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Cincinnati Milacron Heald 273A internal grinder issues

rjohnsonII

Plastic
Joined
Jun 14, 2023
I am working on a 273A Heald internal grinder. The table will shuttle left to right and right to left but inconsistently. I have tried floating the table and the amount it floats on the hydrostatic ways is correct according to the manual I have. I thought it needed to be bled after working on the table in(table left ) cylinder, but think it has been bled well enough but the table still stalls and may/may not start up when the rack and pinion handle in front for the table is pushed a little.

Any suggestions?

Thanks,
 
A guess:
You may need to verify that the table reverse spool valve is moving without binding.

Heald used a pilot valve to control the position of the reversing spool valve. If there is some corrosion or varnish on the spool valve the valve may not move reliably when the pilot valve applies hydraulic pressure. The problem is likely to occur if the grinder has been sitting idle for months. The water in the oil will separate and form a thin layer of rust on the lower portion of the spool valve.

Heald suggests adjusting the throttle valve to fully open and cycling the table to remove the rust or varnish from the spool valve on the 271 and 272 grinders. ( see page 22 in the PDF) The 273 model may have similar plumbing


The sticking spool valve problem should be checked if the table reversing is erratic and the table piston has been purged of air. Heald uses air bleed capillary lines on the table cylinder. Moving the table back and forth will purge the air from the cylinder.
 
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I thought it needed to be bled after working on the table in(table left ) cylinder, but think it has been bled well enough but the table still stalls
They always need to be cycled when you start them. Always. Cylindrical grinders generally do also.

When you first turn it on, throw it in rapid and run the table as far as you can in both directions a few times.

I'm guessing that the hydraulic oil gets little bubbles in it from being pumped, then when the grinder sits overnight they coalesce into one big bubble, but that's just speculation. But cycling the table at startup is normal for every grinder I've ever had/run/been near.

and may/may not start up when the rack and pinion handle in front for the table is pushed a little.
Not sure what you are talking about "start up" ? Table moves when you kick the lever back or forth (and that goes backwards, which is confusing at first), not sure I've ever even touched the table handwheel but "start up" ? It's not supposed to. Does the slide "start up" on a lathe when you move the handwheel ?

Sounds like you just need someone who has run one to spend an hour or two with you.
 
I have a Covel cylindrical grinder.
When the manual handle is pulled out,
it will disengage the pinion from the rack,
and there is a micro-switch in there as well,
so pulling out the manual table traverse handle
will start the hydraulic cylinder cycling the table.
Maybe this is what the original poster means.

-Doozer
 
I have a Covel cylindrical grinder.
When the manual handle is pulled out,
it will disengage the pinion from the rack,
and there is a micro-switch in there as well,
so pulling out the manual table traverse handle
will start the hydraulic cylinder cycling the table.
Maybe this is what the original poster means.
I used the table wheel so little I can't even remember how it works. The left-right handle with the speed lever is so convenient, you end up doing everything that way.

However, pretty sure nothing you do with the manual handle starts the table automatically. I'd always set the lever to table-right and drop the speed to zero before working on that part of the grinder ... there's nothing pleasant about a grinding wheel chewing its way up your arm while you're indicating a part.
 
Thanks for the replies. The "start" is when trying to get the table to shuttle back and forth (either direction). It seems like applying some pressure to the table manual left/right handle (rack and pinion) will assist the table in starting to move.

I removed the table control valve on the front to inspect for the varnish(possibly) mentioned, but found none. There is slight wear on the spools, but it does not seem extreme. I did not find any particles or such in the valve block. As the speed portion does work correctly to control the table when it does shutlle left/right correctly I did not seperate that side of the valve

This problem seems to have just popped up according to the operator.
 
Blown piston seals on the hydraulic cylinder.
Yup. Air in the cylinder. The "seals" on those are leather cups, btw. Kind of a kick.

Umm, I wonder if that will make them hard to get ? Possibly look into it before you take the machine apart ? You can make your own - I did for an alcohol stove - but it takes some practice. You don't want to do this with a job scheduled for the next day.
 
I thought so too!

We have replaced both rod bushings. I call them rod bushings as this machine only has tight slip fit bushings for the hydraulic cylinder rods that run the table; one for left travel and one for right travel. No rod seals,no wipers or even o-rings in there. Different than I have seen.

It has a flow divider hydraulic circuit for smoother movement in both directions . I am about to give in and buy the rebuilt table control valve that is available, but it is quite pricey.
 
yes it moves the left cylinder using some bleed off from right cylinder to keep speed and flow smooth, then does the same with the right cylinder with bleed off from the left cylinder. It seems to have a choke coil in these hydraulic lines too to help it bleed off air in the circuit I believe.
 








 
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