Carbide lathe tool insert questions

[Reddinr]

It has been a few minutes since anyone has brought up carbide tooling, so here goes. I'm shopping for a decent carbide insert and holder setup for my lathe. Details are below but my biggest questions are these:

What is the practical benefit of a 3/8" vs. a 1/4" or a 1/2" vs. a 3/8" inscribed-circle size insert? Cost seems to go up with size somewhat. Are the bigger hold-down screws a benefit? Other practical benefit?

How much of a practical difference might I see with an insert holder with a larger cross-section than the 1/2" ones? My tool holders can easily handle 5/8" or 3/4" but is there much benefit? (Assuming I'll probably not need to hog out industrial level amounts metal per pass.)

I have a budget of $1000-1500 to get this off the ground. (I sold some equipment and that $ has to be spent, you know, for the good of the economy.)

Thank you.

Background:
I have the same set of cheap triangular inserts and holders that came with my lathe and they have worked "ok". I've used HSS quite a bit but really like the results I get with quality carbide threading tools and parting tools. I did an internal acme thread with a carbide tool that was just excellent. It was a happy day. So I'm shopping for a basic profiling/facing setup with right-hand and left-hand holders for 80 Deg. diamond and 135 Deg. for more intricate profiling. I have a 16" lathe with a CXA tool post. My max RPM is 2000, 5 HP. I work on aluminum, various steels, and sometimes stainless.

 

[Aukai]

This would help you a lot, and support out resident author.

Introduction to Indexable Tooling for the Metal Lathe: A User Guide: Best, David P.: 9798753874993: Books: Amazon.com

Introduction to Indexable Tooling for the Metal Lathe: A User Guide [Best, David P.] on Amazon.com. *FREE* shipping on qualifying offers. Introduction to Indexable Tooling for the Metal Lathe: A User Guide

www.amazon.com

 

[woodchucker]

I prefer to go bigger.. the bigger the better...
In my opinion, bigger is always better when you are not constrained by a tight fitting cut.
I prefer to fit the biggest tooling I can fit in a holder and maintain center.

I liken it to more absorption of vibration. Smaller usually will flex more..

I have been on small carbide cutters, and didn't like them. On my little SB9 I prefer 12mm and up shanks. I can and do fit 16mm. I did in the past have to remove some material to fit it in the tool holder, but I have since found out about the XL holders, and they work for me. I was involved in a conversation where the user was unable to come to center with a 16mm.

 

[MrWhoopee]

Definite advantage to bigger boring bars, similar but less so for turning tools because of less overhang. No real advantage to bigger inserts unless your machine is powerful/rigid enough to use the entire face of the insert.

I've purchased a full assortment (turning, boring, internal and external threading) of inserted tooling from Aliexpress and eBay . It has all been of good quality, none of it is junk. I realize this barely touches your budget, but I'd recommend a 16mm set like this, plus a pack of every insert.

49.95US $ 50% OFF|9pcs 16mm Shank Lathe Boring Bar Turning Tool Holder Set With Carbide Inserts Cnc Cutting Tool Holder Lathe Turning Tool Set - Turning Tool - AliExpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

full disclosure: I haven't used one of the inserted parting tools. I had bad experiences years ago and have stuck with HSS ever since.

edit: If you want to blow some money, buy the brand name inserts.

 

[Reddinr]

$50...That's crazy cheap. That entire kit costs less than one ISCAR SCLCR104 holder or 3 iscar CCGT's.
One thing I noticed with my cheaper set was that the hold-down screws won't stay tight, which has ruined a couple of chunks of steel. Have you seen that with this set?

 

[MrWhoopee]

$50...That's crazy cheap. That entire kit costs less than one ISCAR SCLCR104 holder or 3 iscar CCGT's.
One thing I noticed with my cheaper set was that the hold-down screws won't stay tight, which has ruined a couple of chunks of steel. Have you seen that with this set?

I know, it's hard to believe. The first set I bought (12mm) was under $30. I figured it was worth the gamble, and it was.
No, I've had no problem with the screws loosening, or stripping. I've modified some of the holders, they are hardened as they should be.

 

[Aukai]

My link said 59.00

 

[MrWhoopee]

My link said 59.00

Yeah, the old bait and switch.

 

[erikmannie]

When I had this question, I called Carbide Depot. They are in the American South (AR, AL?), & I had a long phone conversation with some guy that had worked there for a very long time. He answered all of my questions in the one phone call, & sold me everything that I needed. I chose Kennametal tool holders.

I think I spent about $500 on that order. Carbide Depot has a house brand (for carbide inserts) which is made in Switzerland. It seems to be just as good as the quality name brand stuff, but it is significantly cheaper.

It was a nice change of pace these days to make an old school phone call, & have a conversation with a knowledgeable person.

 

[mksj]

Your lathe would take CXA holders, so primarily would be using 3/4" tool holders. If you have the budget, I would recommend going with decent insert holders, they have replaceable anvils/hardware, and they are a bit more accurate on how they hold the inserts. Many people start out with a starter kit/set, but they do notice an improvement going to better holders. I recommend trying to standardize on the size inserts that one uses, so if you use say 32.51 inserts, you can use them also for boring bars, etc. Larger holders/inserts can be a bit more challenging for small work, due to the size, but the inserts are usually more durable and should last a long time. With a 16" lathe with 5 Hp you can be a bit more aggressive in stock removal. Many people complain about the cost of the carbide inserts, in my experience as a hobbyist I can use the same insert for months before it needs to be replaced, my laydown threaded is still using the same Carmex after cutting hundreds of threads. It is very cost effective, and should one go south in the middle of a job, I just switch it out and move on with my work.

I would recommend David Best's book, as he lays out specific holders, types, brands, nomenclature, etc. so you are not wasting your time and money on holders you will probably never use. Also some of the other insert holders like cutoff and threading, there can be a significant performance difference between holders and inserts. I started out with a QCTP kit that included a threader, cutoff and a few holders. As time went on the limitations of the kit holders became evident, and I wasted a lot of time, cost and materials trying to make them work. In the end, they all got replaced, and I haven't had any issues parting or threading after that point. Carbide Depot is a very good source of holders and information, if you know what you are looking for sometimes you can get lucky on eBay.