2018 POTD Thread Archive

[francist]

Nice Francist. Which bandsaw is that?

I like the stop. My saw has the original stop that came with it. I seen a stop collar on YouTube so I machined a collars.

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Thanks both.
The saw was tagged "Airco", but I'm sure it's the same basic concept as all the other 4x6's around. Older I guess -- I'd put it to the 1970's or so -- if that makes any difference. I tuned a bunch of stuff on it, re-turned the wheels, etc and it's done alright by me so far.

-frank

 

[GoceKU]

Today i had very little free time but decided to start machining some parts for the little Niva, i started with a 28mm round piece of 4140 steel, i turn it down to 22,7 mm then i cut an 10 degree taper to the middle of the cross drilled holes and hand rounded the end then i partted it off, i need to make 3 more pieces like this and couple of beefy hinges but unrelated i clean up and centre drilled this casting piece that i need to weld up to shaft. I like making parts like this.

 

[GoceKU]

Today i continue making the locking tabs and beefy hinges, i run into a problem with my cheap drill press, it drill the pilot hole no problem but 8 mm drill keep spinning the belt, i slow it down to it's slowest speed and tension the belt with a crowbar and still keep spinning, so i used my lathe to drill the rest of the holes, then i finished machining them, then i took them to the big garage and cut a slot up to the drilled hole this would be a lot easier and quicker if i had a mill but i have to use what i have, this took me couple of hours and the plan is to work all thru the night.

 

[GoceKU]

I continued working late in to the night, trying to finish as much of the welding jobs i can, my work bench in occupied by the trunk lid so to free up my work bench decided to repair the lid that means making new pieces, started with the big inner peace, tried making it from 1.5mm steel but i could not bend it so i grabbed some 1mm cold rolled steel, and managed to make the gradual and constant bends, i trim it to fit and tack weld it in place, this was the easier piece. The outer piece needed a curve, and a overlapped edge at the bottom, i bend it over some big diameter pipe, then started a bend on my hydraulic press, then i put a piece of steel in between and hammer the flange shut, this was quite loud but it come out respectable, i had to spread the edge little to get the piece in between out but it fitted perfectly first time, i also tack welded it in place then i moved to the small square pieces, i used some of the scrap pieces i had left from making the previous panel, i made them all and tack welded them, it become very late so i stopped i'm also considering redoing the gas struts mounts as who ever welded them made a mess.

 

[hman]

Today i continue making the locking tabs and beefy hinges, i run into a problem with my cheap drill press, it drill the pilot hole no problem but 8 mm drill keep spinning the belt, i slow it down to it's slowest speed and tension the belt with a crowbar and still keep spinning, so i used my lathe to drill the rest of the holes

If there's a music store near you, you can try buying a small cake of violin rosin. It's inexpensive and makes a great anti-slip for belts - just (carefully!) hold it against the vee faces of the belt as it's running. The "real" fix would probably be a new belt, but rosin should get you back in business quickly.

 

[francist]

The odds of this helping somebody else is pretty slim I'm thinkin, but I did find it kind of a lucky happenstance. The silver key-hole shaped thing used to be round -- it's actually supposed to be round to work properly. It's been kind of....squished... for lack of a better word.



I've been killing a few evenings in the shop oiling up a couple of vises that I don't use that often. One of them is a small Columbian #1 leg vise. I could see part of something squeezing out from around the opening where the screw passes through the movable jaw, and although I had a pretty good idea what it was I was still a little stunned when I took it apart.



The ring is supposed to fit over the screw and butt against the hub when the jaw closes, I think to keep things nicely centred as the jaw hinges open and closed, and also to act as a bit of a wear surface. Well, this one evidently got pinched off-centre at some point and then over the years just got progressively worse and worse. The vise still worked, but now I had the thing apart so what could I do.

As I imagined turning a replacement on the lathe and what material I would have on hand to do that, the similarity to another familiar part became more and more apparent: a compression ring from an ABS plumbing fitting. And sure enough, I just happened to have about three of them in the plumbing parts drawer!



And there it is, an almost perfect fit right down to the taper angle. Needless to say the action is smooth as silk now with a nice nylon ring in there. How long I'll get out of it, I don't know, but it worth it just to see it fit so perfectly without even trying.



And the happy couple. Don't mind the body-builder slickness to them -- I'll wipe them down in a day or so. I'm not interested in repainting them, so a liberal coat of oil every now and again keeps any rust at bay. Thanks for looking.



