Eagle Mk3 surface grinder rebuild

[Pete.]

Got a good start today hoping to get loads done. Today's job is making new spindle pulleys. The only suitable motor I have is a single phase 1450rpm motor of about 1.5hp so I have to make speed-doubling pulleys.

Here's the old pulley. It's very rusty and has bits of old belt stuck to it.

I had to heat it up to get the grub screw out and gave it a little tap around the periphery to see if it would move but no chance, so I had to rig up a puller. I took off the front bearing retainer and luckily it was the same bolt pattern as the rear cover. This meant I could put it on the rear end, fitted backwards so I didn't mess up the mounting face, and use it to pull against. I put a slug of scrap in the end so I didn't ruin the centre drilling for the shaft, in case I ever have to put that between centres sometime. Rigged up some blocks to stop the pulley against the front of the housing cavity and set up a 2-leg puller to push the spindle out through the pulley.

BTW you'll notice that the grinder head is not cleaned and painted. I wanted to get this work out of the way first and I want to have the bearings out of the head when I hit it with the sander and then paint.

The pulley was on there VERY tight. Even with heat the puller wouldn't move it so I had to resort to more neanderthal measures. I pulled it up as tight as I dare on the spanner and then hit the edge of the pulley to shock it along a tiny bit at a time.

About 15 minutes of that and the pulley is off.

Now it's time to make new pulleys. Vee belts are fast disappearing from motor factors in favour of poly-vee belts so I'm making poly-vee pulleys. Here's the new belt.

And this is going to be the new pulley to suit it. The bottom pulley will be twice the diameter.

 

[mtt.tr]

Be aware that the motor has to be pretty small as the knee screw comes bloody low i hastily started mine up dropped the knee through the junction box, as its a motor i had it now hangs out the back

 

[Pete.]

Be aware that the motor has to be pretty small as the knee screw comes bloody low i hastily started mine up dropped the knee through the junction box, as its a motor i had it now hangs out the back

Thanks, I'll go and check that but I think the knee is almost fully down right now with the motor fitted.

 

[awemawson]

Should have brought that shaft & pulley here Pete. The 60 ton press would have shown it the error of it's ways

 

[pressbrake1]

Should have brought that shaft & pulley here Pete. The 60 ton press would have shown it the error of it's ways

He would have had to bring the whole grinder along!

 

[awemawson]

No just the head assembly

 

[Pete.]

Be aware that the motor has to be pretty small as the knee screw comes bloody low i hastily started mine up dropped the knee through the junction box, as its a motor i had it now hangs out the back

You're right, the screw is actually touching the motor. I'll have to ease the slots open a bit to prevent them from fouling.

New shaft pulley. I cut the grooves to suit the Micro-v belt using a hand ground 40 degree tool. Damn tip snapped off on the last cut of the last groove.

I re-ground the tool and re-cut all the grooves so they are the same. Micro-v belts have 40 degree grooves at 0.140" pitch.

Grooves all cut. I could have sunk the grooves in so the top of the belt was flush but I wanted to keep the pulley diameter as big as possible.

Then I turned the pulley round and faced the opposite side and turned the boss on the pulley. Only the keyway and grub screw hole left to cut.

 

[Pete.]

Went down the local tap room with my brother and had a couple hours nap then got on with the pulley.

Cut the keyway with a hand ground .125" tool. I just engage the spindle lock and keep a hand on the chuck key to keep it lined up.

After that I spent a couple of hours washing the old grease out of the bearings and re-greasing them with some very expensive spindle grease from work. Apparently good for 12000rpm in our work machines. After that I re-assembled the whole spindle. I ALMOST dropped a clanger and fitted it up without the belt, that would have been annoying

Anyway I got the spindle installed with the pulley on it and it turns lovely and smooth - the belt is just about perfect length which is a relief since I only wrapped an old bit of argon hose around the pulleys and used a tape measure to get the length. I wanted 2300mm, the closest belt they had was 2315mm and it just fits at the end of the adjustment. The bigger pulley I have to make will help.

I hooked the belt over the motor vee pulley temporarily and measured the spindle speed so I could calculate the diameter I need for the new micro-v pulley.

Then I ran the machne for the first time since getting it. Tacho says I'm getting 2300rpm

Ideally I want around 2900 rpm for my spindle speed to run my 8" wheels at about 6000sfpm. My motor is 1450rpm and the bottom pulley is 115mm giving me 2300rpm. I need to increase the pulley size to 145mm to get my 2900 spindle speed, so that's my task for tomorrow.

 

[Welderpaul]

Project threads are few and far between these days, thanks for posting Pete, an enjoyable read and you certainly know your stuff

 

[Pete.]

A little update to this thread. It turned out that the spindle bearings were shot. They are a pair of angular contact bearings 1" bore 2.5" OD and 3/4" wide. When I made a test grind I could hear them rattling and my test piece had a fish-scale appearance all over it where the wheel was bouncing about during cutting. I did some experimenting by putting 5 thou shims in between the bearing outer races and that did improve the finish a lot but still it was fish-scaling a but plus the bearings ran warm and were still noisy.

By some providence Ali was giving away some bearings in the freebies section which looked to be about the right size so I begged them off him. Turned out they were the EXACT size I needed but alas not angular contact, which meant they were no good for the front pair but were perfect replacements for the original standard bearing at the rear of the spindle, so thanks @Ali .

