# Parting Blade Question



## WarrenP (Jun 10, 2018)

Hi Everyone, I have what Im sure is an easy question for most of you. I installed a quicj change tool post on my G0752 lathe. With it came a cut off blade holder. It says I need to use a blade that is Parrellel top and bottom. Does that mean I can not use a T shaped blade in it or is that ok? Thanks for your time on this.


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## killswitch505 (Jun 11, 2018)

I’m kinda new if this is what you’re calling a T type blade I use it with my quick change blade holder without issue in fact it’s the best kind of parting blade I’ve used


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## WarrenP (Jun 11, 2018)

killswitch505 said:


> I’m kinda new if this is what you’re calling a T type blade I use it with my quick change blade holder without issue in fact it’s the best kind of parting blade I’ve used



Yes that's the blade im talking about, I like them too, but not sure since the manufacturer says to use a parrellel top and bottom blade if it is ok to use this on my holder. Hopefully someone can answer this... Thanks.


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## Nogoingback (Jun 11, 2018)

Those parting tools can be used in the typical QCTP holders, but benefit from a shim betwwen the lower half of the blade and the toolholder.  This will keep the tool square to the face of the toolholder, as well as the work.  I used a small feeler guage on mine, but anything of the correct thickness will work.


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## MSD0 (Jun 11, 2018)

WarrenP said:


> Yes that's the blade im talking about, I like them too, but not sure since the manufacturer says to use a parrellel top and bottom blade if it is ok to use this on my holder. Hopefully someone can answer this... Thanks.


The top and bottom are parallel.


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## killswitch505 (Jun 11, 2018)

WarrenP said:


> Yes that's the blade im talking about, I like them too, but not sure since the manufacturer says to use a parrellel top and bottom blade if it is ok to use this on my holder. Hopefully someone can answer this... Thanks.


I’m sure we’re using the same tool holder. I run the T type without any issue. The only time I’ve had any issue was setting tool height, that was before using the T type blades once I figured that out parting went from being a nightmare to being just another task.


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## WarrenP (Jun 11, 2018)

OK, sounds good, I will shim the cutoff blade and all should be good (after I get one). Thanks all for the replies. Warren


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## benmychree (Jun 11, 2018)

I use T type blades in my ordinary Aloris tool holder all the time with no problems and no shims; Having said that, I think it would be a good idea to relieve the tool holder in the area of the projecting side of the T.  Another thought; ordinary parting blades are tapered top to bottom for clearance, but the holders such as the Aloris do not attempt to match that angle.


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## 9t8z28 (Jul 8, 2018)

Actually true Aloris parting tool holders do have a groove machined for the top of the T part of the blade.  Every copy I have seen (including mine) do not have the groove cut into them.  I did mill a groove in mine.  It helped a little on the smaller width blades but they still want to twist sometimes


benmychree said:


> I use T type blades in my ordinary Aloris tool holder all the time with no problems and no shims; Having said that, I think it would be a good idea to relieve the tool holder in the area of the projecting side of the T.  Another thought; ordinary parting blades are tapered top to bottom for clearance, but the holders such as the Aloris do not attempt to match that angle.


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## ddickey (Jul 8, 2018)

Some interesting parting blades.
https://www.sommatool.com/catalog/pdf/Somma_Catalog-Cut-Off.pdf


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## umahunter (Jul 9, 2018)

I've tried those what I've liked the best is an indexable parting block kit I got from shars one thing I've found works  really good for me I'm not sure if this is proper but if I'm parting something that's not right next to the chuck and it it has a hole I put my live center on there to stiffen it up to start the cut then toward the end remove it for the last lil bit it really helped stiffen things up you just have to be careful


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## NortonDommi (Jul 9, 2018)

Some HSS part off blades are tapered from top to bottom on one or both sides. One side is the most common. These ones can only be fitted one way and need to have the appropriate tool holder or be shimmed oat the bottom or they will skew first cut and break. A piece of broken blade inverted work in a straight face tool holder


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## WarrenP (Jul 9, 2018)

I bought a T shaped blade and used a feeler gauge to take up the difference in my tool holder. Still have to try it, but im sure it will work as it should.. Hopefully my lathe will too.


