# Surface Grinder Improvement (Ingar RT-618-2A)



## RobinHood (Jul 4, 2019)

As some of you know, I have been struggling getting good surface finishes on my small surface grinder. Some of the issues I discovered:

A) spindle axial end play
B) spindle radial play

The above two were causing wheel vibrations and seemed the main source of the bad finishes.

Here is a pic of the blueprint for reference.






I tackled the end play first. The original design used an internal snap ring to hold the two front angular contact bearings in the housing. There was about 5 thou end play as the outer races of the bearings were not a tight fit in the bore and the whole spindle would move axially.

I mounted the whole spindle on the face plate in the lathe and indicated it to run true with the bore. I had previously made a retaining ring. Threads were cut into the spindle to accept the ring.












Now the ring pushes the bearings against their shoulder in the bore and thus the end play is zero.

Next was the spindle radial play. I discovered that the drive side support bearing was very loose in the bore. Roughly 3 thou of play. There was even evidence that the outer race was spinning in the bore. On my grinder the motor was driving the spindle directly via a Lovejoy type coupling. I believe the motor shaft and the spindle were not in perfect alignment either and thus the rear of the spindle was wobbling around, causing the front of the spindle to wobble as well and the wheel to vibrate. On the newer version of this grinder, the spindle is driven via a belt ( see blue print above). So I decided to upgrade mine to that standard. I thought that it would solve a couple of issues:
1) any vibration from the motor would not be transmitted to the spindle; also,
2) the belt would apply a downward force onto the rear bearing thus holding it tight to the bottom of the bore and prevent any wobble. (If that did not work, I would have to find a way to get a better fit between the bearing outer race and the bore...).

I started by making a new spindle housing back plate. The old one was too short and would not allow the motor plate to be mounted lower down to accommodate the belt drive. I used 5/8” plate for the job as I did not have any cast iron. I scraped the two critical bearing surfaces flat and parallel. Not perfect, but good enough for an amateur.






More images of the two plates




 




The belt system is a Poly-V J6 profile. Here are the spindle and motor pulleys and one of the reference docs to make them












The motor pulley is necked down to allow for the vertical adjust lead screw to pass by.

All the new components ((plus the old Lovejoy type, straight drive for comparison). Oh, I did make stepped keys since I do not have any metric broaches. I used an available 3/16” one instead of the 5mm and 6mm ones on the spindle and motor shaft.






Here you can see the tight quarters inside the spindle housing. The hole on the bottom is where the lead screw passes through.









After all this, some first results in mild steel... I am very happy so far: vibrations are gone and the grinder is running very smoothly. The old spindle bearings could still need replacement, some day maybe.


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## PeterT (Jul 5, 2019)

Wow, I'm impressed! Good problem solving.
So any theories as to how it got to this state given its background? A operational bump somewhere along the way? Or maybe originating to initial setup from the factory?


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## RobinHood (Jul 5, 2019)

PeterT said:


> Wow, I'm impressed! Good problem solving.
> So any theories as to how it got to this state given its background? A operational bump somewhere along the way? Or maybe originating to initial setup from the factory?


There is no evidence of any wear/abuse of the grinder. Other than the usual dirt, and leaky seals, this machine was in quite good shape when I got it.
So that leaves the design/manufacture of the machine from the factory. An oversized bore is not something that is attributable to its age; neither is a sloppy bearing retaining design; it was there from the beginning. They did upgrade to the belt drive system because the direct drive is inferior. The spindle bearings are certainly nothing cheap - them being Fafnir (now Timken) and FAG ABEC 7 precision angular contact and precision ball bearings.
Also, the grinder has X and Y hydraulic feeds and coolant system standard, but there are no gibs in the spindle vertical head ways. It is just precision ground all around and fit into the column. Why did they do that? To save cost? More rigidity? I don’t know.
This machine is certainly no super precision grinder like a Mitsui. It does have a lot of “high end features” that I like that suit me needs.


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## Chipper5783 (Jul 17, 2019)

Very nice job.  I also have an Ingar RT-618, an all manual version.  Mine is the belt drive version.  I've only been playing with it for about 3 months (came to me in pieces, needing repair).  The surface finish is not great.  I lock the vertical head after every down feed adjustment (thumb bolts on the vertcal slide.  I have not been through the spindle as you have (seems daunting - I'm impressed).  Mine now runs, which is a good start - and sooo many other projrcts.

Did you get your machine out of a shop in Red Deer (via an Internet auction house) - I saw there was one for sale about a year (?) back?

Take care David
Have you actually got the manual?  Maybe we could talk?


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## RobinHood (Jul 18, 2019)

Hi David, the machine was a Kijiji find. I believe it came from a High School shop that got cleared out. The fellow I got it from had no use for it - he did keep a bunch of other metal working machines from that shop for himself. It was a package deal for him at the time...

Yes, I do have a manual (paper copy). It also shows your RT 618-1A. Send me a PM and I will see how I can get a copy of it to you.

I did not know that the vertical down feed has a locking mechanism... mine does not have it; the manual does not show one. Perhaps an aftermarket add-on?

Cheers, Rudy


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## Proxule (Feb 21, 2021)

Nice work. Great design. Mind if I direct message you. I acquired one of these and is in need of some advise.
Thanks


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## RobinHood (Feb 21, 2021)

Proxule said:


> Mind if I direct message you.




Go for it.


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## YotaBota (Feb 21, 2021)

Well done and done well.
How is the retaining ring being locked into position?

"Not perfect, but good enough for an amateur"
Compared to me that's like saying Richard Petty only had a learners permit lol


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## Chipper5783 (Feb 21, 2021)

HI Proxule, please tell us more about what you have acquired.  Post some pictures.

I've been using my little grinder for about a year and a half.  I am very pleased with it.  I'm finding that there is quite a learning aspect to getting decent results.  I don't know how much of the less than perfect result is because of my lack of knowledge, or because of short comings in the machine.  Regardless, the results are getting better all the time.  I ended up replacing the spindle bearings, which was quite a project in tool/fixture making and sourcing the correct bearings (with support from "RobinHood" - thank you).  I've set up a flood coolant system, added splash guards, purchased and ground in a permanent magnet chuck, purchased a new wheel, made spindle wrenches & puller, made a wheel dresser, somewhat sorted out wheel balancing, purchased mag parallels - and have probably spent >100 hours cranking the handles.  It seems that the more time I spend grinding stuff, the more I realize that there is a lot I don't know about grinding.  A decent functional SG is a great asset to shop activities and I'm sure you'll enjoy it as you start getting things sorted out.  It does feed that endless pursuit of trying to get better and better results.

Regards, David


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## RobinHood (Feb 21, 2021)

YotaBota said:


> How is the retaining ring being locked into position?



The retaining ring has a fine thread. The face spanner is used to tighten the ring against the front bearing outer race to force it against its seat in the spindle bore. I made the threads in both parts. Originally there was just a snap ring holding the bearings in. No positive force to seat them.


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