A challenge... Machining related...

[camdigger]

Background:
In response to a jab from my conscience fired by the press brake thread, I decided to use my one day a week of shop time to build a simple brake for my H frame hydraulic press. My press is limited to 20T and 28" long.

Materials:
Assorted sizes of drill rod or other rod with a pre-ground finish or a good turned finish - there's lot's of alternatives in my stock for the guide rods. The upper punch and bed will be made out of 1" x 3" HR bar stock. The lower die will be either a pair of rounds spaced 1" apart welded to a plate or flat, or another pice of 1" x 3" stock with a vee milled into it. There's a couple sets of compression springs around in stock. There's a wide selection of angle, flat, round bar, and pipe laying around.

The guts of the challenge:

How to cut a Vee shaped edge on the lower side of the punch without buying more tooling or machines - there's a 5" vise, a clamp set, a partial set of end mills, face mills, and a shop built fly cutter for the chicom milldrill (table dimensions 8" x 30". The mill is eequipped with a table feed. There's cutter bits for the 1440 lathe. There's an import 4" x 6" horizontal band saw. There's an oxy acet torch set, 380 plasma, and a 250 AC-DC stick welder in the shop.

How would various members go about putting an 80 - 85 degree vee on the lower edge of the punch?

[japcas]

Camdigger, without getting into too fancy of an explanation, have you thought about bolting two pieces of still together for the bottom V. This way you can mill half of the angle on each piece of steel and you don't have to have a fancy cutter.

[digger_doug]

You don't need any "V" at all, your air bending.

2 blocks spaced 8 time the material thickness apart will doo.

2 pieces of round rod welded onto a plate will doo.

Bottoming or "spanking the die" is for high tonnage
people in high production that are trying to maintain
a precise bend angle with variations in metal thickness.

Your 20 ton press is good for 1 foot of 1/4" plate.

Or 2 feet of 1/8" plate max.

1/8" plate (sheet) = 1" die opening.

Layout this for the 90 deg. angle to get the rod dia.
(punch penetration, don't want to hit the floor)

[camdigger]

I've seen four basic alternatives for the bottom die. They are, in order of effectiveness and difficulty on fabrication...

1.) simply space two pieces of flat iron on top of a third with a space aligned with the top punch.
2.) Space two rounds welded to a wide piece of flat iron
3.) weld two pieces of angle iron point up onto a piece of wide flat iron
4.) hold a thick piece of steel at 45 degrees to vertical and plow out a vee groove with an end mill.

I've seriously considered 2, 3, and 4.

[Evan]

How would various members go about putting an 80 - 85 degree vee on the lower edge of the punch?

Use 1" square key stock. Mill off one corner about 2/3s of the way to the hypotenuse. Weld it on with the opposite 90 degree angle as the working edge. If you need to for springback then mill off a bit to sharpen the angle before welding it in place. Instead of welding I would arrange some strap on each side running lengthwise to bolt it on so it could be changed easily. The hypotenuse will protrude just enough past the 1x3 on each side to accommodate two pieces of 3/16 strap nicely.

[camdigger]

Use 1" square key stock. Mill off one corner about 2/3s of the way to the hypotenuse. Weld it on with the opposite 90 degree angle as the working edge. If you need to for springback then mill off a bit to sharpen the angle before welding it in place. Instead of welding I would arrange some strap on each side running lengthwise to bolt it on so it could be changed easily. The hypotenuse will protrude just enough past the 1x3 on each side to accommodate two pieces of 3/16 strap nicely.

Would be held how? I don't have a 45 degree block.

[camdigger]

You don't need any "V" at all, your air bending.

2 blocks spaced 8 time the material thickness apart will doo.

2 pieces of round rod welded onto a plate will doo.

Bottoming or "spanking the die" is for high tonnage
people in high production that are trying to maintain
a precise bend angle with variations in metal thickness.

Your 20 ton press is good for 1 foot of 1/4" plate.

Or 2 feet of 1/8" plate max.