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## pdentrem (Jul 9, 2018)

Some parting blades have to fit a holder that has a angle cut top and bottom. Look at this photo. Note the top and bottom of the tool holder. It is cut like this to stop the parting tool from being pushed out of the holder. 
http://www.abmtools.com/product/parting-tool-holder-quick-clamp-parting-tool-holder/


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## 9t8z28 (Jul 9, 2018)

I have 3 of their parting blades in various thicknesses.  2 are T15 and 1 is HSS.  They are the best T-blades I have ever used.  I’ve never bought a Somma blade new.  I was lucky enough to find a bundle of them for $5 but I would purchase them new if I needed a particular size 


ddickey said:


> Some interesting parting blades.
> https://www.sommatool.com/catalog/pdf/Somma_Catalog-Cut-Off.pdf


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## 9t8z28 (Jul 9, 2018)

Nice find !   I like this style and it would be easy to make 


pdentrem said:


> Some parting blades have to fit a holder that has a angle cut top and bottom. Look at this photo. Note the top and bottom of the tool holder. It is cut like this to stop the parting tool from being pushed out of the holder.
> http://www.abmtools.com/product/parting-tool-holder-quick-clamp-parting-tool-holder/


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## Bob Korves (Jul 9, 2018)

9t8z28 said:


> 2 are T15 and 1 is HSS.


T15 is also HSS.  There are two basic types of HSS, one based on Molybdenum (for instance M2, M42, etc.) and the other based on Tungsten (T1, T-15, etc.)  (Also a third based on Cobalt, Stellite.)  Tungsten HSS has often been superseded by Moly HSS in more modern times for cost reasons in a changing metals market.  Simply stated, Molybdenum is cheaper than Tungsten today.  There are also some other subtle reasons why one type might be picked over the other for certain tasks, they are not identical in their properties.  I have a pretty good selection of different HSS tool bits of different alloys from different manufacturers, and it is interesting to see the differences in how they act in the cut under different conditions.
https://www.asminternational.org/do...yNow.pdf/b8f2e317-5089-44bc-a14d-af31f80e33a5
http://www.crucibleservice.com/eselector/prodbyapp/highspeed/highspeedapptitle.html


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## Larry42 (Jul 9, 2018)

There are also P type blades. I think the defining feature is that they are hollow ground on the sides.


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## ddickey (Jul 9, 2018)

What does hollow ground mean?


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## mikey (Jul 9, 2018)

P-type blades have a 5 degree side relief on both sides.


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## ddickey (Jul 9, 2018)

Oh okay. Do they also have the concave ground top?


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## mikey (Jul 10, 2018)

Most high quality blades don't. Chinese ones often do.


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## ddickey (Jul 10, 2018)

Really? My T -Type blades from Somma do.


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## mikey (Jul 10, 2018)

P-type blades usually have flat tops. Don't know about T-type.


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## 9t8z28 (Jul 10, 2018)

I agree with you.  I didnt go into the details about the material type because I didnt want to get to far off of the OP original post but good find and I guess I should have explained.    I have a T15 T-type blade thats 3/32” x 11/32” that I cut the bottom off to fit my 1/2” Aloris parting tool holder.  This is a monster of a blade and I’ve never had any chatter issues or springiness effecting the cut.  I have 2 unique grinds (leading edge reliefs) on each end of the blade for various things I do with it.  The second T15 T-type blade is 1/8” x 1/2”.  Same relief grind on the one side but none on the opposite end. The third is a M2 T-type blade also 1/8” x 1/2”.  I prefer the T15 HSS over the M2 HSS as IMO they are more stiff.  I’d also like to note that my blades must be discontinued.  They are flat on the top.  It appears as though Somma only offers the T-type blades with a concave ground top.  



