7:53 pm
NWBA Member
November 8, 2010
I had a good friend blow me away yesterday with a poor-man's solution to making a damn-near perfect hemi-shaped concave hole.
I'm making some new rivet dies and while I do have a radius cutter, I found that it can take more time to use it than to just rough out a blank and then grind with an abrasive ball on a die grinder.
Denny Jensen came over, took one look at it and made in 5 minutes a great tool from an old bearing; Grind the face of the bearing on a belt sander to sharpen the edges of the race, press fit (or weld) a handle on the inner race and then force it into the cavity with plenty of oil.
Remarkably the inaccuracies of my prior cut were quickly realized by seeing the where the race was indeed cutting down the ridges. It took maybe only 10 minutes to remove enough material to satisfy even the most cue-ball concious.
The race was slightly undersized but as you rotate it, you could definately hit all the spots needed. All in all an amazing back-yard solution~:p
They only remember you when you SCREW UP~!!!
10:26 pm
March 26, 2010
Neat trick cybo.
Till now I've always just roughed out on the lathe then forced an emery flap wheel into it(on a 1/4" shaft) whilst constantly turning it around and around in all ways. Eventually the "wheel" become become convex spherical and it sorta grinds smooth to a kinda hemisphere.
I did seem to recall reading that the makers of concave mirrors for telesecsopes used to do something with grinding one thing into another. Apparantly if done correctly this will (and apparrantly can only end with) a perfect hemisphere ..... I think!
2:19 am
NWBA Member
November 8, 2010
2:43 am
March 22, 2010
So I dont quite follow Steve, are you holding your tool just by hand? is the bearing itself still spinning on the shaft? ( it looks like you just stuck a rod in an old bearing... Could you snap a close up of the sharpend side of the bearing/tool to show us how it looks?
Whatever you are, be a good one.
Abraham Lincoln
2:51 am
NWBA Member
November 8, 2010
That's exactly all it is, Larry. A rod on an old bearing. I didn't get it either but the belt sanded side of the race becomes ALOT of cutting edge. Yes, the bearing does still rotate, although by the time the chips got all caught up in there, it was starting to turn with more difficulty. Still, if you rotate it just a little, you have a new cutting edge.
You could mount it in a holder but it really worked best if you kinda wallowed it around in there. I'll try to get a close-up here tonite.
Speaking of- what rockwell are bearing races?? mid 60's?? Hard enough to cut normalized O-1 it was~
They only remember you when you SCREW UP~!!!
3:02 am
August 14, 2010
3:06 am
March 22, 2010
Ive wallered plenty of things... Most of which would have been better off un-wallered..
Whatever you are, be a good one.
Abraham Lincoln
1:51 am
August 14, 2010
6:05 pm
NWBA Member
November 8, 2010
6:26 pm
May 14, 2010
6:42 pm
NWBA Member
November 8, 2010
Dave- I get laughs when people see that little forge. The fire-chamber is 4"X 10"L.
Honestly, it does probably 80% of what I need and if I need more, I have two others- one from a BBQ bottle, the third from a oxy cyl which I've used less and less it seems.
Someone mentioned alot of what we do is on the end of a bar; finials and such. As long as that's the case, I'm fine. While I've always admired big clamshell forges and such, I'm such a stinge on fuel that I'll stick with it for now.
Despite my liner being partially melted out, it still was capable of these forge welds last night:
They only remember you when you SCREW UP~!!!
11:08 pm
May 14, 2010
Steve, really...I'm not laughing...let's see it. :stomp:
I've got what I consider a small forge and a medium forge. I use the small one a lot more than the medium one. I still need a micro... and a large forge to complete the set. I'm thinking about a brick-up that can be configured quickly. shit...or skip the micro and get an induction heater...:banghead:
-DB
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