MarkC Posted November 27, 2009 Share Posted November 27, 2009 (edited) Don't know if anyone has ever heard of a Dog Chain... it's a means of securing a ladder to the edge of an icy roof, used by firefighters. It's a small hook-shaped device with a long spike in lieu of a hook. The spike is driven directly into the roof, and a chain attached to it's rear is secured to the ladder beam. Two dogs are criss-crossed and driven into the roof to secure a ladder. The title of the post is misleading, I guess. I am forging the dog itself, not the chain. They are fairly old-fashioned, but still widely used here in the New England. No companies seem to still produce them, so I was asked to duplicate one of a pair that was missing it's sister. I am just wondering what color you guys would temper the tip at? and also what color you would temper the butt end, which is an upset hammering surface used to drive the spike in. Please see my very crude drawing attached. The thing is at my shop and I didn't have a photo handy. (and a google search does not find any, thus the reason they have me reproducing it!) Your thoughts appreciated. I'm forging it down from a 5/8" high-carbon masonry star drill shank I had in the shop. finished diameter of the thing is around 7/16", octagonal Mark Edited November 28, 2009 by MarkC Quote Link to comment Share on other sites More sharing options...
HWooldridge Posted November 27, 2009 Share Posted November 27, 2009 I'd bet no one makes them anymore due to potential liability issues. To limit the risk of breakage, I would forge to shape and let it air cool, which should be good enough to resist driving with a hammer. If you decide to harden the whole thing, I would draw the entire piece to blue. Quote Link to comment Share on other sites More sharing options...
Svarttrost Posted November 27, 2009 Share Posted November 27, 2009 Well I think that no roof is harder than that hook of yours so I wouldn't worry about the tempering. But I'm no expert in the subject, just my thoughts. Quote Link to comment Share on other sites More sharing options...
John B Posted November 27, 2009 Share Posted November 27, 2009 What exactly are these being driven into, timber, thatch or other material? I would think you need a chisel point end on rather than a tapered cone point as the taper cone may be more prone to splitting whatever it is being driven into. The driving end should also be relatively soft, not hardened at all. Draw a temper on the point if you wish. How are you intending to make the eyed arm and attaching it? Or are you going to forge the whole item as one piece which would be easy enough to do. I would use the following method to make these if someone had asked for one. IE Draw down to required diameter and overall length, forge the drive in end first, then on the other end forge the ring, about 5.5" from the pointed end, heat and bend the bar back onto itself to lie flat against each other. Reheat this bend end and secure it in a leg vice about 3/4" in, then bend the long end down to 90 degrees away from the upstanding leg. Normalise the whole lot, then heat treat the drive in end if you wish, This should give you the required shape, with no potential weakness points due to welds or tenons, and the driving force goes directly down to the point when hammered in Quote Link to comment Share on other sites More sharing options...
MarkC Posted November 28, 2009 Author Share Posted November 28, 2009 (edited) John, They're being driven into any variety of roofing materials. Anything but masonry. Wood sheathing with asphalt shingles, rubber roofing over wood sheathing, tar-and-gravel roofing over wood sheathing, metal cladding over sheathing/timber, etc. No thatch in these parts. I did plan to forge it from one piece, but you've got a better idea there than I had, with bending them fully parallel and then bending the shank back 90*. Thanks for that. I was going to do the same thing but in another, less simple, manner. I do think the drive end should be heat treated, as the point of the Dog that I am reproducing is bent back and curled over from being driven in so many times over the years. Ultimately there is a chance of it losing any temper i give it by being exposed to the heat of a burning building, which could easily bring it to a red heat, especially being driven through the roof sheathing and being exposed to the heat beneath. These are generally used as men are climbing to the roof to cut vent holes, so there will be extreme heat beneath the roof sheathing to be sure, most times when these are used. The one I am reproducing is extremely old, but still solid and in full time service. The driving point and the shank are actually forge welded together. I got quite a kick out of seeing that. It's important to point out, I guess, that the ladder won't be suspended by these things... they are not like the hooks that go over a ridgepole and secure a ladder on a peaked roof... these only keep a normal ground ladder from sliding left or right, or kicking out from below. So while they are a critical safety device in an icy or windy climate, they are not any kind of full load-bearing device. As for hardening the striking surface... these things get driven in with whatever tool the firefighter is carrying. The flat head of an axe, a sledge hammer, a pry tool... basically way overkill. The only reason I thought of hardening it somewhat was to add some durability and prevent premature mushrooming when firemen, high on adrenaline and moving at 100 miles an hour, start blasting away at it with a flat-head axe (which is usually how it goes). Do you think I should not do this? Is there a good reason not to harden the striking end? Edited November 28, 2009 by MarkC Quote Link to comment Share on other sites More sharing options...
Sam Thompson Posted November 28, 2009 Share Posted November 28, 2009 John, your method reminds me of those spikes that steeplejacks use to hold their ladders onto vertical walls. I'd put some weld between two legs beneath the hammered end to prevent water getting in and freezing. Is it cold in Boston? Quote Link to comment Share on other sites More sharing options...
John B Posted November 28, 2009 Share Posted November 28, 2009 Personally I never like a hardend end on something I am likely to hit with something else that could be hard, in case it chips and flys If you are using a high carbon steel to start with that should be reasonably tough enough, but if you are happy to heat treat it then I would consider after hardening, temper back to somewhere in the range of a dark blue to light blue (about 300 to 340 Celsius) on the struck end, and a reddish brown to light purple (265 to 275 Celsius) on the driven end leaving the centre relatively soft, and try one at that in various materials. If you are not happy with the performance, adjust the tempers until you are satisfied. As Sam says it would not hurt to put some weld down the adjacent folded part to consolidate the total piece Quote Link to comment Share on other sites More sharing options...
David E. Posted November 28, 2009 Share Posted November 28, 2009 Icy roof..........building on fire..mmmmm small window of opportunity I'm thinking. Now tying a dog to a wall, or, whats the word I'm looking for???????? yes.. Bondage!!!!...... maybe a business opportunity:D I once knew a smith in London, made a fortune out of.....that's another story. Quote Link to comment Share on other sites More sharing options...
MarkC Posted November 29, 2009 Author Share Posted November 29, 2009 well, you guys agree on the drawing temp/color. Thanks very much for all the good tips. Will use them all. Mark Quote Link to comment Share on other sites More sharing options...
MarkC Posted November 29, 2009 Author Share Posted November 29, 2009 ahh, is that the kind of hardware one needs to be forging to be inducted into the worshipful company, david???? Quote Link to comment Share on other sites More sharing options...
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