Trouble with manual surface grinder

I have a small 6x12 over 7a. The ways are in amazing shape and I bought new roller beaming sets o the ways. My problem is that I can take one pass and barely speak bu I can go back and oth a few times and on the 3rd or so pass it will seem to drop way down. I can then advance 20 tho and it will not even spark. It seems to not be binding even. When I put a test indicator on the magnetic chuck it only varies 0.0004 across any pat o the chuck. I don’t know what to do next.

QT:[I can then advance 20 tho and it will not even spark. ] that kind of nails it to the down feed. The weight of the wheel head should drop the head to what you hand wheel feed down. With everything in that works turning free..and fixed to each other so nothing is slipping....grit and grub may be in the works. Could be the column is not free for down travel. Cleaning or lube may be a factor. Might set an indicator under the wheel head and travel it a number of times to see it repeats the same each try.
*An almost shot down feed nut can do some odd things, and may even slip a half thread and lock solid, This can make tear down difficult..test the free travel at about 6" above the chuck. Don't crank hard because you might slip it doing that.. with over a half turn free play you better consider replacing that nut.
Next:
Guess you might hand push/pull about the column under indicator for starter.
See if the spindle is moving about in the way it is held in the machine.
Check to see there is no end play in the parked spindle.
Check the down travel nut, set a wood block on the chuck and drop the wheel on it ,then travel down feed to see how much free travel there is...and know that nut and the down lead screw is fixed tight.
Set an indicator some place on your saddle and see if a push pull makes any suspect movements.
Push pull on the cross and see if anything funny there.
Could be the way the machine sets on the floor, taking a clunk,clunk as the table weigh changes balance right and left..
Soft hammer bump the chuck in different directions to see no movement.
Yes this is just for starters

Sometimes when machines get "sticky" like this it helps to run the head up and down until the limits are hit a few times back and forth. That redistributes the oil and wets everything down. It's good practice to do this every time you fire up a machine for the day. I do it on both grinders and milling machines. If that doesn't fix it, start going through MB's checklist.

On a down move try going past it and then back up to your hand wheel number.
This keeps the assembly loaded in the up. Always a up move to size.
This is SOP for us. Down past and then up. It removes the stick or drop during a run.
Not just gravity but SG spindles cock in their up/down ways as the screw is not on the work surface (Abbe error). You need to control that and force it one side.
Also a good idea when programming cnc grinders.
Bob

A .001 feeler shim can be used to clear the down travel clearance.
Amazon.com: Precision Brand PBI-1 High Carbon Steel Flat Feeler Gage Stock .001 Inch Thick x 1/2 Inch x 5 Inch Flat, C1095 Hard Steel: Industrial & Scientific

For only $ 3,25 every grinder hand should buy this for many uses...

Yes I don't know if you get 5 shims or one..even only one would be worth the $3.25 if you don'r have ant .001.

Best to not clean anything on a grinder with an air hose...or a spray can.

Thanks everyone for the replies. I'm only confused about how to use the 1 thou shim. Could you explain a little more. My apologies.

RobbyWeeds said:

Thanks everyone for the replies. I'm only confused about how to use the 1 thou shim. Could you explain a little more. My apologies.

Click to expand...

It can be a method to scrape grit from tight places if unable to tear a machine down. A .001 scraper probe.. Very often people don't have the knowledge to tear down or the tools and gauges to re assemble a machine..Pressure air and spray can stuff can do much damage to grinders.

Plus .001s are very handy in grinding for tipping a part to allow the need take for a part, shimming a warp part to straighten and many other uses. Very good to have a shim set around a surface grinder.
A bargain brand feeler set can be Separated to make a grinder set of shims. Often the .001 is not included in such a set.

Good to place shim at the top edge of a block-in block..this increases the holding ability of the block-in...A low block in keeps a part from sliding but acts like a trip over if the part or block-in is out of square.

You can buy a roll of .001 shim stock cheap from McMaster and cut to length as needed.
I keep a roll in my cart for setting grippers on the presses.

The head should hang on the brass nut. Another way to check it is: after you loosen the gib, mount a mag base on the coulum with indicator on head close to where the head is to hold downs. Then feed down .005". Then either give the head a karate chop on the top or use a dead blow hammer. If the indicator moves, the head is not hanging on the brass nut. It maybe simpler to just remove the head and clean it up. Check for scores the to dink around and screw it upm