. Make sure all gibs are tight and move the tool holder as close to the center of the cross slide as possible. Use the slowest speed your lathe will go to( I start at 30 rpm and since I installed tapered roller bearings on the spindle I can go a lot faster) and plenty of cutting oil. Advance the tool and when it chatters advance it until the chatter stops. When you have it correct the chips will come off in little rolls. Now you need to keep the the same depth of cut throughout the operation and as you get deeper and deeper you can gradually increase rpm. The more rigid your machine the easier it is to part. I drilled and tapped my compound for a lock that presses against the gib to take up all clearance. Also use a carriage lock when parting. It may help to adjust the spindle bearing preload also. Just practice until you get it. I think all of us who own a mini have gone through this. When you get it to the point that it works for you you can try higher rpm's and experiment until you are pleased. Don't give up, you will develop your own technique. You can also drill the cross slide for a lock screw that takes up any gib clearance. Also keep the parting blade stick out to a minimum.

Roy
 
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Pcmaker

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#24
I can’t say for sure since my parting tool holder is the horizontal model, but I’ll throw this out as food for thought. I have seen it said that mini lathes aren’t rigid enough to handle a positive angled parting tool. It tends to dig in to the work piece and the smaller lathes get mucho chatter. Is that what you’re experiencing?

Tom
Yeah, there's some "give" to the carriage, even though I can't rock it by hand and all the gibs are more than tight enough.

I had a feeling it was because I have a small lathe, 7 x 12, but reading that someone with a 10 x 22 is also having issues is disappointing because that's the size I was planning to ugprade to, hoping it would fix all the little issues that smaller lathes tend to have.
 

homestead

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#25
I solved my parting problems on a small la P_20180720_115720.jpg the with this support method.
 

Silverbullet

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#26
There are some ways to help with parting on a small lathe , lack of rigidity . Build a plinth block and not have a compound . Or purpose build a cut off tool with a sliding or roller support that will sit a cross the ways . Watch some YouTube videos on parting in a small lathe. I'm planning on building a power cut off using a slitting saw used on milling machines powered by a battery drill motor .
 

savarin

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#27
Hands up, everyone who has had more trouble parting off than any other operation.
Not since I made the solid plinth.
And always a continuous feed of cutting fluid.
Mild steel and aluminium up to 2" dia and stainless up to 1.25" (so far) in dia.
I dont even set the blade exactly square, just eyeball it and away it goes. Sometimes I dont get it close enough and get a concave or convex cut but other than that no problems now.
 

higgite

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#28
Not since I made the solid plinth.
And always a continuous feed of cutting fluid.
Mild steel and aluminium up to 2" dia and stainless up to 1.25" (so far) in dia.
I dont even set the blade exactly square, just eyeball it and away it goes. Sometimes I dont get it close enough and get a concave or convex cut but other than that no problems now.
Is your blade angled or horizontal?

Tom
 

savarin

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#29
angled with a "T" blade
 

Bobby Bailey

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#30
Maybe I just did it all wrong but, I started out on a Atlas Mk II 6x18 and have never had a problem parting off. Moving up to a south Bend 10K and two heavy 10's and still no trouble.
Make sure the tool is on center line, sharper than you think is sharp, everything locked down as much as possible, and feed right in. I don't even run the rpm that slow.
I find parting to be as easy as anything else.
Don't let it scare you, practice and practice. It gets easy.
My son was parting off the end of a barrel the other day and the chip came off as one continuous coil that was coiled so tight that it looked like a solid disk.
 
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