Are you making fine passes across the whole 20mm depth or one deeper cut and lowering teh cutter in stages?

There is a tendancy for a blunt cutter to deflect sideways, same if there is play in the spindle bearings so make sure anything that can be tightend is tight and you are using a sharp cutter of the largest dia you can hold.

I have no problem doing the same sort of thing on my x3 but 20mm in one pass even if not removing much metal is not the best way

J

EDIT, just saw JS's edit you can tram these mills by shimming under the column.

Edited By JasonB on 20/10/2014 10:13:43

Is the work lifting when you tighten the vice?

Martin.

My understanding of this is that you are moving the head down in small increments Paul.

I don't have an X3 but do own two 'knee' mills. So if we assume that your mill's head is moving down in a truly vertical plane to the table (and you might want to check it) then another possibility is that the 'tilt' of the head is not set exactly at 90 degrees. Depending which way it's tilted, you will not cut at a true right angle and as you may not have side clearance (if it's tilted the other way you would be cutting a series of ridges) you may also start to deflect an extended cutter no matter how sharp it starts off.

So I'd check both the vertical movement of the head and that the tilt is set correctly as a start.

Another thought – and this is just a personal thing. I don't have the ability to sharpen my end mills at the moment, so I tend to save them for when I really don't have other choices (e.g. narrow slotting). For this kind of job (which I can do easily in a shaper by the way) if I was 'down' cutting on my smaller mill – as there is lots of room on the outside of the work, I'd probably use a 'side' version of a small fly-cutter. Just bar stock with a cutter held at 90 degrees by a grub screw. Very easy to make. Then I get the advantage of an easily sharpened single point tool, no clearance problems and a far less flexible tool holder.

Also, I don't know what kind of lathe you have but with a large enough chuck, a sharp tool and very gentle cuts I think you could face off this bar in your lathe. The cut will be interrupted on the corners but will be fine once into the centre. You will probably be able to see the cut 'transition' but it should still be flat (given that "flat" is a relative term!).

Anyway – hope this gives you some other things to think about.

Regards,

IanT

Edited By IanT on 20/10/2014 10:45:49

Paul look at the test cuts I did in this thread, similar to what you are trying to do, came out square.

We are assuming the cut is out of square vertically, if its out front to back then you need to clock the vice fixed jaw in with a DTI.

If you have a face cutter, use it as a face cutter, rather than trying to dress the side of the block.  Last time I had to do a similar sized bit, I clamped it to a pair of V blocks, and stood it on end, and clamped it to the table, but normally I would use the four jaw in the lathe.  You could of course put it in the four jaw chuck and clamp that on the mill.

Ian S C

Edited By Ian S C on 21/10/2014 11:04:33

Co-incidentally I've just faced off a couple of 140 mm lengths of 20 mm square to length in the lathe – no problems, five minute job. It would have taken much longer to set up in the mill.

Russell.

I also misread the original message. Must go back to Specsavers.

If you merely want to face off the 25mm square end the frankly a 4 jaw chuck in your late will do it very well and very quickly. The bar is only 28.28mm across the diagonals and so if it will go into the spindle then this really is the solution. The intermittent cutting at the corners will not affect the facing, and you can always adjust the speed and feed rate to suit. I often face mild steel, of various types but never good old EN1A leaded, aluminium and stainless in my 4 jaw chuck with no detrimaental effect on the finish. HTH and sorry for the confusion earlier.

There are lots of tasks where using the side of an endmill to machine a vertical face has to be done, and as the machine is all-square and this isn't working we should look for a why. An X3 should be plenty stiff enough. Is there a problem with the slides not being sufficiently tight, or is there insufficient preload on the spindle? Or it could be technique.

I would approach any task like this by machining down the height in steps of, say, 5mm, leaving the part overlength by about 0.2mm, then taking one or two shallow finishing cuts across the whole face to take it to depth. I'd probably take 2 or 3 cuts at the final setting if there was any chance of spring in the tool.

I've just squared both ends of 1.1/4" square bms using 4"vertex vice squared to column with the ends of material sticking out of jaws. I used a 7/8 end mill set full depth of material & a couple of 10 thou passes job done, I didn't take my machine apart when I bought it as some people seem to do to check it over I relied on the tolerance certificate and in 18 months I've had it the factory settings were spot on, I do spend try to spend time setting up work/vice etc,if there is a problem with a machine's factory settings it will soon manifest itself and adjustments can be made,

Mick H

Paul which plane is it not square? Climb mill for finish cut?

Guessing vertical plane tapered and what I have said before on such types, the heads moving or deflecting off from the upright dovetail column. You will never ever be able to tram which will constantly change.

Lock the beds down and everything not using.

I have to do such things daily and are precision stuff on tolerance up to 18" long, no probem using side of cutters to mill the sides of job at full depth usually 23.6mm deep. Problem I have is the Lux quill moving on lock up, the quill has worn an oval throwing centre line out 0.36mm at present. Same applies when nipping up the gibs on any machine that's not either set accurate or plainly worn out. Nip gib up and watch the whole head move off!

Did you do each end without removing the bar from the vice? You could measure if it is a parallelogram indicating a tram error or movement off the vice base or a trapezoid indicating cutter bending.

Just to add other options for later readers of this thread with smaller equipment another method is to clamp the bar to a lathe cross slide and improvise a flycutter with a tool held off centre in the 4 jaw.