I Milled!

[mike837go]

ARRRRGGGG! Ratsafratsin off-brand second-rate imitation of a tool!

The draw-in bar pulls the whole collet holder into the quill on the G0516.

The collet holder setup on this thing is an oversized copy of a stinkin' Dremel. The part I hadn't torque-up properly was the 'retaining nut'.

More egg on the face for the n00b.

I googled how REAL milling machines are built. I saw how the draw bar tightens the collet in those.

 

[tmarks11]

The draw-in bar pulls the whole collet holder into the quill on the G0516.... The draw-in bar pulls the whole collet holder into the quill on the G0516.

Your post isn't real clear.

That is how all drawbars work. The drawbar pulls the collet up into the MT3 taper inside the spindle, which forces the collet to tighten on the endmill. Hence the name "draw bar". The collet just about completely disappears in to the recess.

A drawbar arrangement is simplicity in itself, and a quick look at the G0516 parts makes it look just like how a Bridgeport mill works. Although the Bridgeport is blessed with an R-8 taper instead of an MT3 taper.

MT3 taper and collet isn't a "copy of a dremel". MT3 taper has been around a long time, and predates the R-8 taper found in newer/larger machines.

The "draw nut" on top of the drawbar is common on smaller machinery, like my Clausing 8520. Still works the same as a drawbar with a solid top on it. If you want a solid drawbar, you could make one one your lathe. Or make a large nut to fit the top of the drawbar and drill a pin to hold it in place. Or buy one here:
http://littlemachineshop.com/products/product_view.php?ProductID=1414&category=2

I personally hate the MT taper... my Clausing 8520 has an MT2, and the collets get stuck with some regularity... it is classified as a "self holding" taper instead of a "self releasing" taper like an R-8.

Just a note: tightening a collet into a spindle without an endmill in it will damage the collet.

Another note: you can buy an X-2 base from Little Machine Shop for the mill portion of the G0516, and gain a whole separate milling machine out of the deal. Or sell it as a separate unit and buy a mill you like better. Two choices:
http://littlemachineshop.com/products/product_view.php?ProductID=1765&category= (smaller)
http://littlemachineshop.com/products/product_view.php?ProductID=3677&category= (larger)

 

[mike837go]

tmarks11, you are absolutely 100% correct about the construction of good-quality, name-brand, professional mills.

But I just bought a Grizzly G0516. And they do things 'on the cheap'.

I did a little research and looked at the pieces a little more clearly.

Firstly, the quill has a machinist taper (which one, I haven't a clue). Grizzly uses a draw-in bolt to pull the drill chuck or collet holder securely into the quill.

They supplied several 1.5" long collets of various diameters that snap into a nut and are assembled into the collet holder.

The same engineering as a dremel tool. Not the 150+ year proven system that a real mill uses.

I'll try and remember to get some pix and post 'em.

Somebody here already dealt with a similar setup: http://hobby-machinist.com/threads/what-collet-system.35866/

 

[tmarks11]

Firstly, the quill has a machinist taper (which one, I haven't a clue). Grizzly uses a draw-in bolt to pull the drill chuck or collet holder securely into the quill....They supplied several 1.5" long collets of various diameters that snap into a nut and are assembled into the collet holder.

It is an MT3 taper, as I said above.

A draw bar is a "draw-in bolt". Might be fancier on some machines, but it is functionally just a long bolt... or a long stud with nuts on one end.

Initially I was thinking they had provided you with an ER20 collet holder (which a lot of people use to hold end-mills. But 1.5" is a bit long for that size. You said it looks like a dremel... makes me think it is a Double Angle Collet, although that seems unlikely, as that is a superior more-expensive collet design:



I doubt that a chinese manufacturer "invented" their own collet standard when there are so many to chose from already.

Regardless, you should be able to buy MT3 collets and mount them directly in the taper in your machine. Those collets look like this:



The G0516 has been a very popular machine over the years (partly because you could harvest the milling head and add the LMS base, and sell a complete Mini-Mill to finance the purchase of a larger machine). There is a lot of information available from owners over the year; unfortunately much of it is in Yahoo Groups which has been rendered almost useless by their shift to a cumbersome web interface.

