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sbmathias
07-18-2012, 04:45 PM
I needed to do a very small, light internal grinding job on the lathe. I could hold the part OK, but was having trouble figuring out how to spin the grinding wheel. I had an old 1/2hp 3450-rpm motor from a drill press, but that had no way to mount a small wheel on it, and it really didn't spin fast enough anyway.

Looking around the shop for high-rpm motors, I spied a small trim router made for use with wood. It has a 1/4" collet to hold small router bits. I dug through my grinding stones and found one that would work, complete with 1/4" shank. It spins at up to 30k rpm. Now, I just had to mount the router somehow.

I came up the a mounting as shown below, using all OEM edge guide accessories that came with the router. Add a couple of big G-clamps, and presto.
http://img256.imageshack.us/img256/9563/1002971.jpg (http://imageshack.us/photo/my-images/256/1002971.jpg/)

It isn't a real robust, sturdy mount, but this particular job needs only a small amount of cleanup to finish the job. Others may want to keep this in mind for future small grinding jobs.

macona
07-18-2012, 04:50 PM
I think the problem you will see, as I saw when I tried something similar, is that the bearings in these things suck for applications like this. It will really effect your finish.

Make sure you cover everything before doing any grinding. And it helps to have a vacuum near the wheel to help with the dust. Also dont forget you need to dress the stone with a diamond once it is mounted.

And your mounting method is way to flimsy.

Dr Stan
07-18-2012, 05:16 PM
2X on everything macona said. Keep in mind Rigid tools are Chinese so they do not have very good bearings.

At one point I built a fixture to hold a Dayton electric die grinder for a similar set-up that did OK for its intended purpose. Not great, but OK.

One other point is you need to make sure the wheel & the work are counter rotating (opposite directions).

sbmathias
07-18-2012, 06:43 PM
Thanks for all the warnings on things to watch out for. This setup worked fine for my particular task. As I said, it was a very light job.

oldtiffie
07-18-2012, 08:46 PM
All the cautions are noted but if the finish and size are OK with the OP then it is OK.

If it was a case of needing to grind it and if this was all that was available then he really only had two options - grind (which worked) it or leave it alone (which in the circumstances seemed to not be an option at all).

For the OP: well thought out and well done.

oldtiffie
07-18-2012, 09:46 PM
I needed to do a very small, light internal grinding job on the lathe. I could hold the part OK, but was having trouble figuring out how to spin the grinding wheel. I had an old 1/2hp 3450-rpm motor from a drill press, but that had no way to mount a small wheel on it, and it really didn't spin fast enough anyway.

Looking around the shop for high-rpm motors, I spied a small trim router made for use with wood. It has a 1/4" collet to hold small router bits. I dug through my grinding stones and found one that would work, complete with 1/4" shank. It spins at up to 30k rpm. Now, I just had to mount the router somehow.

I came up the a mounting as shown below, using all OEM edge guide accessories that came with the router. Add a couple of big G-clamps, and presto.
http://img256.imageshack.us/img256/9563/1002971.jpg (http://imageshack.us/photo/my-images/256/1002971.jpg/)

It isn't a real robust, sturdy mount, but this particular job needs only a small amount of cleanup to finish the job. Others may want to keep this in mind for future small grinding jobs.

I can't see too much wrong with that set-up as it did the job it was intended to do.

My guess is that the OP dressed the wheel (a lot of those "points" are quite well balanced) and if the wheel and the job were going in opposite directions at the point of contact it would be as good a finish as that set-up would allow - which was good enough for the OP.

But if on the other hand the wheel and the job were moving in the same direction at the point of contact the wheel would have been "climb milling" and would tend to "climb and bounce" (giving a sort of "mottled" finish).

For the OP: nice job.

kd4gij
07-19-2012, 02:43 AM
Nice job A dremel or rotozip work well also if you don't need a perfect finish.

oldtiffie
07-19-2012, 04:50 AM
2X on everything macona said. Keep in mind Rigid tools are Chinese so they do not have very good bearings.

