What's the difference - OD grinding edition

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macardoso

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Help me understand the differences between an OD grinder and a tool and cutter grinder. I understand that an OD grinder will typically handle larger parts and often doesn't do ID grinding by default, but aren't they pretty similar machines for smaller (maybe hobby sized :) ) parts?
 
Are there differences in functionality, accuracy, features, etc.?
 
They are very different machines for different purposes. The OD grinder is normally set up to grind shafts or rods, in other words just makes round things. Think a lathe but having a grinding wheel instead of a cutting tool. Normally full automatic operation.

Where the tool & cutter grinder allows the head to be contorted into any position to be able to grind any angle on a cutter, more like a surface grinder with an articulating head. Normally full manual operation.
 
Jim,

Thanks for the reply. Would a TC grinder be valuable to a hobbist for doing cylindrical grinding? Could you hold tight diametric tolerances or would a tool post grinder on a lathe be better suited? Perhaps if it could be accurate, the flexibility would be desirable?
 
To do cylindrical grinding you would need a powered device (headstock) to rotate the part, then some way of feeding the table at a constant rate. But it could be done. The accuracy should be just as good as an OD grinder , at least within the limits of the machine. The tool & cutter grinder is normally a much lighter weight machine than an OD grinder so just the mass difference will affect the accuracy.
 
Jim’s summary is spot on - they really are different beasts. Although cylindrical surfaces can be ground on a T&C grinder you rotate the part by hand because this function is really intended for sharpening flutes on mills and reamers. I suppose you could make a motor driven workhead but controlling feeds and accuracy would still be an issue. Also T&C grinders operate dry and remove tiny amounts of material relative to cylinder and surface grinders.

I have a T&C grinder in my small workshop but I don’t have room for a cylinder grinder so I use a toolpost grinder on my lathe for OD and ID grinding. Accuracy to tenth of a thou can be achieved by swivelling the compound to 5.7 degrees. At this angle every 1 thou indexed on the compound will give 1 tenth of a thou towards the spindle axis. But there are a few issues you need to be aware of: if you’re working to tenths or microns accuracy you need to control temperature since grinding generates heat which causes measurable expansion. This means your lathe needs a flood coolant system. Another issue is protecting the exposed bed from the effects of the fine particulates generated by grinding. And a third point: can you reliably measure to the accuracy needed? You may need to factor in the cost of micrometers, slip gauges and surface plate if you don’t already have these. Finally, how old and worn is your lathe? My own is about 60 years old and the bed is very slightly worn near the head stock. It’s not enough to worry about for normal turning but it’s enough to make a 12” long shaft 2 tenths larger in the middle than the ends. So I know that for certain work where the geometry is tight I will have to hone after grinding.

I don’t want to put you off either approach, it’ll depend on the type and amount of work you need to do - only you can decide!
 
I agree with what's been stated above. In my search for a tool and cutter grinder for my home shop I have noticed that there are some large tool and cutter grinders that are set up to do some cylindrical grinding. For example, the Brown and Sharpe #13 T&C grinder is one such machine.

See: https://www.sterlingmachinery.com/m...e-no.-13-univeral-&-tool-grinder-brochure.pdf

There is one of these for sale in my area, but it's too big and heavy for what I want. I also looked at a large Covel T&C grinder that was very similar.

There are all kinds of attachments you can get for these large grinders that enables them to do some cylindrical and surface work with probably limited quality, but for a small shop they can serve a purpose.

For the price, I should probably buy the B&S near me, but I don't know how I could unload it off someone's trailer, because the loader on my tractor will only lift around 1600 pounds. The grinder weights 3000 lbs. :confused:

Ted
 
Universal grinder allows you to grind shaft ODs or flip down the quill and grind ID bores also . Most of our grinders were universal of this type , and we had some large ones . Worthington Pump shafts kept me employed for years .
 
macardoso said:
Would a TC grinder be valuable to a hobbist for doing cylindrical grinding?
Click to expand...

I set my T&C ginder up with centers and built a powerable (rotating) end to attempt cylindrical grinding on it and was surprised how bad the shaft turned out.
My lathe would have gotten it closer.
It is a light T&C grinder being a K.O. Lee so maybe with a more substantial one it could work.

I bought a B&S cylindrical grinder and it does great. 5hp motor on the grinding wheel compared to 1/4hp on the T&C grinder. 2800lbs vs 600 might make a difference in rigidity too.

I also have a couple of tool post grinders for the lathe, but try not to use them unless really needed.
 
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