Parting off Boxford

[Niels Abildgaard]

Have a Nokia Lumia 1020 phone and link to Youtube so here comes a parting off picture and a video:


http://imgur.com/GsstOBa



[ame]https://www.youtube.com/watch?v=Sdmqk5oJ7OE&feature=youtu.be[/ame]

http://imgur.com/GsstOBa

 

[tornitore45]

Did you make the whole block and insert holders?

 

[Niels Abildgaard]

Hello Mauro

The block is just a piece of mild steel trued and cleaned in the lathe.
The two blades were standard Iscar items and was glued onto the home made block in the rigth possition,After curing, the block was drilled and tapped very carefully through the three countersunk holes in the Iscar blades.
I cannot remember how the blades were fixed in their rigth place during glueing.
But they are as I very often use this tool for general turning and it leaves no centerpips when facing.

There is some pictures here:
http://www.homemodelenginemachinist.com/showthread.php?t=10176&page=2

If making another, I will not use 1.4 and 3 mm inserts but rather 2 and either 3 or 4.
If a 2 mm chatters it is clearly a hacksaw job.
Go in with 2 mm until scared stiff
Turn tool and widden with the 3 or 4 and repeat as nessecary

 

[Niels Abildgaard]

Holy Moses

Mauro has just improved the breed and given Iscar some future money.
I do not trust the TGAD 1.4mm blade on the two blade block.
It is long and very narrov.
The beauty of the system mentioned first in the thread above is that 2,3,4 and 5 mm wide inserts all have the same seat geometry.That means that a 2 mm insert sit very firmly on a nominal 4 mm blade (3,5 mm thick I think).It will not work of course but if the blade is narrowed down to say 1.6 mm for seven or 8 mm You can cut a 7 mm deep trench 2mm wide with the 2 mm insert sitting on a 3.5 mm thick.blade.
Sideward bending stiffness of a 3.5mm blade is 10 times more than one of 1.6.
After change of garment if nessecary You turn the block round and widden the trench until chattering and then repeat
Thank You Mauro.It is nice to think and invent

 

[tornitore45]

Niels, I can not take the credit for anything, my post was just a question.

I use the same holder but in the conventional mode. Use only the 2mm (actually 2.2mm) and parted 2" diameter without problems. Of course parting is always a teeth clenching operation but these insert work much easier that the HSS T blades or self grinded tools.

I use the Right biased insert to avoid the pip on the falling part. Being on dead center is absolutely necessary, if low the last bit will walk (roll) over and ruin the insert.

 

[Niels Abildgaard]

Enjoy phantasy below of pure toolnography until getting price of 3 TGAD 4N blades.
https://www.cmt-tools.com/c-12-holders.aspx?type=searchterm&value=tgad
But nice to think of.
Probably an overkill.

 

[Niels Abildgaard]

Cheap version made from a TGFH 28MB-4 blade and with TAG 2 and 4 inserts

https://www.cmt-tools.com/p-508585-tgfh-28mb-4-blade.aspx

 

[Niels Abildgaard]

My lathe is a Southbend copy named Boxford that I have put on a block of rock.
Granite in fact and very much better than original.
If I want to part a subject 125mm/5 inch I use the system shown here:

http://imgur.com/jCgll4k

I use the 2 mm insert first for as deep as I dare (Have never dared more than 7 to 8 mm) and then use the 4 mm insert to open the gap.Change again for 2 mm etc until parted or wiser.
Sometimes I use a 3 mm between the 2 and 4.

System is made of TGFH 32-4 blades where one end has been narrowed to suit either 2 or 3 mm inserts that have same seating geometry as 4 mm inserts.

Between 50 and 70 mm dia it would be sufficient to use a system made from TGFH 26-3 blades if 1.4 mm inserts fitted the 3 mm seat geometry.
They do not .

So please write Your Iscar representative and demand that:
Either change the TAG 1.4 inserts or make (for us amateurs with weak lathes) special TGFH 26- (3 /1.4) blades.
The narrowing zone need only be 8 mm long.
Insert shall be midblade and in same relative cutting position as the 3 mm insert at the other end.
If more than three write and we succed,we have not lived in vain.
Iscar is almost there allready.

http://imgur.com/GNw9zCl

Will be a smal step for Iscar ,but an enormeous help for us!

 

[Niels Abildgaard]

When Iscar makes sensible blades, an 80 mm parting off looks like the strip here