Our Fall 2015 Sine Plate Project

[asid61]

Originally Posted by ParisDakar

Tonight we cut one plate to final dimensions of 6.000" by 6.000". After that we used a flycutter to face one side.

Final face cut

Mmmmm flycutter finish...

[ParisDakar]

This week we faced the other side of the plate with the flycutter. Set the tool to cut about a 3.5" diameter circle, so we could face the full 6" plate width in two passes. We cut .003 to .004" with each pass. Only took 3 cuts or about .010" to completely surface this side. 1250 rpm produced the best finish. The cutting tool is carbide tipped HSS. I ground a radius on the point of the tool this week, maybe 3/32". Finish is better than last time when it had a sharper point. Tool rake angle is 0. Feed rate was about 3" per minute for a chip load of a little more than .002".

The mill is definitely out of alignment a bit. When I upload the pics, you can see the difference between a L to R pass and a R to L pass. The tool cuts lower on the left. So on the the L to R pass, the trailing edge of the tool drags the surface producing a fine, sandy texture. Best cut in this case is in the R to L direction, where only the leading edge is cutting.

[ParisDakar]

Originally Posted by ParisDakar

This week we faced the other side of the plate with the flycutter. Set the tool to cut about a 3.5" diameter circle, so we could face the full 6" plate width in two passes. We cut .003 to .004" with each pass. Only took 3 cuts or about .010" to completely surface this side. 1250 rpm produced the best finish. The cutting tool is carbide tipped HSS. I ground a radius on the point of the tool this week, maybe 3/32". Finish is better than last time when it had a sharper point. Tool rake angle is 0. Feed rate was about 3" per minute for a chip load of a little more than .002".

The mill is definitely out of alignment a bit. When I upload the pics, you can see the difference between a L to R pass and a R to L pass. The tool cuts lower on the left. So on the the L to R pass, the trailing edge of the tool drags the surface producing a fine, sandy texture. Best cut in this case is in the R to L direction, where only the leading edge is cutting.

Two shots of the finished plate. Right/upper side is the rough pass.
http://wiki.team1640.com/index.php?t...1209152104.jpg
http://wiki.team1640.com/index.php?t...209152104a.jpg

[ParisDakar]

Making some progress. Milled the groove in the lower plate that accepts the hinge. The tool is a cobalt 1" diameter, 6 flute, center cutting ball end mill. Best speed was about 1250 rpm and a 30" per minute feed rate. A little higher than I expected, but below those speeds, it chattered quite a bit and the finish wasn't that great. The tool really wanted to cut. We took out from .035" for the initial passes to .010" for the final pass.

The final groove depth was 0.156 or 5/32". I had students do some calculations to figure out what was the best depth to give the hinge the most rigidity without being too deep and limiting space between the plates, or limiting the angle to which it can be opened. Calcs showed rigidity increases significantly up to .150", then only marginally past that. Here's the description of the problem I handed out, in case anyone wants to run some numbers. I'd be interested in what you come up with.

http://wiki.team1640.com/images/8/82...te_Problem.pdf

Also put two 1/2" holes in the plate that match the slot spacing in the mill table so we can bolt it down directly if we need to.


http://wiki.team1640.com/index.php?t...1_151216-1.jpg
http://wiki.team1640.com/index.php?t...1_151216-6.jpg

[asid61]

I would be interested in seeing how that was calculated, given the wide range of uses for a sine plate.
Have you checked how flat the plate is with an indicator? I know that when we try doing cuts on the face of a plate it tends to bend due to stresses being relieved.

[ParisDakar]

I haven't checked the plates for flatness. But I'll do that when we get a minute and let you know.

As for the calculations, my best guess was that the horizontal milling forces acting on the hinge would be similar to pushing a car over a curb. If the wheels have x amount of weight on them, how hard do you have to push horizontally to get the wheels to climb the curb. The height of the curb would equate to the depth of the groove.

Of course the hinge won't roll like a wheel. And the milling forces don't produce a straight push on the hinge, it's more of a horizontal torque. So my model isn't an exact approximation.

[protoserge]

This is my kind of project! It looks like it's coming together. Do you have any plans to heat treat for stress relief?

[ParisDakar]

Originally Posted by protoserge

This is my kind of project! It looks like it's coming together. Do you have any plans to heat treat for stress relief?

I wanted to make this project mostly a design and machining exercise. And an inexpensive one as well. So no heat treating. We're using 1018 cold rolled steel, not much you can do with that other than case harden it a little.

I haven't measured the surfaces for flatness yet, it's on my list. We only took about .015" off each side, so I don't know how much effect that would have on 1" thick plate as far as releasing stresses.

[ParisDakar]

Getting close to finishing the project and not a moment too soon. Top and bottom plates have the hinge grooves cut. The gage block area is milled out. The bottom plate holes match the T slots in the mill table.

http://wiki.team1640.com/index.php?t...Bolt_plate.jpg

http://wiki.team1640.com/index.php?t...oth_plates.jpg

[ParisDakar]

Cut the gage block rest. Drilled the hole pattern on the top plate. Left 1" spacing between the 5/16-18 bolts that the holes will be threaded for (20 holes to tap). Need to cut the hinge parts on the lathe, then drill the holes to put it all together.

http://wiki.team1640.com/index.php?t...ar_finish2.jpg

http://wiki.team1640.com/index.php?t...ar_finish1.jpg

[protoserge]

Love it. Now use it to test the possible shooter angles for this year's game down to the thousandth of a degree