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Ask HN: Can you make me a 50 meter scroll saw blade?

6 points by aconz2 ↗ HN
I'm turning to HN as a semi-last resort in my attempts at finding a manufacturer for a 50 meter long scroll saw blade (0.2mm thickness, 0.6mm width, approx 12 TPI, hard high carbon steel like 1065).

I'm hoping for both a) direct responses if you can make this (ideally with price tag!) and b) meta responses on where else to look, how else to look, how anybody finds others willing to take on projects that are slightly "out there", etc.

These blades exist on today's market as size "2/0 scroll saw blade" (google-able) and are about 5 inches. I've been looking for the past several months to create the same thing, but with teeth for a continuous 50 meter length. I would use these blades in a manner like a bandsaw, but without being in a closed loop. I previously worked on a "CNC scrollsaw" (google-able) and this new blade would power that machine's successor.

I've brainstormed and refined many ideas on in-house (DIY) manufacturing, outsourcing, and some combination.

So far, I've tried contacting:

* The 3 well known manufacturers of these blades: 1 got a prototype to me before saying no (the prototype had teeth, then gap with no teeth, then teeth, etc). 1 said no. 1 had no response

* A reseller of these blades who then asked one of the same manufacturers, but got the same response

* Umpteen companies on Alibaba, few leads, no winners

* Multiple manufacturers that do punch & die work, varying levels of no or no response

* A manufacturer that does reel to reel etching, still in discussion, but seems unlikely

* Multiple manufacturers that do custom CBN form wheels for grinders. skeptical responses and I would need a good spindle to run them

* A manufacturer that makes a fairly similar product to what I'm looking for, just in slightly larger size, but they said no

* A discord of machinists, who had some helpful tips, but no leads

* Steel suppliers for the raw material (flat wire/ribbon is likely the best), but obtaining small (ie < 1 ton) amounts has not been fruitful

I think the DIY approach is not impossible for someone with more skills and better space+equipment than me. A 50m length has about 25,000 teeth, so whatever process it is (milling, punching, grinding, <something else>), it needs to be repeatable. The best idea I've had is a purpose built CNC grinder with computer vision for wear compensation and alignment, but a major hurdle with grinding is the corner radius would ideally be <150 um (300 um tooth height, so that leaves half the height as flat). I could ramble about more specifics, but maybe that gives a bit of flavor and intrigue if someone is interested in working on this.

Thanks!

25 comments

[ 2.9 ms ] story [ 70.6 ms ] thread
floxy
What about welding the small blades together end to end? Bandsaw blades are welded, so I wouldn't think there would be a big concern about hurting the heat treat on the blades. Is this a one-off/prototype-type project? GTAW/TIG welders are getting to be really inexpensive these days. I could see it just being a single pulse at the joint between blades.
aconz2
Responded to another welding comment, I am pretty sure its a no-go, but thanks for the thought!

> Is this a one-off/prototype-type project?

It is a prototype but I'd be looking for ~10 blades to start and then 100+ from there

zzz345345
Band-saw blade manufacturers should be able to do it?

https://www.youtube.com/watch?v=zlqEn4Wmfpg&t=1m05s

aconz2
I did contact some band-saw blade makers and the smaller dimensions I'm looking for are a different ball-game for them for so I only got "sorry, no can do" answers.
[deleted]
(comment deleted)
zzz345345
Maybe too skinny for their equipment... so you need the exact same as a 2/0 scroll saw blade except 50 meters long?
aconz2
Yep! Easy to specify, hard to do!
zzz345345
How much do you expect to pay for such a blade?
aconz2
Based on retail price of the existing blades (50 x 100mm blades == 1 x 50m blade) puts it around $125. If they make them for ~25% of that, each blade is ~$30. Though I anticipate a higher cost to develop the process if necessary.
zzz345345
How many blades do you expect to purchase for a given period?
aconz2
Around 50 blades per month for the first year
Someone
> (50 x 100mm blades == 1 x 50m blade)

You’re off by a factor of ten. 50m is 50,000mm, or 500 × 100mm.

I also would expect a very large price premium per unit length compared to the shorter blades, which must be made by the million.

aconz2
Oops, thanks for the catch. That is just a typo though, so the following price is still correct (500 * $0.25 == $125). Retail price per blade is $0.20 - $0.25.

I've thought about the price premium and think it could go either way. The blades from at least one manufacturer are already produced from a single ribbon before being separated, so the process to produce longer blades shouldn't be too different (hopefully!). And if there's a 2x premium, that's fine, if its closer to 10x I would re-evaluate.

entrepy123
Can an equivalent length of available-size blades be welded together (maybe trimming the ends first, if they lack teeth)? A person welds a band saw blade together at 2:50 in https://www.youtube.com/watch?v=yJV0yV5lHXE and it does not look so impossible.