At one point I built a fixture to hold a Dayton electric die grinder for a similar set-up that did OK for its intended purpose. Not great, but OK.

One other point is you need to make sure the wheel & the work are counter rotating (opposite directions).

Irrespective of where they are made, RIGID tools are still pretty good - as they'd have to in this instance in a high speed router.

I'd like to see a documented support of your statement that "Keep in mind Rigid tools are Chinese so they do not have very good bearings" - if you have one. If you'd have said that there may be lesser quality bearing thanif/when Rigid was made in the USA I'd probably have accepted that - with reservations


One other point is you need to make sure the wheel & the work are counter rotating (opposite directions).


Nope.

For external grinding they rotate in the same direction (similar to a lathe in "forward" drive) - this ensures that the wheel and the job points of contact direction are opposite to each other (ie the wheel point of contact - at the front of the wheel - is moving downwards and the work point of contact - at the back/rear of the work - is moving upwards which is why the sparks and coolant are ejected downwards - by the wheel.

In the case of internal grinding the wheel and the job rotate in the same direction so that as before the direction of the wheel and the job are opposite each other at the (grinding) point of contact.

Care may be needed to consider heat due to grinding, the more so if no coolant is used.

The wheel should be dressed initially and kept dressed to keep it sharp.

It is often best if the wheel is dressed to only have a small "land" in contact with the job.

"Climb" grinding is generally a no-no but can be used with caution.

Dr Stan
07-19-2012, 10:15 AM
If one where to look at the set up from the tailstock the work would be rotating counterclockwise (forward). The wheel in this case should be rotating clockwise otherwise the wheel would effectively be skipping on the work surface. This is the way we always performed cylindrical grinding (OD & ID) when I was in industry.

Void
07-19-2012, 10:39 AM
I made a special bracket for mounting a Zip tool to my QCTP for grinding. The Zip tool was fairly new and, in fact, it had never been used for anything arduous before. It worked fine for the first few jobs and I was able to obtain tolerable finishes on hard materials (A2 RC60.) But the bearing went to hell after a student used the setup to part off and groove a bent automobile axle using an abrasive cutoff wheel. The Zip tool was made in the USA. I have no idea where the bearings were made.

-DU-

xs hedspace
07-19-2012, 03:45 PM
Looks better than a Dremel, electrical tape, and a 8" piece of Unistrut on the toolpost that I used to grind a reamer once!!

cameron
07-19-2012, 07:02 PM
I find it as funny as hell when someone shows how he successfully completed a job and a few SAE's jump in to tell him that what he did couldn't possibly work.

tdmidget
07-19-2012, 08:22 PM
I find it as funny as hell when someone shows how he successfully completed a job and a few SAE's jump in to tell him that what he did couldn't possibly work.

"successfully completed a job" doesn't mean much. We don't even have the vaguest idea what the job was and no idea how it turned out , other than "successsful". What is "successful"? Is it +/- .010? Is it a 125 finish or is it single digits?
Thomas Edison was successful with the incandescent light. But by his own account he failed thousands of times in the effort. So how successful was he? If the purpose of a home shop is to piddle away time on a hobby then failure= time piddled= success.
The facts are that the lathe is not made more accurate because someone cobbled up a half ass grinding arrangement or even a proper tool post grinder. It has the same ways and spindle bearings as before. If anything, accuracy is less, because the grinding appliance with, to be generous, bearings of unknown quality has been introduced.
There are basically 2 reasons for grinding, size and finish. Introducing a grinding machine of questionable quality will not improve a lathe's capability in either. With a properly ground boring bar the OP could have held size and finish better without the grinder in most materials. If the material must be ground, not machinable by other means, then he did what he had to do., Until we know what the job was and what "successful" means then this does not look like a good idea.

