Cheap Inserts with Full-Length Cutting Edge

[danlb]

Cheap is not especially bad in this case. It does not make sense to make a tool that uses $30 inserts to avoid buying a $10 dovetail cutter. If you are only willing to pay $5 per insert, then that becomes a criteria for the search.

I've seen a huge difference in prices between seemingly identical inserts . Imagine paying $154 for a single TNG334 insert. ON SALE! Sure, it's diamond coated, but I will never buy one at that price.

I've used a lot of "cheap" inserts as well as a few expensive ones over the last 15 years. For my use, the cheap ones have worked perfectly well on a benchtop lathe. By cheap, I generally mean a few bucks per insert.

[754]

When you cut .25 or more for depth of cut in 4340... I would like to see how the cheap insert holds up...
Alot of heat going into the insert, shim and holder under heavy turning..

But when you are running them at 10 percent of capability...or under..it has an easy life..

[JoeLee]

Hey guys,

I've been mucking around with making insert holders for cheap ebay inserts, and so far it has worked quite well. I made a boring bar, a threading tool and a fly cutter, also tried out a indexable mill insert for a lathe tool and it stinks for chip breaking. Anyway, I want to make a dovetail cutter, countersink and deburring tools as well, but these inserts I have do not have cutting edges running the full length of the triangle.

They are TCMT110204 (TCMT 731) and are only a dollar CAD apiece, 33c per corner.

http://www.ebay.ca/itm/10Pc-TCMT1102...AAAOSw3utY6Hmu

As you can see, the chipbreaker edge is only near the corners and not continuous.



Maybe they did this because these inserts are too small to handle the forces they'd be under for a full length cut?

Has anyone found any cheap triangle inserts from china which are full-length cutting? Any other details on useful geometries that are super cheap and available from overseas?

Those inserts are designed to cut off the points and not the full side.

JL..............

[danlb]

When you cut .25 or more for depth of cut in 4340... I would like to see how the cheap insert holds up...
Alot of heat going into the insert, shim and holder under heavy turning..

But when you are running them at 10 ercent of capability...or under..it has an easy life..

While that's quite true, that particular small triangular insert should have a max DOC of about .050. Specs here

I have similar "cheap inserts" from Carbide depot which were purchased for $3.37 each. They last for months of weekend tinkering with .025 to .050 DOC in 6061-T6 and 4041.

So yeah, they work fine at 50% of the max DOC.

[754]

If it says .050 it must be finishing insert. Not sure of the IC.
I used to plow out 100 thou DOC or more quite often in steel with a 3/8 IC on a small boring bar.... Faster than. Changing drill (usually over 1.5 bore) if I had one.
Yeah it get hot.
I have bought cheap inserts and tried them, but I dont thing I cut that hard to test them.

BTW anyone on here had any luck threaded on welded seam tubing with cheap inserts ?

[danlb]

If it says .050 it must be finishing insert. Not sure of the IC.
I used to plow out 100 thou DOC or more quite often in steel with a 3/8 IC on a small boring bar.... Faster than. Changing drill (usually over 1.5 bore) if I had one.

To give you a point of reference, I used a cheap CCMT boring bar, 1/4 IC and bored a 2 inch diameter .120 wide by .022 IPR. I pushed the feed a bit faster and put enough stress on my little 7x12 to slow it down a little. The insert held up fine.

[BCRider]

A thought about a dovetail cut with these. To get the proper 60° cut the lower edge would need to be flat to the plane of rotation. I'm not sure that would be optimum. Would not "proper" dovetail cutters use a 58° or so angle to avoid dragging the lower cutting edge on the material? Looking online it LOOKS like some cutters use simple 60° cutters while some others use diamond or special inserts. Is dragging the lower edge not that big a deal?

[MattiJ]

A thought about a dovetail cut with these. To get the proper 60° cut the lower edge would need to be flat to the plane of rotation. I'm not sure that would be optimum. Would not "proper" dovetail cutters use a 58° or so angle to avoid dragging the lower cutting edge on the material? Looking online it LOOKS like some cutters use simple 60° cutters while some others use diamond or special inserts. Is dragging the lower edge not that big a deal?

I was going to say that if you tilt the insert mounting face slightly you can alter the 60° angle BUT that works only to effectively increase the angle

[754]

I did a few lathe kits for a buddy , milling vice, cross slide.. Stuff.. Roughed most of it with a flycutter in about. 3 steps, then took off the last part with a multi tooth HSS dovetail cutter.
Had to make sure cutter did all the dovetails..its still good.

[MattiJ]

A thought about a dovetail cut with these. To get the proper 60° cut the lower edge would need to be flat to the plane of rotation. I'm not sure that would be optimum. Would not "proper" dovetail cutters use a 58° or so angle to avoid dragging the lower cutting edge on the material? Looking online it LOOKS like some cutters use simple 60° cutters while some others use diamond or special inserts. Is dragging the lower edge not that big a deal?

Its also non-optimal in a way that the insert mounting screw is handling big part of the cutting forces.

[Yondering]

Has anyone found any cheap triangle inserts from china which are full-length cutting? Any other details on useful geometries that are super cheap and available from overseas?

TT style inserts can cut along the full length of the sides. Victor Machine is a good source for them. They might even fit in the holders you made; the shape and holding style is the same.

[lakeside53]

A thought about a dovetail cut with these. To get the proper 60° cut the lower edge would need to be flat to the plane of rotation. I'm not sure that would be optimum. Would not "proper" dovetail cutters use a 58° or so angle to avoid dragging the lower cutting edge on the material? Looking online it LOOKS like some cutters use simple 60° cutters while some others use diamond or special inserts. Is dragging the lower edge not that big a deal?

My Dorian cutter (3 "simple" triangle inserts) has a 2-3 degree slope at the bottom, and about a 10-15 degree slope back, then twisted slightly to get the 60 degree included angle. A recess near the tip of the insert locks into a "pin bump" in the mount, with most of the support at the back edge.

Similar to this one : http://www.ebay.com/itm/73310165244-...wAAOSwjwlXBJIr

Inserts run about $10-12 each

From their data -
60 degree Indexable Dovetail Milling Cutter
15 degree Cutting Rake Angle
10 degree Axial Rake Angle
14 degree Radial Rake Angle

[BCRider]

Angling the insert like that would certainly do the trick. Thanks for that.