# Parting and Cutoff Issue



## Pmedic828 (Dec 15, 2014)

I know that there are problems with using a parting cut off tool on a lathe - I have a cut off tool that uses a blade that looks kinda like a trapezoid.  It is slightly larger across the top tapering in on both sides down to the base - it's the one that is sent when you purchase an AXA-100 QCTP and tools.  I hate to use this because it never works like it should.  I make sure that the insert is parallel with the chuck by using a 1 inch parallel between the chuck face and the insert.  I also use lubricant on a brush constantly while plunging the bit into the work.  I have made sure that it on center, have ground a slight chip breaker into the blade, and after cutting a groove about .001, move over a slight bit and re-insert the tool to provide clearance if the tool blade were to rub the sides of the cut portion.  Then widen this cut until it part it off but it always fails before the parting off portion!
It always seems to work to a depth of about .300 then, unexpectedly, grabs the work, pulling it from the chuck and flinging the work off the table - I have a variable speed lathe and am only turning about 30 rpm.  (I have tried to vary this from ultra slow to about 100 rpm - seems to make no difference.  My question is I think that I remember reading about some type of "T" type of blade which would provide clearance for the cut but cannot find anything like that in the Grizzly, Victornet, ENCO, or other tool bit providers.  I'm not sure if I am not looking in the right spot, or that they are really expensive and I am not looking at those pages.  
Can anyone provide any information as to what I am doing wrong?  Another post suggested a carbide cut off tool with a carbide insert that was sold by SHARS tool company.  Should I think about purchasing one like this.  I would reason that the carbide would fracture when the tool grabs and self destruct the insert?  Does anyone have one and do ya'll like it?  Suggestions please as this is getting rather frustrating:whiteflag:, not being to part anything off - Sometimes it's just inconvenient to cut stock on a band saw .. My Horrible freight doesn't cut straight either after numerous calibration attempts.  H E L P ?


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## savarin (Dec 15, 2014)

I have the same size tool post and parting blade as yourself.
On my 9x20 I had exactly the same problems as well.
It was very hit or miss as to whether it parted successfully or not.
I think you will find it is possibly  a problem with flex somewhere in the cross slide/top slide/tool post assembly.
I cured my parting woes by making a better fixing to the cross slide (pitkin donut)
http://www.hobby-machinist.com/showthread.php/28057-9x20-tool-post-flex?p=254826#post254826
I am actually astounded at how easy it parts now.
You dont mention what lathe you are using but something similar should be possible for it.


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## NightWing (Dec 15, 2014)

As you get closer to the center, the SFM decreases.  Dropping the spindle speed is going the wrong direction.  Without sufficient surface footage, the blade isn't cutting, it is pushing the piece off.  

CNC lathes and turning centers automatically wind the spindle up to maintain proper SFM.  My Mazaks would hit 6,000 rpm at the center of the nub.


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## PatMiles (Dec 24, 2014)

Savarin,
The link in your reply leads to nowhere.


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## Reeltor (Dec 24, 2014)

Here is a link to the enco page for "T" style HSS parting tool bits.  Have you tried increasing the rpm to around 320?  
For what it's worth, I have flung a few of these parting tools put of the QCTP holder and have gone back to a lantern type parting tool holder.

http://www.use-enco.com/CGI/INPDFF?PMPAGE=163&PARTPG=INLMK3&PMITEM=250-1760


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## Bruce_Mowbray (Dec 24, 2014)

Make sure your tooltip is exactly at center. Make sure you use plenty of lube. More flood then brush. Make sure you get the oil right down at the cutting edge. The chips should be ejecting as you plunge. Make sure they are not getting caught in the slot preventing oil from reaching the cutting tip.Don't push too hard but make sure you keep constant pressure on the tool


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## Micke S (Dec 24, 2014)

I've found it much easier to cut with the power feed instead of manual feed. But you may have other issues as others have pointed out.