Doozer
07-19-2012, 08:28 PM
oldtiffie-

Are you the chap with 3 or 4 newish Chinese cutter grinders in your shop?
I would have thought you would set up your job on one of those.

--Doozer

sbmathias
07-19-2012, 08:40 PM
"successfully completed a job" doesn't mean much. We don't even have the vaguest idea what the job was and no idea how it turned out , other than "successsful". What is "successful"? Is it +/- .010? Is it a 125 finish or is it single digits?
Thomas Edison was successful with the incandescent light. But by his own account he failed thousands of times in the effort. So how successful was he? If the purpose of a home shop is to piddle away time on a hobby then failure= time piddled= success.
The facts are that the lathe is not made more accurate because someone cobbled up a half ass grinding arrangement or even a proper tool post grinder. It has the same ways and spindle bearings as before. If anything, accuracy is less, because the grinding appliance with, to be generous, bearings of unknown quality has been introduced.
There are basically 2 reasons for grinding, size and finish. Introducing a grinding machine of questionable quality will not improve a lathe's capability in either. With a properly ground boring bar the OP could have held size and finish better without the grinder in most materials. If the material must be ground, not machinable by other means, then he did what he had to do., Until we know what the job was and what "successful" means then this does not look like a good idea.

For this job, I had to deepen the bore on a hardened sleeve by cutting back the internal shoulder by just a few thousandths. I tried cutting it with a brazed carbide, but it was too hard for that. I saw no other way to do it except by grinding. I had to go slowly, and use coolant judiciously, but in the end it worked well, with a good finish.
I admit that this is not using the router in its intended way, but it seems like its bearings should be able to cut many linear feet of hard wood with a carbide router bit, and still function correctly. Part of using any tools is to have a sense for how robust the setup and tools are, and push them no harder than they can stand and still do their job. I believe I did that with this setup. Half-assed? Maybe. Successful? Yes.

Dr Stan
07-19-2012, 10:55 PM
Irrespective of where they are made, RIGID tools are still pretty good - as they'd have to in this instance in a high speed router.

I'd like to see a documented support of your statement that "Keep in mind Rigid tools are Chinese so they do not have very good bearings" - if you have one. If you'd have said that there may be lesser quality bearing thanif/when Rigid was made in the USA I'd probably have accepted that - with reservations

OK here's the documentation. Go to: http://www.eng-tips.com/viewthread.cfm?qid=250073

oldtiffie
07-20-2012, 12:14 AM
oldtiffie-

Are you the chap with 3 or 4 newish Chinese cutter grinders in your shop?
I would have thought you would set up your job on one of those.

--Doozer

That's me.

But I am not the OP in this thread.

oldtiffie
07-20-2012, 12:21 AM
Originally Posted by oldtiffie

Irrespective of where they are made, RIGID tools are still pretty good - as they'd have to in this instance in a high speed router.

I'd like to see a documented support of your statement that "Keep in mind Rigid tools are Chinese so they do not have very good bearings" - if you have one. If you'd have said that there may be lesser quality bearing thanif/when Rigid was made in the USA I'd probably have accepted that - with reservations


OK here's the documentation. Go to: http://www.eng-tips.com/viewthread.cfm?qid=250073

Stan,
that is not a "documented support" in that its a series of posts that have a common complaint - it is not specific to the bearings in the "Rigid" router - so it has yet to be proved that the Rigid Router has poor bearings.

