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First post, facing question

Richrd

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#1
Just got first lathe, an older atlas. Trying to teach myself as I go. When facing, do I start outside and cut in or start in the middle and cut out? I thought I have the tool centered, but I having trouble leaving the little tit in the middle.

Thanks
Rich
 

Bill Gruby

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#3
If you are leaving the little nub in the center you are either above or below center. As for cutting I start outside and cut moving toward the center.

"Billy G"
 

savarin

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#4
Rich, you need to get the tool at spot on centre height so it doesnt actually leave that little tit.
If you keep getting one double check to see if you have to lower or raise the tool.
I find it easier to cut from the outside going in but sometimes will take a fine cut from the middle out just to see if theres any difference in surface finish.
 

Uglydog

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#6
As you move the cutting tip inwards try not to let the cutter pass the center point.
As soon as you do then it ends up reversing the direction of rotation relative to the cutter.
If you are using carbide, then you might end up chipping your cutter when you pass the center point.
You might want to start out using HSS for many reasons.

Also, think about how the cutting speed changes as the diameter changes (when you move the cutter inward).
This is interesting for me to consider as I think about speeds and feeds relative to diameter.

Daryl
MN
 

ddickey

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#7
If its a rounded nub that most likely means your tool is to high. Like the others said a straighter tit it's to low.
 

Wreck™Wreck

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#8
Facing is often unpleasant, maintaining a uniform surface is nearly impossible even with a machine that supports CSS. The desired SFM reaches infinity at X zero.

If facing to 0 in X start from the outside, if you try starting a tool at 0 X the work is essentially not rotating, running a tool into a non moving part rarely works well.

If the part has a hole/bore in the center it is sometimes efficient to lightly face from the inside out eliminating some tool moves, I sometimes do this with a boring bar, tread lightly however. Running a tool a near zero surface speed will likely leave a nub at the center.
 
Last edited:

higgite

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#9
You can do it either way. When facing to remove material, I do it from outside in rather than trying to plunge the cutter into the face 10-20 thousandths. When facing for finish, I do it inside out. I just get better results that way. Like WW said, dead center of the face is essentially turning zero sfm or near to it. So, when facing from the center outward, I plunge the tool maybe 2-3 thou into the face a short distance from dead center of the face, then face to the middle and back out to the edge. ymmv

Tom
 
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