Sunday, July 18, 2021

Boring awkwardly placed holes with a brace and bit

Another interesting old drilling accessory, looks like it could bore a hole at up to a 45° angle. 


Dave said...

I found one of those at a garage sale, along with a "chain drill" attachment. Neither are a joy to use, but they make good wall-hangings.

It is impressive what they came up with back in the day though.

rats said...

Dave (et al.). I found an old chain drill for sale online, but I'm not sure it's what you mentioned, and in any case I can't figure out what it's good for or how it is used. Have you got the patience to school me?


(Mr. G, thanks also for the adjustable-angle drill pics. Another objet I didn't know I didn't know about.)

rats said...

Grr. Let's see if the eBay chain drill URL stays put this time.

Dave said...

Well, the chain drill isn't good for anything much nowadays but what you would do is chuck the device into a bit brace or, preferably, a chest drill, chuck an auger bit into it and line the bit up where you want your hole, loop that chain around the work once (I tried it on an 8 x 8 post) and lock it in place. Then you would turn the knob to tighten the bit into the work (mine lacks that feature; you have to crank the drill but I'm going to go take a look and see if I missed something). As you crank the brace or drill, the threads take up against the "arms" holding the chain and the auger begins to feed into the work. I can't really call it "self feeding" because you have to crank like hell to drill a hole. But it does hold the bit into the work, and relatively straight. And when you need to take a break, you can just let go of the drill and the whole shebang stays in place. waiting for you to start cranking again. I can imagine them being used for timber framing, maybe by apprentices but experienced framers probably didn't bother.

A modern-day equivalent would be the (electro) magnet drill, which we use for drilling into thick steel in the field. The same principle, but you can enjoy a cup of coffee while the magnet drill does the work.

Here's a drawing of the exact setup that I have (hanging on the wall, not drilling holes!):

I would be interesting to figure out how much energy goes into making chips and how much goes into overcoming mechanical losses.

Dave said...

Sorry; this is the second time recently I double-pasted an image link. It should be:

rats said...

Thanks, it's all clear to me now. (I originally typed "It all makes sense now," but that isn't exactly so.) I decline to invoke Rube Goldberg, but the chain drill does look like a "transitional technology."