Bob Korves said:


> T15 is also HSS.  There are two basic types of HSS, one based on Molybdenum (for instance M2, M42, etc.) and the other based on Tungsten (T1, T-15, etc.)  (Also a third based on Cobalt, Stellite.)  Tungsten HSS has often been superseded by Moly HSS in more modern times for cost reasons in a changing metals market.  Simply stated, Molybdenum is cheaper than Tungsten today.  There are also some other subtle reasons why one type might be picked over the other for certain tasks, they are not identical in their properties.  I have a pretty good selection of different HSS tool bits of different alloys from different manufacturers, and it is interesting to see the differences in how they act in the cut under different conditions.
> https:n//www.asminternational.org/documents/10192/22533690/06022G_Sample_BuyNow.pdf/b8f2e317-5089-44bc-a14d-af31f80e33a5
> http://www.crucibleservice.com/eselector/prodbyapp/highspeed/highspeedapptitle.html


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## SSage (Jul 10, 2018)

WarrenP said:


> Hi Everyone, I have what Im sure is an easy question for most of you. I installed a quicj change tool post on my G0752 lathe. With it came a cut off blade holder. It says I need to use a blade that is Parrellel top and bottom. Does that mean I can not use a T shaped blade in it or is that ok? Thanks for your time on this.



I guess you have the wedge type parting blade holder. The one I use is called a SHARS P3N "P" Type 3/32, make sure to get the right size. My BXA holder takes 11/16 blades you may need the 1/2" blades at 1/8"? I buy blades one at a time, so the "Discount Tool eBay Store" is my go to place for small purchases. Shars blades have been fine so far. The 3/32" blades hold up better for me on my 12x36.

I ended up switching mainly to carbide insert tooling a couple years ago, I use the MGM-200 size grooving tools with decent quality inserts for the application. I've been using the Korean Korloy 3030 MGM-200 for my steel parting operations and I have a couple other no-name Asian brands that I like too. I do a lot of grooving and I just part with the same tool. Easier that way. So far the Asian tooling has been cost effective with decent durability. I get far more parting operations from an insert tool before I need to sharpen a cut off blade. Its a time saver for me. The MGM-200 size works well enough I haven't tried other carbide sizes. The ones I use are cheap, about $9 to $14 for ten of them. I only have a slow 12x36 lathe, but I find carbide works fine for some things. Its very convenient.

The best thing I ever did to help with the parting cuts was adding a cool mist system, it beats oil and flood coolant hands down. I haven't used flood coolant in a long time. I run a cheap mister from bangood.com with Kool Mist 77, makes things much more pleasant and parts come off just warm to the touch. The air pressuer blows out the chips and the coolant lubricates and cools. I run 6 oz to a gallon. I put these on my Lathe and on the bench mill, they work great IMO for $14: https://www.banggood.com/Mist-Coola...e-Cooling-Sprayer-p-987371.html?rmmds=myorder


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## 9t8z28 (Jul 10, 2018)

I hate to jack the OP thread  but what else do you need to go with the coolmist from banggood ? Does this help directly up to the air compressor and no fluid pump is needed ?   I don’t really know much about any coolant system other than dipping the brush in oil, lol


SSage said:


> I guess you have the wedge type parting blade holder. The one I use is called a SHARS P3N "P" Type 3/32, make sure to get the right size. My BXA holder takes 11/16 blades you may need the 1/2" blades at 1/8"? I buy blades one at a time, so the "Discount Tool eBay Store" is my go to place for small purchases. Shars blades have been fine so far. The 3/32" blades hold up better for me on my 12x36.
> 
> I ended up switching mainly to carbide insert tooling a couple years ago, I use the MGM-200 size grooving tools with decent quality inserts for the application. I've been using the Korean Korloy 3030 MGM-200 for my steel parting operations and I have a couple other no-name Asian brands that I like too. I do a lot of grooving and I just part with the same tool. Easier that way. So far the Asian tooling has been cost effective with decent durability. I get far more parting operations from an insert tool before I need to sharpen a cut off blade. Its a time saver for me. The MGM-200 size works well enough I haven't tried other carbide sizes. The ones I use are cheap, about $9 to $14 for ten of them. I only have a slow 12x36 lathe, but I find carbide works fine for some things. Its very convenient.
> 
> The best thing I ever did to help with the parting cuts was adding a cool mist system, it beats oil and flood coolant hands down. I haven't used flood coolant in a long time. I run a cheap mister from bangood.com with Kool Mist 77, makes things much more pleasant and parts come off just warm to the touch. The air pressuer blows out the chips and the coolant lubricates and cools. I run 6 oz to a gallon. I put these on my Lathe and on the bench mill, they work great IMO for $14: https://www.banggood.com/Mist-Coola...e-Cooling-Sprayer-p-987371.html?rmmds=myorder


