Thread: problems with cutting off

Supply more information for an educated guess as to what might need to be looked at to correct the problem.

This is a pic of the horrible thing ...................

For my 2 cents worth. Is the carriage locked to the bed? Is there any movement in the cross slide, coumpound angle adjustment or compound slide? Parting off requires more rigidity than almost any other process on the lathe. I am used to a rotating tool holder as shown below.

Attachment 179690

This is much more rigid. I have never used a lantern style toolpost, and I would have to say I think yours looks quite flimsy compared to mine. When you add the overhang this would limit this setup. Can you get the tool holder further back into the post, back to where the lump under the front is touching. The next thing to consider is whether you have to part off. Can you cut it some other way and then face off?

I have yet to do a proper part off myself. I have a part off tool holder from a cheap set of 9 carbide tipped toolholders but have not had much success with it. The tip just breaks. I have bought a HSS part off blade and need to make a holder for it.

Dean

Thanks for the reply Dean

Yes, I do resort to holding the work piece in a vice and cut it with a hacksaw , then face it off in the lathe ..but it's tedious as you can imagine .

I have a 1/16" X 4" long cut of blade, I intend to make a solid holder for it with a high degree of rigidity ... with as little overhang as I can get

That pic is just a mock up .

At the TAFE they use a larger version of my crap holder ... but they have larger tool posts , more rigid .

Mike

What Dia are you trying to part?
What speed?
Is the tool dead square the the spindle?
Is it at or below center height?
Is the tip square?
The grinding on the tip looks a little strange.

Stuart

You have a gooseneck type holder, which I think is a good thing. But is it just an illusion, or is the gap closed up? For it to work, it needs to be able to flex at the top of the groove. If it's clogged up or anything, it becomes like a solid holder, and doesn't have the ability to ride out a seizure.
By the way, I found this type of holder great for slotting in my Douglas shaper, which was giving trouble before I tried the gooseneck type.

Jordan

Also consider your chuck. Most of my parting problems went away when I stopped using my bellmouthed 3 jaw chuck. You say the work comes out of the chuck which sounds like it's not holding well.

I have seen guys put a machinist jack under the front of the parting tool which takes makes it more rigid.
You could make up one easy enough to suit, they are only a bold threaded into a piece of solid.
Keeping it cool while parting will help a lot to, because as you parting the material will heat up close in in the tool.

Dave

As asked previously you need to be more comprehensive in the details of your procedure for people to be able to have realistic guessess.

hi mike lots of people don't like parting of. its often the last part of a job and you can get nervous
. i think slow speeds,. good coolant. having the job as close to the chuck as possible and supporting the work with a tail stock help as well. a well ground tool slightly pointed .... helps as well. safety glasses are a must..lately my favourite parting tool is a.rs braised tip carbide toll. i have the 40 and 30 grades. spinning between 300 and 500 rpm.

Originally Posted by Dave J

I have seen guys put a machinist jack under the front of the parting tool which takes makes it more rigid.
You could make up one easy enough to suit, they are only a bold threaded into a piece of solid.
Keeping it cool while parting will help a lot to, because as you parting the material will heat up close in in the tool.

Dave

Dave,

This works OK with a rigid type toolholder.

If it is a gooseneck type holder putting a jack under the front of the holder stops the gooseneck from flexing and being effective. I have a similar holder (i.e.gooseneck). Prior to getting this I used to have trouble parting off on the old, well used 9" Brackenbury and Austin lathe. After getting the gooseneck holder all the parting problems disappeared. My toolholder clamping system (Myford type clamp) is much more rigid than a lantern tool post as shown in morrisman's photo though.

Frank.

Originally Posted by azzrock

supporting the work with a tail stock help as well.

Do you use tail stock for support all the way through?
I've been told this is a bad idea as the part can't fall off, but I haven't tried it.

Stuart

Can be a bad thing depending on the size of the job and the type of material being parted,if caution is not used.
End result could be damaged tooling,damaged job or damaged opperator.

[

QUOTE=Stustoys;1364560]Do you use tail stock for support all the way through?
I've been told this is a bad idea as the part can't fall off, but I haven't tried it.

Stuart[/QUOTE]


im not shore if you should keep the pressure on with the tail stock all the way. I manly cut steel. and I haven't had any problems. i find aluminium a bit more tricky. worse comes to worse you can increase the width of the slot and part of in stages. i.e. take a cut of 5 mm and then next to that one another cut. the slot is thicker it takes longer but seems to work