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Machining a flat face with good surface finish and accuracy

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picclock:
Hi
Bit of an odd question. I have recently had to make a steel plate which had to be flat and have a very fine surface finish (basically mirror). I really struggled with this so it would be useful to know if there was a better solution out there.

I tried fly cutting, but found I could get better results by using an endmill with multiple passes. After that I attached wet and dry paper to an MT2 blank I had which was wider than the part with double sided sticky tape and moved the work under it on the mill whilst it was rotating at low speed. After replacing the paper half a dozen times, and checking it was still flat, the job was done.

I don't have room (or funds) for a surface grinder, but I had thoughts about getting hold of a silicon carbide wheel and fitting it to the mill - somehow - to see if it could work be a poor mans surface grinder. 

Any other ideas most welcome

Best Regards

picclock

ieezitin:
Try a shear tool in the fly cutter. Do you have a shaper?

Anthony.

Pete.:
Buy and old cast iron surface plate and some diamond lapping paste.

PekkaNF:
I would not use abrassives on mill for two reasons: wear and it actually does not increase accuracy.

Surface grinders are next logical step from the mill, but to produce more flat, they are different machine, more accurate way geometry and more accurate spindle, but less load carrying capacity on other directions. Therefore surface grinder attachemets on the mill are usually used when material it too hard to mill, not much extra accuracy is gained.

Your observation on fly cutter vs. end mill is correct. Tramming affects less on cutters of smaller diameter.

You need to define how flat you need that piece first. Here you might resort to scraping, least you need to check it with blue.

Abrassives will then even out surface quality, but will not improve much flatness, easily decrease it actually, specially on the edges.

Lapping on cast iron plate is probably easiest and cheapest - specially if you do have the cast iron plate.

Pekka

chipenter:
I use a 80mm cone grinding wheel in a home made arbor , gets a good finnish needs a realy fine down feed is needed  to mutch and the stone cloges up , cover up well and vacume at the end of the job no problems so far .

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