Ya, I woulda seated the piece further into the jaws so the 2 that are not clamping, would.
BUT! if it works who can say "shoulda"
As it was, if you had first drilled a small center hole in the end and used a live center to keep it from popping out it would've been a LOT safer. Me thinks you got lucky doing without one.
The other two jaws were supporting the work. Plenty of clamping force on the two 'working' jaws. The work would have to move a lot before the support jaws became loose. Plus, light cuts help with the safety factor. Only 0.5 mm per cut.
I couldn't move the work any deeper into the chuck without getting a chuck strike.
I spent some time this week trying to find some bar stock big enough to mill one long dovetail section that I could then cut into individual toolholders. My usual scrap yard was closed, so I tried the Other One. No joy there. I tried several metalworking shops, but none had anything close to what I need. I figured I'd make a few the 'hard' way - one at a time.
I have some 2" and 1 3/4" square bar, so I cut about 4" of 1 3/4". Squared off the ends and used a 3/4" x 6" cutter in the U2 to step down on either side of the dovetail. I tried the shaper to rough out the undercuts but had some trouble and went back to the vertical mill. Cutting dovetails with a single-insert carbide is quite slow.
I finally got the dovetails to a slip fit into both of the slots on the toolpost. The clamp worked very well.
[
attachment=7611]
Next, I milled the slot between the dovetails for the height-adjustment pin, then drilled for the adjusting screw. Almost had the hole tapped all the way through when my nice spiral-flute tap broke off.
[
attachment=7612]
Two days work shot. This piece will have to wait until I build a spark-erosion EDM machine. There's nearly 3/4" of good-quality tap in the hole.
(01-05-2014, 09:46 PM)Hawkeye Wrote: [ -> ]I spent some time this week trying to find some bar stock big enough to mill one long dovetail section that I could then cut into individual toolholders. My usual scrap yard was closed, so I tried the Other One. No joy there. I tried several metalworking shops, but none had anything close to what I need. I figured I'd make a few the 'hard' way - one at a time.
I have some 2" and 1 3/4" square bar, so I cut about 4" of 1 3/4". Squared off the ends and used a 3/4" x 6" cutter in the U2 to step down on either side of the dovetail. I tried the shaper to rough out the undercuts but had some trouble and went back to the vertical mill. Cutting dovetails with a single-insert carbide is quite slow.
I finally got the dovetails to a slip fit into both of the slots on the toolpost. The clamp worked very well.
Next, I milled the slot between the dovetails for the height-adjustment pin, then drilled for the adjusting screw. Almost had the hole tapped all the way through when my nice spiral-flute tap broke off.
Two days work shot. This piece will have to wait until I build a spark-erosion EDM machine. There's nearly 3/4" of good-quality tap in the hole.
Mike
I use a die grinder or Dremel tool with a diamond bit (Cone point or tree type point) and carefully wear away the centre section of the tap until I can break out the rest with a prick punch. Rarely have I ever had a tap that will not succumb to this treatment.
Walter
Bad luck Mike - I'm sure you'll resurrect that part.
Making some tool holders is on my list for when I get my mill up an running. The ones from tool4cheap.net are good but the postage is a killer due to the weight.
I never did like the spiral flute taps.
It never ceases to amaze me the great lengths some people will go through to make their own tooling!
I certainly do not mean that in a bad way either......I quite honestly find this fascinating!! Great job!
Best Regards,
Russ
(12-31-2013, 09:22 PM)Hawkeye Wrote: [ -> ]BTW, I found out what caused those sparks. On a horizontal mill, unlike a vertical, it's pretty easy to put the cutter on backwards. 
Don't feel bad Mike, I've seen sparks like that from band saw blades as well. Only with the defective ones though, that had the teeth ground backwards.
That cast iron looks like it machines very nice. It's been a long time since I've made any CI chips. I've always enjoyed it.
Tom