Seeking Recommendation on a Bench Grinder with Specific Features.

[Scott Memmer]

Pretty much any three phase buffer/polisher will be very good industrial quality. As long as the shaft is not bent and the wheel arbor nut threads are good not much to worry about. Maybe bearings and you do not care about any missing guards or tool rests.
Bill D
Bill D

Bill, thanks. I'm in L.A. and there a BUNCH of used Baldors around me for very reasonable prices. Question, if I may. It appears most Baldor 3-phase grinders run at 1750 RPM. If I hook one up to a VFD, is 1750 the fastest it will go without damaging the motor? I assume so, but I'm pretty much a newb to this stuff.

Thanks Again,
Scott

[Scott Memmer]

Materials listed are all thermoplastics. Have you considered hot wire cutters?

I've looked at this option vaguely. Did you have a particular machine in mind?

The problem is these plastics have widely varying melting points and other properties. Most of them do NOT like my laser cutter and leave a lot of char and clean-up after the cut.

Malcolm, could you please supply a link or two to the kind of machine you're thinking of?

Thanks,
Scott

[Scott Memmer]

What material are you cutting?
IOW, would a tile saw serve you better?
A step up in precision and locational positioning could be a surface grinder. Old mechanical-auto machines are cheap.
Or as has been mentioned, a small horizontal mill, (probably?) with lever feeds. The big old machines are too slow rpm for your needs.
However, some of the small lever feeds can easily be adapted with an add-on spindle. I bought one at an auction last year for $5 and am building the spindle between work on the house.

Speaking of spindles, there are an awful lot of variable speed router spindles available for a few $hundred, including some that are water-cooled. Popular with cue makers.

As also has been mentioned, 3ph with VFD is the modern cheap means to get variable speed for many ops.

smt

Thanks for your post, Stephen. Please see my post immediately about describing the materials I'm using.

Forgive my ignorance, but aren't electric tile cutters very high RPM? I need to be between about 500 to 5000 RPM at the very most.

Could you please post a link of the kind of machine you're thinking of?

Thanks Again,
Scott

[Aaron Inami]

For the round rods, one idea is to get a mini-lathe and then engineer some sort of ultra-thin cutter. It's likely just as much material loss as a bandsaw, but much more accurate.

The Little Machine Shop had the highest quality mini-lathes back when I was researching. This model is a true variable speed using a brushless DC motor (50-2500rpm):
https://littlemachineshop.com/produc...ory=1271799306

If you have square stock, you could engineer a saw cutter blade that mounted in the spindle jaws and then mount your stock on the radial arm. This would allow an ultra precise cut.

[Aaron Inami]

Bill, thanks. I'm in L.A. and there a BUNCH of used Baldors around me for very reasonable prices. Question, if I may. It appears most Baldor 3-phase grinders run at 1750 RPM. If I hook one up to a VFD, is 1750 the fastest it will go without damaging the motor? I assume so, but I'm pretty much a newb to this stuff.

Thanks Again,
Scott

You have to be careful when connecting a VFD to a normal motor such as the ones found in the Baldor 3-phase grinders. These are not considered "inverter motors" and you should really not run them less than about 40-50% (which limits you to about 700-875 RPM.

[Jim Becker]

There are very thin sawblades on the market that are typically used for cutting fret slots. Using or adapting one of these with a "micro table saw" (made for certain kinds of small project hobbies) and a precision sled for thickness stops might be a solution to create your blanks from the rod with minimal waste, but there is also that fine line around ideal blade speed that cuts without heating too much. That's always the big challenge with plastics and similar material.

[Tom M King]

Wire on this is .2mm.

https://www.amazon.com/Proxxon-37080...f_B0017NS8H6/?

[Bill Dufour]

Vfd recommendation is not more then 20% overspeed or underspeed without checking if the motor is designed for more. Lower speeds are not a problem if you add another motor to blow cooling air onto the motor. As rpm drops torque drops the same percent. I run my drill press at 50% speed for several minutes at a time with no modifications. If you want low speed just use a more powerful motor. Example you need one hp at 750rpm. Use a two hp 1500 rpm motor at. 30 hz.
High speed is fine until the rotor or cooling fan fly apart from overeving. Regular ball bearing can go to 5,000 rpm or so just fine.
Bill D

[Tom M King]

And small tile saws:

https://www.vevor.com/power-tile-mas..._010524121464?

[Scott Memmer]

There are very thin sawblades on the market that are typically used for cutting fret slots. Using or adapting one of these with a "micro table saw" (made for certain kinds of small project hobbies) and a precision sled for thickness stops might be a solution to create your blanks from the rod with minimal waste, but there is also that fine line around ideal blade speed that cuts without heating too much. That's always the big challenge with plastics and similar material.

