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View Full Version : Made a tool post grinder....what do you think?



ahidley
10-19-2014, 02:36 PM
Shaft slides in and out via clamps on both sides of the bearings. This makes stick out vairable. Shaft has 1/4 on one end and 3/8 shaft on the other. Shaft is reversable. Because of this both ends have left hand threads.Shaft OD is 12mm. Powered from a harbor freight $9.99 four and a half inch grinder. I also added a router speed control to vary the RPMs. The grinder is rated at 11,000 chinese RPMs and I used a 2:1 ratio for the pulleys which use a vaccuume belt to drive it.
http://i194.photobucket.com/albums/z80/ahidley/IMG_20141018_223118_zpsbab9e78d.jpg (http://s194.photobucket.com/user/ahidley/media/IMG_20141018_223118_zpsbab9e78d.jpg.html)

http://i194.photobucket.com/albums/z80/ahidley/IMG_20141018_222938_zpsaf356445.jpg (http://s194.photobucket.com/user/ahidley/media/IMG_20141018_222938_zpsaf356445.jpg.html)

http://i194.photobucket.com/albums/z80/ahidley/IMG_20141018_222836_zpsa7ae7ae5.jpg (http://s194.photobucket.com/user/ahidley/media/IMG_20141018_222836_zpsa7ae7ae5.jpg.html)

bborr01
10-19-2014, 03:20 PM
I don't think OSHA would approve. The shafts look pretty small for the rpm that they will be running. How big of a wheel are you planning on running on it? Make sure you stand aside if you try it with any wheel at all.

Brian

darryl
10-19-2014, 04:08 PM
I have to agree with Brian on the stick-out. But it's adjustable so you can keep it as short as a set-up will allow. I'd be leery of having that much stick-out on the other end though, if one end is in close.

Of course you can always make a shorter shaft. One thing about grinding is that if there is any possibility of the wheel bouncing off the work, as would happen with a flexible shaft, the result would be a poor finish at the least, and possibly a damaged wheel at the worst. You do NOT want a wheel breaking at speed.

Looks like a functional set-up- some ingenuity, etc- good on ya.

Toolguy
10-19-2014, 04:23 PM
Unless that is a hardened spindle, you will have a lot of vibration. I think it's a pretty smart idea though. The main problem with home made tool post grinders is a lack of power. That will not be a problem on this one. I would do a shorter/larger diam. spindle, but let's see how it works as is first. Be aware that a soft steel shaft that small can bend 90 degrees on you if it has enough forces on it. I would clamp it to the workbench and run it for a while before putting it on the lathe.

alanganes
10-19-2014, 04:25 PM
With the concerns about the length of the shaft sticking out (even the "unused" end) noted, I have to say this is pretty clever execution of the concept. I appreciate the minimalist approach and the rather nice way of incorporating the cheap-o angle grinder to drive the thing.

With a long shaft I'd be a bit concerned about the long free end whipping about and self destructing. Could be nothing to worry about, and I'm sure you are more than smart enough to exercise all due caution.

Nice job and do let us all know how it runs.

Thanks for posting.

The Artful Bodger
10-19-2014, 04:33 PM
Yes, a very nice job and the angle grinder is a great example of innovative use of a common power tool.

I too would be worried about the long shaft but presumably you could easily make a shorter shaft for experimentation?

John

loply
10-19-2014, 04:48 PM
The shaft whipping would be a concern, only experimentation will reveal if it's a problem or not, but you could make up various shafts of different lengths rather than having one large one which you move back and forth...?

Look really good otherwise though!

ahidley
10-19-2014, 07:14 PM
It worked fine on the bench. The biggest wheel is 3 inches. . I made the shaft out of O1. I hardened it and when I threw it in the oil it warped about3/8 of an inch. Made another one but did not heat treat it.... I could make shorter shafts. Or just cut that one in half....

ahidley
10-19-2014, 07:22 PM
What rpm is optimal for aluminum oxide wheels. Say 1, 2, 3 inch in diameter? The 3 inch ones say max of 11k

mickeyf
10-19-2014, 07:29 PM
I have never had a tool post grinder, but my impression is that the bearings are a critical part. What sort of bearings did you use? This looks like a great idea. No reason a person couldn't do this but with a larger diameter (stiffer) shaft.

ahidley
10-19-2014, 07:46 PM
When grinding something, say an ID, how to you keep the ID from tapering due to the wheel wearing down?. All the stones I have , have either 1/4 or 3/8 mounting holes. Many are rated as Hard. I assume that would help with stone wear?

