The Shop > Tools
The Sajo mill is here
Trion:
Thanks Bernd, though the outer weld is just melting the two plates together. The fillet weld which holds the smaller pipe to the plate is far from that nice ::)
Here's a small update for you all
I have been thinking about making a whole bunch of T-slot nuts and blanks for future use, so I found a proper sized piece of steel, a 20mm indexable end mill with fresh inserts and milled it down. I started at the far end of the plate and worked my way back and forth with 10mm wide cuts. Dept of cut was about 0,5mm. I used about 500rpm and 110mm/min feed and ended up with this finish
It is a bit wavy on the middle of the plate, but at each end there are noticeable deep grooves, so I knocked on the dial indicator to measure the height differences, without changing the setup since the milling was done.
A close-up of the finished surface, showing very irregular cutting patterns. The wider spots are low, while the small spots are high.
Set the DI at 0 on a high spot
On a low spot, it is measuring about 0,04mm (0,0016") lower.
When i milled it, I took care to lock the Y-axis before every cut. I also tried to switch on the backlash eliminator on the X-axis but I guess this is worn out, judging by the lack of resistance in the lever.
The way I see it, the contributors to this poor finish might be X and Z axis wear, do you agree? Other suggestions?
AdeV:
It looks to me (from my position as a bit of a newbie) that your mill is out of tram:
Where the mill has "dropped off" the edge of the plate, it looks like there's a significant ridge, with the right-hand-side of the mill (as it appears in the photo) cutting lower than the left. At a guess, this could be your knee drooping forward? Or the head being tipped slightly forward.
What I definitely don't know is why you're getting that "fall off" at the edges...
cidrontmg:
To another newbie, it sure does look like the tram really is a bit off. And that there is some play in the quill axially. The quill seems to drop a bit when part of the milling cutter passes the workpiece edge. I.e., it no longer is "supported" for its whole perimeter. And it seems to drop more as more and more teeth become unsupported. Something in the quill is not spot on. Either there´s play in the bearings, the knee flexes, or ???. :scratch:
:wave:
Bernd:
Looks more like chip drag on the back side of the cutter. Try getting the size down to within a few thousands and then switch to a fly cutter. This will tell you if the head is out of tram.
I also get a finish like that on my Bridgeport. I'm sure the tram is out by a .001" (.039mm) or so. I'm not to worried about that.. I'd be more concerened that the part comes out square and parallel.
Bernd
Trion:
Thanks for the quick reply! :nrocks:
AdeV: The tram is problably contributing quite a bit. Thoug I trammed the head right before making this cut. Unfortunately tramming is very hard to get right because the table is so full of marks, the indicator needle will easily wobble about 3-4/100mm around the places I am measuring. I try to measure on the highest flats, as I believe this might be original table height.
I will try to tighten all the screws on the head and ram to see if it helps. But since the cut was only 0,5mm, I find it hard to believe that anything would flex.
cidrontmg: Axial play makes sense, but I sure don't hope it is that, as I just rebuilt the head. Maybe I need to tighten the bearings a bit more, as they have got some time to run in now. I will try this the next time I'm in the shop!
There is quite a bit of wear on the X-axis ways, could it be that the full cut forces the table down a bit, and when the cutter is exiting the pressure is reduced and the table is allowed to move up a slight bit?
Bernd: Chip drag, one of those things I would not have thought of! A fly cutter is on my to-do list, but it comes quite a while after making T-slot nuts and end stops for the lathe. But I'll try it when it's time :dremel:
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