Making Parallels

[rock_breaker]

Following the steps in Harold Hall's book on milling I started making a set of parallels today. The "fix it before you use it" bug seems to have taken up permanent residence here. Anyway the mill, a RF 31 is in a trailer next to the shop so making several trips between the mill and the shop for tools took up a lot of time. The parallels will be 3/16" thick, 3/4" high and 6" long made from mystery metal. The first cut was made with a 1/2" roughing mill (not the most high dollar available) and somewhat dull but it left a good surface the second pass was with a 1/2" four flute end mill that came the RF 31. The spindle speed was changed from 850 to 1200 RPM during the first stages with the roughing mill. It took sometime to get set up and do the job by the "seat of pants" method, the milling was smoother at 1200 RPM. Didn't finish the second side today, so more fun tomorrow.
Have a good day
Ray

 

[rock_breaker]

Thanks guys!
Back with the results of todays efforts. The run-out of one parallel is 0.007" and the other is 0.003" so not very good.

Here we go, greenhorn blaming his tools. First the angle plate is too short for this length. The supports are only 3" apart. Which causes a lever action on the work piece near the ends. The angle plate didn't know it was supposed to be longer.

Second, only one clamp was used to hold the work. Rudy Kouphut (no doubt miss spelled) in his training manuals said everything needs 2 clamps. He is right!

Third, Only 1 finishing pass with the 1/2" four flute endmill at about 0.012" doc. Perhaps the mill should be larger.

This work was the first run on the new to me mill, I like it!!! Seriously I need a larger angle plate or make one where the supports are near the ends and possibly a third in the middle. As Rudy said at least 2 clamps. At least 1 more finishing pass with a very shallow depth of cut at slow traverse speed.


Have a good day
Ray

 

[ericc]

Angle plate? Is this what is being used to hold the parallel you are making? I have a hard time visualizing the setup. I would think a vise would be used.

 

[rock_breaker]

An angle plate is what Mr. Hall used in making his mill and I was trying to follow some of his procedures. No doubt a vise could have been used but a great deal of time would be spent in insuring accuracy of the table tram as well as the vise ways. As I understand Mr. Hall's purpose was to economically develop tools for milling while learning to operate a mill. If his projects were followed I think a vise is made later in the program.
My project scope is different in that this was a test run of the new to me mill which was accomplished and a decision made to keep it. I also learned a lot about work holding and set-up. The angle plate was already set up from another project. Future plans to improve the accuracy of the parallels are on line after the mill is moved into the shop and set up.
Have a good day
Ray

P. S. An explanation of the setup is: Two round cylinders (3/4"+/- long) having a reduced diameter on one end are bolted near the top and on each side of the angle plate, The reduced diameters are against the vertical side. The plate is mounted parallel with the X axis on the mill table and flats milled on the top of the round pieces at the same height. The intended parallels are clamped vertically on the flats then the top edges are milled. After finishing passes are made the two intended parallels are turned over to mill the opposite side.

 

[ericc]

Oh, thanks for the explanation. That sounds like a pretty good method. 0.007" variation in the parallel sounds pretty large. Something must be moving.

 

[rock_breaker]

I think you are correct. It seems like there is a leverage action as the cutter nears the end of parallel which is approximately 0.75" above and 1.5" beyond the circular piece with the horizontal flats. When I get around to improving the accuracy of the parallels the circular parts will be as close to the end of the parallels as possible with a clamp near each circular piece. Obviously the angle plate will be replaced with a longer support that will probably be held in a vise. Trying to cut metal to an accuracy of grinding is difficult if not impossible to do according to what I have read. In the end I may blanket the mill and try grinding. It's all a learning experience.
Have a good day
Ray