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View Full Version : Why tanged MT so common on boring heads?



Arthur.Marks
05-02-2010, 08:51 PM
I have always wondered this, as I have a mill with a Morse Taper spindle. I always insist on a drawbar threaded shank for my Morse tooling---unless it is for Z-axis drilling only. Yet, especially on boring heads, I see so many that are sold with a tanged MT shank. This is on high quality heads, too: Narex, Tree, Gamet, Wohlhaupter, etc. In other words, the kind where a user would be expected to know better.

Is there some reason a boring head would be safe without a drawbar? My understanding is the side-loads are pretty high due to off-center cutting load and the fact that it is cutting on one side of the bore as it travels through a revolution. I figure there is also the lever effect of the boring bar increasing the side load over the force of resistance to the downward travel.

I also notice that the Wohlhaupter heads have a shank that is threaded, but it includes a tang which is installed in the thread and locked with a set-screw. So there must be a genuine use where it is considered safe. I'm thinking in radial drills or large drill presses where no drawbar exists... but how is that example any different than in a milling machine?

Case in point:
http://i771.photobucket.com/albums/xx357/Arrak_Thumrs/DBG/L6304.jpg

uncle pete
05-02-2010, 09:18 PM
Art,
While I can't answer your question I can state that Narex shanks for their boring and faceing heads have the tang threaded into the shank. This is further retained by a cross hole taper pin, At close to $200 per shank I was a bit freaked when I got mine till I took a good close look at it. Criterion offer a MT 3 shank for their boring heads but it's one piece with a tang? I just don't see useing a boreing head in a straight MT without a drawbar. The whole thing seems pretty stupid to me. From what I can see Criterion do not offer a MT 3 shank that can be used with a drawbar yet their MT 2 shank is set up for use with a drawbar.

Pete

.RC.
05-02-2010, 10:35 PM
A lot of small mills have MT spindles and use a drawbar.. My chinese round column is like this..

You cannot use a boring head without a drawbar, it will just fall out fron the sideways forces...

Arthur.Marks
05-03-2010, 09:03 PM
bump. Reading through the archives, someone here has a Wohlhaupter UPA2 with an integral shank MT2. Of course, it has a tang. I just don't get the logic...

Timleech
05-04-2010, 05:09 AM
bump. Reading through the archives, someone here has a Wohlhaupter UPA2 with an integral shank MT2. Of course, it has a tang. I just don't get the logic...

I've got a UPA3 with integral tanged MT4.
Bought it for use in my mill, with an adapter, because it was at the right price & couldn't find anything at the time with the right shank (pre-ebay days).
Wasn't satisfactory because of the loss of daylight, but I've hung on to it because it's occasionally handy in the lathe.
I imagine they're made that way for drilling machines (& Jig Borers?), the sideways forces won't be huge with most boring head operations. There seem to have been lots made that way, so it must work??

Tim