DR-1 (Sands): Builders Group - Page 109

franzkait · 25 February 2006, 12:13 PM

do not make it to the finish sice, make it bigger, every side one inch bigger, cut later after pressing . do not use heat, put oil to the tool. cut the hole smaller, if you like to cut the hole to the finish sice hold the part in place with 4 1/4 inch screws, 2 each side

Machinbird · 25 February 2006, 01:13 PM

Jeff Brooks. I don't claim to be a professional tool & die maker, but there are a few points on your die design that may make a difference. The shape of the punch should be somewhat rounded at the tip so that you push the metal out of plane before you really begin to form it. Similarly, the anvil portion of the die should have a rounded inside edge to give the bend a radius and to decrease the shear at the inside edge. Be sure you have enough room between the punch and the anvil for the metal to form. As Franzkait says, you can make your part bigger and cut it down to size afterwards. This spreads out the stretch in the metal and reduces the need for clamping force. And as Franzkait says, be sure to use lots of oil.
On the shape of the inside hole prior to forming, don't leave any nicks in the edge prior to forming. This area has to stretch and any sharp spots may create a tear. In general, higher strength steel is harder to form successfully. Once you get your die working right, you will wonder why it was so hard the first time.

ulpilot · 25 February 2006, 01:22 PM

Jeff,

Give me a call, I can help you out on this. If needed we can go over to where I work and fix up your tooling, and possibly run them off there.

Vet

Jeff Brooks · 25 February 2006, 02:54 PM

hey all,

I appreciate all your help.

I have made sure both the die and the pressing piece have smooth edges. I also used oil when pressing. I made sure the tool has enough room between the anvil & jig to allow for the metal to fit without shearing.

Probably the one area I have been lax is making sure the piece to be pressed was free of burs & sharp edges on the inside of the hole. I will try again. I will also trying milder metal to see if that makes a difference.

franzkait · 25 February 2006, 05:03 PM

the piece you press in is tapert, if it is 2 inch long, make the taper 1.5 inch long.

franzkait · 26 February 2006, 04:50 AM

I am using sheet metal with 60kg to the mm², your 4130 has 68 kg to the mm², this can not be the problem

Jeff Brooks · 26 February 2006, 05:23 AM

that's good to know ... I'll try again today

hank jarrett · 26 February 2006, 07:02 AM

This may seem off subject but bear with me. Ever wonder why the Central Powers had helmets that came down so far on the sides a lot like the modern US helmets and the poor Tommies were wearing little flat shaving bowl helmets? The Germans found out you could deep draw the steel if you did it in stages. Multiple draws allowed the steel to streach evenly. When the English tried to copy the German design the tops either tore or got so thin they didn't provide any protection. The allies didn't figure out how the Germans were doing it till well after WW-I and I think only the U.S. could actually get the new manufacture process into production by WW-II.
Now for the connection! How about drawing the parts in multiple steps? It was a technology that was well known in Germany at the time (they didn't even think it was a big secret. They couldn't figure out at the time why the Allies kept using such rotten head protection). It would require extra mandrels but would eliminate the thin areas in the single draw process.
By the way, the single WORST thing you can have with any drawing process is surface and edge damage. If there is a nick in the edge it will tear under tension every time. That will still need to be taken care of before the draw.

Fritz Kempf · 26 February 2006, 05:58 PM

Roger Freeman of Vintage Aviation Services is putting together a kit for the people building the Ron Sands Dr1. The kit is for all the plate steel plates that need to be cut out, like all the wing attachment bracket and inter-plan strut brackets, the inter-plane strut “boots”, pulley brackets, landing gear end boxes and ears. I think the tail skid and wing tip skid brackets are also included but don’t quote me on this. The parts are just cut out and NOT formed and hence NOT welded. There may be other parts that I’m not remembering there may not be, I’m waiting for an email with all the particulars. The price is $350.00. It does not need to be said that this is a bargain, and a real time saver. If you are interested you need to contact Roger at: vahf@gvtc.com

Fokker210 · 26 February 2006, 07:34 PM

Ed,
Please keep us updated on this ! Sounds like a great deal and, as you say, quite a timesaver !