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I Forge Iron

Is it possible to forge a...


brianklein

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internal spline into a square block of metal (steel) like this:

image 1

image 2

I'm trying to figure out if i have a 6"X1.5"X1.5" piece of steel, in which i need to put a 5/8 OD spline centered in the middle, how would one be able to do this??? How would i be able to heat forge the spline shape into the piece??? Or is this something that blacksmithing can't do???

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Do you want a shaft with the splines outside (male) or a square block 6" long with a 5/8 splined hole inside (female)?

I would not try to put accurate splines on a long internal hole, thats more of a job for a shaper that can index and bore out the grooves. External splines are more often rough forged and at least finished by milling , if not cut from the raw stock entirely with a mill.

You almost need a milling machine to make a die to form the splines to make a rough forging that you might need to mill for accuracy. Chicken and egg.

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A number of years ago the smiths at Williamsburg made a clockwork mechanism for turning a spit in a fireplace. Of course they made it the period authentic way.... by using files.

Yes I believe a smith could make the splines, with a lot of patience, elbow grease, lots of test fitting, graphite pencils, and files. Wherever the graphic rubs off, you gently file and test fit again. ;)

Edited by UnicornForge
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Do you want a shaft with the splines outside (male) or a square block 6" long with a 5/8 splined hole inside (female)?

I would not try to put accurate splines on a long internal hole, thats more of a job for a shaper that can index and bore out the grooves. External splines are more often rough forged and at least finished by milling , if not cut from the raw stock entirely with a mill.

You almost need a milling machine to make a die to form the splines to make a rough forging that you might need to mill for accuracy. Chicken and egg.


It is possible to make a die with an external shape of the spline and make a slight larger hole in the center of the block anf then hammerthe outer block around the spline???
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I think that it would be possible to get the rough size. If you can get it hot enough and move fast enough.

Here is how I contemplated doing the same. I have not attempted, let me know how it goes ;). Drill a hole to the ID of the spline Then using some good hot work steel S-7 or H-13 create a punch that has a long lead which will slide through as a guide. When the steel gets hot it will expand so the hole becomes smaller, allow for this.

Next create the flats on the outside of the bar a little smaller than needed. The ends should be square to cut through the material and produce a slug on the back side. You will need a bolster block and some type of punch lube. Also once the splines are cut through you, will need to be able top drive it clear so relieve the back part. Allow for mushrooming the head as you drive it. I would heat treat this to be a little harder than usual to avoid deformation.

I doubt that you can do this in one heat with a hand hammer. Off center blows will warp your tools, necessitating dressing or replacing. Especially as you are trying for 3 diameters depth. It will be money the hard way.

This is the kind of job I no longer attempt as it distacts me from doing what I really want to do. So if this is an exercise for you, I'd like to hear how it goes. If this is trying to avoid a machining bill then you need to ....widen your circle of friends :).

Good luck.

Edited by Mills
Clarity
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  • 2 weeks later...

Typically when one forges on the outside of a cylinder with a hole in it and with any type of a bar in the hole in the cylinder, the hole in they cylinder gets bigger with the forging. At least that is the way larger cylinders were made out of smaller cylinders on the big old steam power hammers. That principal works when hand forging also. With enough trial and error it might be done. It might be possible to make a proper sized flat piece maybe 3/8" thick, put grooves in it, and then bend it into a circle/tube. Of course the grooves would need to be size to be square after the bend. If accurate enough it could be slipped into a hole in your block and welded in. Just a thought and a lot of work. It would be a lot easier to have a machine shop do it and save tons of time.

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The Machine shop is the way to go. Still if you really want to try it you could try to drift the splines in. A drift is sort of a primitive broach. Make an indexing device that will index each 45 degrees and a bushing to fit your blank. This bushing will have a slot to accept your drift. Old blacksmithing books illustrate these drifts. one may take multiple cuts using a shim behind your drift, like a keyway broach.
Warren

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If you have a piece of the female spline just drill a hole in the end of the block and silver solder or braze the sleeve in the hole. Even if you do not have a femail piece of the spline it would be easier to make a short section by hand using files and than solder it in. It would make a difference if I knew what this was going to be used for. If its a slow turning machine you could possibly get by with drilling holes through your 6 in piece of stock and putting in stubby pins that would ingage the male part of the spline. Good luck and think simple...

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Warren's closest to how it was done back when. You need a "spline broach". It's basically an indexable broach and you cut each keyway one at a time. Actually Warren's probably right on the money, the only difference between these types of broach would be how you use it.

Trying to forge the block down onto a die isn't going to work. In reality you'll make the hole larger.

IF however you were able to forge the hole smaller it'll trap the die just like swedging a barb fitting into a hose.

Frosty

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