Technical question on milling R8 adapter

B

Black Jack

CGN Regular
Rating - 100%
13   0   1
Location
Ottawa
I have a question for those who have a mill similar to mine. I just got a B096 Busy bee mill/drill. I got a few tools with it but all the adapters are for MT3. According to the specs my mill has R8 spindle taper. I went to BB to get some end mills to start playing around. They told me I needed a set of collet to be able to use them so I bought them. I removed the facemill that was attached to the mill with the draw bar. All ok for now. When I tried to insert the R8 collet I noticed that they do not fit in the spindle. I looked around to understand how it works and then realized that the drawbar I got would not screw in the collet I got from BB. Today I called them up and the gentlemen told me it was because I had the small draw bar and with the 7/16 NF I would be able to take the adapter out and then insert my R8 collet. So I bought the bigger drawbar. I put the drawbar in the hole to screw it in the adapter.... head hits the bottom without screwing in anything. I checked the lenght of both my drawbars and the 7/16 one is about 4" shorter. I take a mirror and look inside from the top and the bottom with a flashlight. I can clearly see a straight hole with no threads anywhere for the drawbar to screw in.:confused::confused: I can also see that the lower section is tapered the way it should for the MT3 tools to attach properly. Then I thought, maybe the adapter from R8 to MT3 has to come out with the driftkey. I can see the slot in the quill but it's completely blocked with the adapter. It goes higher then the slot in the quill. So I'm really confused. Not sure what exactly is this adapter but it accepts MT3 holders. I cannot see threads and the drawbar BB sold me doesn't seem to work. Where do I go from here :) Hope somebody had same problem at one time and can help me out. I will eventually go back to BB but it would be nice if somebody had an idea of what's the problem. Tks

We can see the fly cutter that was attached to the mill originally. It's an MT3 holder with the 2 slots each side for that kind of fly cutter and slip in to hold.

mill_tools.JPG
 
According to the specs? Huh?

How about you look and see if you have a R8 or MT3 version of the mill.

Start there.

Once all the tooling is removed, an R8 taper looks different enough from a Morse taper that you should be able to tell without any trouble.

R8 tapers are self releasing, Morse tapers need a solid thump with a chunk of something heavy.

I'm betting that you have a MT3 taper mill. Lots of them around.

"According to the specs" is a great way to pee away your money on tooling you cannot use. Hope they will give you a refund.

Can you see all the way up through the spindle when your drawbar is removed? If yes, and the R8 does not fit, try the MT3.
That'd be about all it would take to convince ME that it was a MT, not an R8.

Cheers
Trev
 
My old BB mill is MT3. You said the taper fits the MT3. Make sure that the mill is in fact R8 with an MT3 adapter before trying to drift out what might actually be part of the machine and not an adapter.
 
All the tooling you showed us in your previous thread on this mill indicates that you have a MT3 spindle taper in this mill and you would need a set of MT3 (Morse taper) end mill holders which have a 3/8"-16 draw bar.
 
I would say that the specs could be wrong in my manual but I have another question. Being R8 or MT3 holders. Should I be able to see right through the quill in the slots along the body so a drift key could be used for a drill chuck? If it's the case, something is inside because I cannot see through it. Or maybe you are not suppose to see through when it's a MT3 adapter?? Tks again
 
if your spindle is R8,there is a 7/16 hex bolt head on the top of the spindle to change tool
slack it a few turns and give a little tap to push down the tool shank
it is possible to have a R8 spindle with a MT3 adaptor in it
 
Most of these older mill/drills had a MT3 spindle taper, and there is no such thing as a MT3 to R-8 adapter, you can get a R-8 to MT. You have to remove what is in your mill spindle and try installing some of these end mill holders and other tooling you have there, make sure it is all very clean, and lub the threads on your draw bar.
 
As mentioned a few times now you can't go by the specs for today's model. Busy Bee keeps the same model number even when some of the specs on the machine changes from year to year.

Since there is clearly no R-8 tooling in that other thread it's pretty much an iron clad cinch that you have an MT-3 spindle.

The nose of the spindle on my own MT-3 mill has those same slots to engage the drive dogs found on the face mill as well as some other larger cutting tooling. That portion is NOT an adapter, it's the actual spindle.

Do you have a lathe as well as the mill? If so you can make a lot of your own end mill holders that will have a lot less leverage and wobble than the extended holder shown in your other thread. Busy Bee sells MT-3 soft end machinable blanks which have a nice short 1 inch diamter by 1 inch long annealed stub on the nose of the taper. These can be chucked in the lathe with no chuck mounted by using various Morse Taper adapters to hold the stub as accurately as the centering on the lathe spindle and adapters. Once mounted drill out undersize, bore to a few thou undersize to remove any runout then ream to the size of the milling cutter shank. Drill and tap a hole for an allen set screw and you have made yourself your own Weldon shank end mill cutter holders that have far less overhang than the one shown in your other thread. The greatly reduced overhang will result in a lot less risk of flex and chatter. These stubs are good up to 1/2 inch shanks. For my own 5/8 shank holder I used the same MT-3 stub but press fitted on a 1.25 inch collar over the stub before machining so I'd have more support for the set screw. For my 3/4 inch shank holder I actually made my own from scratch along with a few other MT tooling holders Yes, I machined my own morse tapers. It wasn't as bad as I would have thought for the doing of it. But the thinking of how to avoid any problems was a mind bender... :D

Actually it was an excellent exercise. Much of metal machining is figuring out a method that reduces or cancels out errors in tolerance and how to test the things you do machine for accuracy. Making the MT tooling shown below was very much filled with these basics.

