how much to leave for surface grinding

[mark roberts]

I've been making a strip to go in the slot on the bottom of my vice so it can register in the mill table slot. I machined it oversize by 1.5mm thinking .75mm each side would not be too hard to surface grind on my little eagle. It took bloody ages. My arm felt like a teenager again. I think the wheel is 80grit. After a few goes I measured it and it was bigger. Got to 0.4 oversize and left it for the night

 

[Agroshield]

After a few goes I measured it and it was bigger.

The arm or the piece of metal?

I think you could assess the situation yourself. You now know depth of cut Eddie is comfortable with. Decide how many passes you want to grind. Multiply A x B. Note that B will vary depending on how consistent the previous machining operation is. Somethign hacksawed out of gauge plate will not be as good as something milled.

 

[tigdlo]

How much you leave for grinding would depend on how accurate your previous operations were, for example, could you mill to within .05mm square and overall size? If so machining within .20mm all round shoud give you plenty of room to correct any errors.

80 grit is pretty fine for surface grinding, my 46 grit wheel leaves a good surface finish, better than would be needed for a vice key.

.75mm could be a lot of material removal depending on the surface area for what I'm gussing is less than a 1hp spindle.

 

[Shiny Steve]

Normally about 0.3 depending on size of part and chance of distortion. Ideally remove equal amounts from each side to minimise distortion/ bending.

Keep the heat in the component to an absolute minimum, that’s probably why it seemed to get bigger.

 

[Pete.]

Use a 40 grit wheel and make sure you dress every wheel for every job.

10 thou should be plenty to leave for grinding.

 

[mark roberts]

Many thanks. The piece was only 1" by 8", still took quite a few passes to remove the last .2mm. I had to put a step in it to match the table slot on my mill. Bloody cutter started to drop down mid cut. I thought it was tight. The wife always asks what I want for christmas and I say nothing, maybe a new collet set.