What's wrong with my threading technique?

[Cenedd]

The previous owner appears to have been really fond of triangle inserts......I seem to have better results from diamonds, both 80 degree and the smaller ones, 15 degrees?

You'll probably want to have a look at this link (or something similar: http://www.carbidedepot.com/formulas-insert-d.htm

Triangles are probably TCMT. 80° diamonds are going to be CCMT and the smaller ones either DCMT or VCMT.
As far as I'm aware - and someone please correct me if I'm wrong, this is just what I've put together from web-trawling - the shape of the insert doesn't make a difference to the finish, it's just a trade-off between being able to get into tighter spaces (pointy diamond) vs having a stronger edge (square). Some shapes give you more cutting edges per insert too.
There are different grades of carbide for different metals/situations. I suspect this isn't going to be particularly important unless you're pushing them to the limit - like a commercial situation where every second is money.
There are different edge geometries for different metals. You'll find that a CCGT is usually a sharper insert for aluminium - although you can take lighter cuts in steel with them too for a better finish.
You can also get different nose radii (last number in code) which is supposed to change the finish depending on the depth of cut. Not sure I can help with which way that trade-off goes though.

[txfireguy2003]

You'll probably want to have a look at this link (or something similar: http://www.carbidedepot.com/formulas-insert-d.htm

Triangles are probably TCMT. 80° diamonds are going to be CCMT and the smaller ones either DCMT or VCMT.
As far as I'm aware - and someone please correct me if I'm wrong, this is just what I've put together from web-trawling - the shape of the insert doesn't make a difference to the finish, it's just a trade-off between being able to get into tighter spaces (pointy diamond) vs having a stronger edge (square). Some shapes give you more cutting edges per insert too.
There are different grades of carbide for different metals/situations. I suspect this isn't going to be particularly important unless you're pushing them to the limit - like a commercial situation where every second is money.
There are different edge geometries for different metals. You'll find that a CCGT is usually a sharper insert for aluminium - although you can take lighter cuts in steel with them too for a better finish.
You can also get different nose radii (last number in code) which is supposed to change the finish depending on the depth of cut. Not sure I can help with which way that trade-off goes though.

Yeah, in slowly picking up on the codes, just wish my inserts were labeled on three insert so I could identify then once out of the box. I've got several boxes of inserts with a mixed set of different inserts in them. When I find one that I like, I have to try and figure out what it is so I can reorder. That's what I like about the Shar's holders, they are labeled right on the side which inserts they take, but there's still a ton of options in each shape and size

Sent from my SAMSUNG-SM-G891A using Tapatalk

[Cenedd]

If it takes that shape and size of insert - for example a CCMT 06, it'll also take a CCGT 09 (for aluminium) or a grade for hard metals like stainless or a CCMT. It'll also take different nose radii such as CCMT 06 02 04 or CCMT 06 02 08 . As long as it's Cxxx 06 it should fit - although, that said, the 2nd set of numbers are thickness so there probably are some that don't fit, you're just less likely to find them commonly for sale.
The aluminium inserts are worth getting if you're machining aluminium. As it's softer, it can take a sharper edge without it breaking so easily. Also seem to work well on hard wood too.
You'll also find tool holders that take the same insert but at different angles. If you've got a QCTP it's quick and easy to change tool so that you can chamfer a corner at a consistent angle rather than swing the toolpost round 'a bit'. I've got one that takes a square insert point forwards so that I get a 45° degree chamfer on either side. Also
have an MGEH parting and grooving tool that's great. 2mm groove, parting and it seems to give the best finish when doing light cuts too.

[J Tiers]

yeah, can also be your enemy. There's no vetting of what gets posted and so many expand 15 seconds of content into 10 minutes of blabber. imo, one would be better off with a used high school senior or college machining text book that walk though it step by step. imo books are faster and vs the wild west, there's some quality control

+100

I have seen the most utter BS presented on youtube, by people who clearly have less than zero clue. And in many cases, it probably would look credible to a person who did not know any better. That's not to mention the long time it takes to get anywhere... videos really suck unless they are focused exactly on a "how to do this specific thing".

On the other hand, you will not get any BS out of the general run of shop books. Any of the Audel's books, shop class textbooks, those are usually very reliable, and apply to the equipment you have, in general, as they are mostly pre-CNC and often have sections covering shapers, etc.

With a book, you can flip back and re-read, you can have it with you as you work, etc.

When I got started in this hobby (which morphed into real work as the "model shop" for more than one employer), I made it a rule that I would only buy a machine if I had done my study homework on it, if I knew how it worked, what the various functions were, where they should be, what they do, etc.

That has served me well, allowing me to avoid some dogs, and use what I bought without too many surprises or missteps. I recommend it.

The exception is welding. I took an actual class for that, and am glad I did. I am sure you can teach yourself to weld, but it goes easier and you get to use more methods, when you take a class.

