How much grinder do I need?

[eKretz]

I have run plenty of surface grinders with 3/4 Hp and they did just fine with the wheel diameter that fits the RPM..and the stock removal that dosent slow the RPM greatly/

3 or 4" (small) wheel does not give more power to the grind, when you get your Surface speed slow enough you begin honing, not grinding
surface speed is what makes grinding work and in the rough ballpark of 5000sfpm is what you need SFPM plus, up to around 6000-6500 with watching out for the specified RPM on the wheel label..

It does give more torque and therefore help prevent stalling though. You mentioned a 1½" wide wheel, that's pretty darn wide for ¾ HP. Could always compensate by using a harder wheel at the smaller diameter. Even so, it's a tricky game grinding very hard steel without the proper wheel and speed. And preferably flood coolant. Like Roger mentioned, it doesn't take a whole lot to cause all sorts of trouble. Probably the best approach all told is just to use the right wheel speed and have enough horsepower to do the job.

 

[Cyclotronguy]

A nice looking fixture: that said as an ex "grinder" I see one issue an operator would squeak about, and that would be cleaning between cycles.

Grinding is a dirty process and the swarf gets into everything. If you want an accurate grind, someone is going to find it necessary to strip, clean and lube that fixture between cycles, or you need a fixture without pockets and clamping devices more tolerant of contamination where the machines flood system is sufficient to clear the work envelope of debris.

 

[michiganbuck]

guess it best to recommend for improving grinding techniques would be for a person new to Surface Grinding would be to try a piece of secure shape stock (for holding on the magnet) and try both down grinding and incremental cross-feed grinding. Both methods are essential in surface grinding.

DG: To remove .010 stock starting with .0002 down feeds with the full wheel width working up to what seems to strain the machine RPM or some other adverse condition like too much heat, and note how long it takes to remove .010. This would be full wheel width and using only down and long travel feeds(no -crossfeed). It is not uncommon when using down grinding to skim dress, and then take an incremental cross for size or surface finish.

Incremental cross-feed grinding to remove.010. Take a down feed off the part and then with Incremental cross-feed movements and long travel, cross step across the part with trying varied amounts of fixed down amounts and varied amounts of cross travel

Try this with hard and mild stock / wet and dry/ with a valid amount of taking.

Both methods are essential in surface grinding and it is not uncommon to use both methods together to complete a grinding task.

 

[Houndogforever]

Since I'm so unfamiliar with down grinding can you explain it a little clearer? If I understand, I would position the part under the wheel, drop the wheel down .XXX and then activate the table travel??? Do I let it go back and forth a few times before it sparks out and then drop it another half thou?
My digital only has 0.0005 resolution and the handle has maybe 1/8" between .001 marks so hitting a consistent 0.0002 down would be hard.
Do you guys have any down feeding videos you would recommend for me?
thanks again guys,

 

[michiganbuck]

Down grinding is down feeding on the part with every long travel, not using the cross travel feed at all. One might down feed .0002 or .005 with each long travel depending on the capability of the machine and wheel. One might also down feed only on the grind-side of the part(not on the climb-side.)
This kind of grinding is common for all form-grinding (having a part shape dressed into the wheel to be made onto the part), and is a common method of higher stock removal rate. Often the long travel feed rate(speed) and the off-the-part time at the ends of long travel regulate the element of heat. And it (down grinding) can be highly effective for a rapid means of stock removal for simple topping a part(taking stock from the top of a part).

Incremental cross is the other most common type of grinding where one has a set down amount and travels across the part horizontally with steps of cross feed amounts.
Question: (Do I let it go back and forth a few times before it sparks out and then drop it another half thou?( No, most often you find the amount of down feed the machine and wheel is comfortable with and feed down at every long travel / or every other long travel if feeding down only on the climb sided. One factor in regulating the down or feed speed amount is spindle RPM, lowing RPM is nearing the limit of the amount of down feeds for each long travel.

For one example of down-grinding is grinding the V way when grinding a machine bed way. The V shape or angle is dressed into the wheel and the wheel is fed only down to the part( machine bed)...another example might be grinding the V in a V block..another might be to grind a concave radius along the top of a rectangular part or simply grinding the flat top of a part.

One advantage of down grinding is that you have the whole wheel width so to stay sharp and unloaded longer, rather than just the leading edge as you do in incremental cross grinding..

As with all surface grinding the wheel must be tight, as tight as you can with about a 6 or 7" wrench , and then just a tad tighter,