Collets vs Tool Holders - AKA: More R8 Mumbo Jumbo

[Bob La Londe]

Do you have a machine with an R8 spindle? Do you put every tool in an R8 collet or do you use tool holders? Either set screw or collet tool holders. What pluses and minuses lead to your choices?

I have one machine currently in operation with an R8 spindle and I put a tool in a tool holder and put it in the R8 collet. Generally speaking the holding part of the tool holder and the tool are below the spindle (but braced against the spindle nose due to its design). Often I am putting a tool in an ER collet in such a tool holder and then putting the tool holder into the R8 collet. When you think about it there seems to be quite a disconnect there allowing for stacked tolerances to cause issue, but in practice it works ok.

I am gearing up for the new mill that might get here someday, and I plan to do atleast some moderately heavier work with it. My instinct is that a properly fit solid one piece set screw holder would be more rigid than a tool in a collet, but it does have the set screw and most of the tool below the spindle nose.

Just rambling.

I do have a tool grinder so adding a flat to a carbide tool is no big deal.

[nickel-city-fab]

I don't have a lot of experience milling, but half of what i have was on a nice Bridgeport clone. They had all the tooling setup in R8 tool holders with ER collets. Basically some of the fractional sizes: 1/4, 5/16, 3/8, 1/2, 5/8 and 3/4 already setup. Plus a big face mill and the drill chuck. System worked good for me, but I wasn't trying to push the machine.

[old mart]

The two mills at the museum share the tooling for their R8 size spindles.
We use er25 collets for most straight shank cutters up to 16mm.
Small size Osborn Titanic II for threaded shank cutters, 1/4", 3/8", 1/2" and 5/8" shanks, plus 6, 10, 12 and 16mm shanks.
Shell mill holders 22mm, 1" and 27mm fitting. (shell mills from 40mm, 50mm, 63mm and 80mm)
A complete set of metric collets plus some of the common imperial sizes
MT2 sockets drawbar and tang type.
Shop made tramming tool.
Optical edge finder (Swiss).
Cutwell 1/2" keyless chuck (integral shank).
5/8" keyed chuck on R8 adaptor.
1/4" keyed chuck on R8 adaptor.
50mm Maydown three insert for aluminium, integral shank (very low profile).
2 and 3 insert APMT type from 12mm to 25mm (25mm shank reduced to 18mm to fit in collet).
Common cheap 3" boring head on R8

I can't think of anything else at the moment.
This stuff has been acquired over some years, many were bargains from ebay.

[Doc Nickel]

About 90% of the time, I use standard collets- I splurged a few years ago on a shiny new set of Hardinges (you really only need five) but there really wasn't much difference between those and the unbranded imports I'd been using for some time previously.

Minimal stickout, best concentricity, and I rarely cut steel, or really "push the envelope" of trying to hog lots of material off. They work great.

For the other 10% or the time, it's one of half a dozen face mills (my favorite being a 3" Glacern unit with honed, high-shear inerts; on aluminum, it produces a near-mirror finish) or one of three or four ER holders.

The primary use of the ER holders is for odd shank sizes like spotting or stub-length drills. I'll also occasionally use those when I need to mill down into a pocket or near a tall feature, and need the extra reach.

Doc.

[Toolguy]

I have lots of R8 collets, but most often, when CNC milling something I'm using an ER 16, 20, 25, 32, or 40 collet holder with an R8 shank. The cheap Chinese ones are pretty darn good these days. I also have lots of drill chucks, face mills, boring heads, stub arbors, all with R8 shanks. Even a 3" 3 jaw lathe chuck with R8 shank. A couple sets of setscrew holders for roughing cuts where you don't want the tool to pull out. I have used a 1-7/8" insert drill to drill 6" deep from solid in alum. for one job, then thread milled a 2" - 10 stub acme thread 6" deep. All with an R8 BP type spindle. I had to custom make the thread mill because no one makes one that long. The R8 tooling repeats super accurately for depth in the spindle.

[Rich Carlstedt]

Many Years ago I screwed up a big Stainless part $$$$ because I used a 3/4" R8 collet. I was too lazy to put in a R8 3/4" Endmill "Holder" and the endmill was sucked down .010"
It happens ! So for expensive or critical work, and especially larger endmills , ( .500 + IMHO) or when dealing with SS, use a Holder.
So here are some things to do
With Collets, especially large stuff, get some RED Fingernail Polish and place a dab right at the juncture of the collet and the cutter shank after you tighten it. Nail Polish drys fast and HARD..now when milling
with the cutter, the juncture will appear to be a red pinkesh blurr, but it the endmill pulls , even a few thou. you will see a distinct thin silver line at that point . The nailpolish will "crack" and expose the cutter shank.
If using a Endmill Holder , always pull the cutter downward (or out when tightening the set screw !
This gives you the longest setting of the cutter and if it moves, it can only move upward in the Holder and thus saves your working depth. If you shoove is full depth in the Holder, you risk the cutter being pulled and the cut being deeper than wanted

Rich

[oxford]

At home I mostly use collets unless the tool has A 1” shank then it goes in a holder. 4” boring head and drill chuck have r8 shanks on them.

