Indexable endmill: my first shot = Tri-Dex bad

[Ryobiguy]

Today I just returned my first indexable tooling I bought for the Bridgeport: a 2" Tri-Dex endmill, 3 insert TPG style endmill. I don't have R8 so this is the only straight shank model that I see on Enco (my eyes tend to miss expensive.)

I used it for few seconds but it sounded more like a fly cutter. One of the inserts was much lower than the other ones, and was the only insert cutting.
Removed and checked inserts - all within less than a thou or so, so it's gotta be the pockets on the endmill. Pockets checked, cleaned up, checked for rough edges, and inserts are indeed seated perfectly.

I chucked up the endmill in the lathe, and dialed it in the 4 jaw to within a few tenths. Using the test dial indicator, I carefully measured the endmill length/depth on each insert tip. Total difference was 0.010". That is to say that relative to the middle insert, one was higher by 0.005" and the other was lower by 0.005" when endmilling.

Is this something that just slipped by quality checks or am I expecting too much from economy tooling? I don't know if I should try the same model again and see if it cuts OK, or just get something different altogether.
What do you think?

-Matt

[AlanHaisley]

Suppose you try another of these and it is off by "only" .002"
I would think that would still be a severe problem. Check a reasonably good HSS endmill the same way and I'd bet that the variance will turn out to be unmeasurable.

[PaulT]

Unfortunately tooling using TPG type inserts is still heavily promoted to home shop users when there are much better tooling types available, particularly on home shop sized machines.

I'd recommend getting rid of that end mill and getting one that uses the APKT type insert. This is a much more modern "highly positive" type design that cuts much more smoothly on smaller mills than that older design.

I've been using the APKT type faces mills made by Bison, often marketed under the Toolmex and Dolfa brand names. I believe this guy- www.shars.com may handle these, or Penn Tool is another source.

Regarding index height matching, it should be in the ballpark of +/- .001" or just a little more than that. I swap my inserts around to get that as close as possible.

On your lathe, also dump any TPG tooling and go to the CCMT or TCMT based tools, much nicer cutting and you can get extra sharp inserts for aluminum that cut as well as HSS (as least as well as the HSS bits I'm capable of grinding).

For more info, search APKT and CCMT in this forum and the Practical Machinist forum.

Paul T.

[lazlo]

To add to what Paul said, that TPG facemill has the inserts laying flat, which will slap on the work, pound the machine, and leave a natty finish.

The better TPG facemills tilt the insert back and inward, which creates an axial and radial rake. That creates a lot less hammering, uses a lot less horsepower, and leaves a much nicer finish (I have both).

But like Paul says, there are a lot better inserts available: the 45° "shear mills" like the SEHW's, the Sandvik RA-245, and the helical inserts like APKT's. The APKT's are great, but they're 2 - 3 times more expensive than the 45° inserts:

[pcarpenter]

The TPG face mill I have (came from Grizzly) does not have the inserts lying flat. They are canted in two dimensions to create just the shearing function discussed. The key is not the insert type, but making sure that the rest of the architecture of the tooling is correct....regardless of insert type.

Me....I hate paying $10 per insert if I can avoid it. Hit something you didn't intend and it ends up being a $50 mistake.

Paul C.

[J Tiers]

Today I just returned my first indexable tooling I bought for the Bridgeport: a 2" Tri-Dex endmill, 3 insert TPG style endmill. I don't have R8 so this is the only straight shank model that I see on Enco (my eyes tend to miss expensive.)

I used it for few seconds but it sounded more like a fly cutter. One of the inserts was much lower than the other ones, and was the only insert cutting.
Removed and checked inserts - all within less than a thou or so, so it's gotta be the pockets on the endmill. Pockets checked, cleaned up, checked for rough edges, and inserts are indeed seated perfectly.

I chucked up the endmill in the lathe, and dialed it in the 4 jaw to within a few tenths. Using the test dial indicator, I carefully measured the endmill length/depth on each insert tip. Total difference was 0.010". That is to say that relative to the middle insert, one was higher by 0.005" and the other was lower by 0.005" when endmilling.

Is this something that just slipped by quality checks or am I expecting too much from economy tooling?

-Matt

That part may be DESIGNED like that......... it sounds nutty, but it was not uncommon for cutters to be designed so that the depth of cut was distributed among several edges.

Were the pockets also possibly different radially? That would confirm it.

The shallowest one would be out slightly further than the deepest cutting one, so that the cut would progress in steps of, in your case, 0.005" , as you fed it.

