Tormach Flycutter with SEHT Insert

[Anonymous]

Posted by Paul Fallert on 21/04/2017 22:07:19:

Off topic: WHAT DOES HE MEAN BY “TOXICATED MYSELF WITH ALUMINIUM” ?

There is a theory that aluminium has a role in dementia, although the evidence is conflicting, so the link is far from proven.

In this case I'd translate the comment as ignore the dross dressed up as knowledge that is on Utube.

Andrew

[Paul FallertParticipant @paulfallert28101]

For those unable to view the ScPatent dovetail video cutting 42CrMo4 steel with a TCMT inserted shop-made tool at 2,900 rpm (est. 64mm dia).

As Andrew pointed out in his comments, finish in certain steel workpieces can dramatically change when surface cutting speed increases beyond a certain point. Here the sfm is est'd to be 1,900 sfm. Others have pointed out that tool system vibration can smooth out at higher rotational speeds. Unfortunately, HSS tools are usually ruined when guideline maximum surface speeds are exceeded.

My take-aways

1) Pursue carbide tooling at higher rotational speeds, since HSS cannot operate at these surface speeds.

2) Test a single flute inserted end mill (Andrew pointed to real "issues" with fly cutters), and those issues would be worse at these rotational speeds, e.g. bits of the fly cutter and swarf flying about and toward the operator.

3) No or air only coolant stream (avoid carbide cracking if coolant is intermittent) and a coolant storm at higher speeds would be unacceptable in a home workshop.

4) Focus on widely available positive rake inserts such as SEHT, TPxx, CCMT/CCMG.

5) Construct a thick LEXAN safety shield to protect the operator from flying swarf and (tool)bits.

Paul

[MuzzerParticipant @muzzer]

Also, some cutters have "wiper" areas to produce a polished finish by avoiding the scalloped surface (ridges) caused by normal inserts.

The cutting forces actually reduce at sufficiently high cutting speeds (that carbide can achieve). This is one of the concepts referred to as "high speed machining", although that phrase seems to have been applied to a variety of techniques including adaptive toolpaths.

But many modern inserts simply require lower cutting forces due to their high rake angles. As well as the improved cutting due to the rake angle, this is handy for less rigid machines and tools including fly cutters. As I said earlier, it's a pity that many of the rather agricultural indexable milling cutters offered to hobbyists use zero or negative rake geometries. I feel these are particularly unsuited to our needs.

Murray

[John ReeseParticipant @johnreese12848]

For those who want to make a tool holder for their existing flycutter, Banggood had the SEHT inserts. They offer both those intended for steel and the polished inserts intended for aluminum. I have used them in my face mill. The quality is decent, price low.

[Author]

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