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View Full Version : So, just how tight do ya tighten R-8's?



Buckshot
07-11-2011, 03:01 AM
The drawbar, that is. I've had my Enco 9x42 mill a couple years now and never had a problem with a tool slipping, but this is a question that has honestly floated through my noggin' many times. Since I was here and it popped up again I figured it'd be a heckuva good time to ask:-). Since I've never read it anywhere possibly it isn't very important.

Rick

SGW
07-11-2011, 07:06 AM
"Moderately tight." If you've got good collets it shouldn't take heroic measures.

IMO collets are one of those things where it's worth the money to get really good ones, at least for the most-used sizes.

A.K. Boomer
07-11-2011, 07:32 AM
It is important and it's a good question and one Iv discussed on here a few times - there are many on this site that don't think it really matters and they are incorrect in their thinking.
I have a pet-peeve about this subject, every single endmill or cutter is either a different size or is being used for a different task at hand, for instance - flycutters NEED to be cinched down tight due to the single cutting bit and the general mechanical imbalances - they should be fairly tight just to be safe , and if your hogging with them they NEED to be close to the maximum.

on the other hand - keep in mind that you have an incredible leverage ratio in the R-8 system --- its a taper getting drawn up by the incline plane (threads)

There is no way in hell you need to put on anywhere near the amount of force on a little 1/8" endmill that your putting on for the large ones - think of the unit pressure of that little endmill and what it's going through - what for? to wear out your draw bar threads and spindle bore?
also think of the cutting radius on the little 1/8" endmill - next to nothing, yet there's some guys out there that enjoy wearing out their equipment by over torqeing tiny little endmills that are being used to machine plastic ---

the fact is is that every time you install a cutter you should be thinking of what its up against and tightening your drawbar accordingly - this is the mechanics way of machining,
This is why I do not like power drawbars on systems like the R-8

it the same reason you wont find me under someones dashboard installing their radio with my 1/2" "get it gun" and the compressor turned up to 150 psi.

there are levels of refinement in everything we do - or not.

Save your drawbar threads and your spindle bore taper for when you need them - To date Iv never had a large endmill slip in a collet cuz I know when to pour the coals to my drawbar threads...

my two cents - but remember - not a machinist here - just a mechanic...:)

MikeHenry
07-23-2011, 01:09 PM
The results of collet slip testing that Tomach conducted with their tool holders is presented here:

http://www.tormach.com/document_library/TechnicalDocuments/TD31090_ToolHolding.pdf

and you might find some useful info there.

Mike

Tinkerer
07-23-2011, 01:36 PM
The drawbar, that is. I've had my Enco 9x42 mill a couple years now and never had a problem with a tool slipping, but this is a question that has honestly floated through my noggin' many times. Since I was here and it popped up again I figured it'd be a heckuva good time to ask:-). Since I've never read it anywhere possibly it isn't very important.

Rick
Had that issue at one time and came up with a fix... http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280708552229&ssPageName=STRK:MESELX:IT

Allows you to snug up the drawbar... have not had a tool walk since I made up the first one.

Yes a little shameless promotion. ;)

mochinist
07-23-2011, 01:51 PM
It is important and it's a good question and one Iv discussed on here a few times - there are many on this site that don't think it really matters and they are incorrect in their thinking.
I have a pet-peeve about this subject, every single endmill or cutter is either a different size or is being used for a different task at hand, for instance - flycutters NEED to be cinched down tight due to the single cutting bit and the general mechanical imbalances - they should be fairly tight just to be safe , and if your hogging with them they NEED to be close to the maximum.

on the other hand - keep in mind that you have an incredible leverage ratio in the R-8 system --- its a taper getting drawn up by the incline plane (threads)

There is no way in hell you need to put on anywhere near the amount of force on a little 1/8" endmill that your putting on for the large ones - think of the unit pressure of that little endmill and what it's going through - what for? to wear out your draw bar threads and spindle bore?
also think of the cutting radius on the little 1/8" endmill - next to nothing, yet there's some guys out there that enjoy wearing out their equipment by over torqeing tiny little endmills that are being used to machine plastic ---

the fact is is that every time you install a cutter you should be thinking of what its up against and tightening your drawbar accordingly - this is the mechanics way of machining,
This is why I do not like power drawbars on systems like the R-8

it the same reason you wont find me under someones dashboard installing their radio with my 1/2" "get it gun" and the compressor turned up to 150 psi.

there are levels of refinement in everything we do - or not.

Save your drawbar threads and your spindle bore taper for when you need them - To date Iv never had a large endmill slip in a collet cuz I know when to pour the coals to my drawbar threads...

my two cents - but remember - not a machinist here - just a mechanic...:)I've had em slip, but it was always my fault...phone rang, customer came in, something that interrupts me before I tighten it down, then I start cutting a slot and wonder why it looks like it is getting deeper...oh sh!t, f**k, dammit:mad:


As for how tight, I've never tested it on a R8 but after reading that ER32 collets should be torqed to 100 ft/lbs both for stiffness and run out, I started doing that and the run out was definitely improved and no more endmills pulling out of the ER32, which was a problem for the other machinist I work with.

