A fly cutter, and some questions

[PaulL]

Ok, checked my tram, carefully. Table was good. Vise was out by (get this) 2 thou in 6". Or just over 1 thou between the leading and trailing edge of the fly cutter - dead on the error.
Turns out I had somehow not adequately tightened one of the screws holding the fixed jaw when I trammed it in. I expect some of my "learning" moments nudged it out of true.
So now it's true again and I get this finish, running the feed pretty fast:

Note the small trailing edge scuffs, except for that outlier where it looks like I grabbed a good piece of swarf.
I can do better still, I'm certain, but this meets my current needs.

 

[Susquatch]

Ok, checked my tram, carefully. Table was good. Vise was out by (get this) 2 thou in 6". Or just over 1 thou between the leading and trailing edge of the fly cutter - dead on the error.
Turns out I had somehow not adequately tightened one of the screws holding the fixed jaw when I trammed it in. I expect some of my "learning" moments nudged it out of true.
So now it's true again and I get this finish, running the feed pretty fast:

Note the small trailing edge scuffs, except for that outlier where it looks like I grabbed a good piece of swarf.
I can do better still, I'm certain, but this meets my current needs.

Looks great to me.

The trailing edge scuffs are to be expected. I think the only way to get rid of them is to deliberately tilt the head a bit which has its own set of issues.

Damn those lonely swarf devils!

Are you putting your work on parallels?

If so, I'm not sure I understand how the Jaws create this issue. The parallels should locate the part parallel to the vise base independent of the Jaws. Unless you are certain of what happened, you might want to recheck everything again.

If not, then I assume you have ledge type jaws. Which would explain what you are getting.

 

[PaulL]

Looks great to me.

Thanks

Are you putting your work on parallels?

Oh oh. Yes, I am, and see immediately that tramming in that edge does nothing.
So *by luck* this worked. I removed the vise, cleaned and stoned it , and re-mounted it carefully (and for this purpose uselessly!) checking the top edge of the vise. I should have been checking the bottom and thinking of shims, if needed.
So how in heaven's name did I "fix" it? I have to assume I had a spec of something under the vice, and I never knew because I made the same error the first time. I'm guessing the vise is better machined than I've given it credit for!

 

[Susquatch]

Thanks

Oh oh. Yes, I am, and see immediately that tramming in that edge does nothing.
So *by luck* this worked. I removed the vise, cleaned and stoned it , and re-mounted it carefully (and for this purpose uselessly!) checking the top edge of the vise. I should have been checking the bottom and thinking of shims, if needed.
So how in heaven's name did I "fix" it? I have to assume I had a spec of something under the vice, and I never knew because I made the same error the first time. I'm guessing the vise is better machined than I've given it credit for!

Yes, I'm glad I asked about it. Everything makes more sense now.

Ya, dust matters. Even a human hair can throw things off a thou or three depending largely on colour.....

 

[PeterT]

Your 1018 is I suspect cold rolled? Even though flycutting is small DOC & there is likely no heat in cutting, the material is probably stress relieving as you are progressively removing material. Very common for some distortion once of out of the vise. Actually it can distort even clamped inside vise under certain conditions. So its a good practice to flip flop the part to mate the parallels better & help equalize bending. The raggy edge you get on one side due to tool rotation direction on single pass flycutter. Some prefer to traverse the cutter the same so like up the left & down the right. This is actually more significant for end milling (higher DOC & more chance for chip tearing the edge off vs cutting into it). Remember to dress the edges with file & cleaning before resetting in vise.

The finish looks nice. 1018 finish can vary with the same tool just as function of the stock for some reason, at least that's been my experience.

 

[jcdammeyer]

When I was over at Paul's for a shop tour he showed me the fly cutter he built. We were discussing the supporting edge and seems what I remembered wasn't accurate as to what edge was supporting what.

Contrary to what I remembered the cheap BusyBee cutters do not press the leading edge of the cutter along the slot centerline. In fact the two anchor screws push it away from the center line.

I have a fairly round tip on my cutter with back and front relief.

You can see it this last photo the cheap setscrew still in there is also cracked which is why the other one was replaced with a hex cap screw.

 

[PaulL]

It's clearly the side with the most "meat" left over to hold the screws. But yeah, thinking about it it's odd to have the screws pushing away from the center line.

 

[Susquatch]

It's clearly the side with the most "meat" left over to hold the screws. But yeah, thinking about it it's odd to have the screws pushing away from the center line.

I think it looks and sounds worse than it is.

Besides the fact that it obviously works, the very slight offset from center is probably more or less meaningless at that kind of radius.

It might become more important if you used a smaller piece of hss tool - say 3/16 instead of 3/8 or whatever that is and thereby ended up much further off center.

Even so, one could simply adjust the relief angles at the tool tip such that the attack and relief angles are all based off of the vector from the center of rotation to the cutting tip.