Thread: Brown & Sharpe #2 grinder restoration

Hi Ewan,
i understand your concerns and considerations and appreciate them.
A more sophisticated grinder like RayG's gives very precise indications of the cuts made, but they too are 'only' vertical movements, as far as I know. Are there methods by which the wheel wear can be measured or predicted?

R.C.,
I just calculated that a stepper motor with the reductions in the drive I have would take 88 half steps per 0.001 spindle movement. Using 4 or 8 or 16th steps selected in the driver, it would be relatively easy to have exact moves of 0.0001 or less I believe.

I'm in a conversation with Steve Ward (of Worldofward.com and the initiator of the digital rotary divider project) about adapting the firmware and hardware of that controller for this purpose. It may come to something down the track and will be easy to exchange the DC motor for a stepper then.
My thinking about the formware is that the controller could have multiple speeds for jogging (up and down positioning moves iby push bottons), option for setting total planned grinding depth, dividing that into the number of passes at a specific depth, spark-out pass count, advance by limit switch(es) - at the end of each in/out pass (Y-axis) and an external relay connection to switch off the table drive(s).
THat would allow me to roughly position the spindle, then move it manually to touch the work piece, then set the contorller to zero, key i the total planned depth and the depth of passes, spark-out passes, set the table going (once motorised), press 'Go' and take my hands off.....
Sounds like a modern surface grinder to me.... We might yet see how this works on a 1930s model B&S

Well the 58' Blohm could have come with all that. No transistors mind, mine has one valve and spaces for another 2 for the rapid and downfeed. It and i think Rays machine use a "microtip" downfeed unit, Rays with a linear actuator to drive it. https://www.youtube.com/watch?v=w55vLyjN-uI

As for coping with wheel wear, big cuts will wear the wheel faster, i tend to stick to .001" unless i have a lot to remove. If i do take a lot off i generally have to dress again before finishing.
For the .015" (i'm going to work in imp as that is what the blohm is) you took of Aarons part, i would take .014" off first, then measure to find how much i have left to go. It may be .0011 or .0015 depending on the size of the part. Then feed from there. The other option, as i said is to clock a gauge block or sample and then the job to see just how much is left. If you can avoid taking the job off the table you remove the risk of putting it back down on a bit of grit.

Ew

The automatic downfeed on mine is a tiny hydraulic cylinder that drives a ratchet, similar to the buttons on Ewans, there is a second hydraulic cylinder that engages it and a knob that allows you to select the number of clicks of downfeed.

At the end of each cross feed the crossfeed reverses and triggers the downfeed cylinder. When in slotting mode I have a microchip pic controller that picks up a proximity switch and drives the downfeed. the prox is in the center of the travel, and the micro measures the time between pulses and calculates when the end of travel occurs and times the downfeed accordingly, I added a pot to select the number of passes between downfeeds.

For what Joe is thinking, I think a stepper motor controller would do nicely.. or a solenoid and ratchet would work as well..

Ray

Well, I managed to fit a 24V 100W DC motor and drive to the vertical feed. Looked OK.
When I connected it temporarily for a trial, it was able to slowly crank the spindle down - drawing about 7-8A (design motor current 6A max) and the voltage dropping quite a bit, but no go winding it up at all.
So I tried a BIG power supply, since the motor would never be running continuously, that made the poor motor draw over 10A and it got hot quickly (not surprisingly) it was JUST able to wind the spindle up slowly....
Back to the drawing board....
I'm actually wondering it the slides are too tight since I scraped them. Might have to revisit that too....

Here is the general arrangement in its 'raw' state:

IMAG1326.jpg IMAG1325.jpg

Should there be much force involved winding the spindle down?
I'm guessing there should be some to stop the spindle riding up (within the backlash of the screw & nut) when cutting uneven surfaces to start with - or an accidental heavy feed. I just don't have any sense of how much force it should take.... Winding up would obviously be that force plus the force required to lift the weight of the spindle block and motor.
Any opinions?

Originally Posted by Ueee

As for coping with wheel wear, big cuts will wear the wheel faster, i tend to stick to .001" unless i have a lot to remove. If i do take a lot off i generally have to dress again before finishing.
For the .015" (i'm going to work in imp as that is what the blohm is) you took of Aarons part, i would take .014" off first, then measure to find how much i have left to go. It may be .0011 or .0015 depending on the size of the part. Then feed from there. The other option, as i said is to clock a gauge block or sample and then the job to see just how much is left. If you can avoid taking the job off the table you remove the risk of putting it back down on a bit of grit.

Ew

That will depend on how you use your grinder, 0.001 doesn't strike me as a heavy cut, and you may try to reduce your stepover and increase the downfeed. My grinder is a toy compared to the ones you guys use, yet I normally grind with a 0.10 mm (4 thou) downfeed but a small stepover. I tend to favour feeding in one direction too, with the work feeding from front to back. What happens then is the wheel wears with a ramp on the leading edge, but the rest of the wheel holds its size well and sparks out the work as it steps across. For the finishing passes I step the reverse way and use the relatively fresh edge on the other side that I keep in reserve. No point in using that when just hogging off material.

