Equalizer Fulcrum Machining Help

[Dale Grice]

Help my poor depressed soul??

Been attempting to machine silicon bronze castings equalizer fulcrums. Today was a disaster. I have a bit of machining experience. But I just broke the end of my end mill and bent it.

I have a Bridgeport series 1 and I was using a 1/2" diameter HSS new end mill. I did not like the reach. But soldiered on. I completed one equalizer, barely. The second killed the end mill. I was getting all kinds of chatter (to be expected) milling in a standard direction. I was using rustlick (Sp?) for flood cooling. I tried a 0.015 pass climb milling when the end mill came apart and bent. The equalizer is bolted to the steel block after I square up the casting and drill and tap holes. I could not hold the equalizer fulcrum in the vice otherwise because it would shift. The upper or left slot is 9/16 wide and the lower right slot 5/8. Here is a pic of the setup. The picture is a simulation of the set up. This on is one I tried to hold in the vice by itself and you can see the ding on the left.

How do other people handle this "reach" or get a square in the end. I don't have a horizontal mill.

Thanks for helping my poor depressed soul,

Dale

[James Powell]

A couple ideas- first would be an external holder like:

1. http://www.kbctools.ca/products/WORK%20 ... /2604.aspx

used to extend down to a more regular milling cutter size. This should increase rigidity, by being more meat than a 1/2" tool is.

2. Cut/File/drill as much of the material as you can away before trying to mill

3. Shaper (that'd probably be my go-to in dad's shop, for something like this)- I think the least we paid for a 7" shaper was <$300, which is a heck of a deal in a one person shop with space for one, and a bit of time.

4. File. Of course, that's hard work ! (or filing machine, which is quite a bit quicker)

5. Drill the part through from the side, cut it in 1/2, and mill without as much obstruction, then screw/braze back together

I'm not the best machinist in here though, so read other's advice too.

James

[Dick_Morris]

That sure is a long end mill! I've never have had much luck with really long ones.

If the cutter wasn't bent I'd say to try using a lot of light cuts, feeding down whatever amount is comfortable for each cut.

Since you need to buy a new cutter, build (or buy) a mandrel to hold a horizontal milling cutter, 3"-4"diameter and about 1/4" wide. Lay the piece on its side to machine it. I found a couple of side and face cutters on Ebay ("horizontal milling cutter") that would do the job at less than $20.00 each.

[jpfalt]

I would suggest making up either a stub arbor that you can mount a 4" diameter or larger slotting cutter and take the slots in steps or make up a fly cutter that will extend a lathe tool bit out far enough to cut the slot. The part would start laying on it's back for cuts on one slot and then flip over to cut the slot on the other side.

[Harold_V]

I'm troubled by the comment about the end mill bending. They generally don't, although they are known to shatter. End mills, unlike drills, have hardened shanks, generally over 60Rc, so they simply won't bend.

I tend to agree with using alternate methods. Die sinking end mills can be very difficult to use, especially in copper based materials. If you must use one, use a larger diameter, or resort to one of the suggestions provided by others. And, if you take any climb cuts, make sure your machine is not sloppy, and do so with some drag set by the lock. Light cut, too---ten thou or less.

You can expect the end mill to lose its sharp edge rather quickly when machining silicon bronze. Even faster if the piece happens to be sand cast and it's not free of sand.

Slow spindle speed, in this case, is better than a fast spindle speed.

Harold

[southwestern737]

Dale,
That is probably the most difficult part on the Mikado to figure out how to hold. I got so frustrated doing mine that I gave up and bought a set of lost wax castings that didn't need any machining in that slot. Anyway take a look at this web site http://www.neidrauer.com/heavymikado/ he has pictures of how he held it, if that doesn't help there is another web site with a build log with pictures that might have a better setup I just couldn't find it right now. Hang in there I know it can be done the way you are doing it because I know several people that have successfully done it that way. Hope the web site helps.
Brent

[Marty_Knox]

It seems to me it would be easier to machine this piece on a shaper. Or, if you have an even more obscure machine, a slotter.

[cbrew]

just a quick search on google, and i found this,

750-2-Uncoated-HTC.png (38.67 KiB) Viewed 8926 times

http://www.the-carbide-end-mill-store.c ... -2508.html

now i did not search for a cutter specifically for silicon bronze, but it may just do the trick

[Dale Grice]

Hi all,

Thanks for all the thoughts and suggestions.

I was quite surprised that the end mill bent. I thought I might have done something to the collet or the end mill had got pulled out some and was not running true. I took a shorter end mill, put it in the collet and it ran try. I put the long one back in and it wasn't true. Scrap bucket - sniff.

I thought about a shaper or slotting head. No experience with a slotter, except in theory. But since I have neither....

I also thought about trolling ebay for a Bridgeport horizontal mill accessory. Middle of the night I thought about making a mill extension as James suggested. For the deeper pocket in the pic and from the drawing, I could use 1" diameter extension for a 1/2" dia end mill. 1/4" wall seems a bit light to me. Might have to go off and buy a 1/2" chucking reamer.

And an arbor with a large diameter cutter sure has merit. Been thinking about a home grown R8 arbor. Ones that I bought for slitting saws have all not run true and caused much angst, high blood pressure, and sweat.

And I will slow down the spindle speed. Any recommendations for end mills, 2 flute vs 4, HSS vs. carbide?

These are lost wax castings. Hate to cut the casings apart. Others have accomplished the end goal without resorting to this.

Yes, filing - also a possibility.

Again, thanks very much,

Dale

[Glenn Brooks]

I had an end mill bend once . Cheep poorly made Asian imports from Grizzly tools. They looked perfect, but we're NOT HSS end mills - just looked like end mills! Actually bent two from the same order, all in a matter of five minutes. Very discouraging. But don't be dismayed by junk. As others have sAid, get a regular end mill and soldier on! It's amazing how you will improve and overcome with decent tooling.

[Happycamper]

Lay it on its side and machine the majority of material out. Then set upright and with lite passes machine the radius left by the side milling.

[RET]

Hi Dale,

That long an end mill will deflect sideways very easily (even when it is sharp) so it is difficult to get a good cut. As the cutting edge deteriorates, the cutter will deflect even more. Light cuts are required and a slow rpm., slow enough so you can just barely see the individual flutes as the cutter rotates. Most importantly, never let the cutter rub without cutting, that will dull it even faster.

While climb milling is easier on the cutter, to use it, you must have a machine that has absolutely NO play of any kind. Usually this requires ball screws although adjustable double nuts are also possible. If there is any backlash at all in the table screws, the cutter will grab and pull the table into the cut. When that happens, something will give, usually your part will be messed up or the cutter will break. As Harold says, good cutters will break, not bend. Drills will bend because the shank is softer, but as Harold says end mill shanks are hardened. Thanks Harold, I didn't know that, but it does make sense, because end mills cut sideways.

On looking at your picture, the casting appears to be very good and close to size, which lost wax castings usually are. If it were me, I wouldn't bother machining the slots at all, I would simply drill the pivot holes for the equalizer and brake hanger and use the casting as is. Once the part is assembled, you won't be able to see if it has been machined or not and it will perform just as well. You might have to make the mating parts a little thinner to fit, but the assembly should perform just as well in either case.

Hope this helps.

Richard Trounce.