So you will have to do better than that to support your specific assertion.

oldtiffie
07-20-2012, 03:55 AM
"successfully completed a job" doesn't mean much. We don't even have the vaguest idea what the job was and no idea how it turned out , other than "successsful". What is "successful"? Is it +/- .010? Is it a 125 finish or is it single digits?
Thomas Edison was successful with the incandescent light. But by his own account he failed thousands of times in the effort. So how successful was he? If the purpose of a home shop is to piddle away time on a hobby then failure= time piddled= success.
The facts are that the lathe is not made more accurate because someone cobbled up a half ass grinding arrangement or even a proper tool post grinder. It has the same ways and spindle bearings as before. If anything, accuracy is less, because the grinding appliance with, to be generous, bearings of unknown quality has been introduced.
There are basically 2 reasons for grinding, size and finish. Introducing a grinding machine of questionable quality will not improve a lathe's capability in either. With a properly ground boring bar the OP could have held size and finish better without the grinder in most materials. If the material must be ground, not machinable by other means, then he did what he had to do., Until we know what the job was and what "successful" means then this does not look like a good idea.

My guess is that the OP made the best of what he had to grind someting that was too hard to turn - and did it to his satisfaction - so in his eyes its not only a satisfactory job but a good one.

I'd agree with that.

If some here can and do turn to 0.0002" (5 microns) there is no good reason why that machine/lathe can't grind just as accurately.

For those that might not be aware what a surface finish to grade 125 is perhaps this will help:

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/hardness_table1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/hardness_table2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/hardness_table3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/Machining_finishes3.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/Machining_finishes2.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/Machining_finishes1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Surface_finish/Surface_roughness_card1.jpg

mikerolly
07-20-2012, 10:11 AM
A timely thread.

In regards to internal grinding and seeking a fine finish and a tolerance of 0.002" or better, what would be suggested for use on the lathe?

Say, grinding D-2 at around RC 46-48 with a ID of .3755"?

Thanks in advance,

Mike

Dr Stan
07-20-2012, 12:21 PM
Stan,
that is not a "documented support" in that its a series of posts that have a common complaint - it is not specific to the bearings in the "Rigid" router - so it has yet to be proved that the Rigid Router has poor bearings.

So you will have to do better than that to support your specific assertion.

You need to read my original post as I referred to Chinese bearings in general, not Rigid specifically.

oldtiffie
07-20-2012, 09:19 PM
2X on everything macona said. Keep in mind Rigid tools are Chinese so they do not have very good bearings.
At one point I built a fixture to hold a Dayton electric die grinder for a similar set-up that did OK for its intended purpose. Not great, but OK.

One other point is you need to make sure the wheel & the work are counter rotating (opposite directions).
Stan,

that remark was about as specific as you can get about a specific product - ie Chinese bearings in a Rigid router.

If you'd made a general remark about Chinese bearings in that some were not too good and further if you'd said that Rigid routers "may" as opposed to "do" have had such suspect bearings I'd have agreed with that.

The "documentation" you gave was anything but specific to anything and certainly not as as regards Rigid bearings. That link was only a discussion topic on allegedly "bad" Chinese bearings - much of which may have been true and lot of other parts of it just a "rant" or "me too" slant.

Specific documentation does not include general case discussion or inferring a specific case from it.


Originally Posted by oldtiffie

Irrespective of where they are made, RIGID tools are still pretty good - as they'd have to in this instance in a high speed router.

I'd like to see a documented support of your statement that "Keep in mind Rigid tools are Chinese so they do not have very good bearings" - if you have one. If you'd have said that there may be lesser quality bearing thanif/when Rigid was made in the USA I'd probably have accepted that - with reservations


OK here's the documentation. Go to: http://www.eng-tips.com/viewthread.cfm?qid=250073

I suppose its fair to say that I have the odd Chinese tool or two and having used them all, I can say that given the light work I do and that I don't abuse them, that I've never had to replace a bearing or regard any as suspect.

I've never had to dismantle any of my machines and though I could ask for better in some cases they perform adequately for my purposes.

Given your "all in" remarks and the number of Chinese bearings that I have all together, I guess that the probability of a bearing failure should be as high as many here - but to date has not shown any sign of happening - which may seem to rebut or question the veracity of your statement.

My concern is that some who are new or learning may take your remark as "gospel" when while it may be in many cases is not the case generally.

If the readers regarded it as a caution I'd have agreed with it - but it wasn't.