On top is the 3/4 shank end mill holder machined from one solid piece of 1.25 inch steel, on the lower left is a slotting saw holder machined from another piece of the same 1.25 inch bar stock. On the lower left is a store bought boring head mounted on my own shop made taper to threaded adapter. All three are threaded on the rear for the typical 3/8x16 drawbar to use with my mill.

Tapers.jpg


Oh, one more thing. My own mill does not use a through slot for a taper to knock the arbor out of the spindle. And it would be a PITA to run it down each time to use if there was one. Instead I only lightly pinch the draw bar tight so it's not locked silly tight into place. To knock the arbors loose I loosen the draw bar bolt about two turns then smack the end of the draw bar smartly with a big lump of lead I have. It was an old 5 lb scuba weight. It knocks the arbor out of lockup neatly. And by keeping all but two of the threads in engagement there isn't a big amount of stress on anything.

And when I say that a light pinch tight on the draw bar is all that is needed I mean it. I tighten the drawbar with a bit of a flick of the wrist on the wrench while not holding the spindle from turning at all. So obviously I can't tighten it much because the spindle turns with not much friction. But that is all I've ever needed to lock it in place. And by not tightening it any more than this it makes it fairly easy to knock it loose.
 
Black Jack said:
Yep, thank you guys. Did some research with my serial #. My specific mill has MT3 spindle. All good, will return the collet and the draw bar :)
Click to expand...

Yeah.
Don't get all down in the mouth about it being a Morse rather than a R8 taper. R8 would be a choice to make when buying new, but the MT3 mills are as good, just a few different things to watch for.

The advice to not torque the drawbar up past very light torque, is some of the most reasonable and accurate advice I have seen online with regards to these mills in years.

The upside of the MT taper, too, is that these mill-drills make a damn good drill press, and if you set them up so you can swing the head around behind the table top it is sitting on, you can place a small drilling table there so you have fairly large clearance under the head for drilling purposes. Then you can use the head rise and fall for the coarse adjust, and the quill travel for the work. A decent drill press is getting hard to find!
At one point, I had spoke with a Thomas Skinner employee about the Mill-Drills they stocked, and they told me that they were selling them mainly to shops that wanted them as drills, so they usually had them with a taller than normal column, and only stocked the Morse Taper model.

So it ain't all bad!

As far as I know, Busy Bee has a set of collets in a holder, that will fit the Morse spindle. The collets are a double taper type, that must (MUST!) be clipped into the nut before being tightened on to the adapter, or they will be truly miserable to remove. But they grip an end mill well, and will not cause you too much undue grief.

The B360 MT3 collet set, would be something to avoid, at this time. The reason I say this is that they need to be tightened up a fair bit to grip an end mill well, and have no provisions to stop the mill from turning (though you could drill out a spot for a locking pin or screw.PITA). They do offer the advantage of allowing you full use of all the limited headroom under the spindle (ie: the cutter can be mounted as high up in the machine as possible) but it is also possible to spin the cutter in the collet and ruin it, fairly easily.

The one to look at is the ER32 or ER25 collet set with holder. Sadly, I cannot see them on the BB site, with a MT3 shank, but I know that they used to stock them.
Lesse... OK. Do a search on Ebay for "MT3 ER Collet" and you will see exactly what I am on about.

The real advantage to the ER collets is that they can hold, nominally, a full millimeter range of size, so a full set of them is not as many as would be needed for covering all the things you might run across. This is a much wider range than most collet systems, and allows you to use the same collets to hold a wider range if tools (inch, metric,drill bits, and so on) safely (meaning it won't eat your workpiece and set you back to the start again).

The different numbers (ER16, ER20, ER25, ER32, ER40) refer to the collet size they fit. Useful info when shopping for spares. The smaller collets are more useful for smaller cutters, and you can see what is going on at the work.
I would figure for a MT3 mill, I would look pretty hard at a ER32 set, and get a couple set screw type holders for larger diameter end mills.

I could go on and on...:)

Cheers
Trev
 
I've avoided the ER collet sets strictly due to price. However I do salivate freely when I see a boxed set behind the glass.... :D

Oh, another hint on the set screw style weldon shank holders. There will always be a stacking up of the tolerances. After I made mine I tested them at various positions in the spindle to find where I got the minimum of runout. This being tested using a dial indicator on the round portion. The spindle was marked using an "I" from my letter stamp kit and the holders all got a matching "I" witness mark at the position that resulted in the least runout. It made a big difference in how smoothly they cut. Before I'd randomly get a smooth cut then a varying cut. After the testing and indexing I realized that I could get a max of 2 to 4 thou of runout. When minimized simply by finding the least out of position spot I was able to reduce it to around a thou or less. BIG improvement that can be done to home made or factory holders. In fact I'd even say it could be worth the testing for an ER or other collet holder.

It all comes down to the idea that you can never assume that anything is exact. The only time you can say for sure that something is centered is if ALL operations are done at one time in a lathe. Then, assuming the bearings are in decent shape, you can safely consider that all those cuts are centered. Everything else is suspect and needs to be dialed in if centering truly matters.
 
You must log in or register to reply here.
Back
Top Bottom