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View Full Version : Carbide inserts and toolholder confusion..??



krems
01-05-2007, 02:14 AM
I've been spending a lot of time lately reading about the different toolholders and carbide inserts. I've decided on buying some Sandvik toolholders to replace my import stuff. I've decided to get away from the triangle inserts and get some of the newer designs. My main area of confusion is toolholder shank length and IC (inscribed circle) sizing. I'm using a 13" lathe, Quick release toolpost, turning mostly 3/4" or less diameter aluminum or mild steel. I'm looking for finish quality and precision over speed. What kind of advise can you offer on the following:

1. 5/8" shank toolholder 4" length at present. Would you stick w/ the 4" length or would a 5" shank length offer any advantages...??

2. 3/8" or 1/4" IC on the inserts: I'm looking at a 80 degree rhombic for facing/turning, a 55 degree rhombic for most of the longitudinal cutting, and a 35 degree diamond for the detailed profiling and small diameter stuff.

Any advice would be appreciated, Thanks in advance.....................Krems

DR
01-05-2007, 06:16 AM
1. Assuming you're talking about turning holders as opposed to boring bars....

Shank length has very little to do with the choice. You never want to have the shank hanging out away from the holder. Buy the shortest if they're less expensive.

2. Whatever style, be sure it isn't unique to Sandvik. You don't want to get tied to one manufacturer's insert style, especially an expensive brand like Sandvik.

Not sure why you're thinking of 55 degree for longitudinal turning when the 80 will also do it. 80 is a good choice because as you say it'll both turn and face.

35 is okay if you really need it. Keep in mind the cutting edges are weaker, the sharper the angle.

1/4 or 3/8" IC? It really doesn't matter. Check to see if you can use the same insert in boring bars. Makes life easier if both turning and boring holders use the same insert. For small diameter boring 1/4" is the choice obviously, so maybe that's the best choice for your turning too.


Give thought to whether your machine is rigid enough to handle negative rake inserts, or whether you want positive style, or both. A different holder will be needed for both pos and neg. Since you're doing small diameter work positive would be my choice.

Negative style are nice for hogging crusty casting and going through tough welds, so not a bad idea to have at least one negative holder.

A common style of insert like CCMT (80 degree diamond) comes in positive and very high positive, same holder. The high positives are razor sharp (CCGT) for aluminum, plastics, light finishing on stainless. Not sure if rhombics come as high positive.

krems
01-05-2007, 10:11 AM
I'll be buying the screw down type holders (coro-turn 107) w/ positive inserts. I thought about the 55 degree for most of the turning between centers because of better clearance than the 80 degree inserts. Right now I'm leaning towards the larger 3/8" IC for both the 80 /55 degree inserts and 1/4" IC on the 35 degree. I don't bo a lot of boring but it makes sence to double up w/ the inserts when posible. I just priced the Sandvik line out...expensive. I may have to scale back a little and rethink this.

Life was much simpler when all I had was the generic toolholders w/ TPMM inserts for everything. Always seemed to get the job done. Maybe the saying is true "A fool and his money will soon be parted"

Krems

Spin Doctor
01-05-2007, 11:10 AM
A lot depends on just what type of Tool Post System you are using. If you are using one of the Aloris type (piston or wedge) I think you would be surprised at the improvement in proformance that using an insert holder with a big enough shank to to be modified to fit the dovetail on the tool post. For probably 90% of your lathe work the 80D CXXX-43X Series will beat most of the other options IMO. A CXXX series tool holder with a 1 or 1/1/4 shank utilizing negative rank design with shim inserts is to me ideal. But just because the tool holder is a negative rank design that does not mean the inserts have to be. This is an Aloris model sized for the A series tool posts. It should give you the idea of just one of these can look like

http://img.photobucket.com/albums/v19/markandannie/tool%20holders/MVC-002S.jpg

IMO stick with a 432 sized insert as they are more available and for specific geometry the CNMP works well. The 433 and 434 feature bigger radiuses on the tool nose and take more HP to run effectively
Another option is to go with an ISO positive style inserts. It would allow you to use the same inserts in a wide range of holders and boring bores

http://www.valenite.com/

krems
01-05-2007, 02:48 PM
SD, nice looking tool. Is that one you made yourself or is it one that Aloris sells. Looks very rigid. I can see where that could be ideal. What size machine are you running that on...just curious.

Krems

Alistair Hosie
01-05-2007, 03:43 PM
I like the look of it too and also wondered did you make the tool holder yourself ?Alistair

kennyd4110
01-05-2007, 07:53 PM
As someone is just starting, (still putting my lathe back together after painting) I am very confused also:confused:
I am getting a Aloris QCTP and some misc, holders from a for sale add, But I have NO IDEA what type of cutting tools to get! There are so many options its just overwhelming to a newbe like myself.

Ryobiguy
01-05-2007, 10:08 PM
The other day on ebay I spotted one like the above that had a second tool on the back. That seemed like the way to go but I couldn't find any others like it. Know any sources of BXA quick change insert holders?

It sure looks rigid. It also looks like the tip of the insert is further away from the toolpost, almost like a standard shank insert holder that's permanently extended a little ways beyond the QTCP holder slot.
But, does having it all be once nice clean looking piece add much rigidity compared to having a qctp holder clamping onto a separate shank?

JCHannum
01-06-2007, 08:44 AM
Forrest has mentioned that the one piece tool holders are OK until the pocket becomes deformed by a wreck or wear, and he is correct.

I recommend the Aloris 20 series holder. It uses the economical and readily available 3XX triangular inserts. It is adjustable for positive, neutral or negative rake as well as for turning, facing, turning to a shoulder and large ID boring.

The insert is held in a cartridge that is less expensive to replace than the complete holder when the need arises.

http://members.aol.com/jchannum/aloris

Spin Doctor
01-06-2007, 10:36 AM
SD, nice looking tool. Is that one you made yourself or is it one that Aloris sells. Looks very rigid. I can see where that could be ideal. What size machine are you running that on...just curious.

Krems

This an actual Aloris product that I was using on Hardinge HLV-Hs, I did make up some of my own out of 1" shank Valenite tool holders. One with this size insert, one with the VMXX-33X series for work where I have to get in closer to the center plus a couple more for the one edge parting and the dogbone inserts. We also used this style tool holders in B and C series tool posts on larger lathes.

http://img.photobucket.com/albums/v19/markandannie/tool%20holders/MVC-003S.jpg

As I said in the post above I would stick with the models that use hardened shims between the insert and the holder. That way the cutting forces don't go directly into the tool holder and if you do have a crash it is likely the shim will take the damage rather than the tool holder. Some of the other tool holders and inserts out there I really don't think are suited to the home shop. Most HSM lathes don't have the ability to really use the insert threading tools. Not because they lack the speed but they lack the ability to control the tool in the cut and at the end of the cut. Insert tools do not take kindly to over running the back of the thread. For that you really need a threading system that allows the half nut to stay engaged but the whole lead screw is stopped and reversed with out reversing the spindle. If you ever used a HLV you know what I mean. Other lathes have had similiar systems also. I plan on building one of my own to fit my lathe (eventually).

http://img.photobucket.com/albums/v19/markandannie/Leadscrew%20Reversing%20Drive/LeadScrewReversingSystem5.jpg

But to have one of these you almost need a lathe without a QCGB for feeds and threads. Or the QCGB needs to be hung off of the back side of the head stock. Another thing to stay away from IMO is the negative rake inserts with really large edge widths. For these to work effectively you need a feed rate that is grreater than the edge width. And lets face it. Most of us dopn't have the horses to run stuff like this.