how do I grind a parting tool

[j45on]

Hi guys I have just got a cheep qctp for my chester comet/sieg c4 and it came with a parting tool and holder
but the tool appears to have no cutting edge ? are there proper angles to grind these things to ?

The tool post



the parting tool

[lordedmond]

Just grind the top flat leave the end as is

[andyf]

I may be wrong, but think the top is supposed to remain as it is, and any sharpening done by grinding entire the angled front end back a little, thus preserving the angle it makes with the top.

Andy

[Mike K]

I have one of those blades.  I've only ever ground the front face, right against the the grinder wheel.

[dsquire]

Just grind the top flat leave the end as is

If you grind from the top surface then you will lower the cutting edge below center and will have problems when parting off. Only grind on the front face. 

Cheers 

Don

 

[lordedmond]

Just grind the top flat leave the end as is

If you grind from the top surface then you will lower the cutting edge below center and will have problems when parting off. Only grind on the front face. 

Cheers 

Don

 

what's that adjusting screw for on top of the holder , I think its for adjusting the tool hight 

I still say grind the top flat, the bevel on the top is for the blade to seat in the dovetail in the holder its like that so you can use it both ways ( reverse front to back  )

Stuart

[Bernd]

what's that adjusting screw for on top of the holder , I think its for adjusting the tool hight 

First of all that looks like custom tooling and nothing like what can be bought on the market. It is still necssary to locate the tool on center though.

I still say grind the top flat, the bevel on the top is for the blade to seat in the dovetail in the holder its like that so you can use it both ways ( reverse front to back  )

Stuart

Conventional wisdom has it that the tool get's sharpened on the end and not the top. I've always been taught to grind the end and that comes from 30+ years in the tool maching trade. Also found in many maching books.

Bernd

[lordedmond]

what's that adjusting screw for on top of the holder , I think its for adjusting the tool hight 

First of all that looks like custom tooling and nothing like what can be bought on the market. It is still necssary to locate the tool on center though.

I still say grind the top flat, the bevel on the top is for the blade to seat in the dovetail in the holder its like that so you can use it both ways ( reverse front to back  )

Stuart

 

Conventional wisdom has it that the tool get's sharpened on the end and not the top. I've always been taught to grind the end and that comes from 30+ years in the tool maching trade. Also found in many maching books.

Bernd

The tool post in question is a Myford Dickson QTP that is the very one I use they are sold as a set that includes the aforementioned plating blade holder

the top of the blade is ground to fit the dovetails in the holder, if left would throw the chip out to the sides thus jamming the blade , if you want to have a vee in the top it should be the other way  as a letter V .

Yes I agree normally yo would grind on the end but as bought that blade will not work very well

I use a rear TP with an iscar insert parting tool blade works very well , also I do use the normal HSS blade for brass flat topped

I would suggest as a trial the OP try it as is sharpened on the front and the grind a small flat on the top say 1/16 long so not to waste the blade and repot back as to which one works best

[Ned Ludd]

Rather than grind the top, if you have a carbide end mill, mill the top. By milling you are more likely to machine the surface you want to be flat and square. Works for me!
Ned
PS yes you can mill HSS.

[j45on]

Thanks for all the tips guys
I think I will have to grind the front face as it is quite rough but should it be square or at a slight angle ?
Also the top I was confused about
my other parting tool which is basically a smaller version has a flat top then I found this
http://www.the-alchemist.com/partingtool.html which was all I could find on grinding parting tools which confused me even more 

First of all that looks like custom tooling and nothing like what can be bought on the market. It is still necssary to locate the tool on center though.

not sure what you mean by custom this is the set it came from which is made by soba
http://www.axminster.co.uk/axminster-quick-change-lathe-tooling-prod21295/
I only paid £70 for it though as it was a customer return so I took a gamble on being able to make it fit my lathe

[Davo J]

I think this link will help you out with angles etc.
http://www.cutterod.com/cutter_zone/General/How_To_Grind_Lathe_Tools.pdf

I have also had a Dickson style tool post like yours only mine is a little larger for my 12 x 36 lathe.
https://www.machineryhouse.com.au/Products?stockCode=L295
I bought mine from over here in Aus and they have them up to a body size of 175mm square x 120mm height
https://www.machineryhouse.com.au/Products?stockCode=L298

I have never tried them but I see a lot of people in the US argue over the piston and the wedge style Aloris tool post. Not sure if there any better but in the 6 years I have had my Dickson style, I could not be more happier with it, they are a good easy to clean tool post.

Dave

[Bernd]

Lordedmond,

Ah yes I now see that inverted "V" section and understan why you need to grind the top. Never seen a tool like that or a holder like that. I've always had the striaght top cut off tools.

That tool holder looked custom made, again since I never knew one like that was/is available for cutoff tool's.

Looks like I just got educated about some tooling. 

Bernd

[fatal-exception]

The angle on the end looks OK, but definitely you will have to grind the top to get rid of the chamfer. I'm not sure why, but every parting tool I've ever bought here is the same, they all have that chamfer on the top. Maybe it's to let you know that it isn't ready for cutting, that you will have to grind it parallel to the axis of cutting?

Paul

[sbwhart]

Hi Guys

I've one of those Dickinson tool posts and parting tools, I've found it very good as some of you have said the chamfer on the top is for gripping the top needs grinding.

Here's a collection of my parting tools has you can see they have done some work, I find the two HSS tools on the left good for most work but sometimes I run up against a bit of tough steel then I use the tip tool.

As you can see all three have a hooked top and front clearance.



Just one safety tip the back of the blade sticks out and is as sharp as hell I wrap the end with gaffer/jumbo tape to avoid bad cuts.

Hope this helps

Stew

[SKIPRAT]

Hi All

I will agreee with Stew i usually grind a top rake of about 7 degrees with front clearance and mine look just like Stew's as a tool on a small lathe cannot cut very well without any top rake there is not enough horsepower available available to cut metal without a positive top rake as the tool uses a shear action to cut working very much like a chisel, larger production machines with lots of horsepower can use tools with zero or negative top rake.

[sbwhart]

Paul

I agree with your comment about horsepower and cutting tools, if you look closely at the cutting edge of tipped tools they are very blunt, this isn't an issue with a machine with plenty of power, they just knock the stuff off, as an old work friend (long gone) use to say "if you put a clog nail in it will cut" small home machine just haven't got that power thats why I think you can struggle sometimes with tips, I've got a good cheap supply of tips but in my home shop with its small cheap Chines machinery, I find myself using HSS more and more, with a good sharp HSS tool I find it easier to hit and keep size. With a tip I think what happens is the inherent flex in the machine holds the tool off, you put a bit more cut on and bingo the tool bites you get that cut plus a bit from the previous cut and your undersize, with a good sharp HSS you don't get that effect so much.

Any way thats just my take on it.

Stew

[Davo J]

I couldn't agree more with what Stew said above. HSS will work when insert tooling wont on smaller low horse power lathes.
I only turn to insert tooling on hard stuff that HSS wont touch, even though I have a 2hp 12x36.
HSS is also a lot cheaper and can be ground to any shape in minutes, instead of having to order a specie insert which could take weeks to come in and cost an arm and a leg.


Dave

[jim]

the top of the blade sould be ground. this will give the blade clearance on the sides (the blade is thicker at the top).

[Boucher]

You can also grind a round chipbreaker with a dremel tool. If done properly it will supply the positive rake to roll up small tight coils that eject nicely. A good old fashioned cutting oil helps immensley when parting off.

Take a look here:
http://www.cnccookbook.com/MTLathePartingCutoff.htm