Help! > Mistakes, muckups, and dangerous behaviour

Grabby Gunmetal and Stupid Setups

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smfr:
Well, this was disaster waiting to happen. All the warning signs were there, but I just ignored them and soldiered on  :disappointed:

I was trimming the yoke end of the eccentric to thickness with the side of a 4-flute endmill. I had the eccentric bolted to a 1-2-3 block, which was bolted to the table. I was conventional cutting, but approaching from an end.

Warning sign no. 1: it was 10pm and I was trying to "get this done" before I turned in.

Warning sign no. 2: At first, the yoke end was hanging out in thin air, but even light cuts were giving ominous "grabby" sounds and a very poor finish:



Warning sign no. 3: with a slightly heavier cut (20thou), then endmill grabbed the end of the part, and swung it and the 1-2-3 block around (it only had one holding bolt, because the hole spacing doesn't match the T-slots on my table). The part survived, but with some gouges on the end.

So, I clamp things tighter, add another 1-2-3 block and a G-clamp, and try again.

This time it grabbed again, and, of course, bent the yoke end into a nasty angle:





 :facepalm: There was much sighing. Attempting to persuade the part back caused cracking:



which I guess I could try to silver-solder. But I already had to mark out the end hole a little short because of lack of material (odd because I thought I was pretty close when slitting the part), and the gouges on the end won't get fully removed when it's rounded over:



So, these eccentrics may end up with steel rods. I'll see how much material there is around the strap end to attach a steel rod and yoke part.

Simon

Stuart:
just cut the bent/cracked bit off and silver solder a new lump on

you could use a bit of brass if the engine is not going to do a lot of work  if it is use brass and press in a couple of PB bushes


of course a bit of PB would be better but don't use PB1 as its pink and if grabs like crazy evan griping drill bits



Stuart

mzt:
If I got it correctly, You supported the wp. on the wrong side, allowing it to spring in the direction where the depth of cut would increase.
Thank You for the heads-up.

Marcello

swilliams:
"(it only had one holding bolt, because the hole spacing doesn't match the T-slots on my table). "

I realise this isn't your main problem here, but experience has lead forced me to my own personal little rule that one clamp is never enough.

Steve

steamer:
Thanks for sharing that Simon....I've done that.....though it seemed a good idea at the time...it ended similarly....

Tried getting "one more thing" done by 10pm too........that didn't work for me either....... :hellno:

Hang in....I have faith...you'll get it.

Dave

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