Flexible Grinder Shaft Expriences/Opinions

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gwrdriver
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Flexible Grinder Shaft Expriences/Opinions

Post by gwrdriver » Sat Sep 13, 2003 4:49 pm

I occasionally need a pretty stout hand-held buffer and so far have made-do with 3M-ite wheels in a large hand drill but I now have a spare 3/4hp/3450rpm x 5/8" shaft available and wondered what, if anything, is available in a hand-held flex shaft attachment. What experiences or recommendations do you have? I'm HSM but I want to have a good piece of long-lasting gear.
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Orrin
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by Orrin » Sun Sep 14, 2003 8:09 pm

I purchased a home-made, but fairly well built flexible shaft setup at
auction and used it until it nearly broke my leg.

The cable was substantial, being about 3 or 4 feet long and having 1/2"
diameter motor and accessory shaft diameters. I was using a it to clean the
rust off something. The bristles dug in, placing excessive torque on the
unit. At this point, the shaft started winding around itself, essentially
stalling the inner core. With it brought to a sudden stop, the 1/3rd h.p.
electric motor started spinning! It whipped around and banged into my leg,
severely bruising my ankle. The green and black colors remained for many
months afterward.

BTW, the electric cord wound around the spinning motor until it was yanked
out of the junction box. At that point I had bare, energized electrical
wires to worry about!

I'm now *very* leery of flex cables driven by anything larger than a Dremel
motor. Flex cables have a torque limit, for sure; but, I don't ever recall
reading any safety warnings about them. I learned the hard way.

[img]/ubb/images/graemlins/cool.gif"%20alt="[/img]Orrin
So many projects, so little time.

Al_Messer
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by Al_Messer » Sun Sep 14, 2003 8:32 pm

Harry, I use an old Dumore that was given to me by a friend. It had belonged to his father who had been a watchmaker and jeweler. I have no idea as to how old it is, but it has a foot rheostat and is just the thing for some teeny tiny grinding jobs. A small vial full of very tiny drill bits came with it but I have not had the courage to try to drill anything yet--my hand is too shaky. Having said all this, Brownells sells both the Foredom and Dremel flexible shaft tools and accessories. Traver's Tools sell a 1/2" flexible shaft atttachment for $30.50 and the foot speed control for $53.00. They also sell the complete Dumore, Foredom, and Dremel kits.
Al Messer

"One nation, under God"

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Victor_R
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by Victor_R » Sun Sep 14, 2003 10:13 pm

Everyone,

I have a Foredom flexible shaft grinder that I got at auction some time ago. You know, the standard type with a tenth horse motor that hangs. Well, I felt the bearings in the hand piece were just a tiny bit noisy or maybe a little stiff feeling when I removed it from the cable. So I took it apart to clean or replace the bearings.

The bearings used are standard metric types 608zz or 38dd (whatever) double shielded. 22mm by 8mm & 7mm wide. Since I use this size elsewhere I had new ones around but decided to try ceramic bearings that are used in skateboards and inline rollerskates. These are the super hard zirconium oxide jobs.

Since these motors run ten thousand RPM or better, I figured they would be and improvement. And they are. They're also very cheap if you get the imports from eBay. Just search for "ceramic bearing*" and you'll find them. (I use the wild card to get pluarls too)

These bearings use oil instead of grease as well as non contact seals for low friction. They also fit other make hand pieces like my K&L. (or is it L&R ?) And they probably would the imports too. I probably don't need to say this but, just be sure to install them square and true without stress. And don't tighten the locking nut much at all.

Now all I need to do it put them in the motor as well assuming they use that same size.
Will try to put a pix of one up.
The machines are gaining ground upon us; day by day we are becoming more subservient to them ~ Samuel Butler (1863)

jpfalt
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by jpfalt » Sun Sep 14, 2003 11:56 pm

Flex shaft string trimmers usually handle about 1 HP and run up to 13,000 rpm, depending on cutting attachments.

The flex shaft is usually 6mm, 1/4" or 5/16". Liners are vinyl, made by a company called Vinylex. A company called Elliot Cable specializes in flex shafts and assemblies, some of which use rigid outer tube and some which use a flexible outer tube.

If you can find an Elliot flex shaft assembly with a Vinylex liner, it should handle the job. Stihl ran into problems with one of their lawn edgers and had to upsize from 1/4" to 5/16" cable to get away from breakage with a 1.2hp engine.

The outer tube needs to have some limited flexibility to avoid rolling up as described in one of the other posts. Shindaiwa has a 35cc backpack brush cutter that uses a 3 foot length of 8mm flex shaft in a rubber housing with twin spring wire wraps to avoid such kinking at 1.7HP. I would be leery of using anything more than about 5 feet in length to avoid getting "Pythonned" by a jammed tool.

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Lee
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by Lee » Tue Sep 16, 2003 6:42 pm

Yes they are available. I used to use one on a daily basis to clean up stainless sinks that I had welded in to stainless foodservice equipment. The base was simply 2" square tubing welded to form a "+" with another piece of 2" square tubing welded vertical in the center of it. There was a piece of 1/4"x2" flat bent into a U shape, big enough to accomodate the motor, welded to this so the legs of the U were pointed upwards. The a piece of 1/8" flat plate bolted to the motor, also with 2 legs bent upwards. This and the U had 1/2" holes drilled in them to accept a 1/2" rod so that the motor could pivot (hanging horizontally). This allowed the whole thing to be "kicked" around to wherever you needed it. Very handy. We just called them "Cable Buffers". You definitely have to hang onto them when you are using them (Orrin explained why in his example). I have attached a link to one on the Harbor Freight website. It's not exactly what you are looking for, but it could be made to work. Hope this helps.

http://www.harborfreight.com/cpi/ctaf/D ... mber=44600
I always like to learn, but I don't always like to be taught.

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gwrdriver
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by gwrdriver » Wed Sep 17, 2003 8:31 am

Thanks for the information. I've seen the kind of buffer setup you describe in auto body and sheet metal shops. I think that setup is called a "gimbal" mount.
GWRdriver
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Al_Messer
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by Al_Messer » Mon Mar 08, 2004 8:25 pm

Victor, the hand-piece on my DuMore flexible shaft set-up looks as if it is/was packed with some kind of White Grease. Do you suppose that I could use White Lithium Grease without damaging the bearings?
Al Messer

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jpfalt
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Re: Flexible Grinder Shaft Expriences/Opinions

Post by jpfalt » Mon Mar 08, 2004 9:33 pm

If you grease the flex shaft, white grease is OK. However, try to avoid overgreasing it. Apply grease to the cable and then wipe it nearly dry. The helix on the cable will pump any excess grease down the cable and pack it into the handpiece. When in the handpiece, it will cause overheating.

A better choice might be a dry film lubricant like molydisulphide, teflon or graphite as it won't migrate like grease.

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