Sub-millimeter precision cutting jig for brass tubing

[phinds]

The positions along the V bed are; Adjustable stop, unit being cut, cutting disk, remaining available stock held by hand beyond the V bed.

Ah ... I see why I was confused. Good design. I'm not used to thinking in terms of the cutter not just slicing all the way through in a chopping motion.

 

[DaveC426913]

They (409's) most definitely flex excessively while cutting. That's why they're so easy to bind if over-fed. And you have to run at close to max rpm's to get anything done; they won't cut wax at low speed.

Oops. I've been running only at medium-high, to cut down on noise.

Also, effectiveness diminishes with wear, since the rim (cutting edge) speed at the same rpm is related to the diameter, and the loss of diameter accelerates.

Yes. I've been finding this. I step up the speed as the diameter drops. Or better yet, get a fresh disc.

You did effectively shoot down my idea, though, with your observation that the tool would be in the way of the stock. I somehow overlooked that, much to my embarrassment.

This is actually a systemic issue. All setups have it in common. One of the factors in determining my max length of ~40mm is that that is the maximum length I can cut anyway.

But putting a stop inside that 40mm distance reduces it correspondingly (see attachment in post #28, bottom diagram).

 

[Danger]

This is actually a systemic issue. All setups have it in common.

Okay, let's set that aside for now and get to the staging mechanism. Would your required tolerances allow the use of a model flat-car on a piece of HO gauge toy train track? (I'm not being facetious; I've made some assuredly adult-only devices using parts from toys.)

 

[phinds]

Not yet. Thanks.

http://www.incrementaltools.com/Metric_Original_INCRA_Jig_p/ij32metric.htm

 

[DaveC426913]

Okay, let's set that aside for now and get to the staging mechanism. Would your required tolerances allow the use of a model flat-car on a piece of HO gauge toy train track? (I'm not being facetious; I've made some assuredly adult-only devices using parts from toys.)

That's an idea. Though I see two problems:
1] They tend to rock. I'd need ... four?
2] They tend not to stay on the tracks. I'd be constantly having to put it back together.

But the gist of it - trucks on tracks might be modifiable. Hm.

 

[DaveC426913]

http://www.incrementaltools.com/Metric_Original_INCRA_Jig_p/ij32metric.htm

I've been looking at their stuff, yeah.

Not exactly sure what that one you linked to is supposed to do...

 

[Danger]

That's an idea. Though I see two problems:
1] They tend to rock. I'd need ... four?
2] They tend not to stay on the tracks. I'd be constantly having to put it back together.

But the gist of it - trucks on tracks might be modifiable. Hm.

Never having owned one, I was unaware of the rocking problem. Is that because they are accurately modeled to the point that they have suspension systems? If so, can the springs be removed and replaced with something more sensible like JB Weld? As to staying on the track, I figured that you'd just hold the thing down by hand. If not, some sort of hold-down mechanism such as siderunner wheels might work. I suspect that you would need to mill grooves in the vertical faces of the rails for that, though.
Anyhow, almost anything that I say off the top of my head is just a jumping-off point for something that inevitably becomes monstrous.

 

[phinds]

I've been looking at their stuff, yeah.

Not exactly sure what that one you linked to is supposed to do...

It's a mm-adjustable push block. Set it for your first cut, make the cut, move it n mm, make another cut, repeat until you've moved it all the way to the end or have run out of tube. This way your "stop" is away from the Dremel and you get as much as you can get considering the Dremel body problem.

 

[DaveC426913]

Is that because they are accurately modeled to the point that they have suspension systems?

Yes. They have same issues with leaning into and going around curves and the "prototypes"* do, just writ small.

*the term model train hobbyists use when referring to real trains

If so, can the springs be removed and replaced with something more sensible like JB Weld? As to staying on the track, I figured that you'd just hold the thing down by hand. If not, some sort of hold-down mechanism such as siderunner wheels might work. I suspect that you would need to mill grooves in the vertical faces of the rails for that, though.

Yeah. This has got me thinkin'

You and I think alike. I'm pretty fast & loose with bashing other equipment to get what I want. Drives em crazy at Home Depot, when I try to describe what I'm cobbling together, but can't describe an actual piece of something.

 

[Danger]

You and I think alike. I'm pretty fast & loose with bashing other equipment to get what I want. Drives em crazy at Home Depot, when I try to describe what I'm cobbling together, but can't describe an actual piece of something.

Together, we can rule the world. I believe that one of my first posts on PF detailed the bother that went into my Alien Hallowe'en costume. The jaw/tongue drive mechanism alone included a brass gear from a Mechano clockwork motor, a section of garage door track, a seatbelt shroud, the carriage rack and bevel gears from a 1920's era Smith-Corona typewriter, a baseball batter's helmet, a tongue-activated momentary contact DPDT toggle switch, 4 metres of welding rod, a cupboard door hinge and also the magnetic latch from the same, a sheet of aluminum grill, the 6-way power seat motor pack from a '67 Mustang, about a square metre of galvanized sheet steel (furnace ducting), a welding helmet, and a bunch of other stuff that I can't even remember. That helmet was heavy. I caused a bit of pain to some folks on the dance floor, but nobody was actually injured. The whole thing, including air conditioning and tail-drive motor, was powered from a 12 volt 6 amp-hour gel cell battery from an alarm system with a motorcycle recharger built into the tail for sitting next to a wall socket and juicing up. It took a fair while to build and cost about $300, including the deep-sea wetsuit that I originally used as the base body material, but nabbed me a bit more than that in bar costume contest prizes. All in all, it was worth the discomfort.

All hell's going to break loose when I finally get my mitts on a 3-D printer. It's in the works.

 

[Danger]

Oh, bloody hell! I just re-read this thread, had an "aha" moment, and kicked myself in the ass so hard for missing it earlier that I couldn't type for 10 minutes.
Just grab a scrapped printer and replace the head with a clamp to hold the Dremel. Strip it down to the bare bones, and you'll have a pre-made super accurate rail/carriage system, with positioning motor, for free.

 

[DaveC426913]

What are you saying'? I could program my cuts?
How would I control the position of the head?

 

[256bits]

Something like these would do. But I doubt they're affordable.

].

Would it be that difficult to make a Dremel into a miter saw?
Might be a worthwhile project.

Or,
Secure the Dremel, and hinge the working surface with the V guide, to go up and down.

For either,
To set the width of cut, attach a collar around the piece, tighten the collar with a set screw.
The collar has to be on then uncut length of the tube, and placed up against the V.
If you scribe the tubing for multiple cuts, taking into account the width of cutting blade, and honing, each ring cut should be the same.
Just move the collar to the next scribe for the next cut.
Hone the end of the tube after each cut for at least one smooth and planar surface

 

[Danger]

What are you saying'? I could program my cuts?

I wasn't actually thinking of that, but I'm sure that it could be done somehow or other. That's way beyond my knowledge. Maybe someone in the Computer section can come up with something along that line. I merely meant that instead of positioning the Dremel manually, you could apply current to the drive motor to get it into place and let the drivetrain mechanism hold it there.