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Help with milling issue

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redhouseluv:
I've started this as a new thread and as its a general issue not specific to the build I'm working on. I'm a bit puzzled and frustrated and I've ground to a halt due to the following and looking for some help please.

I'm making the split bearing in the picture and noticed a discrepancy in the slot I had cut.

- 0.010" difference over 0.982" - cutting along y-axis
- I wondered if the mill jolting I had earlier this week created a the problem so trammed the y-axis
- 0.0005" difference on the gauges across 130mm (see pic) so it can't be that?

What could be causing the problem?

- I used a mini level in the picture and needed 0.0065" of packing underneath one side to get it level. This to me indicates the entire mill is not level, but is that relevant if the tramming gauges indicate what they do?
- Could it be the vice I'm using?

I need to understand what is causing this and correct it before doing anything else!!  :headscratch:

Jasonb:
To me that is a glorified drill vice and you may well be getting jaw lift.

Put a similar size piece of stock in the vice and rest the dti on top of it and see what readings you get on the back and front as you tighten the vice.

redhouseluv:
Ha - I think you are right!

I've just this second taken some new measurments across the vice jaws; I had the work piece sitting on the edges and not on parallels and look at the difference. That according to my mm to inches conversion is 0.0035" - 0.004" across such a small gap. Also the difference changes up/down depending on where you measure along the x-axis :-\

I need a new vice - any suggestions?

crueby:
The screwless vise type is what I  use. Rather than a horizontal screw at the back of the jaw, there is a screw running diagonally down through the jaw to a cross pin that engages a series of slots underneath. They come in a variety of sizes and are not too expensive.  There are also other types of milling vises, but I don't  have experience with them  so I will  let others speak to them.

redhouseluv:
Have you a picture of one please?

I just realised I have this one, which was given to me some time ago. It looks and feels substantially better engineered and weighs double the other one. I'm not sure in terms of accuracy, but as Jason mentioned, I'm sure a piece of scrap will determine that.

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