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## SSage (Jul 10, 2018)

9t8z28 said:


> I hate to jack the OP thread  but what else do you need to go with the coolmist from banggood ? Does this help directly up to the air compressor and no fluid pump is needed ?   I don’t really know much about any coolant system other than dipping the brush in oil, lol



The mister uses an 8 mm air line, thats 3/16" I.D. vinyl line I think. That line slips into the mister's connector and my other end has a hose barb fitting connected to a quick disconnect coupled to a little regulator which feeds from shop air. I use a dedicated regulator because my shop air stays at 80 psi and other people are using it too. You could run it directly to your compressor and use the regulator on it set at 20 psi or so. 

I got the small fittings and the clear vinyl hose at my local Ace Hardware cheap. The clear hose is really low cost and I ran about 10' off each machine overhead out of the way to my wall air outlet. The little air regulators at Harbor Freight work good, I have a few of them in different sizes. I use a small water bottle as a coolant reservoir, one at each machine. I like to refill often, say once a week or so to keep the coolant fresh and clear. A 12 oz bottle works fine. The mister comes with the suction line set up. There are two valves on the mister, one for air flow and one on the suction side. I run enough air to blow chips away and enough coolant for the job. The adjustments work good, you want the model with the two valves. I've had mine for a couple years now, my oldest one is still working like new. 

I JB welded a 20 lbs magnet on one, it sticks to the side of my PM-727M very well and can be moved easily.


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## Bob Korves (Jul 10, 2018)

SSage said:


> The mister uses an 8 mm air line, thats 3/16" I.D. vinyl line I think.


8 mm (.315") is equivalent to 5/16" (.3125").  That is the correct size for the vinyl tubing needed for the air connection.  The connections are quick, foolproof, and easy to install and remove.

I use Kool Mist per the instructions, 4 ounces per gallon, I actually use 2 liter soda bottles and use 2 ounces for an almost full bottle (2 quarts.)  That easily lasts a full day's work, with overtime.  I have not tried richer mixtures, because it works great at the recommended lower concentration.  I also suppose a richer mixture would leave a sticky residue.   Those Chinese mister units work just fine, the one I have cost around $11.50, including freight!  It works so well, and is so cheap, that I am considering getting a couple more, one for my lathe and one for my mill.  The one I bought has become pretty much dedicated to the surface grinder, where is makes a night and day difference in the quality of the work that comes off the machine and in the quality of the air I breathe while grinding, even with a dust mask on.  At the price they sell the misters for it is affordable to buy a separate one for each machine.  The flood coolant on my 13x40 lathe has never been used, and I doubt it ever will be while I own it...


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## SSage (Jul 10, 2018)

Depends on how the vinyl hose is measured. Locally, my favorite store measures the I.D. size and the sell US made hose, so its in inches to start with. Those 8mm push in connectors work perfectly with *3/16" I.D. *size clear vinyl hose. Lowes had an 8mm O.D. vinyl hose in a big roll, but I didn't test fit it. I just bought mine by the foot at my local lumber yard / Ace Hardware, it was about $0.16 a foot there.

6 ounces per gallon has worked for me, I tried 4 ounces at first and my larger drill bits squeaked more. I use the coolant for drilling and boring large holes on my mill. Bits last longer than when I used dark cutting oil. The biggest improvement with drilling was with 3/8" bits and larger. I've doubled the useful life of my expensive 1" bits.


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## 9t8z28 (Jul 10, 2018)

SSage and Bob.   Both of you gave me lots of good information.   This seems like a really great cheap solution


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