Latticino Posted February 7, 2018 Share Posted February 7, 2018 I'm considering hot fitting a wrought iron guard onto a hidden tang Bowie that I forged, ground and heat treated recently. This will be the first trial at hot fitting a guard on a knife (did it once on a sword in a class), but I wanted to try it this time because when I punched the guard while forging it I got a nice "dimple" on the blade side that I'd like to keep rather than grinding that surface flush. What I'm trying to figure out is how close to the ricasso I should file the slot before hot fitting. The taper angle on the tang is fairly standard (maybe 15 degrees, though I don't have it with me right now, and I currently have it cold fitting down to around 3/4" from the final resting place). I could probably do the math for thermal expansion ratio and the like, but there are a couple of variables that are not necessarily clear (like how much drifting of the slot can be expected from hammering it into place). Any experienced folk have a general rule of thumb for this? I'd like to get it close before I do the final shaping on the guard. Thanks. Quote Link to comment Share on other sites More sharing options...
TwistedCustoms Posted February 7, 2018 Share Posted February 7, 2018 I haven't found a tried and true formula for this. No matter how many times I do it there remains a "hit or miss" factor. If the tang is cold and the guard is @ forging temp the guard is going to shrink as it cools making a tight fit. I have never had a guard tear or split from shrinking but I have had a few shrink up so tight that I damaged the guard hammering it off cold. I mention this because my usual method is to set the guard before the edge bevels are hammered in and sometimes before fullering. Also I have done this with 5160 and mild/A-36 for the guard material, not wrought. If you have enough wrought to run some tests fits on various tangs it might save your finished work. As for the 3/4" you mentioned, I have had good results with a 16 degree tang hot fitting the last 1" with the tang at forging heat with light taps using a piece of "squished" 3/4" pipe as a sleeve over the tang to tap the guard down. I look forward to seeing pics! Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted February 8, 2018 Share Posted February 8, 2018 I have used up to .003" - .005" difference when heat shrinking hubs onto shafts. This was on a candy panning shaft that was over 2.5" dia. Heated the hub to a dull red and the shaft dropped right into it. Cold press fits for bearings can be as little as .0005"-.001" , for heat shrinking I would say .003" would be a good place to start. You should not have to hammer it at all, just slide it onto the tang before it cools. Quote Link to comment Share on other sites More sharing options...
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