I hear ya. I'm looked at those solutions and I've used and do have those blades -- like, 5" w 320 TPI. Still iffy. This solution is better, I think, Jim, because the water offers superb cooling and avoids that overheating. The Buehler saws are superbly accurate too, with an armor that moves the workpiece in precise increments.

BTW, Jim, I just thought of something. I have a raw case of the same saw (pictured below) that came without a motor. I wonder if I could jury-rig this by inserting a higher RPM motor in there. I would probably want something in the one hp range, variable from 1000-5000 RMP.

What do you think?

Thanks,
Scott

[Scott Memmer]

You have to be careful when connecting a VFD to a normal motor such as the ones found in the Baldor 3-phase grinders. These are not considered "inverter motors" and you should really not run them less than about 40-50% (which limits you to about 700-875 RPM.

Thanks, Aaron. That would probably be fine. What about the top RPM with a Baldor? How high could you go? Thanks again.

sm

[Wes Grass]

I did a nowhere near comprehensive search for carbide slitting saws. I'm thinking 3" dia the minimum for getting to the center of a 1.5" bar. The thinnest 'stock size' being 1/32" ...

Diamond being about the worst thing I can think of for plastic, basically 'sanding' the thing off. But if the waste is that expensive...

Possibly custom saws that are thinner ... but you also need a decent ... no, REAL ... spindle to put them on.

Hot wire sounds interesting... might also smell 'interesting' ... if not also toxic.

Too bad it's not available as sheet.

[Jim Becker]

I
BTW, Jim, I just thought of something. I have a raw case of the same saw (pictured below) that came without a motor. I wonder if I could jury-rig this by inserting a higher RPM motor in there. I would probably want something in the one hp range, variable from 1000-5000 RMP.

Sounds interesting, but I'm not a machinery guy for the most part.

[stephen thomas]

Thanks for your post, Stephen. Please see my post immediately about describing the materials I'm using.

Based on materials, i think you need coolant, but not abrasives.

Forgive my ignorance, but aren't electric tile cutters very high RPM?

See my previous note, i now disagree with abrasives. To answer your Q, no, not particularly high rpm, but they do have coolant. I think mine is 3250 rpm, but have not looked at the dataplate in years. (see post with pix someone else put up regarding tile saw) I can see very faintly possibly modding a tile saw to take a small saw. However, there are intrinsic limits to the control the sliding table offers. OTOH as a cheap "what-if?" i might well shop flea markets etc for a cheap one and try it out. Again, i would make an arbor to use a small saw and adapt the rest of the machine to suit.

One of the problems you need to understand, is that the saw (or the table) needs to travel so that the saw plate is perfectly flat to the plane of travel perpendicular to the cut. Anything less causes deflection for thin blades. Your idea of abrasives is a bandaide to (slightly) mask that problem, but it will still bite.

Could you please post a link of the kind of machine you're thinking of?

Well seeing more info on your project, slicer-dicers do come up on eBay sometimes for very low money because the chip fabs are done with them, and no one else has a use. So there's a thought.
Slicer-dicer's started out as factory modded surface grinders optimized to abrasive cut silcon wafers off the cast bar. You think your plastic is expensive per slice.

One thing about surface grinders is that they are optimized for feeds (steps) in increments of .001" and .0001". So after making a cut, you can reliably feed it in, say, .010" and that will be accurate if you know the actual cut thickness. Then you are just down to part-to-tool alignment, and deflection. Slicer-Dicers automate and optimize that process.

Sorry i don't have any easily accessible pix of better approaches to your specific project.
However, this is an over-view of the process. Spin the slug in a fixture, cut it off with the live spindle. Could be a lathe, or mill, too. I agree you need coolant, but still think a saw or parting tool is the better cutting implement.

smt_rubberflexhardinge1.jpgsmt_rubberflexhardinge2.jpg

I'm actually modifying a (hardened) Cat50 shank collet chuck, and making a taper socket to fit one of my Hardinge lathes.....to run Ultem. (among other products)

smt_rubberflexhardinge4.jpgsmt_rubberflexhardinge5.jpg

If i get a chance, i may be able to mock something up on a mill to show the saw process with Ultem 1000. But don't count on it before next week.

smt

[Bert McMahan]

Vespel is definitely not a thermoplastic, and you definitely do not want to cut it with heat. I'd suspect the same with PEEK but I haven't tried that one.

I'd vote slitting saw. They get crazy thin.