[Ryobiguy]

That part may be DESIGNED like that......... it sounds nutty, but it was not uncommon for cutters to be designed so that the depth of cut was distributed among several edges.

Were the pockets also possibly different radially? That would confirm it.

The shallowest one would be out slightly further than the deepest cutting one, so that the cut would progress in steps of, in your case, 0.005" , as you fed it.

That's something I was wondering about - this is (was) my first indexable tool. Radially they were out by about +/- 1 thou or so, but I didn't match up the shallow one to see if it had the greatest cutting diameter, so I'm not sure. The sound it made and the finish it left seemed to indicate that it was not like that - one of the inserts was doing all of the work. But maybe that's something that one could easily mistake.

I looked at the tools that Shars has. Has anyone used the APKT tools from them? They're so cheap I have to wonder... Maybe I ought to troll ebay for some brand name tools.

Shars also has one model of face-mill that will fit the oddball 1.25" facemill arbor that came with my machine. Is 4" going to be too large for the Bridgeport? Mainly just for cleanup of steel and aluminum plate.

-Matt

[J Tiers]

Is 4" going to be too large for the Bridgeport? Mainly just for cleanup of steel and aluminum plate.

-Matt

I'd call it a 'cringer"....... and say yes it's too big.

[lazlo]

The TPG face mill I have (came from Grizzly) does not have the inserts lying flat. They are canted in two dimensions to create just the shearing function discussed.

I have a Bison TPG face mill that has the TPG's correctly tilted as well, but the Grizzly is cheaper, and looks just as nice.

The key is not the insert type, but making sure that the rest of the architecture of the tooling is correct....regardless of insert type.

An SEHW/SEHT or RA-245 shear mill (with a 45° lead angle) cuts so much nicer, and the inserts are really cheap -- about $2 each.
I recently started using an APKT facemill, which cuts even nicer than my RA-245, but like you say, the inserts are around $7 each, so if you crash it, you're out $80 in inserts.

There're also only 2 edges on an APKT, where there are four on an SEHW/SEHT or RA-245 insert.

[Ryobiguy]

I have a Bison TPG face mill that has the TPG's correctly tilted as well, but the Grizzly is cheaper, and looks just as nice.

BTW, the Tri-Dex that I returned DID have the inserts raked positively in both directions.

Rats, dunno if I'll ever get to make use of the oddball sized 1.25" facemill arbor. So far I've found exactly just the one (4" too big) facemill that will fit it.
Maybe I could carefully trim down the arbor to a more standard size so it could fit a facemill in the 2" range or so.
Knowing my luck, I'd probably pull an "oops" on it and make it too small for a lousy fit.
On the other hand, runout from the spindle/arbor would be closer to zero if I "lathed" it in the mill.

The square inserts with the raised diagonal corners look really nice. I think I'd like to get those in a larger (2") facemill and a smaller (1") APKT for square corners.

-Matt

[ngriff]

people pay for inserts? LOL. Might be worth getting a part time job just to keep inserts stocked at home at those prices.

I second a vote for the APKT style face mills. while very expensive, if you are careful they outperform the other options. we just recently got to get our hands on these for the manual small mills at work. compared to the other style face mills we have these are much quieter and use far less horsepower to cut. my co worker is kinda "rough" on cutters and i've found these actually stand up better to abuse compared to the square or octagonal inserts.

regarding the triangle inserts. you have to run these very hard and fast to make them work effectively, somewhat harder then you might feel comfortable running them. start at 1600 rpm and min. .030" depth of cut. and move up from there. i've taken .150" cuts on our TOS FNGJ32 when you find the sweet spot for the feed. I don't think that it matters too much about them being a little off on the bottom tips. we run 3 insert cutters with only one insert occasionally to get a fine finish on aluminum and i've never noticed a problem. it's possible they are staggered on purpose for finish purposes.

[PaulT]

I looked at the tools that Shars has. Has anyone used the APKT tools from them? They're so cheap I have to wonder... Maybe I ought to troll ebay for some brand name tools.

Matt, if you want a reasonable quality tool, which I'd recommend, don't go any cheaper than the Bison/Dolfa/Toolmex brand. However, check with Shars, some of the tooling they sell is from Bison, although I don't know about the specific one you were looking at, so I'd ask them who makes it.

Regarding getting quality APKT inserts for reasonable prices, I'd check www.carbidedepot.com and also the guy that runs this site: www.latheinserts.com . That site currently only has lathe inserts up, but if you contact him he also sells milling inserts and he also carries a good line of APKT based mills, I believe it may be the Bison ones.

Good luck-

Paul T.