High speed belt or chain drive?

I have a recurring need to reach inside a closed space and grind a weld.
Sometimes I have enough room to get a right angle die grinder in
there, if I distort the shape, but then I have to distort the shape
back, which is kind of a pain. Sometimes there is not enough space to
do that, depending on the size. I use a 2 inch Roloc disk on the die
grinder as a kind of miniature right angle grinder. The headroom
requirement for that setup is 4 inches, more than I would like.
I was thinking that I might make a stationary tool, basically offsetting
the Roloc disk a few inches via a drive belt or chain, to reduce the
headroom required to get inside and grind the weld. The Roloc disk
mounts on a 1/4 inch shaft, so perhaps I could put two bearings and a
pulley on that 1/4 inch shaft, and then run a drive belt to the die
grinder, which would have another pulley on it, using a 1/4 inch shaft
mounted in the die grinder. The sketch at the link below should help, I
always have trouble visualizing what people describe in words, a picture
is worth a thousand words, etc.
formatting link

The problem with this concept is that die grinders typically turn at
20,000 RPM. Are there any small drive belts or chains that would
survive that kinds of speeds?
Maybe there is another solution that I have not considered.
Richard
Reply to
Richard Ferguson
Loading thread data ...
Richard: Google Dynafile. I've also seen belt attachments for right angle 4.5" grinders. Check with your abrasives dealer. -Mike
Reply to
mlcorson
I've used band grinders for close quarters, if there's room enough. HF has a conversion kit for an angle grinder cheap, if you just want to try the concept out. I've got my eye on one of the pneumatic dedicated units, though. The HF unit works well for snagging castings and welds in odd spots. Just not going to be that long-lived, it's cheaply built.
Here's one type, there's other sizes:
formatting link
There's also a pneumatic right-angle micro die grinder:
formatting link
Both on sale, how's that for timing?
Hope this gives you some ideas
Stan
Reply to
stans4
At 20,000 RPM, I'd say BELT. Less stored energy when the chain breaks.
For this you want the smallest pulleys possible to keep the linear speed down- less stored energy.
20Krpm, 1 inch diameter pulley, the belt's moving at, lets see...
dist at edge = radius times theta, theta is 2pi, 2 x 0.5 xpi = pi inches per rotation. 20,000 pi is 62831. So 62.832e3 inches per minute, or 87.3 ft/s or just about 60 mph (which is 88ft/s).
Not sure a belt will survive turning a tight radius at these speeds.
Maybe a housing with a shaft drive and bevel gears might be found? You could come straight off the die grinder and just do 1 90-turn at the head.
Dave
Reply to
spamTHISbrp
Are you looking for something like this?
The picture at
formatting link
is broken, so you have to live with the german text. For english description, see Fein's homepage and use this article number: "MSfv 649"
We call that "long neck angle grinder".
Nick
Reply to
Nick Müller
Google Porter-Cable offset router base for ideas on how this can be done . They use a belt to drive a cog pulley that's less than an inch in diameter . Also has a collet for 1/4" tooling ...
Reply to
Snag
I have one of these:
formatting link
The threaded part of the collet nose on mine looks like 5/8" - 24TPI, YMMV. (Mine was bought 20 years ago) If you unscrewed the collet ring, remove the collet and cut the collet housing off just at the end of the threads (leaving the threads), the height would then be about 2.1". Perhaps you could then make an adaptor that screws on to that and accepts your Roloc wheels.
You might have to tape the trigger down and use an external air valve, as from a blowoff nozzle.
Reply to
Don Foreman
C.C. Specialty makes a heavy-duty 90-degree head for the Foredom style flexible shaft porting tools that might work if you must have the tool perpendicular to the weld:
formatting link
I think I would try using an oval-shaped carbide burr on straight handpiece first. David
Reply to
David Courtney
I am really impressed with all the ideas that people came up with. I usually get good advice here, but these were really good, and everyone had a different approach. I went ahead and ordered the angle die grinder from Enco, 801-1685, even though the information about it was sketchy, just a tiny photo. I hope that it has a pad to accept pressure-sensitive sanding disks in some standard size. They said that I could return it within 30 days if I don't use it. It looks a little on the wimpy side, but with patience I think that it would work. It looks like a very small tool with maybe 2 inches of headroom needed, but I will get to see it next week.