Axkiker
10-19-2014, 08:11 PM
I have also thought about building something similar. I also have heard that the bearings are what make or break a tool post grinder. out of curiosity what kind of bearings are used on the professional models. I would assume something like 2 sets of tapered bearings with some sort of play adjustment would work. Am I way off base ???

JoeLee
10-19-2014, 08:14 PM
That's a clever idea but I have to wonder if the welds will hold!!!!!

All kidding aside, I think there is going to be a lot of vibration transmitted through the base plate from the grinder and it will yield a poor finish.
If you bored the spindle housing prior to welding it I would imaging it has warped or deformed some and will have some effect on the bearing alignment.

JL.............

cameron
10-19-2014, 11:36 PM
Those long shafts do look scary. If you hit a resonant frequency and they start to whip, you may not get hurt, but it won't be because you had time to duck.

thaiguzzi
10-20-2014, 12:03 AM
Read (past tense) the Quorn book. Studied in depth the spindle and bearing details. Made my Stent T&CG spindle housing from a block of steel, made the spindle, and.... used 2 x common normal sealed small motorcycle ball bearings off the shelf, with a tiny amount of pre load. Hundreds of hours later, everything is still fine, finish is good, no vibration to speak of. What i'm trying to say is don't bother going over the top bearing wise in a home designed tool on the home workshop enviroment. Simple works fine.
Back to the Quorn book, the only thing i copied was the spindle end design with the spigot tapered mandrels for holding various wheels.
Your TP grinder, nice thought out tool design. I like it.
Mike.

darryl
10-20-2014, 01:21 AM
I've made a few TP grinders, one takes 1/8 inch shaft tools, one takes 1/4 inch shank tools. For another I custom made the spindle to take the 3 inch stones I already had. With an adapter it takes the common cutoff discs as well. This one I use a lot. The bearings are nothing special, but I did try to select them for smoothest and quietest running. One end of the spindle has a nylon bushing about an inch long slipped onto it, then the end cap is screwed on. This was my idea for a pre-load. I figured that there would be enough 'scrunch' in the nylon to keep things snug without becoming over-tight. Seems to be working. I also made this TP grinder to come in from the back side, with the motor further to the rear. Also made a collection tray that bolts to and follows the carriage. This isn't insurance that no grinding dust gets on the ways, etc, but it sure helps.

How to eliminate taper from a grinding job- usually I grind to within a couple thou of the finished size, then it's back and forth several times while watching the wheel spark out. By the time it's done, the size is pretty much where it was supposed to be, and the sparking is minimal and consistent over the length of the grind. I call that good.

chipmaker4130
10-20-2014, 10:27 AM
. . .when I threw it in the oil it warped about3/8 of an inch. . .

Did you toss the shaft in the quench horizontally? For long thin work I use a 'quenching tube' made from large diameter exhaust pipe which allows for dropping the piece in vertically and that minimizes warping.

gzig5
10-20-2014, 11:52 AM
I don't think the hardness will significantly affect whether the shaft whips, only how bent it becomes once it starts whipping.

DR
10-20-2014, 12:20 PM
Geez, I see so many problems with the design and build, but the results will be hard to argue with. So, we'll see how well it works.

I have a couple Dumore tool post grinders. Both bargains, price-wise. I find they aren't as useful as I thought.

For OD grinding wheel wear is a real, major, major problem. When you think about it, you have a small wheel, 2 to 3 inch diameter by maybe a 1/4" or slightly wider. And you're grinding dry. You compare that to an industrial sized OD grinder with a 12" wheel that's several inches wide and grinding wet.

One thing I'll add to the OP's project. Built a diamond dresser holder. The Dumore one clamps onto the lathe tailstock barrel and can be adjusted to place the diamond near to the work piece diameter (sometimes) which makes the needed frequent dressing a bit easier not having to crank the slide a long distance.

Rosco-P
10-20-2014, 12:58 PM
Any imbalance or vibration in the angle grinder motor or gear train will be directly transmitted to the grinding arbor as they are rigidly coupled by the mounting plate. I'd think that would have a large effect on the finish. What kind of bearings in the arbor? What kind of bearing are in the angle grinder?

ahidley
10-20-2014, 01:45 PM
Chipmaker 4130 I did throw it in horizontally. My bad..