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Cutting down QCTP tool holders

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We've touched on this subject. The BXA QCTP I bought for my Grizzly G0773 lathe / mill combo (12 x 27 swing & c - c) doesn't sit low enough on my cross slide. I couldn't begin to mill the holders as they are too hard. So it was suggested that I mount 1 up in the 4 jaw & starting from the center, cut it to size. OK, got it chucked up. What insert or cutter should I use?

IMG_20181025_221617593.jpg
 

Comments

#2
Depends what you have available. As it will be an intermittent cut I'd consider which of my current tooling has the strongest cutting edge. For me it is a WNMG cutting tool. Maybe also have a look to see if any inserts are available for intermittent cutting as these will have a stronger cutting edge.

That being said most any carbide tooling should work OK. Just take it easy and expect that you may chip a few inserts.
 
#3
We've touched on this subject. The BXA QCTP I bought for my Grizzly G0773 lathe / mill combo (12 x 27 swing & c - c) doesn't sit low enough on my cross slide. I couldn't begin to mill the holders as they are too hard. So it was suggested that I mount 1 up in the 4 jaw & starting from the center, cut it to size. OK, got it chucked up. What insert or cutter should I use?

View attachment 278418
How much over height are you? Aloris and Shars both sell oversize tool holders for BXA. The floor of the Aloris 2S slot is 7/16" and for the Shars 201-XL, its 3/8".
 
#4
That looks spooky, I would think carbide end mill should cut it, better yet surface grinder
 
#5
This is a Shars AXA boring bar holder that I modified. I used an insert boring bar, bur the cut became interrupted as I got into the pinch bolt bosses. Nevertheless, it machined without much effort.


(from mobile)
 
#6
I hardness tested a Chinese AXA boring bar holder, and it came up as Rc30, not so very difficult to machine, especially with carbide.
 
#7
I am surprised that a part like this could be machined on a lathe but not on a mill. Comments?
 
#8
I am surprised that a part like this could be machined on a lathe but not on a mill. Comments?
Likely, it could be milled just as easy, but for the holder being bored as is shown, it would be faster in the lathe; if the bottom was to be machined as in the original post, if one had an insert end mill or face mill, milling would likely be faster, and its likely to have the bit or insert chipped when passing center if done in the lathe.
 
#9
I am surprised that a part like this could be machined on a lathe but not on a mill. Comments?
I think that it has something to do with the quality of the tool and the rigidity of the setup. Somehow, facing on a medium lathe is more solid than surface milling with a Jet Bridgeport clone. That was what I found at Techshop, when I was a member. I was trying to cut 4140 prehard, and the heavy mill felt like it was about to shake its table off. There was little progress on the slot I was cutting. The lathe tools, while hand sharpened, probably had a superior edge in comparison to the cheap Chinese gold colored public end mills. Since I had to cut a slot, I eventually TIG welded a small vertical geometry fly cutter with a cobalt (hand sharpened) lathe bit in it. It was able to finish the job on the mill where the cheap end mills failed. Even a broken drill bit in a block toolholder is capable of doing some tough cutting in a lathe.
 
#10
Thanks guys. Still using the mini mill on the combo. Just too Shakey. Updates to follow.
 
#11
Pick a negative rake insert like a TNMG, CNMG or WNMG, something that will take a beating. Were it me, I'd use the 100 deg. corner on a CNMG432. Of course, it may not be worth the expense of buying a holder and inserts for this job unless you're just looking for an excuse. If not, use what you already have and get the job done.
 
#12
I needed to skim the bottom (and cut a step) in my 40 position style QCTP holders. I made up a mounting peg to hold the tool post (with a piece of threaded rod all the way out the back of the headstock to pull the mounting peg in securely) onto my drive plate. Then I just used the locking of the tool post to hold the holder. I trimmed ~8 holders (took about 0.1" off the bottom of each, cut the step, beveled the splines). There was nothing really special about the tooling - somesort of generic TNMG for the facing and CNMG in a carbide shank boring bar. It all worked out great (getting a nice finish took a few tries). For the primary tools/holders I skimmed them just enough so that the holder sits right down on the compound - no adjustment needed (I took the adjusters off) - afterall the tool will likely stay in that holder as long as I own the lathe.

The point being that while the holder material is pretty hard / tough material, skimming the holders was not a big deal.

Let us know how you make out. David
 

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