Major issue with B&S Micromaster 510 Y-Axis

dmanthei · Jul 20, 2020

I recently landed an old Brown & Sharpe Micromaster 510
and I finally was able to get it settled, wired, and tested yesterday.
After making a diamond dresser and dressing the wheel,
I noticed that it seemed to be wearing a groove pattern into the wheel
and that the grooves seemed to correspond to positions of the handle for the table lead screw.

Running an indicator on the table (from the column), the X-axis traverse is pretty dead nuts,
but the Y-axis seems to jump +/- 5 thou :confused:

leading me to believe that the Y-axis lead screw is bent or something like that.

When I was picking up/moving/landing the machine,
I failed to understand how the table worked,
so I definitely put a bunch of undue stress on the Y-axis.

Is there deeper troubleshooting I should do?
If it is a bent Y-axis lead screw, is it simply a matter of replacing it?
Or is there no "simply" about that sort of operation?
I'm a pretty new, relatively self-taught machinist,
so I'm good at figuring things out and fixing them,
I just don't have years of experience under my belt.

Thanks in advance for the help.
I've used this forum for answers for a long time,
but have never had so specific an issue as to warrant joining and making a thread.

Attached is an image of some test grinding I did after dressing the wheel.
The milled surface finish is visible on the left (and pretty flat)
vs the very obvious grooves generated by the surface grinder on the right.

Mr_CNC_guy · Jul 20, 2020

Can you remove the Y axis lead screw and repeat your dial
indicator measurements by sliding the saddle by hand? This
would tell you if your problem is with the lead screw.

dmanthei · Jul 20, 2020

That sounds like a great idea.
I'm not entirely sure how to go about removing the lead screw, though.
Probably need to get up and into the machine from the inner cavity?
I'll have to look at it later when I'm free.

michiganbuck · Jul 20, 2020

New grinder manufacturers call the axis differently so it is good to call Long, Cross and Vertical.

dmanthei · Jul 20, 2020

michiganbuck said:
New grinder manufacturers call the axis differently so it is good to call Long, Cross and Vertical.

Thanks, I'm unfamiliar with the vernacular.
The handle that traverses the table left and right reads true,
but the wheel that cranks the table in and out (forward and backward) seems to be where the trouble lies.

The vertical axis/wheel seems to be true as far as I can tell as well.

michiganbuck · Jul 20, 2020

Could be a bent screw and could also be the machine level...Oh, and could be cross travel is dry.
How much free travel do you have in the cross feed? as it could also be the thread wore to have some angle.
Be sure to turn your diamond to point up a diamond facet edge.

Might take hold of wheel head and push pull to see little or no end movement...same with the wheel.

Photo looks like the finish is good for a time/distance and the gets poor/stepped, is that the case?
Wheel tight? as tight as you can hand on wrench and hand on wheel. then set the wrench on a block and make a little tighter.

I’m just guessing here and perhaps some of the other PM guys can think of more possible reasons.

Some gear travel long travels can have the gear get high for a scraping job and so make the table want to rise...or cause surface errors .and when the gear is tight/close and gets dirty. Often the rack bottom is shaver if needed after a scraping job.

I think you would feel a bent screw with turning it..

dmanthei · Jul 20, 2020

Cross travel is definitely well-lubricated
and the machine is close to level, though not perfectly level.
It's definitely on a solid footing, though: no rocking/movement.

What do you mean by "free travel in the cross feed"?
I was able to crank it fully all the way in and all the way out,
as best I could tell. It's definitely a little stiff, though,
especially compared to my old SAIMP mill table travel
which, though old and worn, cranks much more easily.

michiganbuck · Jul 20, 2020

Free travel is hand wheel sloppy with .010 to .060 feels free handle movement with the table not moving.

the long trave is on rollers they may need be cleaned..\good to keep air hose away from any grinder..as grits can get blown under table and on the works.

dmanthei · Jul 20, 2020

Rollers are clean and well-oiled.
I removed the table a few days ago and found that someone hadn’t positioned the rollers properly,
so I cleaned everything thoroughly, re-oiled,
and repositioned the rollers to be in the correct orientations.

The table moves much more smoothly after doing all of that.
Again, the left and right movement of the table is very smooth.
I can push it easily with my hand alone.
The forward and backward hand wheel motion is much stiffer.

rustytool · Jul 20, 2020

The table does not move in and out.
It's the column that moves in that direction if that makes a difference.

Mr_CNC_guy · Jul 20, 2020

dmanthei said:
That sounds like a great idea.
I'm not entirely sure how to go about removing the lead screw, though.
Probably need to get up and into the machine from the inner cavity?
I'll have to look at it later when I'm free.

