2016 POTD Thread Archive

mattthemuppet said:
ah, right - yours is a double ended motor, that's interesting. I would use the existing pulley, turn it down and press fit the new drive pulley on top. Then take the motor shaft out, mount it between centers and turn the new drive pulley true. If you don't need to reverse the motor, just orient the motor so that the shaft is turning against the threads (ie. won't loosen) and then wire it so that it turns in that direction.
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You won. My internal threading tool didn't work very well. I didn't have enough clearance to get the full thread depth, and it was already flexing quite a bit. Started out as 1/4" round CRS with a 9/32" perpendicular hole near the end for a piece of the shank of a broken 9/32" drill bit, Loctited in. I ended up turning it down to about 0.2" after the first failed clearance effort and then it still didn't work. The bar rubbed before the bit reached the thread root, and the bit couldn't be any longer or the whole tool wouldn't have fit inside the minor diameter drilled hole (0.4xx, I forget the exact figure now). It was already flexing enough (3 passes at the same depth before the spring cuts were done) that I didn't feel it would be worth trying to shave the bar any further.

I wasn't interested in spending any more time trying to make a different threading tool from what I have on hand (just a worn-out spade bit; I did order some drill rod for next time), so I just turned the 1.15" poly-v original drive wheel down to 1.02" (it left maybe 5-10% of the original V roots, which gave the extra thickness somewhere to deform into), and pressed it into a scrap piece of 2" OD, 1" ID (nominal, visibly eccentric) piece of mystery steel tubing. I would have liked to have bored the ID to be concentric first, but then it would have been too large for the existing drive wheel. A couple dozen passes with the deburring tool cleaned up the slight mushrooming of the aluminum at the very face and it now mounts solidly.

I can mount the flywheel end in the chuck (without the flywheel) and this new end will fit nicely on my live center. Hopefully I'll be able to turn it down this evening and then all the hard parts of the 2x72 will be done. All that will be left is mounting the motor and idler/tracking wheel at consistent distance from the frame, then two more wheels on an arm for the platen. Everything else can be built as I need it, later on.
 
RJSakowski said:
When cutting thread with a die, leave some extra length on the part and turn it down to the tap drill diameter. This does two things: 1. it gives some purchase for the die before it has to start cutting the thread, thereby eliminating slipping, and 2. it helps to keep the die running concentric to the part being threaded. When I have finished threading, I cut the excess off and chamfer the end.
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I did it this way and it worked great. I also gained a greater appreciation for the difference between calipers and micrometers. I used the calipers first but the die didn't fit over the minor diameter. I figured it might have been a matter of tolerance with the die, but when I checked with the micrometer it was almost 10 thou oversized. Weird. I could have sworn it was clean and zeroed properly. Anyway, I did the rest of the project with the micrometers (I need more practice reading them; it's so slow at this point that I just always grab the calipers instead) and it went great.

...

Until it broke again after a few minutes of service. It snapped right at the thread clearance section at the back of the 1/4"-20 thread. I left that the same larger size as the first (incorrect) minor thread diameter, figuring it doesn't really need to be turned down all the way, weakening it.

For now I'm going to just replace it with a piece of 1/4"-20 allthread. But first I need to figure out why I'm getting so much torque right there. It really shouldn't be breaking these. All I can figure so far is that I'm overtightening the nuts, though I didn't think I had. I think I'll replace them with nylon locknuts instead, then watch it carefully while it runs with the gears engaged and see what happens.
 
I do have to say, though, that this was a testament to Loctite 242 (blue). I'm out of red, so I just used the blue, and the bolt itself broke rather than the bond.
 
kvt said:
Wife gest upset with me at times for saving all that stuff, That is until she needs something fixed and I just happen to have the stuff that will work saved out in the shop somewhere. But by the next day it is back to the complaining.
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I had that same experience in the past. After a number of times making repairs be pulling some part or material that saw the end of its life decades ago, I no longer get hit with "why are we saving that?" In fact, it has become something of a bragging point for the wife that I am able to come up with these items.
 
My wife's great-grandparents passed on a bunch of toys to us when we got married. These are OLD toys, the likes of which you almost never see anymore. My wife grew up playing with them so it's kind of a big deal to her that we have them.

There's an old rotary "phone" among them, complete with bells and hammer. It was in rough shape when we got it and our kids finished it off. She brought it to me in pieces recently, all of the parts of the rotary dial mechanism having come apart. It took me maybe 5 minutes to find a new spring and pin (and another 20-30 to actually assemble the tiny thing...) and I had it working again.

You don't have to do too many repairs like that before the question of why you have "so many little things like that" stops coming up. :)
 
intjonmiller said:
You won. My internal threading tool didn't work very well.
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I'm sorry to hear that. I guess at that depth and diameter you need to think about a solid carbide thread cutting bar. Looking forward to seeing your belt grinder build though!

finished off the body part of a QCTP "live" drill chuck, now I need to turn and thread the shaft that will hold the chuck and be gripped my my hand held drill.
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BTW, how was Zootopia? :) My kids have been telling me I need to see it with them, but then they say that about anything their mother takes them to see. Which is everything.
 
My lathe's previous owner drilled and partially tapped a hole in the saddle for a light. I did not like the light and picked up an LED light at IKEA ages ago.

This weekend I decided it was time to make the adapter for the new light. I tapped the hole and working off a sketch on the back of an envelope managed to mill up a workable adapter.

It is nice to have more light on the lathe.

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