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Boring Head recommendations

Perhaps I can clear the backlash thing up. Craig was disappointed by the backlash in his BB head.

There are a bunch of causes for backlash, but the primary one is incorrect use. (I wouldn't dismiss manufacturing error as another likely cause).

-- I was taught to snug the 3 Veeway screws after making an adjustment, loosen them to make another, then retighten. An error all to easy to make is to leave too much pressure on the screws, resulting in excessive lead screw wear or damage. Note i said SNUG. it is a feather touch on the allen key, not a wrenching pressure. The load on the single point tool is very light: 20 kilos or less. You should never take large cuts with a boring head. It is not designed for deep cuts in heavy materials. My average cut in soft steel: 5 thousanths. In soft brass maybe up to 10 thou.

My lead screw has about ?5 thou of backlash, but since I'm always moving the head in one direction, I've never noticed it. My other boring bar has about 3 thou backlash. Same scenario.

An autofeed boring head has a completely different mechanism, and should not be fiddled with... you dial it in, and cut.
 
Susquatch said:
... mention of backlash was just a reflection of my thinking that "who cares?" if you lock the travel by tightening the v-ways, backlash doesn't matter. I ALWAYS tighten all adjustable movement into the work not away from it...
Click to expand...
I think backlash can matter, but kind of depends on application & circumstances. There are many machine/mechanism examples where the friction drag of the movable surface is set independent of the locking mechanism. What can happen is the act of 'locking' can physically displace the movable surface, depending on the machine design & tolerances. So for example, you set the dial to 0.001, apply the lock & the surface physically moves to 0.003" equivalent (even though the dial still remains reading 0.001"). Gib screw arrays without an independently acting lock can be more prone to this behavior because the tightening torque occurs in same direction, so each screw can provide a little displacement nudge in succession. If the backlash is high & the base drag is loose the combination can contribute to higher setting error. One of the most revealing things is put a dial (or DRO) on a movable way surface like your lathe & watch what happens when you simply lock. Ideally do it with machine running (surfaces on older / less accurate machines machines can get lively under vibration). If the needle remains perfectly still after lock, you have a winner setup. If it moves, its something to factor into consistently hitting dimensions.

In terms of tightening into/away from the work, you may not always have that choice. Consider a lathe out-feeding to a target bore diameter vs in-feeding to a target shaft OD. The leadscrew direction is reversed whereas the gib tightening direction is the same. Boring heads can similarly extend both inward or outward but probably most people bore holes the majority of time.
 
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Thanks guys, I think I have all that straight in my mind. It's something I will have to investigate on my own tooling to know how much it affects me.
 
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