A lot of machines have the Y axis feed screw held at only one end.
Generally this means a ball bearing in the flange behind the crank
handle. If you remove the bolts from the flange you should be
able to unscrew the lead screw and thereby free up the Y axis.

eKretz · Jul 20, 2020

If you lifted or tilted the upright while moving the machine it's very possible that you bent the screw. The only thing holding the upright down is gravity, so it's easy to do damage. The manual gives a procedure for moving the machine that includes lowering the head down onto a block and throwing a strap clamp over the top of the upright.

By your photo it sure does look like the machine is lifting up at regular intervals... I'm guessing you probably did bend the screw. I would remove it and check it. You'll need to pull the handwheel and remove the cover under it to do so. After the cover is off you should be able to just unscrew the screw from the nut. If it is in fact bent, it may be possible to straighten it if you take it to someone who knows what they're doing.

dmanthei · Jul 20, 2020

Yeah in all my handling of it I never realized it was only gravity keeping the upright down.

Thanks eKretz.
That gives me a good idea what direction to go.

Brandenberger · Jul 20, 2020

The leadscrew goes from the handwheel through a bearing on the front of the machine, then through the nut on the bottom of the column, then a pinned stop collar behind the nut, and then finally the leadscrew shaft is held by thrust bearings on either side of a block accessible when the rear way cover is removed.

So to check the leadscrew shaft you might be able to remove the locknut from the threaded end at the rear, remove the thrust bearings then spin the handle and see if you have run out?

To get the whole screw out you need to remove the stop collar which is a bit annoying to get to through the column base. And probably quite dirty in there... well mine was!

Phil

thall · Jul 20, 2020

Manual machine IIRC
Crossfeed screw anchored at handwheel end with a sealed bearing, pressed on the lead screw shaft, on back side of machine with a 'thrust' bearing mounted in a block attached to base of machine.
The lead screw nut anchored to the upright, usually a cast housing with a brass insert screwed and doweled to the upright.

If screw is bent, then yes, possible lifting action.

remove the rear cover, with upright positioned nearest the table, there should be a locking collar on the thrust bearing, remove it, separate the bearing... should be a flat 'washer' with radial bearing race on opposite side, then a caged round ball bearing, and another flat 'washer'....
could be thrust bearings on each side of the end block.... its been 20+ years since i have messed with one...

ensure there is no retaining cap for the sealed bearing on the handle end under the handwheel, and i believe you can 'unscrew' the lead screw after removing the thrust washer.... it should feed the entire screw out the front end... you can 'then' check the screw for bend, and "maybe" straighten it.

the thrust end of the screw may be fitted in the thrust end mounting block, which would prevent loosening the thrust washer and allowing the lead screw to 'float' a bit.

the block mounted to the upright probably has a brass acme female threaded insert the lead screw acts upon... ensure the oiler is not blocked... usually a bijur drip arrangement.

good luck.

Brandenberger · Jul 20, 2020

Had some photos on my phone.

Thrust block with nut on end removed...

Brandenberger · Jul 20, 2020

thall said:
Manual machine IIRC
Crossfeed screw anchored at handwheel end with a sealed bearing, pressed on the lead screw shaft, on back side of machine with a 'thrust' bearing mounted in a block attached to base of machine.
The lead screw nut anchored to the upright, usually a cast housing with a brass insert screwed and doweled to the upright.

If screw is bent, then yes, possible lifting action.

remove the rear cover, with upright positioned nearest the table, there should be a locking collar on the thrust bearing, remove it, separate the bearing... should be a flat 'washer' with radial bearing race on opposite side, then a caged round ball bearing, and another flat 'washer'....
could be thrust bearings on each side of the end block.... its been 20+ years since i have messed with one...

ensure there is no retaining cap for the sealed bearing on the handle end under the handwheel, and i believe you can 'unscrew' the lead screw after removing the thrust washer.... it should feed the entire screw out the front end... you can 'then' check the screw for bend, and "maybe" straighten it.

the thrust end of the screw may be fitted in the thrust end mounting block, which would prevent loosening the thrust washer and allowing the lead screw to 'float' a bit.

the block mounted to the upright probably has a brass acme female threaded insert the lead screw acts upon... ensure the oiler is not blocked... usually a bijur drip arrangement.

good luck.

Only thing I would note is the stop collar on the shaft (in between thrust bearing and nut) will stop you doing this, IIRC. There is a setscrew or two that lock that collar. So loosen those setscrews and unwind that collar too.

Brandenberger · Jul 20, 2020

One other note

When I first ran mine the finish was terrible too. The leadscrew handle was not easy to turn and inconsistent.

I found the ways for the upright were oil starved from plugged lube lines and had lots of debris and gunk. I took the upright off, cleaned and replaced the bijur meter units after blowing out the lines.

Once properly cleaned and lubed the handwheel for the upright is blissfully smooth.

Phil

dmanthei · Jul 20, 2020

Thank you Phil! You guys are awesome.
I've got some great information to go off of now.
I just need to find the time to do it.

I'll report back with findings.

wesg · Jul 20, 2020

Do these have a lock on the cross feed?

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