[danlb]

I find that the "technical resource" pages on Carbide depot are quite informative. For instance, http://www.carbidedepot.com/formulas-insert-shape.htm has a chart that shows which inserts are most appropriate in 12 different areas. Want to use the best for deep, fast stock removal? They show 3 different inserts. Want to do intermittent cuts? They show two shapes that are recommended, 3 that are OK and two styles that will break fast.

It's worth noting that the triangular insert is rated as suitable for more things than just about any other shape. Used in a suitable holder you can cut left, right, to a shoulder and threading too. You can rough with it, take interrupted cuts and finishing cuts. It's less likely to vibrate than many other shapes so can help if you are getting chatter too. It's not perfect, but they make a good general purpose insert to have on hand.

As for figuring them out, the main determining factors are the shape (easy to see), the thickness (easy to measure in 1/32) the mounting style (easy to see the hole in the middle) and the inscribed circle.

The inscribed circle (IC) is probably the most problematic, since it's measured in 1/8 inches and is the "largest possible circle that can be drawn on the inside of a plane figure." The easiest way to measure the IC is to use rod of known size. A 3/8 inch drill bit, for instance, will fit exactly within the profile of a tcmt32.51 and will also fit exactly in the outline of a SCMT321 insert.

Of course, that's for the inserts made to the ANSI standards. ISO uses the cutting edge length for the size, with different measures based on the insert shape. For instance an ANSI insert of size 2 will have an IC of 1/4 inch regardless of shape. It's ISO equivalent will be 5,6,7or 11, depending on the shape.

See? Easypeasy.


Dan

[tomato coupe]

You'll find that a CCGT is usually a sharper insert for aluminium ...

The difference between a CCMT insert and a CCGT insert is just the size tolerances. You can buy both in various grades for different materials, as well as "sharp" versions for aluminum.

[MattiJ]

The difference between a CCMT insert and a CCGT insert is just the size tolerances. You can buy both in various grades for different materials, as well as "sharp" versions for aluminum.

Like Ceneddd said: "usually"

While what you say about tolerance is correct in theory in some ways you could say instead of usually "almost always": Try finding "dull" CCGT insert or really sharp CCMT insert.

[Cenedd]

Cheers Danlb - looks useful. Will have a read up.
Tomato coupe: noted, thanks. Was confused by only ever seeing the G's for sale as alu profile.

[tomato coupe]

Like Ceneddd said: "usually"

While what you say about tolerance is correct in theory in some ways you could say instead of usually "almost always": Try finding "dull" CCGT insert or really sharp CCMT insert.

I've got plenty of normal CCGT inserts for cutting stainless, and lots of sharp CCMT inserts designed for cutting aluminum. The "G" vs. "M" designation is not about sharpness.

[MattiJ]

I've got plenty of normal CCGT inserts for cutting stainless, and lots of sharp CCMT inserts designed for cutting aluminum. The "G" vs. "M" designation is not about sharpness.

Yeah...but never seen anything else than light finishing inserts for (stainless) steel in CCGT form (pretty sharp too but not as sharp as alu CCGT inserts)

Like I said it's USUALLY better than 90% proof identification of aluminium or sharp(ish) steel insert even if in theory its all about tolerances.
I guess no point of grinding the inserts at factory unless they need to be somewhat sharp and once you go at trouble grinding them you might make them G-tolerance as well.
Milling inserts are bit different as the size tolerance is more important.

[Cenedd]

someone please correct me if I'm wrong

It'd be churlish of me to complain when Tomato Coupe did MattiJ. I had seen that the third letter is about tolerances - which is far more relevant to repeatability in close-tolerance CNC work than in a home shop - but haven't seen the lesser-spotted sharp CCMT or dull CCGT in the wild. I'm hardly shopping the high end of inserts though. More than five bucks a piece and I'm already getting twitchy!

[Cenedd]

Okay, here are some pics from this afternoon: This is the tool I was trying to use.

Not sure if it's of help or if I'm just stating the obvious but those inserts look like TNMC inserts which are supposed to be used "on-edge" like that but the holder I've seen seems to - as suggested - have the top of the insert level.
I wonder if that holder is maybe for an ordinary TCMT and you're just holding it on-edge when it should have the insert on top.

Edit: correct insert code.

[J Tiers]

OP stated that it was like that when he got it, and likely you are right about it being a turning tool holder that has been re-purposed badly b y the previous owner.

[danlb]

OP stated that it was like that when he got it, and likely you are right about it being a turning tool holder that has been re-purposed badly b y the previous owner.

Nope. Cenedd got it right. In post 202 txfireguy said that it was in a similar but different holder when he got it, but he broke that holder.

I could be totally wrong as I didn't purchase it directly. It was assembled in a small box with a similar holder that was neutral rake angle (flat on top) which I broke when I first started trying to thread stuff a few months ago. It was my fault, can't remember what I did exactly, but it was no fault of the tool's.

[J Tiers]

Buried in 224 posts? OK.