# Flycutter and 0.40mm TiR?



## jdm23 (Mar 19, 2021)

I have just started with milling on my combo machine. Trying to clean a bit a piece of structural steel (I know is one of worst materials ever, but I have nothing else easily available), not knowing jack about the ideal shape I've just ground some back relief in an 8mm square HSS.







The result is less than perfect, I used a slow power feed, but something must have moved at some point






Probably it has nothing to do with the above but it bothers me that I can see the top of the spindle wobble a bit, in fact I measured as per topic title, where the picture is taken. In another topic I had reported about a slightly better TiR measured at the collet chuck and was told that the machine is useable anyway.





This is a 550W machine with a MT2 spindle. Any chance that the bearings can be adjusted? Replacing them could improve the situation?


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## DavidR8 (Mar 19, 2021)

Oops looks like a couple of your pics didn't load correctly.


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## jdm23 (Mar 19, 2021)

DavidR8 said:


> Oops looks like a couple of your pics didn't load correctly.


Thanks, should be fixed now.


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## pacifica (Mar 19, 2021)

jdm23 said:


> I have just started with milling on my combo machine. Trying to clean a bit a piece of structural steel (I know is one of worst materials ever, but I have nothing else easily available), not knowing jack about the ideal shape I've just ground some back relief in an 8mm square HSS.
> 
> 
> 
> ...


Is spindle holding flycutter  tight?


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## Aukai (Mar 19, 2021)

The draw bar shaft on top will wobble, indicate at the spindle, chuck/arbor, and tooling.


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## jdm23 (Mar 19, 2021)

Aukai said:


> The draw bar shaft on top will wobble, indicate at the spindle, chuck/arbor, and tooling.


I am not about the draw bar. There is 0.40mm TiR on the spindle just below the wrench cut.


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## Aukai (Mar 19, 2021)

What is it at the working end of the spindle?


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## jdm23 (Mar 19, 2021)

Aukai said:


> What is it at the working end of the spindle?


Better than that, but I don't think that is normal. 
So my question again:

_Any chance that the bearings can be adjusted? Replacing them could improve the situation? _


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## WCraig (Mar 19, 2021)

0.4 mm is about 0.016 inches.  That is far, far too much runout for a mill spindle.  Can you take a picture of how you measured this?  If you hold something that is known to be straight (say drill rod; aka silver steel), does the measured runout get worse further away from the spindle?

Is your combo machine new?  If so, contact the dealer.  If used, what do you know about the history?  A morse taper 2 spindle isn't very heavy duty so it is possible that the spindle got bent during a crash.

Craig


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## markba633csi (Mar 19, 2021)

If the bearings are the tapered roller type then they should be adjustable.  If they are ball bearings then usually not.
Does this machine have a quill like a drill press?  If so you would want to lock it down before testing for runout, and during most milling operations
The milling you did on the square piece of tubing in post #1 looks reasonable as far as the scalloping pattern you would expect. Clamping hollow material can be dangerous though, be careful.  Pieces can pull out and launch themselves suddenly in any direction, with bad results. This is especially true when drilling large holes, as the drill bit breaks thru.  Passing a piece of bar stock or even lumber thru the part being machined, with both ends of the bar stock fastened to the table is recommended, in addition to the vise.  Yes it's more hassle but better than getting hurt.
Spindle runout should be much less than one thousandth of an inch with good bearings FYI
-Mark


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## T Bredehoft (Mar 19, 2021)

jdm23 said:


> something must have moved


It appears that the back side of your cutter is closer to the table than the front side. This indicates that the spindle is not square (perpendicular) with/to the table.  If this is so, the spindle is out of "tram."


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## jdm23 (Mar 20, 2021)

markba633csi said:


> If the bearings are the tapered roller type then they should be adjustable.  If they are ball bearings then usually not.


The top at least is a ball bearing.







Since for quill operation the black section pictured above freely slides inside the silver sleeve held by the circle-clip, I'm now thinking that because of that some play in the top (fixed) section is inevitable, and causes the runout that I measured there. It gets actually smaller closer to the bottom.



markba633csi said:


> Clamping hollow material can be dangerous though, be careful.


I'm very concerned about safety. The work is fastened to the cross-slide with T-bolts. Incidentally that is also its final destination - a makeshift support for something that I will show in another posting.








T Bredehoft said:


> It appears that the back side of your cutter is closer to the table than the front side.



I'm not sure why you say that. The cutting edge is on the left in the picture, and much closer to the work. The top edge is horizontal and parallel to the  cross slide. 






However I have then seen that since a fly cutter has the cutting edge inline on with its center, the back of the tool runs outside the circle if a relief for that is not ground, thing that I did then, as well honing a small radius on the nose. Ran a minimal cut it again with some spray fluid and I can barely feel the marks with a finger, so I'm OK with the result.


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## markba633csi (Mar 20, 2021)

Most flycutters I have seen hold the bit at an angle so that only the tip needs to be sharpened and the rear of the tool clears automatically- Yours may be different
-M
Bolting the workpiece down is certainly safe- I didn't know if you were using a vise or not


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## rwm (Mar 20, 2021)

Regarding that top part with the wrench flats: Is that really the spindle or the spindle cap that attaches to the spindle? If it is the spindle cap, runout would be unimportant except for vibration maybe.
Robert


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## jdm23 (Mar 20, 2021)

markba633csi said:


> Most flycutters I have seen hold the bit at an angle so that only the tip needs to be sharpened and the rear of the tool clears automatically- Yours may be different


The blank tool (on the left) comes cut to  neutral rake, but you still need to grind back relief angle. Indeed the under relief that I ground is not necessary. 








rwm said:


> Regarding that top part with the wrench flats: Is that really the spindle or the top hat that attaches to the spindle? If it is the top hat, runout would be unimportant.


The hat. As explained above, I came to the same conclusion.


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