1/8" plate (sheet) = 1" die opening.

Layout this for the 90 deg. angle to get the rod dia.
(punch penetration, don't want to hit the floor)

Yes to all this. I agree I don't have enough tonnage to do any thick stuff, but I have some 1/16 Aluminum that is a bit heavy for a common brake to do for another project. A true vee/spanking/bottoming die would be nice for the
90 degree corners I want for that. Any suggestions for the upper punch?

[Evan]

[camdigger]

Neat idea Evan, but I'd think long and hard about countersinks. I want to be sure the die is firmly against the upper block, otherwise the screws might bend making them a Pita to deal with.

How, with the list of tooling given, would I hold this keystock to mill away the corner to create the flat?

[Evan]

As for the countersinks, drill, tap and then screw on the straps to the upper block. Make the straps so they have a bit of clearance to the nose piece. As the last step in building the press bring it down on the nose piece and tack in place. Perfect fit.

Make a simple Vee block for the vise to hold the part at a 45 degree angle to square. I'm sure it will be useful for other things like holding tubing etc.

[camdigger]

Holding a 24" long punch in a 6" vise seems a bit too flimsy for me.

I'll show you what I did in a minnite if'n all goes well with the pic postin'

[camdigger]

rough, but tough enuff

I took a piece of scrap 2 x 2 x 1/4" angle and welded 1 1/4" x 1/4" strap iron lugs across the open side of the angle to create an inverted Vee. with sides inclined at 45 degrees.
Then I took the 1" x 3" punch stock and laid it along the vee tipped over to just over 45 degrees then skip welded the punch blank to the jig.
took all over to the milldrill and clamped the whole shebang onto the table and clamped it down with 4 clamps.


Back inna minnit with a pic or two ( I hope)


It kinda worked. Just had to cut the welds off with a cutter disc and touch up with the angle grinder.

To do the other side I'll have to shim the punch and set it up on the jig and possibly bolt it on so I can move it to indicate it in for setup. I took advantage of the solid set-up to remove most of the material on the other side of the vee by plunging the end mill. The working edge is presently a 90 degree edge tilted off axis.


Best of all, no trip to town for 1" keystock or additional tooling...

[Roy Andrews]

when i made mine i used two 3/4X2 bars. i laid them on the bench in an upside down 80 deg v and tacked them together and then tacked them to the bench to keep them from moving. i then filled the shallow top v with weld. after cooling cut from bench and place on mill. fly cut weld to make smooth and flat. now place fly cut onto 2X2 solid and tack together. now tack 2X2 to bench. stitch weld together. now remove from bench and place back on mill table V up. align with table travel. clamp top die to one side of bottom die V so that it is tilted at 40 degree angle. now using the edge of an end mill take off half of the edge of the top die. flip over and repeat. wa la top die.

Evans way of mounting the top die is nice if you plan on having multiple top die profiles. then you can make them less substantial and the holder caries the brunt of the work.

i forgot i also welded a plate down both sides of the bottom die to support the V wings. and yes my welding table is sturdy 4X5 1.5" plate with support and 8"pipe legs

[snowman]

To do the concave portion you can rough it out with an endmill like you did, then grind a single point tool and make a quick arbor to mount that in, much like a flycutter.

So the die would actually be laid flat on the table, and the arbor would be in the mill perpendicular to the table. The single point tool would be perpendicular to the arbor. You can always use a half inch tool blank as well, and grind the radius right in, then just flip it over and do the other half of the die.

Fed at a conservative feed it'll work out quite well.

[darryl]

I did mine just like Japcas said. Two pieces of flat material held in vee blocks so I could mill the angle with a straight end mill. Then I bolted them together with a third piece between them, adjusted to give some depth at the bottom of the vee.
No reason you can't shim in the vee blocks to change the angle slightly- you're looking for 80 to 85 degrees total, so you'd set up to go a little steeper than 45 degrees for each piece.

In my case, this assembly slides up and down while the upper part (the punch?) remains fixed.