Buying A Surface Grinder ?s

[Cheeseking]

Along with what Bob said above, don't buy one sight unseen like I did.
But if you have to buy one sight unseen do your homework first. Get lots of pictures from the buyer. If they won't provide addition pictures, walk away. Do some research on the brand/model. Lots of information out there on most of them out there on the internet. Think about the things that may require fixing like the bed ways or if on linear bearings. And as Bob mentioned above, the spindle, will it need to be rebuilt? Not a easy task for most of us to encounter and get it right when it goes back together. A spindle rebuild on most SG could require rebalancing the spindle besides spending upward toward $800-1000 just for bearings. Not saying every used SG has bad bearings. I got lucky on mine, good bearings! But I had to replace the motor and electrics on mine. It was wired for 575 volts! No changing out motor leads! And last, be prepared to tear it down and do a thorough cleaning, they get clogged up with the nastiest crud you will ever see! Ken

Ha! Went thru the 575v fiasco with a press brake bought at auction. It was in Canada and when we got it back discovered our "little" oversight. $$ fixes most everything

 

[AGCB97]

rotary (punch type) grinding

I'm unfamiliar with that operation. Just a little explanation please.

 

[Holescreek]

Most people think of a "surface grinder" in a world is flat sense and forget that surfaces can also have shapes. With the right accessories a surface grinder is actually a very versatile and very precise machine capable of grinding contours, diameters etc. Wheel shaping is accomplished through different styles of dressers. I use a Yuasa style import model capable of grinding angles and radii.

Punch grinding is a catch all term that includes rotary or "spin grinding" and actual punch shaping with dressed wheels. I use spin grinding to grind OD's on various projects using a home made motorized attachment that takes 5C collets. I used the spindle from a 5C indexer, added bearings and a motor.

 

[Holescreek]

Set the 5C fixture on top of a sine plate and you can grind your own tapers. Making B&S #7 holders from straight shank Ebay end mill holders here:

I had to dig pretty deep for some photos.

Recently I needed to make a hinge. It's a lot cheaper to dress a wheel for the radius than purchase a custom cutter.

 

[Cheeseking]

Nice work on that motorized collet fixture. One thing that always amazed me about grinding forms is how they hold precise dimensions considering the shape must change as the wheel breaks down.

 

[AGCB97]

I notice a few have plain bearings. I assume this is journals and shells like a car engine. Anything to stay away from or old technology? They must run in oil or be somehow fed with oil. I used to shim auto engine bearings to get precise clearance with tapered shim stock and checked with Plastigage.

 

[rgray]

I notice a few have plain bearings.

Not a disadvantage .... probably an advantage as long as they aren't worn out. Plain bearing spindles have a certain amount of oil in them just like ball bearing spindles do. They will have their ideal clearance when up to temperature. So many of these machines are left running to keep their spindle temp up during the day if they were going to be used on that day. And the reason many of these machines carry a warning sign. My one machine has two stickers one on the column and one on the wheel guard. On the column "CAUTION wheel may be in motion" on the guard " Grinding wheel may be unmanned and in motion approach with caution"

If you found two old machines that had been sitting around and had not had a huge amount of use the plain spindle machine could be the better choice it's bearings would probably survive non use for much longer.
One of mine is air bearing, like plain bearing on steroids, but that's another story.

 

[AGCB97]

Holescreek
From what I can see, your "home made motorized attachment that takes 5C collets" has a divider plate (are you limited to number of dividing holes?) A speed control (What is the speed range as shown Also what type of motor and HP did you use?)

I'd like to make one similar to use my ER40 collets. I already made a collet chuck for my lathe and a collet block (hex) for the mill.

Thanks for whatever info you can share.
Aaron

 

[Holescreek]

I used an AC motor, probably around 1/6hp but don't remember. If I had it to do all over again I'd use a DC motor with a PWM control board. I only run it at it's slowest setting as is. I've never measured the rpm of the spindle. The disc on the spindle plate has the typical 36 holes that all the import dividing heads come with which are further broken down with the 10 hole positions on the face of the bearing block, they're visible in the 2nd photo.

 

[AGCB97]

Thanks.
I was thinking even a gear reduced motor w/ speed control. Can't figure it needs to go very fast