If you are googling for info, looking for "Sieg C6 lathe" might help; that is the lathe model that the G0516 is built on.

 

[mike837go]

Unquestionably the milling tool clamping system is a Chinese copy of a good design.

If I had remembered last night, I would have snapped a pic of the whole kit: collet holder, nut, a bunch of collets and a wrench.

I'll try and remember tonight. Thought the finish mower is back online, working better than when we bought it. And the lawns haven't been done in 3 weeks....

 

[brino]

I had to go download the Grizzly G0516 pdf manuals to see what this was all about.
I had seen collets with draw-bars _or_ nose nuts, but not both.

http://www.grizzly.com/products/Combo-Lathe-w-Milling-Attachment/G0516

Here's what the parts manual shows:


So rather than use MT#3 collets and a simple draw-bar, they use an MT#3 to something adapter and a bunch of smaller collets with a nose nut. It probably is some known standard taper and collets, but they do not say what.

Too bad, this system is likely more limited in holding capacities than the MT#3 set Tim shows above.
I'd be tempted to throw the Grizzly supplied set in a box, and buy the MT#3 ones.

It looks like that original set of collets has a groove that should be used by an off-centre holding ring in the nut to pull the collet from the taper on extraction. The collet should be installed in the nut, before the nut/collet and put into the adapters taper. Otherwise the nut will actually push the collet off centre and possibly damage something. I saw no mention of that in the parts or owners manuals!

One advantage of the Grizzly supplied collets; they get loosened off the work by loosening the nose nut.
Unfortunately, you still have to use a soft hammer to remove the adapter from the mill spindle.
They just moved that problem(having to pound on the end of a threaded shaft) from one place to another.

-brino

 

[mike837go]

Dats dem alright!
'ceptin the nose nut has flutes and uses a spanner. Not the hex pictured in the parts list.

And yes, you clip the collets into the nut before screwing it on the holder. Otherwise, the pieces go way off center! First-hand experiance there.

 

[tmarks11]

Hmm, looking at Grizzly's site, they sell the "Quick Change" collet set, that looks like a bastardized ER32 collet set. The angle on the collets isn't quite as steep as it is on an ER set. Guess I was wrong about the factory not "inventing their own standard". Does your kit look like this? The diagram in the previous post makes it look like the end that mounts into the mill is cylindrical rather than tapered.

I have an MT2-ER25 collet holder that I use with my Clausing. Very popular accessory because you can swap out endmills faster with it than by using the drawbar and conventional spindle collets.

The nut on the ER collet is designed with an off-axis hole to make inserting the collets into the cap possible (and quick)... by design. Putting them in the holder, and then screwing down the nut does not work, as it sounds like you discovered.

Unfortunately, you still have to use a soft hammer to remove the adapter from the mill spindle.
They just moved that problem(having to pound on the end of a threaded shaft) from one place to another.

The idea is that you can leave the collet holder in place, and only loosen or remove the collet nut to swap endmills... which works until you have to use a drill chuck.

The downside of the MT taper is that it is not "self releasing", and sometimes requires some good smacks to get it to pop out. Sometimes requires quite a bit more than a "good smack".

 

[brino]

that looks like a bastardized ER32 collet set

You got that right!!!!

It's not just the angle:
-those slots are only cut from one end, that means it will only compress and grip at the front edge, the tool/work will still be "tippy" in those even when tight!
-looking at those holes near the back end, the collet is just a thin shell on all diameters; there is nothing at the back edge to grip the tool/work!

The real ER-32 type collets are split alternately from each end and are the stated internal diameter at least an inch in for the small diameters and all the way thru for the ones larger than about 3/8".
When they contract they grab for nearly the entire length.

Here's some shot I just took of a 1/8" er-32 collet:


and a 3/8" collet:



-brino

 

[mike837go]

You got that right!!!!
It's not just the angle:
-those slots are only cut from one end, that means it will only compress and grip at the front edge, the stock/work will still be "tippy" in those even when tight!
-looking at those holes near the back end, the collet is just a thin shell on all diameters; there is nothing at the back edge to grip the work!
...snip...

That would explain why my cheep hobbyist mill has them and the professional units still use the more accurate, tried-and-true system.