HSM May/June 1988 - The Surface grinder (Part4)

[carrdo]

The 3/8" dia. gashed end mill shown in the previous post was then used to machine a pocket in one of the parts of the retractable guide mount which is made from hot rolled steel angle.

See the attached photos for the results obtained. The smaller through central slot was machined with an undersize 4 flute regular end mill. Both the through central slot and the surrounding pocket had to be dead central with each other, dead centered on the arm of the part and made exactly to size to fit two other parts which are very close shakeless sliding fits . I don't have any digital on the mill so everything was done as a toolmaker would have done it (pre digital) 70 years ago. It was a major exercise all by itself.

What were the results?

The positives:

The sharpened and gashed two flute end mill left an excellent surface finish on hot rolled steel and was able to finish the pocket on size, on depth, and was straight, square and dead concentric with the central through slot.

The negatives:

This end mill had been sharpened many times previously on its end only which left the remaining spiral flute cutting edges VERY dull. As a result I could only feed the end mill 0.002" deep per pass to retain the excellent surface finish i.e. only very light facing cuts could be made. I did try to cut deeper per pass and the end mill definitely did not like it.

The end mill threw up very large edge burrs as one worked deeper into the cut.

The speeds and feeds which I use in a home shop are far below that recommended in the literature as these standards have been set for industry. The gashed end mill definitely needs the much slower speeds and feed rates. A two flute end mill will give just as fine a finish as a four or a 6 flute end mill but one has to remember that there are only two cutting flutes and one has to reduce the feed rate accordingly.

So that was it. The end mill behaved as I suspected it would. If you want a better end mill performance, one will have to sharpen the spiral flute cutting edges as well with the limitations that ultimately involves.

It is a trade off - time vs $$$ and the equipment one has or doesn't have to do the job.

[Cowboy00]

This was very inspirational. Perhaps I can convert an olde English horizontal mill.

[Jon]

Cowboy00 - got any pics?

[Cowboy00]

Cowboy00 - got any pics?

Here are links to good pictures of the subject mill:

Model Engineer
Perris Milling Machine | Model Engineer

These are the only ones I have found on the internet.

The mill was mfd by Perris Engineering, Ltd. ( Worthing Sussex, England ).

Here is a link to Tony Foale's idea for a surface grinder along the same lines:

http://www.homemadetools.net/forum/h...-machine-55333