split & drifts

[haw_thrn]

HI, I've done a few small jobs that contain lots of splits and drifts, but I always have the worst time getting consistently accurate holes and getting the drifts on several bars to meet up so that verticals may pass through them.
I'd like to do a split and drift room divider but I need an efficient and accurate method of doing it. Could someone here who has done a lot of this sort of thing give me instructions or even point the way to some good ones. Thanks Jeff

[Chris Pook]

you can make a test piece with several splits and drifts and take note of how much material length is lost when you split and drift. Then taking this info you can lay out your pieces for splitting. You can predrill very small pilot holes at each end of your splits. This will help keep you accurate, and will help center the splits.

good luck.

[HWooldridge]

The short answer is that it's usually best not to layout all the holes ahead of time. I often make one or more test pieces (not only when splitting but for anything that is going to be made in multiples) and keep careful measurements so I know how much movement occurs from various processes. It's surprising how accurate forging can be once some repeatability is attained in the methods.

For a bunch of splits in one bar, make a fixed gage to divide the holes and work from hole to hole rather than one big layout. For example, if the drifted hole is 1/2", make one side of the gage fit the hole with a scribe on the other side to mark center. Cut the stock long so there is extra material from the last hole to the end of the bar, e.g., you want 6 inch centers on all holes so start 7 inches from the first end, estimate the length for the whole bar and leave 8-9 inches from the last hole. If the gage is right and the splitting consistent, you'll have a bunch of holes on 6" centers with surplus material to remove at the ends for final fitting.

[Ed Thomas]

Jeff: Here are some ideas that may help...

1) Don't slit. Use a slot punch. Using the circumference of a hole, you can figure the circumference of a punch. For instance, the circumference of a 1/2" hole is pi * 1/2", or about 1.5". Use a slot punch that has that same circumference. So the circumference of a 1/8" wide slot punch would then be 1/8" + 1/8" + 5/8" + 5/8". In other words, use a 5/8" slot punch that is 1/8" thick. Instead of drifting the hole open, upset it to open. Only use the drift to bring it to final dimension.

2) The amount of material movement to do this can be calculated, but it is easier to just do a test piece. If you carefully mark the location of the slot punch with a center punch, and make very sure you have the slot punch right, the holes MUST form the same way each time. Measure the test piece before you punch, upset, and drift. Measure the distance between the holes before you make them. And then measure how much they move the material after you do the forging. If you do the same thing each time, the real pieces will inevitably move just as the test piece. Generally, a slot/upset/drift will make the material slightly shorter.

3) CENTER the slot punch very carefully and hit gently for the first blow or two until you are sure you are right in the middle. Make sure you have a completely even heat or the punch will wander to the hotter side even if you are centered.

4) When you open the hole by upsetting, make sure you evenly heat the hole. The hotter side will give first and you can wind up deforming the hole too badly to use if you don't correct early.

5) These are FORGED pickets. That means once you have the holes done this way, they should be very close. All you have to do is stretch or upset each picket somewhere other than the holes to bring them into near perfect alignment and length.

[Ed Thomas]

We all replied at the same time. Obviously, we all believe in making a test piece. :)