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Where’s precision downfeed on Proth PSG surf grinder?

Ot:
Grinder long travel rate on modern surface grinder machines is about 200 to 900 Inches per minute.
Older and some new machines don't tell the IPM so a quick method to tell is:
Measure the travel length then count the seconds going from stop to stop as
one hippopotamus, two hippopotamus three...
So perhaps you might travel 12 inches in 3 seconds.
12" / 3 = 4" per second x 60 = 240 IPM, a slower but OK rate for a hard par, and depending on the depth of grind along with the cross-feed amount.
(300 to 500 is a common LTF, long travel feed).
With practice one can calculate this in their head...and adding a note to a part print can save re-engineering the grinding process every time that job comes up...and help an apprentice learn to approximate feed rates.
One might print note "LTF 300ipm 46H w"
With a too-fast long feed rate, one can actually slow the wheel RPM and lift the wheel head (the formula for burning/scrapping the part). an example is pushing a piece of steel into a bench grinder to the point of pushing the whole bench.
Counting one thousand, two one thousand is Ok ..but thousandths are for measuring stuff.
One old method to gauge/estimate long feed rate was to watch the spark as to the space between sparks
 
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If the wheel was an H hardness likely it might not load up, but being a 60 gt, not very open, and a harder letter hardness (if so all three) then early loading could occur.
QP"s part is likely a 10 to 12-minute job plus wheel change and dress.

And hardness is tricky because one wheel brand's L wheel may be harder or softer than another brand's L wheel..good to take a pen and mark a wheel's hardness where you can see it when mounted(if there is some blotter you can see). Good also to "mount -up" mark a wheel.

Always turn off the coolant, spin 30 seconds, and then park the wheel

It would be good if they would take that wheel off and let us know exactly what they've got.

And my little Brown & Sharpe hits about 100 FPM table speed, or 1200 IPM, according to the brochure. I haven't actually checked it though.
 
If I rember right Clausings go to about 1100 or 1200 Ipm. that is pretty fast. I don't think I ever ran that fast.
Here is a grinder running at 975 IMP
likely taking .001 and passing over 10 times to get .010.
 
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Hi again Cannonman:
That's a good general purpose wheel for plate grinding, and should be able to run a 0.001" DOC and a 0.250" WOC on 4140 without any issues on a machine with a reasonable number of ponies that's reasonably stiff.
IMO, your wheel is not the source of the grinder bogging down.

On another note, I've looked at your video, and I cannot see what eKretz is seeing and I can't hear what he's hearing.
That doesn't mean it's not there, but it seems pretty subtle to me, even after I've been alerted to its presence and am looking and listening for it.

So are you SURE the wheel is bogging down?
I ask because videotaping notoriously distorts the sounds of machine tools, and I find I can usually tell nothing from listening to a machining video unless it's pretty obvious.

So, eKretz, if you're willing can you tell us in more detail what you're seeing and hearing?

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 
I hear the motor decelerating every time it comes onto the part at both ends. Then accelerating back up to speed again after it clears the work. Listen to the hum of the motor. You can hear the frequency of the sound change. Put an optical tach on it if you've got one. Maybe there's a power issue... What are you running the machine with?
 
Haha, I'm pretty attuned to things like that. Always have been. I see and hear things that other people don't notice all the time. And they're usually not my imagination... :D
 
I ran a surface grinder that had a dial/meter that displayed the drag on the spindle I think it registered ohms or ampers, when it started bumping over 6 I had to back off. ... A Reid 6-18 with a 3 HP Pope spindle...but not a roller way so took some arm power.
That Norton 46j white wheel is a good wheel for the task.
46J in a brown wheel last longer for wheel life but has a greater tendency to get hot/burn.
Seems that the/some old Nortons were as good as a Radac.
Since St Globain took over I think they lost some grinding ability.

The wheel finisher portion makes for optimal/best surface finish quality..
With the big stepover technique often used today the whole wheel can get loaded up and the surface finish quality of the finisher portion can be lost...The small stepover allows the follow area of the wheel to still be load free.
 
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Hi michiganbuck:
Yeah, I'm not a fan of the big stepover technique on a wimpy grinder either.
Not only does it tear up and plug up the wheel as you describe, I also find that on a floppy grinder like a Proth or a Kent, it makes the head hump up and down, it burns the shit out of the job whenever the head drops and it tends to warp the job if the depth of cut is not very consistent and light.

I've never been keen on pushing grinders hard...often (in moldmaking at least) you've already got so much invested the parts that fucking them up on the grinder is extraordinarily discouraging.
So I typically grind very conservatively and I usually get a better outcome than the guys who go balls to the wall on everything.
Something for the OP to consider once he gets comfortable with the machine.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com
 








 
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