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## Bamban (Dec 24, 2014)

Not meaning to hijack the thread, have y'all tried this one? It appears to have some merit.


http://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=31&Itemid=45


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## Cobra (Dec 24, 2014)

I am with Micke.  I used to manual feed and very low SFM but have found better luck with a normal speed and power cross feed. 
With steel or stainless, still lots of lube. 
Jim


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## xalky (Dec 24, 2014)

I had started a thread cussing about my parting woes a while back. A few people had suggested that I try an Iscar style parting tool that uses carbide inserts. I bought one and tried it...loved it. I'll never go back to those old style parting tools.


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## Round in circles (Dec 24, 2014)

message deleted  ..... its been already said  .


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## Reeltor (Dec 24, 2014)

xalky said:


> I had started a thread cussing about my parting woes a while back. A few people had suggested that I try an Iscar style parting tool that uses carbide inserts. I bought one and tried it...loved it. I'll never go back to those old style parting tools.



Could you please post a link to the tool holder and insert that you are using?  There are so many different ones, I don't know where to start when considering an insert type holder.

Mike


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## savarin (Dec 24, 2014)

PatMiles said:


> Savarin,
> The link in your reply leads to nowhere.



So I have just found. I cant find any reference to the original post either.
Admins? any ideas?


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## JimDawson (Dec 24, 2014)

savarin said:


> So I have just found. I cant find any reference to the original post either.
> Admins? any ideas?




I looked for a post addressing that issue, the only thing I found was this one.  http://www.hobby-machinist.com/showthread.php/8602-gib-play?p=72315&viewfull=1#post72315

and maybe this one
http://www.hobby-machinist.com/show...2Z-qctp-to-AXA?p=225006&viewfull=1#post225006


EDIT:  I found this link http://coleman-family.org/Files/Donut Compound Mount for the 9X20 Lathe.pdf

I also found the original post by searching Google, but the link is dead.


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## ARKnack (Dec 24, 2014)

anic:





JimDawson said:


> I looked for a post addressing that issue, the only thing I found was this one.  http://www.hobby-machinist.com/showthread.php/8602-gib-play?p=72315&viewfull=1#post72315
> 
> and maybe this one
> http://www.hobby-machinist.com/show...2Z-qctp-to-AXA?p=225006&viewfull=1#post225006



Actual I believe there is a serious bug with this site. Twice I have suddenly lost my membership even though I was a donator. I could log on one day but not the next. When I rejoin, all my posts appear to be gone. Makes me wonder how many members have been dropped unknowingly.


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## Doubleeboy (Dec 24, 2014)

I long ago quit using HSS parting tools, got a holder that fits in a standard quick change holder the holds a blade that hold the little parting inserts.  In thousands of uses I have gone thru 3 inserts.  I cut dry and power thru it on power feed.  MGTBN is the block holder, then you get the blade that fits in it, then the insert.  Every once in a while MSC, Enco, Travers will have a sale on the whole package which makes it reasonable.  Maybe the discount China places like Shars or CDCO sell them but for me parting is one place to buy quality.  Seco, Escar, Nikole are some brands that make em, the Nikole are miniature though.  

edit: Hertel makes them also and could be the one I have   
http://www.use-enco.com/CGI/INPDFF?PMPAGE=180&PMITEM=359-1326


hope this helps
michael


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## savarin (Dec 24, 2014)

JimDawson said:


> I looked for a post addressing that issue, the only thing I found was this one.  http://www.hobby-machinist.com/showthread.php/8602-gib-play?p=72315&viewfull=1#post72315
> 
> and maybe this one
> http://www.hobby-machinist.com/show...2Z-qctp-to-AXA?p=225006&viewfull=1#post225006
> ...



Thats the link to the pitkin donut I referenced in my original thread '9x20 tool post flex'
It looks as if the whole thread has gone into the wild blue yonder.
The donut has made my 9x20 so much more rigid that I think it should be the first mod done to these machines.


