using end mill in collets?

[sourdoughsmitty]

I purchased some r8 collets for holding the end mills in my mini mill , These were from grizzly evn when the collet is sucked down tight as the existing draw bar will let me i can still move them in the collet ??? When I get to work tonight I will look and see what we have for shim stock as well as making a longer draw bar these are the only things I can think of to do ,I have no way of checking the tapper accuracy up in the spindle , my end mill measures dead on at .500 while the hole in the collet measures aprox .485 when the collet is relaxed have not had a chance to measure it wen it is drawn up any ideas here or perhaps i should have actually bought mill holders in the first place ;D thanx smitty

 

[Blogwitch]

Unfortunately R8 and 5C type collets do not compress down like ER collets, so the tool has to be a good fit in the collet to begin with, otherwise you can do permanent damage to the collet by overstressing it.

Are you sure you haven't bought metric collets and tried to fit imperial cutters, or vice versa. For a 1/2" cutter, you have to use a 1/2" collet.


Blogs

 

[sourdoughsmitty]

nope I checked all sizes are american ,of course when one is buying from china and india their interpretation is a bit off on sizes sometimes if my previous post remedies do not fix this then i will just bite the bullet and buy some mill holders given the low cost for the collets it would not be cost effective to return them besides I can use them somewhere else thanx for the input smitty

 

[rtp_burnsville]

I would measure the hole in the collet and also the diameter of the bit. That should quickly tell you where the problem might be. Is the drawbar length correct for the collet? Just another possibility.

 

[kvom]

Seems unlikely to be the drawbar, esp. if other sizes collets are working.

 

[1hand]

Stupid Question here. But doesn't the mini mill have a Morse Taper?

 

[joeby]

If they are the correct collets for your mill spindle, try tightening the collet without a tool in it (not 'till you damage the collet) just enough to see if you are having interference problems.

Could you possibly be running out of thread on the drawbar or is the collet bottoming out?

Kevin

 

[hammers-n-nails]

i have r-8collets from grizzly and have not had this problem, however i have had problems with the mill being pulled out while milling, i recently got a set of endmill holders and they work much better.

 

[ksouers]

Stupid Question here. But doesn't the mini mill have a Morse Taper?

Matt,
The X2 can have either a MT3 or R8 spindle, depending on the vendor.

 

[Stan]

I use Import MT3 collets with no problem. It takes a bit of effort to push the end mill into the collet and it doesn't fall out when putting it in the mill. MT3 collets are only made to fit the size stamped on them if they are made correctly in the first place.

 

[1hand]

OK, didn't figure it be a simple fix like that. I also have a set of grizzly R8 collets for my SX3 and haven't had a problem. Are the sizes giving you problems or just the 1/2"? Could be the collet.

 

[Lew Hartswick]

If your measurments:

"my end mill measures dead on at .500 while the hole in the collet measures aprox .485 when the collet is relaxed "

is right, How did you get the cutter into the collet? If you had to "strech" the collet
to get the cutter in it isn't holding except by a very narrow line of contact and would
"wiggle".
...lew...

 

[Lew_Merrick_PE]

I purchased some r8 collets for holding the end mills in my mini mill , These were from grizzly evn when the collet is sucked down tight as the existing draw bar will let me i can still move them in the collet ??? When I get to work tonight I will look and see what we have for shim stock as well as making a longer draw bar these are the only things I can think of to do ,I have no way of checking the tapper accuracy up in the spindle , my end mill measures dead on at .500 while the hole in the collet measures aprox .485 when the collet is relaxed have not had a chance to measure it wen it is drawn up any ideas here or perhaps i should have actually bought mill holders in the first place ;D thanx smitty

Smitty, The collets are probably NFG. I am positive that, so long as massive time has not accumulated since you received them, Grizzly will make good on them. R8 collets may be a couple of thou "off" in the "relaxed" condition, but not a whole lot more than a couple of thou off (call it .497/.503 for a nominal 1/2 inch collet). If the rest of your collet set is good in that way (stop and measure them now!), the people at Grizzly are likely to just send you a new collet based on your say-so. If the most of or the entire set is bad, they will probably want them back to shove down the throat of their supplier.

If you "tap" the collet all the way "up" into your spindle, the drawbar should sit loose (i.e. no threads engaged) with its shoulder about 1/2 inch above the bearing surface on the end of your spindle. If it is sitting (say) 3/8 inch or less, a new drawbar is in order. If it is much higher (say more than 3/4 inch), then you should make a special washer to move it down into the 1/2 to 3/4 range (there is almost an inch of thread in a standard R8 collet). I have the specification drawing for an R8 collet if anyone is interested.

It's less about who you buy your collets from than who made them. Royal and Lydex collets are rarely more than .0005 off dimension with runout in the .0002 range. I see many of the import collets having a runout in the .0015/.0010 range. I have even seen some of the early Chinese collets that were so bad that you could see the runout with your naked eye (though, I admit, that was years ago and I have not seen such a situation since)! I have become quite a tool snob over the years.

 

[sourdoughsmitty]

Great info here,
I will check the draw bar height and also check with an empty collet too , It was slow at work last night si I made a measurement of the collet bore in relaxed mode and found that my first measurement was off (aint being a senior fun :big it is closer to the .500 diam of the mill bit. I recieved the new grizzly catalog today and noticed that they have a new "quick change" collet set#T10068 for r8 these collets look like they will squeeze down better than the standard one , someone here did mention that point with the r8 ,5c types anyone used this setup ? meanwhile down to the dungeon to test out the drawbar length etc, thanx all agai for the help :bow: :bow:
smitty