At that length, you would need a jig or straight edge to keep it linear, not to mention a large space. But it does not seem impossible.

Maybe ask a number of machine shops or even a general contractors to assemble it for you, suggesting this method, especially if you bring the supplies? I would try a small prototype first.

The punch and die shops probably focus on their specific type of product (punches, dies), so I would look broader.

Or maybe put the project on the Handy app? (A hungry person may be happy to do it for you, not thinking more than twice about how unusual it sounds.)

Asides: I wonder what the required blade tension would be and how machine will maintain tension on the blade. Also I wonder why the blade needs to be so long.

aconz2
Thanks for the thoughts!

> Can an equivalent length of available-size blades be welded together (maybe trimming the ends first, if they lack teeth)?

I don't think so, these blades are very narrow and thin -- 0.2mm x 0.3mm cross section at the spine -- and I'm pretty sure a weld would not hold and if it did, you'd still have to grind it down flush. And I'd guess the joint would also fatigue which is an issue since the blade needs to get wound/unwound repeatedly during cutting. Also, I think the heat of the weld would probably effect the already hardened steel.

> I wonder what the required blade tension would be

The tension on existing scroll saws is 10 - 20 lbs for blades of this size.

> how machine will maintain tension on the blade

The blade gets unwound off a spool which maintains the tension through a torque motor.

> I wonder why the blade needs to be so long.

Minimum usable length is ~10m, but I figure if you can make 10, you can make 50. The longer the blade, the longer you can cut before you have to rewind. And the longer the blade lasts before the teeth are dull and needing to be replaced

floxy
>you'd still have to grind it down flush

Not if it was a fillerless weld.

>I'm pretty sure a weld would not hold

...thoughts on why a full-penetration weld not be as strong as the parent material?

>I'd guess the joint would also fatigue

This is based off of previous experiments? Conversations with a metallurgist? Other?

>The longer the blade, the longer you can cut before you have to rewind.

Any particular reason the reciprocating action of a normal scroll saw doesn't work for your application?

aconz2
Idk, not a welding expert, maybe you're trying to tell me it is a-okay? What about the heat affected zone? What welding process are you thinking?

> Any particular reason the reciprocating action of a normal scroll saw doesn't work for your application?

It works... just not well. Reciprocating is only 50% time efficient (only cutting on the down stroke!), wears out the blades by rubbing on the up stroke, and the very small length wears out quickly so they have to get changed often

moistly
Japanese pull saws have the kerf you seek and cut on both strokes. What they lack is the narrow depth that would allow for tight radius turns. Regardless, the tooth pattern for a scroll saw that cuts in both directions exists.
floxy
>What welding process are you thinking?

A pulse of GTAW. You can set your welder to just give a short duration weld pulse, and you'd have it set so that a single pulse would complete the weld on the saw blades without using filler material. Search on youtube for people welding razor blades together to get an idea.

Someone
It’s not what you ask for, but one thing you can buy is diamond wire used for cutting large blocks of stone. For example https://www.dexpan.com/collections/diamond-wire has 100ft wires, and they sell a hydraulic crimper. To me that suggests it is possible to connect two of these to get that 50m length.

That is a lot thicker than what you ask for (about 1 cm², compared to your 0.0012 cm², so about 800 times as thick) and more flexible.

Unless you’re cutting a very weak material, I would think that thickness is as good as unavoidable. If you pull at one end of a 50m saw, and, say, 25m of it grips the thing being cut, would the fairly small pin through the end of the blade that you pull on be strong enough to not break? Or are you going to move the blade very slowly through the thing being cut? Alternatively, maybe you want fewer teeth, to decrease the maximum force needed to pull this blade through whatever you’re trying to cut?

aconz2
I've come across those in my searching before, they are very cool! There is a guy on YT that did a CNC wire cutter for cutting sculptures out of big blocks of granite.

For my application (wooden puzzles), the kerf is essential to be ~0.2mm so I can't use this. The 50m blade length won't be all in one stretch, it is unwound off a spool and wound onto another; though that is a great/funny sight to imagine

moistly
Have you considered using a water jet?
aconz2
Yes, but most numbers I've seen on nozzle size / kerf size are too big by a factor of 2. In the worst-ish case for a cutting process that cuts a pill shape (rectangle with semicircle ends from a translating circular cut) by plunging in from the edge, my total tooth height is 0.3mm so if I aim for 0.1mm of flat, then that leaves 0.2mm of radius == 0.4mm kerf. Most typical numbers I've seen are more like 0.9mm and the Wazer for example is 1.2mm.

Maybe worth another look though to see if there are more specialized machines. The thickness & total amount of material I'm removing is nothing so maybe there's something out there

moistly
Pinhole breaks in hydraulic systems have seriously injured/killed workers, so I believe that a water jet could be made small enough… but whether that’s practical is another matter entirely. The passage of abrading grit might wreck the nozzle in short order.