After having my eyes opened, I found some alternative approaches that no one has yet suggested.
1. Buy a right angle adapter for a Dremel, and mount a sanding disk on it. Micromark has 1" dia pressure sensitive disk pads with 1/8 inch shank. (One of the problems that I found was that almost all the sanding disk pads had 1/4 inch shanks, so incompatible with Dremels, Foredoms, etc.).
2. Micromark has a small right angle sander with a 2 3/8 inch diameter sanding disk. It runs on 12 volts. I would also have to buy the disks from them, as that is not a standard size of pressure sensitive sanding disks, at least in the USA.
3. There are 2 inch dia. air powered disk sanders available for $300-$500 US. The ones in the MSC catalog are made by Dotco and Dynabrade. These look like right angle die grinders with a sanding disk pad, but appear to require less headroom than a standard right angle die grinder with a separate disk pad. This option is rather expensive, and I am not sure how much headroom I would pick up, so this does not look very attractive at this point. I found one catalog that indicated a height of 3 3/4 inch, not much better than my current 4 inch height. But I expect that these would be powerful industrial tools. I put a lot of hours on my current right angle die grinder with sanding disks on it, maybe it is worth it to upgrade.
From the catalogs, it is hard to determine the actual headroom that each tool needs, that number does not seem to be listed, so you have to guess based on the photo and whatever other dimensions are provided.
Thanks to everyone for their thoughts, and I will watch to see what else people think of.
Richard
Richard Fergus> I have a recurring need to reach inside a closed space and grind a weld.
Reply to
Richard Ferguson
I like the style of that grinder, very low headroom, but it looks like it is too big. I don't read German, what is the disk diameter? My guess is that the disk diameter is 125mm, which would be 5 inches or so, much too big for my application.
Richard
Nick Müller wrote:
Reply to
Richard Ferguson
The technical data can be found here, as I sayed:
formatting link
article "MSfv 649"
If you want it smaller, then look a
formatting link
for a similar but smaller product. But if the long-neck grinder is as bad as their homepage is ....
Nick
Reply to
Nick Müller
I like the Proxxon long neck grinder, it looks like the right tool to meet my needs. It is available from a variety of sources in the USA, mostly wood carving or model making suppliers. Of course I cannot tell the quality from the web. The only downside is that the 2 inch disks are kind of oddball, so you may have to buy the Proxxon disks. I may buy one even if the little angle grinder from Enco works out, I have a feeling that the Proxxon would be more powerful than a tiny angle die grinder.
Richard
Nick Müller wrote:
Reply to
Richard Ferguson
As I noted in an earlier post, I ordered the mini angle die grinder from Enco, 801-1685. When I got it, I found that it used very strange donut shaped pressure sensitive sanding disks, and I had no idea where to get more. The package that I had appeared to have been opened. I suspect that someone else had bought it, figured that he could not get these abrasive disks, and returned it to Enco.
I liked the die grinder, so I started thinking about how I could convert it to use standard abrasives. The backing pad screwed on using a 7 mm by 0.75 pitch thread, kind of an odd thread. What I ended up doing was buying a 1" Roloc backing pad and a tap for the 7 mm thread. I drilled out the 1/4 inch threads in the Roloc backing pad, retapped it to 7 mm, and that got me to where I could use standard Roloc abrasives. The headroom required is 2.5 inches, a big improvement over 4 inches.
I have only used it to try it, but I think that it is going to help me with my sanding problem.
I did like the small long neck angle grinder that someone suggested, but it uses special abrasives, not available from the standard industrial suppliers. I may yet end up buying one.
The rec.crafts.metalworking crew came up with solutions, again. Thanks to all.
Richard
Richard Fergus> I have a recurring need to reach inside a closed space and grind a weld.
Reply to
Richard Ferguson

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.