slitter

Is there a formula for making a slitter? What I am wondering is if the hole I want to produce is a 1 inch diameter should the slitter be a 1 inch long cutter area or longer? Not the cross section but the longer, thin one. I would assume the slittr should not be smaller because the slit should be made in as few trys as possible??

My first tomahawk, a slab forged, wrap around eye, 1700's style turned out very nice thank-you very much. Now I wanna do a through-eye but would like to get my slitter as close to correct the first time as possible.

Oh and Dana, first guy that looked at my war club bought it. Felt pretty good.

Moving molten metal is kewl.

ghostdog

You are right, it shouldnt be shorter.
There are a few formulas but I have forgotten them. What I do is to make the edge just a bit longer. Think about the hole you want to end up and just estimate. In my experience (admittedly limtited) hot forging doesn't require as precise measurements as machining or fabricating. There are a few other things to consider to consider though, which are more important than the width of the slitters edge:
1. get that puppy sharp and thin! I mean sharp and thin!!! My one inch slitter is+ - .187. and sharpened at about 33dgs included. You have to be careful about keeping the chisel cool, but it is worth it in performance.
2. break the transverse edges behind the blade.
3. make sure there is no back taper.
probably the most important:
Start with stock that is oversized, because when you slit you will drag material down with the chisel in a crater shape, and in dressing you will reduce thickness.

More notes:
If you are doing this in wrought, choose a good grade as it will have a tendancy to split.

If you run out on one side flip the piece and eyball a correction in the other side, this will leave a crooked hole, but keep mass even on either side. the hole will drift straight, but if you get more material on one side than the other it is hard to correct.
good luck and post pics!

The book by Francis Whitaker, "The Blacksmiths Cookbook", has a table of Slitting chisel edge-length for drifted holes. A 1 inch hole uses a slitter 1.4 inches wide or 1 37/64" in fractions. I have a couple slitters made from S7 and two storebought made from H-13.

Thanks guys. It seemed to me that longer would be best.
That thin huh? Well it makes sense. I was not going to go that thin, thanks for the tip on that. I thought I should mark both sides with a cold chisel to keep me lined up.

Gene I am making this one from a cold chisel, have no idea what the metal is but it does get hard in oil.

I don't have the ability to post pics since my 1400 dollar scanner died at 2 years of age.

ghostdog

Ghostdog, plain high carbon steel works, you can heat treat it but when slitting thick stock it will heat up enough to temper the chisel softer. best to always to keep the slitted piece at orange or high red heat. Marking on both sides is good, even drilling a 1/8" hole on each end of the mark makes sure where where the end is. Even Francis Whitaker did this if I remember correct. Our blacksmithing group had him for a demostrator several times in the 80's, was a real treat for this novice to watch a master in action.

When my slitting chisels get red from slitting hot iron I never quench them, could make them too brittle without tempering. Thats why I like some of the S-7 and H-13 stock I have made some tooling from.

My guess is your cold chisel is high carbon steel maybe 1 % carbon or more. A spark test might help.

GD, Gene is right on the money, (thanks for the location on on eof the formulas Genen I couldn't remember to save my @$$!!
Alot of folks lay out and there is no shame in that. I used to but stopped under orders from my master. now I just eyeball, setting in lightly for the first couple of licks and correcting if necessary. My advice on that would be to lay out And drill if the slit is critical, but to practice with your eye on some scrap. You don't want to wreck a piece. A word on organization for those who may not know: Arrange your work so the tricky stuff is first if possible, this eliminates the four heats spent hammering the blade down before you wreck it with slitting.
I just slit through onto a piece of copper sheet, slitting thick stuff you dont even need the sheet cause the chisel will hang up in the thickness( Hole looks thus >< )
Some folks use a tight "U" shape of heavyish square.
vise jaws work as well.

To keep that thin chisel cool I would play 1,2,3, a dip in the h2o 1,2,3, a dip in the h2o ..... keep a little pot close and handy and you will soon develope a rythm that keeps the chisel only warm and doesn't waste any time.
hope this helps

I figure I will take my time on getting the slitter through, might take a few more heats than you experienced guys and will definetly keep an eye on the slitter and IT'S heat. I had thought about drilling holes but will try the mark first. Didn't get a chance to finish slitter or drift yesterday and won't today.


Thanks a bunch.

ghostdog

Bumping this up for Mike.




ghostdog

Thanks Ghostdog, that answered a BUNCH of questions for me!

Mike