Mill at work has a r8 to er40. Seems to work well for most things but does add some additional stick out over a collet. Also in that one double ended endmills 5/8” and over are really to long as they can’t go up in the holder far enough.

Mentioned above, endmills in a collet pulling down can be a problem and I have had it happen before.

[BCRider]

I've not had any collet pullout. But I freely admit that I'm limited to smaller cross sections of metal removal per pass or the machine starts making funny sounds and vibrating in fear.... It's smaller and probably 1/3 the weight of a full B'Port.

That may change when I finally get around to ordering up a set of hogging end mills. We'll see.

So I would suggest that the answer is "it depends". But if it comes down to that I think I'd go holders with screws. I don't see trading one collet for another. Plus the R8 to ER chuck types I've seen seem to have fairly long overhangs. I guess it's unavoidable since they all have room for wrench flats and the collet nut. Looking at an R8 to ER25 adapter has a good 2" or so of stickout.

So I'd shop around and find holders where the stickout is the least amount possible. This would mean holders where the clamping screw is as close as possible to the spindle nose. For example I really like THIS SET. Not great reviews on it so likely would not buy THIS set but I'd be looking for something similar.

I also like how the noses of the holders taper in. So the whole shank right up to where it starts to have the flutes is supported for less flex but our sight line down to the cutter is going to be a little more clear.

[J Tiers]

................

That may change when I finally get around to ordering up a set of hogging end mills. We'll see.
......................
r.

Corncob roughers seem to have almost NO tendency to pull out/down.

[Bob La Londe]

Corncob roughers seem to have almost NO tendency to pull out/down.

I can't speak to all, but I know that has been my experience with 3/8 corncobs pushing as hard as I dare trying to get the MRR up as much as I can. They just throw tiny little chips everywhere.

The worst pullout I have experienced has been with a 1/2" aluminum geometry 3 flute. A couple different brands. I suspect it might by the flute angle that lifts chips out also pulls the tool in. If there is the tiniest chatter there can be problems.

[nickel-city-fab]

So I'd shop around and find holders where the stickout is the least amount possible. This would mean holders where the clamping screw is as close as possible to the spindle nose. For example I really like THIS SET. Not great reviews on it so likely would not buy THIS set but I'd be looking for something similar.

I like that set too, and that's a great price. I'm going to remember it when I am finally shopping for mill stuff, thanks!

[BCRider]

Corncob roughers seem to have almost NO tendency to pull out/down.

Thanks, that's great to learn.

I might just have to open up Amazon later today and order up a couple of size options. And yes, I see the big question mark forming over everyone's heads. But up my way we don't really have any equivalent to MSC or McMaster-Carr other than KBC's Canadian ordering point.... which to be fair I should at least check for prices on stuff like this. But then again it's hard to argue with my free delivery Prime account....

Bob, I'm sure you're right about the helix angle. Your post isn't the first I've read about something similar.

NCF, just read the reviews before you leap. Most are good but there are a couple related to mis-labeled holders and lousy set screws. Not sure what the outcome was with the mis-marked holder order but there it is. As for the set screw quality that's obviously an easy enough fix. And that particular set did not include a 1/4" option which I would like to add to any order of mine. But the style of the design is as close to ideal as any I've seen short of custom making them and really focusing on the least possible overhang.

[Doozer]

Buying a 5hp
and R-8 brand new mill,
instead of NMTB40,
is like using slot head wood screws
instead of phillips head wood screws,
just because you have a slotted screwdriver.
The pain ain't worth the effort ! ! !


Just bustin' on ya!

-Doozer

[Tundra Twin Track]

I did have a 1” 4 flute pull out of my TG 100 collet once on steel,never figured out why possibly Endmill had some coolant on it when I installed it or not tight enough.

[mickeyf]

Buying a 5hp
and R-8 brand new mill,
instead of NMTB40,
is like using Phillips head wood screws
instead of Robertson head wood screws,
just because you have a Phillips screwdriver.

If using a Endmill Holder , always pull the cutter downward (or out when tightening the set screw !

Yup. Learned this the hard way.