POTD- PROJECT OF THE DAY: What Did You Make In Your Shop Today?

[woodchucker]

Not much really. Made a pseudo tap for 3d printed threads. Couldn't see spending the money (and waiting) for a 3/4-20 tap. Single pointed the threads for 1" thread length, then ran a 3/16" mill to form the grooves. Didn't have a ball mill the right size, but still wanted to get it all done. Was thinking of using a 5/16 carbide router bit and thought better of it. This was simpler. Not pretty, but functional. It's not a forever tap, if you know what I mean! Took a bit of work to clean things up again after that slot made a mess. I ended up putting the piece back on the lathe and re-synching the thread to "chase" it. I then used a stone to clear out the crud at the thread ends. I didn't have the right kind of steel, but for cutting/chasing threads in PETG, I figure 12L14 will be more than ok.

My printed threads were only a little bit small. Here's the fuzz my tap cut. The black stuff on the edges is the PETG. The tap was clean of all chips and debris before tapping. The tap threaded in only using my hands, no wrenches. That was going to be plan B, install a handle, or cut a hex. Plan B wasn't needed.

FWIW, the corresponding item was 3/4-20 printed at 0.2mm layer height, with a 0.4mm nozzle. Some people have problems with printing threads. Mine weren't that far off, as seen by the minimal amount of swarf generated.
View attachment 465672
I could see doing this again for some un-obtainium thread, in a better material, it wasn't that tough to do. Might even consider hardening the result (using O1 perhaps?). Maybe I could use a slitting saw for the slot?

You need to add some back rake to the tap . Just a little. You can grind it, sand it. 10 thou for cutting plastic should be enough.

 

[Firstram]

Not much really. Made a pseudo tap for 3d printed threads. Couldn't see spending the money (and waiting) for a 3/4-20 tap. Single pointed the threads for 1" thread length, then ran a 3/16" mill to form the grooves. Didn't have a ball mill the right size, but still wanted to get it all done. Was thinking of using a 5/16 carbide router bit and thought better of it. This was simpler. Not pretty, but functional. It's not a forever tap, if you know what I mean! Took a bit of work to clean things up again after that slot made a mess. I ended up putting the piece back on the lathe and re-synching the thread to "chase" it. I then used a stone to clear out the crud at the thread ends. I didn't have the right kind of steel, but for cutting/chasing threads in PETG, I figure 12L14 will be more than ok.

My printed threads were only a little bit small. Here's the fuzz my tap cut. The black stuff on the edges is the PETG. The tap was clean of all chips and debris before tapping. The tap threaded in only using my hands, no wrenches. That was going to be plan B, install a handle, or cut a hex. Plan B wasn't needed.

FWIW, the corresponding item was 3/4-20 printed at 0.2mm layer height, with a 0.4mm nozzle. Some people have problems with printing threads. Mine weren't that far off, as seen by the minimal amount of swarf generated.
View attachment 465672
I could see doing this again for some un-obtainium thread, in a better material, it wasn't that tough to do. Might even consider hardening the result (using O1 perhaps?). Maybe I could use a slitting saw for the slot?

That looks great. I wonder if cutting the grooves first would help or hurt with threading.

 

[WobblyHand]

You need to add some back rake to the tap . Just a little. You can grind it, sand it. 10 thou for cutting plastic should be enough.

I used a diamond card to work on the edges by hand. I'm sure there's practically no back rake. If I had some kind of tool grinding setup it would be a lot easier to accomplish. I don't have anything to fixture something like that. This tap is fine for it's planned use. (Chasing printed plastic threads.) I'd have to put in some back rake if I wanted to cut anything for real.

 

[WobblyHand]

That looks great. I wonder if cutting the grooves first would help or hurt with threading.

I threaded this with a HSS P10 blade for an AXA-8. So it could take the interrupted cut, I guess. Doesn't sound like a nice thing to do though.

The threads really got mucked up after the slotting operation, but I did that single pass width, so I kind of expected it. I did take only 0.040" on the first cut though. It almost made me give up after that pass, but I decided to keep on going and just clean it up at the end. It took a little perseverance, but came out good enough for my application. If I had a die that I could trust, I would have used it, but if I have 3/4-20 it is some HF special, which I have learned long ago are not true to size. The thread I single pointed is to nominal pitch diameter, so I know it is good.

 

[extropic]

@WobblyHand
I think what you made is perfectly adequate for the intended task, and that's the point.
That opinion seems to be supported by your reporting that it worked just fine.
I try to read and understand all the words which includes that, right up front, you identified the tool as a "pseudo tap", not a tap.

I do have a suggestion that may be useful in the future.
Prior to cutting the flutes, thread the blank further along and install a nut. Cut the flutes with the nut installed (but out of the way). Use lapping compound and the nut to remove fine burrs.

 

[WobblyHand]

@WobblyHand
I think what you made is perfectly adequate for the intended task, and that's the point.
That opinion seems to be supported by your reporting that it worked just fine.
I try to read and understand all the words which includes that, right up front, you identified the tool as a "pseudo tap", not a tap.

I do have a suggestion that may be useful in the future.
Prior to cutting the flutes, thread the blank further along and install a nut. Cut the flutes with the nut installed (but out of the way). Use lapping compound and the nut to remove fine burrs.

Agreed. It's good enough for this use. Is it a "real tap", nope. Is it a stepping stone to think about making a tap? Maybe, but I'd have to do things different.

Using a nut is an interesting idea! I'll store that idea for future use. In this case, I had no nut, so I would have had to make one. Honestly, cleaning up the threads wasn't that onerous, it took about 10 minutes, of which 4 minutes were thinking about what to do first.

 

[pontiac428]

Offseting the slot will give you rake, just like Harold Hall says.

 

[woodchucker]

Offseting the slot will give you rake, just like Harold Hall says.

so you are saying off center, toward the back end of where the rake would be

 

[dkemppai]

two is well, redundant . I would think that one would do it..but they put two in...
Nice solution..

I have the exact machine. You really need both to lock it well. The thing I HATE is reaching under the screw to tighten the lock screw. Then the tab of the lock screw is always hitting the machine base, and stops the Y travel movement. Back it up, flip it over, and continue...
It's a good solution, I've been thinking of for a while, but never got around to!

Was it a pain in the arse to time them?

Wondering the same thing myself.

 

[pontiac428]

so you are saying off center, toward the back end of where the rake would be

Yes, towards the side that leads the cut. I think there is advantage to a somewhat narrow slot and a shallow cut in this case, not much room is needed to clear chips so go for maximum support of the thread diameter.