Hello, I have been looking to purchase indexable tool holders for use with my 14X40 lathe. The selection is quite vast and am hoping that someone may suggest what manufacturer and types would be good for a home shop starter set.
If Enco still has their 3/8" indexable set, that's what I have, and it works quite well for the kind of stuff I do. If you do a lot of heavy stock removal on steel, you might go for the 1/2" set, instead.
You need to get holders that use postive rake, take a look at
for some good background on this.
I like to get cutting tools that all use the same insert, and an insert that's widely available and inexpensive. I have well made cutting tools from Valenite that use the popular TPG-221 and 222 inserts. I bought them from MSC so if you dig around in their catalog you'll find them. APT makes some additional tooling such as boring bars that also use these TPG inserts.
I like the Valenite tools because the clamping system is sturdy and well made and replacement parts are easily available.
I really dislike the cheapo tools from Enco and others that use the inserts that have a small screw through the middle holding them, they are troublesome and I would stay away from them.
The link above mentions tools from Microdex that also sound pretty good.
To my mind, with that size of lathe, you would want at least
5/8" shanks on the tooling, and perhaps more if your toolpost can handle it. The fatter the shank, the less likely that the shank will contribute to chatter. If I could handle a CXA toolpost size, I would opt for 3/4" shanks instead.
I like the Valenite insert tool shanks, with negative rake, and the TPCN (IIRC -- it is too late to go down to the shop and check, now) Triangular, Positive rake with the aid of a special chipbreaker groove.
Iscar makes a similar quality shank which will accept the same inserts.
Note that you can sometimes get the inserts for little money in large quantities (e.g. 100 at a time) from eBay auctions. This makes the extra money spent on a good Valenite insert shank to be well worth it. The cheap sets with 1/2" or smaller shanks have too thin a positive-rake insert, and it breaks easily under heavy cutting. And the cost of the inserts in that size (not an industry standard -- for good reason) will make up for the additional cost of good insert shanks in not too long a time.
But what I *really* like for most work these days is an Aloris holder for their quick-change toolpost which accepts the inserts directly. I'm using a model 16N (the 'N' for negative rake), which holds two inserts -- one in the right position for turning, and the other in the right position for facing. I'm using this on a Phase-II wedge style toolpost -- series 200 (BXA size equivalent).
Ted will show up with his web page telling you how to make your own as he does. (His may already be one of the articles out there which I have not yet read. :-)
I bought a set of these indexable toolholders from JTS on Ebay:
$17.95 plus $6 shipping it is hard to beat. One thing that makes them a particularly good deal is that five inserts are included. The tools are nicely finished and they include 5 extra screws which are well made. I have an older set of 3/8" toolholders from Enco which are OK (I still use them), but Enco's set does not include the inserts. I rate the ones from JTS as much better made. I can take .250" off a CRS round so I guess the 1/2" toolholder should probably be large enough for my 12 x 36 lathe.
O.K. I finally got time to go down to the shop and check. They are TNMG. Now -- why did I mis-remember the designator that badly.
Anyway -- it should be just a chipbreaker groove, but it behaves nicely on my 12x24" Clausing, which suggest the either it is working as a positive rake modification, or that the Clausing is rigid enough to handle negative rake tools. :-)
Probably the later. :-) Get a hold of a TNMP and compare it to the TNMG with a magnifier (or, if you wish, I could e-mail you a close up photo of the two side-by-side.) You will find that the "chip-breaker" groove of the TNMG goes _almost_ to the edge leaving a narrow flat to produce a right angle edge and thus negative rake. The groove in a TNMP goes right out to the edge to produce an eighty degree angle. When the TNMP is angled down 5 degrees, it still has 5 degrees _positive_ rake.
I don't have the TNMP available to examine, but the TNMG does have the slight flat. But with a heavy cut, it is ripping the metal apart wide enough so it doesn't touch where the edge would be, anyway, and thus is acting as a positive rake tool to all effects. (Granted, you have to be able to take that heavy a cut. :-)
O.K. Are these coated or uncoated inserts? If coated, how much does that dull the edge?
They're available both ways. As you suggest the coating significantly dulls the edge. I made the mistake of ordering some. Won't do that again. As you know, I'm using a comapatively light machine so cuts that would use a TNMG as positive rake just aren't on.