For R8's I usually hand tighten the draw bar, and then put my 7/8 box wrench on and turn it another quarter to half a turn.

Arcane
07-23-2011, 01:58 PM
The results of collet slip testing that Tomach conducted with their tool holders is presented here:

http://www.tormach.com/document_library/TechnicalDocuments/TD31090_ToolHolding.pdf

and you might find some useful info there.

Mike
Thanks Mike. That was a very useful site.

Black_Moons
07-23-2011, 03:09 PM
ER collets definately need to be INSANE tight, also look how huge the thread is, they can take it!

R8 has a tiny thread and can't take it. Really we'r all full of **** untill you see someone say ft/lbs torque for tightening. Loose to one guy is tight as nails to another. ft/lbs is ft/lbs no matter who you are or how strong you are, or if you work all day removing tractor trailer lugnugs or tiny philups screws from electronics.

One thing I can say for sure, is look up the recommended torque for a 3/8" bolt (Or whatever size your drawbar is).. And don't exceed that. Maybe get it close for the bigger endmills/flycutters/facemills etc.

beanbag
07-23-2011, 03:39 PM
The results of collet slip testing that Tomach conducted with their tool holders is presented here:

http://www.tormach.com/document_library/TechnicalDocuments/TD31090_ToolHolding.pdf

and you might find some useful info there.

Mike

Excellent report

lazlo
07-23-2011, 06:13 PM
Excellent report

Ditto -- that testing was extremely well-done!

2500 lb pullout with a clean collet and 30 ft/lbs of torque :eek:

macona
07-23-2011, 08:04 PM
Yeah, that report was good. But it is not a straight pull out that causes a tool to pull out, it is the side pressure working it out. It would be a little more difficult to simulate that though.

I don't think I have ever had a tool move in an ER collet other than when I crash.

gwilson
07-23-2011, 09:29 PM
It is very important to not let any OIL be on the mill's shank,or worse,get into the R8. I haven't had any pull loose,but my journeyman had a 1/2" endmill come out and kiss the mill's table. He wasn't to happy about it,and I wasn't either,but stuff happens. Plus,the mill was about 15 years old by then.

Black_Moons
07-23-2011, 10:12 PM
It is very important to not let any OIL be on the mill's shank,or worse,get into the R8. I haven't had any pull loose,but my journeyman had a 1/2" endmill come out and kiss the mill's table. He wasn't to happy about it,and I wasn't either,but stuff happens. Plus,the mill was about 15 years old by then.

Im sure dry grips better, but I HATE rust, So I bath everything in oil regularly, Never had any slip... Id say proper tightening, lack of debrie (Oily = OK, Dirty is not!), is more important then dry. Not using damaged collets or shanks.. etc. ER collets of course requiring more torque then is sane, and can't really be applyed with the tiny wrenchs they give you, and doubtful it can be applyed while in the mill unless you have the worlds strongest spindle lock.

I wonder about maybe switching to oiling my tapers and tools with CVT transmission fluid? Iv heard its actualy designed to improve grip under high loads, while acting as an oil for rust protection and light slip lubrication.

PS: my mill leaks oil like its going outta style, INTO the spindle, So removing a solid shank tool after a few days and theres a spoonful of oil in there. Any collet with a tool drips oil. Drying things seems pointless. I think I should just call it through spindle coolant... Or 'Chassie lubrication system' is another term I like for leaks that end up onto spining parts that fling it EVERYWHERE.

Black_Moons
07-23-2011, 11:59 PM
Intresting, just got done reading http://www.tormach.com/document_library/TechnicalDocuments/TD31090_ToolHolding.pdf

They say that an oiled tool is very bad. But if you look at the data, you'll realise they mean the heavy *grease* that comes on a tool, Light oil makes very little diffrence. (1850 pounds dry, 1500 light oiled at 20ftlbs, 700 with 'shiping' grease on it)

And that a MUCH worse thing is to have dry threads/thrust washer/taper.
(about 600lbs dry vs 1000~1600 oiled)

So, It looks like if you had to pick, You should slather oil on everything, After cleaning the hell outta it when you first get it. I don't know how you oil the outside of a taper without some getting inside when the collet has slits in it... wipe carefuly with an oily rag? My spindle leaks into the spindle so not much I can really do anyway.

If your REALLY paranoid, they have that clover laping compound.. But ehhh. Id be more paranoid about the laping compound.

Now im left wondering, What about on non drawbar tapers?

I oil my MT tapers. Iv never had one slip on me, though I keep them VERY clean and rust free, allways oiled.
Does this let them seat harder, due to less force needed to seat it deeper, Or does it make it slip easyer, due to oil reducing friction?

Or does it initialy seat harder, then displace the oil for ultimate benifit? Gotta look into CVT transmission oil someday!