For me it is rare to get as good a finish when side cutting as face cutting on top of a workpiece. Here are some things that may help.

You are using a 2 flute cutter. Another thread regarding slot cutting has the mention by Jason that he always uses 3 flute cutters. These are a better option than 2 flute because they are stiffer. A 2 flute cutter can be looked at like a twisted ribbon, even carbide 2 flute cutters are not as stiff as 3 flute cutters.

I think there may be too much play in the gibs and when you are unlocking an axis it becomes too loose, try pinching the moving axis slightly so there is some drag and see if that improves things.

I would not rely on just two clamps holding that vice to the bed like that, I would use four because a heavy cut may grab the workpiece and twist the vice if there are no tenons locking it into the slots.

Try a larger diameter 3 flute HSS cutter with a polished finish, coated cutters are no good for aluminium alloys, the coating just encourage the aluminium to stick to the cutting edge and give a poor result. See if you get a change in the finish from a faster or a slower speed or feed, sometimes the cut just hits a resonant frequency of the machine and a different number of cutting edges or a small change in speed (with a corresponding change in feed rate) may change the frequency and completely change the resonance of the machine, these mills are only small even at 300kg compared to an industrial machine. This makes them more prone to resonance and vibration. Make sure it is always cutting and not rubbing, this will show up as a constant flow of evenly sized chips coming off the cutter.

Martin C

Ps Get a ball bearing nut for the ER collet chuck if possible. They allow a far greater clamping force on the tool with the same applied torque, there is a possibility that the collet is not closed down tightly enough.

Edited By Martin Connelly on 09/01/2022 09:27:49

Feedrates are way too slow, leading to rubbing rather than cutting. With the parameters given I'd be feeding five to ten times the rates stated. Plus one for an aluminium specific cutter. Aluminium is one of those materials when climb milling on the final cut can be advantageous in getting a good surface finish.

Andrew

I used to suffer with this problem many years ago when I first had the first of my FB 2's.

The finish using the side of the endmill in the X-Axis was always perfect. However when using the same cutter on the Y-Axis it was a different story.

Holding the machined face at different angles to catch the light would show striations along the face. Aluminium was particularly bad at this, but steel being better.

First thoughts were the Gib being loose on the Y-Axis, but this adjustment met with my satisfaction.

I finally traced the problem to the actual cutters being used. These were made by Osborn, so a good make. However the cutting angle on the side of the Osborn cutter was 5 degrees. Changing this to 7 degrees totally removed the problem. The cutters also cut with less effort. The downside is the cutter life is less when compared to the 5 degree. As I sharpen my own cutters this is not a problem for me.

I have found the Helix angle of the cutter also influences this problem. Some straight flute cutters I have do not show any signs of this problem.

Regards

Gray,

I think when you are cutting along the Y axis the force vectors on the cutter are acting approximately towards or away from the column centre so rotational forces on the head are unlikely to cause any rotational deflection as they are small. When you are doing the cut along the X axis the force vectors are well away from the column centre line so there is more likelyhood of the head and the column twisting under the forces. Even though the movement is small it could be enough to cause issues as it is significant compared to the cutting depth. Personally I have never cut an edge along the X axis because I have never needed to so I don't know if what you have got is typical of these machines.

Martin C

Y C Lui's deflection measurements would probably be impressive for a small jig borer. I wondered how my FB-2 would compare. My FB-2 is accessible, but not set up for use. However, the locks work well, and everything relevant that should be tight is tight.

My spring balances have gone into hiding, so only a very rough test was possible. The head was eyeballed to be about the same height from the table as in the pic. Applying something like 20 kg force to the head casting, along the table (x-axis) in each direction produced a TIR in line with the quill of approx 0.03 mm with the vertical lock tight, and 0.1 mm with the lock free, confirming my reservations about this aspect of the design. This is an order of magnitude worse than Lui's measurement! Now I'm worried!

For completeness, corresponding y-axis deflection test produced about 0.05 mm TIR and wasn't affected by the vert. lock.

I'm not surprised by the results I got: if you lean on machine tools with enough determination, you discover they are made of rubber. It would be interesting if one of the other FB-2 users, who get reliable results from their machine, could possibly do a similar quick test, and post results. Any takers? Joe? Gray?

Rotational deflection of the Column is resisted by the Guide Bar set into the Column. In order to allow the Head to slide up and down there needs to be a small clearance. If this clearance were 0.001mm then the deflection at the clock just taking up the clearance would be 0.01mm as the lever ration is a factor of 10.

I doubt the slide would move with such a small clearance, it would be more likely to be 0.01mm to start with, which would give a deflection of 0.1mm at the clock. (Oil films do need a space to work in)

As regards adjustment of these surfaces there is only one way to do this, and it is not, with the feedscrew attached.

The head needs to be removed from the Column. It will rest happily on the table with a couple of parallels and no heavy lifting is involved. As the separation movements can be controlled by the table feedscrews.

The Column is removed from the Casting Socket and the above mentioned Gib slackened. My bench vice with suitable protection pieces will just grip the Column. Adjustment can then be made to the Slider to Column interface. It should glide effortlessly from one end to the other with a faint hint of resistance, or drag, but no play.

I find this adjustment gives a better result with dry contact surfaces. Oil is only applied once the slider to column is adjusted.

The Gib is then adjusted such that it removes any rotational movement but does not interfere with the initial adjustment.

Do this the other way around and expect trouble.

Having the above adjustments too tight will just prematurely wear the feed-nut, (expensive), and the handwheel bearings.

Back to the original plot,

The Vice set-up shown in the picture is not what I would do. It is probably done to maximise the amount of slideway contact, but the clamping arrangement is nowhere near where the cutting is taking place. It induces another Lever moment.

The main force resisting cutting, when cutting with the side of the endmill in the Y-Axis, will be along the Y-Axis. The reaction to this force will tend to deflect the head upwards, if it can. A small Resultant reaction force will be trying to deflect the milling head to the right in the set-up shown, but will also be trying to lift the job, the vice, the table and the Y-Axis slideway. (Helix angle on the cutter).

This is why manufacturers of our range of machine tools always tell us to lock those slideways not in use.

Regards

Gray,

Edited By Graham Meek on 10/01/2022 12:12:28