-frank

 

[Franko]

Here is the thing I made.
Its purpose is to position a 3-D camera so it can rotate 360º around the subject's outstretched arm to document upper arm flab.
The client is a skin product testing lab. It is of my design. They told me what it needed to do and I figured out how to do it.

The base is made of Baltic Birch plywood and painted with spray pickumup truck bed coating. That stuff is great. It covers well, needs no priming and is tough as nails.



the original idea was to weld the joints, but I wasn't up to it. It is 16 ga. aluminum square tube. I practiced for hours but couldn't manage two successful welds in a row. I think the problem was the thin edge end of one tube butting against the side of another. The corner made that piece thicker and more of a heat sink. I couldn't get past the difference in thickness. Try as I might, I couldn't make the puddle go down the seams. Hot enough to puddle the side melted the end away.

So, I resorted to plan B, attatch the tubes with joints and hardware. A detail of the noodley elbow joint. This took a long time to make.
All those holes at all those positions and angles were difficult to clamp tight and square, and drill. Clamping and drilling it under the head of the mill was complicated and tedious.



The hub and counter weights so the arm would balance with the weight of the 3-D camera. It has a disk break and clamp to hold position attached by a T-bushing of delrin-like plastic.

The USB cable from the camera passes through the axle shaft so it won't wrap around the axle.

The hub was equally tedious to make with a flange, section of square tube and two .25 x 2" straps. Welding would have been so much easier and faster. The weights are mounted on an oak angle attached with a 5/8" bolt, fender washers, and 1 inch bushings



This is a detail of the camera mount. A couple of arka clamp mounts so the camera can adjust forward and back, and a Panoramic swivel so it can swivel. It focuses with two laser dots that converge. Upper arms aren't cylindrical or symetrical, so the camera has to move in and out and rotate to compensate and keep the dots in the center of the upper people arms. Each image requires at least 4 images from 4 angles. That's why the 3D camera has to travel around the arms.

The raw camera images are fed into a computer which assembles them to make a virtual arm that can be twisted and turned and viewed from all angles.



This project took a week to concept, make plan drawings and complete. I vastly under bid the job and had to live with my estimate.

 

[hman]

Maybe I'm just blowing smoke here, as I'm NOT an experienced welder. But I own a Millermatic MIG welder and have used for several projects. What's always bothered me was that the blanketing gas (CO2) shuts off as soon as you release the trigger. I've always been paranoid that with the gas shut off, the fresh, hot weld can oxidize. So I devised a circuit that would keep the gas valve open a while (0 to 10 seconds) a the end of the weld.

Took a while to figger out how and where to access the various supply voltages and the solenoid valve signal from the main circuit board, then try to develop the timer circuit. Once I had that all squared away (see schematic), I needed a way to physically mount everything so it would stay secure. Also a convenient way to allow (re)setting the timer dial. I used a couple lengths of 10-32 all-thread and a scrap piece of 5/16" Delrin bar, plus a bit of steel bar (possibly overkill) for strength. Milled a pocket in the Delrin for the DPDT relay and secured it with zip ties.

The assembly mounts nicely inside the "rear" case, held by acorn nuts on the "front" side. All connections to the original wiring are by spade lugs. If necessary, the circuit can be removed and the original wiring restored intact.

Here's a look at the "front" side of the case, showing the timer dial and the acorn nuts.

Looking back on the project, I guess the most difficult task was drilling through the center wall of the case WITHOUT getting conductive swarf all over the circuitry. I first drilled three #10 holes, properly spaced, in a piece of scrap steel. Used masking tape to attach swarf catchers (printer paper) to both sides of the wall. Held the steel to the wall with C clamps and used it as a drill guide. Then the big fun - the 1 ⅜" clearance hole for the timer dial. I did that with the largest step drill I had. It was a little bit noisy, but the hole was OK after I'd deburred it. Sure wish I'd had a Greenlee knockout punch!

Anyway, the circuit works as designed. Minor hiccup of gas through the torch when power is first turned on, but I'll call that a feature, not a bug. It guarantees that there's fresh charge of shielding gas in the torch hose, ready for the first weld!

PS - I've done some asking around. Turns out that what I've cobbled up is called "post flow," and is very common with TIG, but also used with larger MIG welders.

 

[extropic]

As pretty much an electronic novice, I very much appreciate your providing a comprehensive schematic of your timer. I could actually replicate that. Thanks for posting.

 

[savarin]

The plastic arms on my desk chair broke (I think I lever myself up with them)
I had some scrap aluminium plate so made a very quick pair of braces.

Now the back does not flex when I sit in it.
The bad part is I have to overcome the habit of falling into it and catching myself with hands on the arms.