Unless it's critical grinding I'm doing, I'll rarely bother dressing the wheel before use. The soft-start/stop gently brings the wheel up to speed and slows it afterwards, so runout isn't an issue. Although it's still grinding perfectly to size, eventually that ramp creeps far enough across the wheel that it's not efficient to keep persisting. But the main reason to dress the wheel is because the abrasive particles dull and the wheel just doesn't cut as well. It's very easy to tell the difference, mainly in the finish, but it just doesn't cut as aggressively. It would be a big factor in a commercial shop, but doesn't bother me as much, and I'd rather have longer wheel life.

It's possibly a slower way to grind, but I've found it works well and saves constantly dressing wheels, and I'd suggest giving it a try to compare with how you're grinding now.

I thought with step over it should be around 2/3rd wheel width per pass...

Interesting, I normally run with a .100-.150" step over, it's a bit random sometimes.

If I need to take a lot of the machine will easily eat .004" per pass, normally I drop the step over to .050" and slow the feed down a bit. Depends on the wheel type and bond too of course.

Ew

Originally Posted by .RC.

I thought with step over it should be around 2/3rd wheel width per pass...

Yeah thats what I've been taught to, and 1-2 thou deep for rough passes and half a thou or less for finish. On the grinder at work we can get 3thou deep but its a pretty rigid grinder. We dont dress the wheel very often on the grinder a work and we dont have any problems. Pete do you have problems with heat buildup with your method? or do you have coolant?

Originally Posted by .RC.

I thought with step over it should be around 2/3rd wheel width per pass...

Yes that's the "traditional" way to grind; small downfeed and large step over. I was screwing around trying different things and independently discovered (well re-discovered, I'm definitely not trying to claim any credit, I was just ignorant of other possibilities), doing it the way I suggested above. It works very well, at least in my opinion. My grinder doesn't have a very large wheel or more the point motor, so I can't push things too much, but I believe some guys with "proper" grinders like yours are downfeeding much deeper than I can.

It's dinner time and the wife has cooked lamb (yay!), but I'll try to dig up some references.

Oh sorry I forgot the question. No particular problems with heat, I don't use coolant so that's always a constant battle for me however. Indeed I feel there's less heat put in the work this way. It could be different for you guys who could hog deeper cuts however. My motor will bog down if I get greedy.

Grrr, I typed and posted a message with links but the server was overloaded and dumped it

Ok I'll try again, briefly, as I'm in the middle of machining gudgeon pins ... 1.5 mm gudgeon pins. My life has reached a new low

Anyway, what I said are here are a couple of links to what I was referring to. That Chaski article is credited as behind this method, although I find that difficult to believe. As I mentioned above, I found this method myself just by bumbling around, and I'm no Einstein, so I can't believe others didn't already discover this before the age of the internet. I only found these references when I saw Richard referring to 0.001" as a "deep" depth of cut, I was surprised as I thought everyone did it the way I do it these days, and I searched to try to see what others were using. I was using 4 times that depth on a grinder a quarter the size! Credit however really goes to Phil (Machtool) for getting me to traverse the table faster and prevent the work burning.

Here's a couple of links that discuss it better than I can.
Surface grinding- Deeper cuts for better finishes ?
Grinding help

Pete, as a reference point, what's your grinder and it's specs?

Michael

It's a small Hercus surface grinder, not too many of them about. Specs I have no idea about, but it's reasonably accurate, good enough for what I need anyway and I never have problems with that side of things. It came out of a University so I don't think had seen much use.

The issues with it however relate to the fact it's a completely manual machine, and that gets VERY tedious after a while. It's not very powerful, no doubt appropriate for its size however. But other than being manual my main gripe is it doesn't have coolant, and I need to be very conscious of heat at all times. Oh, it's only a 6 x 12" machine, so I run out of room at times, in Z as well occasionally, typically when I'm trying to bodge it to be used as something other than a surface grinder! I wouldn't call it an ideal machine by any stretch of the imagination, but the reason I have it is because it's a small footprint so i can actually have a grinder! My workshop is weeny and I need to shoehorn lots of machines in, if it wasn't small I couldn't have one, and I use my grinder a LOT! I wouldn't want to be without one.

Thanks. It sounds of a similar size and power to mine, so I'll have to try it. Small compared to something like Ewans can sometimes mean a 2 hp job with a 14x6" table. As I'm 3/4hp with a 10x5" it may well be worth a try once I am powered up.

On Edit: the links are interesting too and worth reading. Thanks.

Michael

Originally Posted by jhovel

Should there be much force involved winding the spindle down?
I'm guessing there should be some to stop the spindle riding up (within the backlash of the screw & nut) when cutting uneven surfaces to start with - or an accidental heavy feed. I just don't have any sense of how much force it should take.... Winding up would obviously be that force plus the force required to lift the weight of the spindle block and motor.
Any opinions?

Joe, I measured the torque required to wind my grinding head up and down and found that very little effort was needed, about 15in/lb going up and slightly less on the way down, around 13 - 14in/lb.
I used a dial type torque wrench directly on the hand wheel shaft nut.

Regards, Lex.