More parting off questions?

[torker]

For the HSS crowd! I also got a few new HSS blades that I need to build holders for now.
These new blades all came with a wicked bevel ground across the top, for the entire length.
I'm thinking the bevel would be good for a top clamp to hold onto but surely...you don't use this bevel when parting off?
All the other HSS blades I've had, have the top flat. I've tried grinding a bevel but always found that it'd "steer" the cutter and usually bugger it or the cut up.
These blades also have both sides beveled(a pretty steep bevel)...looks good for the clearance but will make a bit more work to make a block that they'll sit straight in.
Thanks!
Russ

[John Stevenson]

Let me go find that damn camera, knew I should have bought a Cannon, Nikon, Sony, Hassleblad - [ delete as required ] instead of this cheap one made by Alzheimer's...........................

.

[Norman Atkinson]

Who'is this Stevenson Chap?
Russ, some short time ago I posted a fairly lengthy whatsit on parting off.
Now, with this Megala-mania thing, I cannot post the drawings of either George Thomas in Model Engineer or his excellent Model Engineers Workshop Manual or a similar tool in Model Engineers Workshop. Of course, I have one on one of my Myfords but it costs nothing to go to HemingwayKits site and see one.

You will see it is on the rear of the saddle working upside down with the lathe running normally. It points down at 7 degrees and has a front clearance of 7 degrees. OK? Now the top has a vee cut in it of 140 degrees right along the 1" it protrudes. Why put a vee in? In effect, the peeled swarf thins into a narrower roll and being upside down- falls down.

Frankly, I heard that you had a T&C thingy and this is just the horses do da's to fancy grinding.

Oh, I do wish I had a Box Brownie , Kodak doofer- hows your father?
Or a memory to understand how to send things in a bucket

Norm

[torker]

Norm...you are right! I'm taking a bit of a break from work on the T+C grinder but I've already used it to grind chipbreakers in a couple of wee HSS boring bar bits. Just got a diamond dresser for the machine also. It sure is the cats meow for dressing the wheel.
I'm really going to have to add on some type of vise to this grinder to hold tools such as parting blades etc.. It would be nice to grind a top groove the length of the blade....wouldn't be that hard with the right setup.

[TGTool]

Russ,

As Norm mentioned, George Thomas did some experimenting and wrote several paragraphs in his book on the results of different geometries. I believe the last iteration he mentioned had the V-groove in the top edge, and a convex V on the front edge. That is, instead of being flat on the cutting end, it had a shallow point(another 140 degrees). One beneficial effect of this is to make the geometry of the two outer corners a little more substantial so they don't break down as quickly.

jm

[Norman Atkinson]

Thanks JM. I was struggling to give Russ the salient details without having to get into the realms of the geniuses who can use Photo*ucket.
You are quite right- of course. The 7 degree angle saves 'hooking' the top of the parting tool.All that needs to be done is regrind the front and move it up a fraction.

Russ, leaving JM's valued comments aside, you are now realising that this T&C lark gets pretty addictive. You are going into four facet grinding?--- Oh, No! Not that!

Good Night, God Bless

Norm

[torker]

Thanks guys! Hmmm...interesting stuff. Geez...lots of fooling around to get the 2 1/2 deg side cut in the new block. Finally going to use my new Groz "Tilt-n-Turn table for something.
The more I think about it the more I see my wizzbang T+C grinder being used for this kind of thing also. If I had a way of holding it I could grind the undercut grooves in the slots to hold the blades. Wish I could find the neutral switch for my brain...get far too many corny ideas
Russ

[Norman Atkinson]

You Hairy git
Your E-Mail don't like me.
OK?

N

[DICKEYBIRD]

Hi Russ,

I got a couple of those tapered cut-off blades with the bevel on top in a package deal somewhere but I never tried them until recently. I got an AXA QCTP (Chinese clone) for Christmas and decided to try one. I scratched my head for a while but never found the gumption needed to make a special toolholder so I just stacked the 2 back to back with the tapers reversed and voila! The pair clamped down in a regular toolholder just fine.

I let the outside blade extend out past the extra one just far enough to make the cut and it works just fine. Crude, buts works for me. By the way, they cut great!

They allow me to part off steel confidently for the 1st time since I got my lathe. My previous attempts usually had me ducking for cover with a snapped off chunk of HSS zinging past my head sounding like a bullet ricochet from a cowboy movie.

[Norman Atkinson]

****eybird,
What makes you think that you have an exclusive to shrapnel flying about? This is why I keep writing to try to avoid someone being injured apart from being the English Admiral Lord Nelson.
The French Fleet was sighted 200 years ago. Horatio was in his cabin and his second in command announced " Horatio, the French Fleet has been sighted"
" OK, tell my steward to lay out my red jacket so the blood wont show" " Horatio, there are 33 battle ships and 2640 guns" " OK, tell the steward to put out my brown trousers"
Parting shots are not new!

Norm