Surface grinding with a horizontal miller

[John Rudd]

Is this possible? Replacing the cutter with a small grinding wheel running at the machine's highest speed?

Should it be done? Is it safe?

Do I need to have a word with myself?

[NickG]

I always wondered this as my centec mill used to have a quick rack mechanism on the slide too. However I think the general consensus was that most mills aren't as accurate as surface grinders and the spindle wouldn't go fast enough / shouldn't with the type of bearings in it. Still as long as the right precautions are taken it might be worth a try?

[rotorhead]

Hi John,

From experience, the most important factor would be a substantial metal wheel guard, other than that, providing you have a high enough spindle speed, and a good coolant flow you should be alright.

Chris

[DavidA]

Do you really want all those grinding particles on your mill ?

Also,  you need very good control of the raising and lowering. A high speed grinding wheel will NOT be forgiving if you take half a thou too much.

I wouldn't risk it.

Dave

[NickG]

That's a good point the screws must be a much finer pitch to raise the table on a grinder.

[John Rudd]

Ok gents,

Points considered, I wont do this...

Thanks for the guidance

[Lew_Merrick_PE]

John,

At the risk of reiterating everybody's comments:  (1) Your milling spindle is unlikely to reach the rpm's necessary to do a decent job.  One "trick" is to mount a die grinder (or something like it) in your spindle offset to spin the wheel.  (2) Not having guards can be a very bad thing when a wheel finally let's go.  (3) You are going to coat all your precision surfaces with bits of abrasive that are a PITA to clean up.  And (4) the resolution of your vertical controls is pretty loose for grinding...

On the other hand, a decent surface grinder is not all that tough a project.  Linear bearing rods on a solid base; a table that rides on them with adjustable "stops" that reverse either (A) a double-acting pneumatic cylinder or (B) an appropriate motor for the X-axis drive; a cross-feed driven off an appropriate screw thread with a star-wheel incrementor and a reversing lever; a tower supporting your grinding head mounted on a dual screw drive (a coarse adjust full-height screw and a fine adjust screw angled at (say) 5.7° so that .001 inch on your screw-feed is .0001 inch of motion (half-an-inch of travel should be sufficient); and Bob's your uncle!

I have built (and then sold off rather than move) several such beasts over the years.  I have come to the conclusion that pneumatic drive is better than electric drive for the primary table motion.  My latest version (currently in storage) uses a 1/2 HP motor with an o-ring drive to power the spindle.  I spent the $$$ for ABEC-5 bearings for the spindle and see no different in results when compared to the one I build using ABEC-7 bearings previously -- though markedly better than the ABEC-3 version I first built.  Thin (1/16th inch) neoprene covers protect the precision surfaces.  The whole thing is covered with a plywood case that has (3) acrylic windows (each with a sacrificial acrylic sheet prophylactic) that opens up for access that keeps abrasive dust from migrating through my shop.  A pair of 5-gallon buckets provide coolant & recovery via gravity.  I probably spent $350 on materials and purchased parts back in 1996 when this (14 X 8 X 6 inch) version was built.

[Rob.Wilson]

John ,,,,,,,,,,you still got that Adept shaper ? 


Rob

[John Rudd]

John ,,,,,,,,,,you still got that Adept shaper ? 


Rob

I certainly have...

What you thinking?

[Rob.Wilson]

Was thinking this 


dose work ,used above set up pre Wilson owning a surface grinder ,actually pre Wilson owning a mill . Anyway if your only doing small parts a TP grinder and a micrometer barrel fitted to rear of slide would do the job .


Rob 

[loply]

I think you could do small bits of grinding on a mill, but 'surface grinding' I'm not sure about.

Typical surface grinder spins at 2,400rpm or so and would have a 7 or 8 inch wheel, giving a speed of 2500 feet per minute or thereabouts. If your mill spindle is slower and your grinding wheel is also smaller you will quickly end up a million miles off the required surface speed.

On top of that the traverse speed needs to be very high to get a good finish and the depth of cut tightly controlled between less than half a thou up to a max of about 1.5 thou, half a thou too much and things begin to get ugly, a thou too much and you're in dangerous territory.

[philf]

I've been thinking about making a surface grinder based on an Alexander engraving machine base.

I envisage using the original 5 tpi z axis leadscrew which is driven via a 1:2 bevel gear from the handwheel - a 10:1 worm box would enable me to get 0.0001" steps in z.

I have a J&S? grinding spindle which I acquired about 20 years ago and feels nice and smooth. (Need a wheel arbor to fit.)

The original y axis will suffice but the x-axis only had about 8" travel. I have a beautiful very heavy duty crossed roller slide which would be easy to protect from grinding debris with skirts and extensions at both ends. This has about 14" travel.

I wasn't thinking about powering either the X or Y axes. I was going to drive the x axis via a handwheel driving a timing belt.

A wheel guard would of course be added.

I have a Union T & C grinder which I thought would be nice for surface grinding of small parts but the maximum reach of the wheel is only about 2".



Phil.

[DavidA]

...Typical surface grinder spins at 2,400rpm or so and would have a 7 or 8 inch wheel, giving a speed of 2500 feet per minute or thereabouts...

I get closer to 5040 foot per minute for an 8"dia wheel.

Can someone else give an opinion.

Dave

[RussellT]

8/12 times 3.142 times 2400 = 5026 fpm

[DavidA]

yes,  that is closer.

I rounded up on the wheel circumference.

Dave.

[mattinker]

Hi,

I realise it's not what you want to do, but it would be much easier to make a shaper run as a surface grinder.

Regards, Matthew