Anyway, I decided to bite the bullet and use modern bearings as they were 1, cheap and 2, plentiful if they ever needed changing. So a pair of NSK 7206 bearings were procured that meant I had to make adapter sleeves for them.

Here is the sleeve to make the 62mm bearing fit in the 2.5" housing. It was all turned and bored in one setup and the wall thickness is just 0.75mm. It's made as a light press fit in the housing and a sliding fit for the bearings. The bearing sits proud by 0.5mm so that the two bearings are clamped together tight by the front cap.

After that I made another sleeve for the 1" diameter spindle with a press fit 30mm sliding fit OD for the bearings (no picture of that I'm afraid). Both sleeves have a 6.1mm lip on the back side to make up the thickness difference between the new 16mm and old 3/4" wide bearings.

I put it all together and did a test grind. The back half is the new grind test and the front half was with the old (shimmed out) bearings. The first test was much worse than both.

So that's a vast improvement and now I can comfortably finish the last bit of assembly and painting. I'll make a table guard and fit a new work lamp, The only other thing I will consider is cwapping the single phase motor for a 3-phase. I reckon that will improve the finish even more.

 

[scottmk1]

Good work Pete. Regarding the new bearings, was it still possible to get the correct size version if wished to go that route?

 

[Pete.]

Good work Pete. Regarding the new bearings, was it still possible to get the correct size version if wished to go that route?

I had several places which were advertising the correct size angular contacts as NOS, but none returned my emails. After doing a bit more research I found that they were a common size for British Leyland (I think) wheel bearings from the '70's and the ones on offer were those type.

I figured that even mediocre modern bearings would be as good as spindle bearings from 50yrs ago so I bought some new NSK angular contacts with standard c3 clearance.

 

[Pete.]

Making a guard for the grinder today. This one is a 'W' model for wet grinding which originally came with a nic cast ally guard but the guard was not with it when I got it. I brought home some ally angle pieces salvaged from site. They were trim support brackets for double glazing in a large building. More use to me than just throwing them in the scrap.

Marked out the end pieces and cut out for welding. It's just a guard so no need for super-accuracy.

Set up for welding the corners.

I needed to fix the ends down in order to make the middle section, which has to be lower and wider to give access to the mag chuck handle. So I drilled the first hole and made a transfer pin to mark the adjacent ones.

Transfer pin gets the mark spot on for drilling

I fixed the ends down and made a section for the middle. Tacked it up in place on the machine.

 

[mtt.tr]

Thats my next job for mine, smart job pete

 

[pressbrake1]

I had several places which were advertising the correct size angular contacts as NOS, but none returned my emails. After doing a bit more research I found that they were a common size for British Leyland (I think) wheel bearings from the '70's and the ones on offer were those type.

I figured that even mediocre modern bearings would be as good as spindle bearings from 50yrs ago so I bought some new NSK angular contacts with standard c3 clearance.

I’d say ordinary bearings are good enough for your application but to say high grade spindle bearings from 50 years ago (1970)are equivalent to average modern bearings is nonsense

 

[Pete.]

If I'd said that it would be nonsense. I don't think they are anything more than 'ordinary' grade TBH. The last spindle bearings I had cause to remove were covered in a myriad of annotations etched on different faces. These have nothing more than a bearing number.

I wouldn't call the Eagle anything more than basic TBH.

 

[Pete.]

The bottom part of the guard is finished and ready for paint. The end guard is going to be a separate piece that bolts on.

Hopefully I can get the head stripped down in the next hour and a half and that ready for painting too.

 

[Parm]

@Pete. Thats going to be better than new by the time you’ve finished with it

 

[Pete.]

@Pete. Thats going to be better than new by the time you’ve finished with it

Nice of you to say that Parm but I'll make do with 'as good as I can get it'

Anyway, the spindle has a hole in it which I assume must be for a spindle lock pin but I see no facility for a pin so I've knocked up a quick spindle lock and drilled the top plate for it.

Here's the spindle lock, it's just a couple of pieces of ally and a cut down 8mm bolt and a spring inside.

And here it is installed. now all you have to do is press the plunger and turn the wheel so that the hole lines up, then you can put a spanner on the front nut and remove the wheel.

 

[Pete.]

Yesterday after a bit of a family bar-b-q I got stuck into re-fitting the electrics. Not much to it just a lead with a plug into the motor switch and down to the motor. I had forgotten to paint the wiring conduit so that's a job for another day but here it is installed. Whilst I was about it I made a mounting plate for my de-magnetiser, I mean what better place to keep it than on top of the machine that requires it's use? Didn't get around to taking pictures yesterday so I took some this evening.

Also found a nice sheet of steel at work today to make a new back cover for the base. And some 2.5mm flex for a power lead. Also needs painting some time later.

And finally some pics of a few test grinds. I'm a grinding novice but I'm quite pleased with how they have come out. I didn't buy super-expensive precision bearings for the spindle just a triplet of matched angular contact bearings. The originals had none of the markings you normally see on old super-precision bearings, just a stampled bearing number so I doubt they were anything more than standard jobs. Also there's no facility for balancing the wheels like on other grinders so all I could do was dress the wheel with a diamond.

Still, the results are satisfactory enough...