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## stupoty (Dec 25, 2014)

savarin said:


> Thats the link to the pitkin donut I referenced in my original thread '9x20 tool post flex'
> It looks as if the whole thread has gone into the wild blue yonder.
> The donut has made my 9x20 so much more rigid that I think it should be the first mod done to these machines.



Is that a ring that sits under the compond slide?

ive had some amazing parting tool explosions on my 9x20 when the top slide and everything sudenly bends a little bit.

stuart


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## savarin (Dec 25, 2014)

stupoty said:


> Is that a ring that sits under the compond slide?
> 
> ive had some amazing parting tool explosions on my 9x20 when the top slide and everything sudenly bends a little bit.
> 
> stuart



Yep, thats the one, its takes the place of the 4/2 bolt clamp and the degree ring.
I also tapped for a 5mm bolt at each corner of the bottom of the slide.


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## savarin (Feb 13, 2016)

Just in case anyone wants to read this here is the new link
http://www.hobby-machinist.com/threads/the-9x20-mods-thread.30050/


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## Mike Jones (Feb 28, 2016)

Have you ever tried parting off with an inverted tool. held in a rear mounted
tool post.For years I parted off with a front mounted tool ,but since I made
myself a rear mounted holder I find it is far better and safer and tool breakage
a thing of the past.


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## Reeltor (Mar 1, 2016)

As I said in a previous post, the no-name QCTP holder wouldn’t grip the HHS cutoff blade correctly and I reverted to the old “lantern style” cutoff holder with good results.  In the past, I’ve tired “carbide” on my lathe bits and didn’t care for the results at all.  The bits were inexpensive cemented ones from Harbor Freight and the like.

I found NOS carbide insert cutoff tool holder and absolutely love the results.  I am now using Iscar Self-Grip Carbide inserts and bought the “kit” that included the blade and holder block, and 10 inserts; the block is held in a standard QCTP holder.

http://www.iscar.com/eCatalog/Family.aspx?fnum=386&mapp=TG&GFSTYP=M


http://www.iscar.com/eCatalog/Grade.aspx?grade=IC328&item=6003292&fnum=75&mapp=

I liked this so much that I went back and found a few carbide lathe bit holders and am getting very good results even at the speeds that my old 1944 lathe produces.

If it’s in the budget try (some quality) carbide it’s like night and day.  I really didn’t have a clue on what the retail price of these holders are.  I paid less than $20 for the entire kit and didn’t realize what a great deal it was.  For us hobby guys, paying retail prices is (at least for me) out of the question.  Maybe something will turn up on Ebay.


Good luck,


Mike


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## Tozguy (Mar 1, 2016)

I had the same problems when starting out but with a BXA size, piston style QCTP. From what I have gathered, the best solutions for parting  involve replacing the QCTP with something more rigid mounted on the cross slide or compound, either in front or back, or inverted or not.  The lack of rigidity of a QCTP is less of a problem for other types of cuts (turning, facing, boring) because there are ways to compensate that are not possible when parting.

Note that the no. 7 parting blade holder is sloped upwards and creates positive rake on the cut. This is suitable for a few materials but is prone to digging and jumping on most steels. There is no way a tapered blade can be ground to reduce the top rake so the no. 7 holder should be the first to go. 

Parting blocks as mentioned in previous posts are level with the cut (neutral rake) and would be more suitable in some cases. However this does nothing to improve the QCTP itself.

Carbide parting tools tolerate chatter less than HSS and really only have their place once your act is together with HSS and you want higher production rates. Carbide is by no means a solution to chatter in a poor set up.

If your QCTP replaced a 4 way tool post (like those often supplied with a new lathe) it could be reactivated and dedicated to parting. A four way tool post is more rigid than a QCTP. One or more parting blades would only have to be mounted once in it. Then all you do is swap the tool posts on the compound when its time to part. 

Ultimately the parting holder that mounts directly to the cross slide would have the most potential to be rigid. How far one is willing to go is a personal decision but parting with a QCTP and No.7 holder combination is not hard to beat.


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