twisting

[gonefhin]

i have to twist a 3/4" bar, the bar will be 32 1/2" and the twist will be 18" long. The catch is I have to do about 120 bars, and try to keep the twist consistant. When doing it the old fashion way, heating the bar into the vise and using a twisting wrench, the end closest to the vise cools too fast and does not twist as tight, also the wrench end does the same thing, but not to the same extent. I think a better jig set up with a wheel spin faster may help, Any ideas?? Thanks

[Chris Keppler]

I have seen on youtube videos people pouring water in the middle of the twist so that it cools at the same rate as the outside ends. Atleast that was my take on why they would pour water on the twist. After looking at this link i am also guessing that the water helps losen the scale?

Chris

YouTube - Ornamental Wrought Iron I Pt.5 of 6

[Francis Trez Cole]

Chris could not have chose a better example Francis whitiker was awsome.

[Ramsberg]

gonefhin,

I have never had to make 100 identical twists so I have never triedt this, but something that I have often considered trying is to heat a portion a bit longer then the twist and cooling both of the end at once with a split line of water.

That is, make an attachment for a garden hose or elevated water tank that splits the water into two branchs, preferably with small dia copper tubes soldered together. That way they could be bent for different twist lengths or a set of them made for different lengths.

So basically, heat the length that needs to be twisted plus a few inchs on both sides. Take out of fire and over the slack tub or drain use the tubing to cool both ends of the bar at once, a setup that had a pair of V blocks for the bar to sit in and be turned while being cooled by the two water steams would make things go faster and be more acurate.

Then place one end in the vice, making sure that the vice only touchs the cooled bit of metal and twist like normal.

Like I said, I have never tried this, but it seems to me that it would get around the differential cooling effect of the vice and twister and not be too complex to build and use.

Just an idea.

Caleb Ramsby

[Glenn]

There are a couple of ways to use solve your problem. The first is to use propane or a gas forge. The heat will be more stable, more even, and more controlled than that of a coal fire which must be controlled manually. Even heat yields even twists.

The second solution to your problem is to apply water to cool overly hot areas of the steel and bring everything back to an equal temperature. This creates a problem when the overall heat of the stock differs one to another as the twist is being made. Hot stock twists easier and at a different rate than stock that is cooler (hot but not at the same temperature of hot).

This is solved by applying heat to the cool areas of the stock with a ox/ac torch using a rosebud. The rosebud puts out large amounts of heat and lets you control heat loss from the entire length of stock or just heat a smaller working area.

Another solution would be to jig up and twist cold. The jig could consist of two stationary sleeves with the open area available for twisting. This takes a bit of energy (motors, long lever arms, etc) but is doable with a little ingenuity. Add heat from a rosebud and the process is easier but you must control the temperature to control the twist. Differences in temperature will result in differences in the twists.

One of the easier methods would be to set up induction heating with a jig for doing the twist. The induction heat could be more easily controlled temperature wise and the jig would then control the twisting procedure making it repetitive. The combination should produce twists that are very close to identical.

As with all things, if you need 120 twists, you will need to make twists until you get enough made to select 120 that are the same or at least look alike. The actual number would be what ever is needed to get the process down (practice) and then maybe 140 as several will be discarded for being out of spec. with the rest. This can be kept to a minimum by using ONLY ONE GO BY twist as a sample to which all others are matched.

Bottom line is keeping the temperature constant, the method constant, and practice till you have a procedure down that gives you the results you desire. Finally when the twisting is complete, cull out and discard any twists or pieces that are out of spec. You can not develop a scrap pile of discards by doing everything right all the time. (grin)

[mike-hr]

For repeatability and quick, I would suggest cold twisting. I can do 1/2 inch square cold in the lathe, for 3/4 stock, you would need to build a twister machine with a 3 foot or bigger hand wheel. Not difficult, just use big I-beam or channel for the frame. I can usually beat the fab shops to a railing with twisted pickets. The ones I've done have great timing, so the light reflects the same on each facet all the way up the stairs onto the loft. Hard to do if you buy twisted stock and cut it into bits for the job.

[Warren Nakkela]

I would make a set up to twist them cold as Glenn suggests. Shouldn't be too hard.
Warren

[Ten Hammers]

As noted, gas forge. 3/4 cold or hot rolled square is a fair twist.

If I read your figures correctly, you have a remainder of about 7" on both ends ( centering the 18" twist). You will need an end fence to set the clamp in the vies with. Maybe something clamped to the back jaw. I am right handed. YMMV. Working from right side of vise. Clamp stock so that 7" mark is on right side of jaw ( and fence or stop out on left side ). My leg vise has 5" jaws so I would need a 2" stub and tab out on the left side to stop and clamp evenly each time. Feed stock into the vise from right side to left.

Stock stand from floor or table mount that is strong. Need a piece of pipe with ID just large enough to accept the 3/4 stock. Whatever works. This is the right side of the twist. The pipe is extended out past the place where the twist wrench attaches to accomplish the same twist length every time. Other words you have a fixture that stops the hot stock from doing anything but twisting and staying fairly straight. Stock stand must be anchored and stay in same position. One thing to do this with 3/8 or 1/2. 3/4 needs pretty stout setup.

Set the stock in the gasser so the right amount heated of course. The vise jaw will eventually quit suckin (heat sink) so much and you will get consistancy. Make sure the test piece is as hot as the others will be. Heat, remove, feed through the pipe into the vise to the stop, clamp the vise. Place the twisting wrench at the right end (left end of the pipe). Make your twist. Plan your work, work your plan. PROBABLY will have to hold right end, unclamp vise and remove to the left if the pipe is tight enough fit. The twist may not go through the inside of the pipe. I’d for sure have the coffee close and the ashtray empty. You should be able to sight these bars out the door or window to sunlight to check for straight but once you get the groove it should go ok. I’d also have a good place to infeed and outfeed materials. Remember that start/stop will be affected in the vise jaws and the pipe end for heatsink. This will be a warm project that will keep you busy for a while. Should be able to attain consistent twists located in same space of each piece if the heat going in is the same. I would really hate to twist 3/4 square cold in my shop. My story and I'm stickin to it.

Edited March 28, 2009 by Ten Hammers

[rokshasa]

to do twist i have a square tubing with 2 rings welded on it one slides back and forth and the othere is stasionnary, i have bits that fit in both rings that hold 1/2 and 3/4 in square stock ,the back of the stasionnary ring is in the shape of a hex and i have a huge wrench to turn it , i can also adjust the second ring so that the length of the bar doesnt matter, i can just twist the middle or i can twist the whole thing, works great, i'll get picks up as soon as i can.

[unkle spike]

One thing is the metal itself. I bought a 20 foot stick of 1/4 square, I make nail or drive hooks at demo's enmasse. I noticed that some of my twists were uneven end to end in the short distance. I found one of my "old" pieces of stock, and it was fine. Even with careful even heat, sometimes the scrap in todays metal makes for uneven twisting.