Surface Grinder Finish

[Roy BirchParticipant @roybirch29994]

Hello All

I dont know if the above image is good enough for people to see but does anyone know why I am getting the lined finish from my manual surface grinder?

Kind Regards

Roy

[mgnbukParticipant @mgnbuk]

On a manual Ingar RT612 surface grinder where I used to work, similar finishes were apparent when the wheel required dressing or the DOC was a bit heavy. That machine seemed to give the best finishes with a DOC of 0.001″ or less with a freshly dressed wheel. No coolant on that machine, just dry grinding.

Even when the wheel was freshly dressed & with a small DOC, the finish was not as visually “perfect” on that machine as would be expected with an automatic SG with coolant, though the banding didn’t exhibit the burning / wheel bounce marks shown above & could not be felt or seen uisng a 0.0001″ dial gauge on a surface plate.

Nigel B.

[Roy BirchParticipant @roybirch29994]

Nothing can be felt or detected on the finish in the photo, the material was cast iron, I did wonder if this was caused by a coarse wheel or spindle bearings. The grinder is a capco.

 

Kind Regards

 

Roy

[Pete RimmerParticipant @peterimmer30576]

You may get an improved finish on cast iron with a very open wheel

If it’s spindle bearings the finish will probably improve with a heavier cut unless they are very bad. It would probably also improve with a narrower (therefore lighter) wheel.

Did you dress the wheel beforehand? If not, dress it and try again. Dressing the wheel will true it and make it cut more readily. If you dress the wheel and find that it cuts much better but quickly deteriorates then you need to swap to a softer/more open wheel.

[Chris CrewParticipant @chriscrew66644]

I get a similar, but finer, ‘grain’ finish on a J&S 540 using auto-traverse. I have to grind dry because I cannot justify keeping the coolant unit full of soluble oil for the small amount of work I do on the machine. As the graining I get is ‘regular’ using auto-feeds the finish is quite cosmetically acceptable but obviously not to a tool-room standard.

I have experimented with different cuts, dwell and table speeds but the results are always more or less the same. I fitted a new wheel-head drive belt after the old one perished but this made no difference either. I have been meaning to replace the wheel because I don’t know exactly what type is fitted, it was on the machine when I bought it years ago, as it looks like it’s getting a bit undersize now, but whether this will make any difference I have no idea.

The machine is powered by a Transwave static converter which will not supply a true three-phase output, so whether any imperfections in the motor feed current produces small variations in the wheel speed or torque, I have no idea either.

[Robert Atkinson 2Participant @robertatkinson2]

A capacitor type 3 phase “converter” like the Transwave will certainly cause significant torque ripple in the motor output resulting in cyclical variation in speed within each revolution. This may well cause surface patterning.
Connecting a unloaded “slave” motor in parallel with the grinder motor may improve things. If connecting one changes the pattern it would confirm this theory.

Roy, what type of motor and power does your grinder use?

Robert.

[Kiwi BlokeParticipant @kiwibloke62605]

Is the wheel properly balanced?

[noel shelleyParticipant @noelshelley55608]

Kiwi beat me to it. Wheel balance ? Having a worn machine this may cause alsorts of issues. My drill grinder, I fitted a new wheel and turned it into a useless bit of junk. Only after I bought a J&S balancer did I find out how far out this wheel was (and the other 2 this supplier sent ) ! Even with the wheel close tiny pattern could be seen. I find it surprising that EVERY grinder is not made with the ability to be able to balance the wheel, fine when the machine is new but by the time it gets into our hands worn ways or guides will soon show up at the merest hint of out of balance, even if all seems tight. Good Luck. Noel.

[Pete RimmerParticipant @peterimmer30576]

The Capco is a close cousin of the Eagle which has the wheel mounted directly on the spindle. They cannot be pre-balanced if thatvis the case since there is no removable arbor to mount it to.

[peak4Participant @peak4]

I find I get more of a pattern with a fine 60 grit wheel, so maybe because it’s effectively pushing harder, than a 46 wheel which cuts faster. It gets better the thinner a cut I’m able to take, but there’s no fine vertical feed on my Herbert Junior.
I’m starting to think my bounce pattern wavelength is the same as the rack feed tooth pitch.
It also uses 6″ wheels, and there’s no inbuilt method for balancing wheels; I should have considered that when I made a news set of wheel carriers, though I could obviously modify them.
Fortunately I have a set of balancing rollers, so I’m able to get the wheels as close as possible, by using a dummy spindle.
I keep meaning to make us some balancing washers out of 1mm steel, but not got around to it yet.
Essentially a pair of washers with an ear/lobe sticking out one side; they can be used as a pair to help balance a wheel carrier. Think about the cross section of a camshaft lobe
For those with access, there’s a few photos from someone else here, on mig welding forum
https://www.mig-welding.co.uk/forum/threads/eagle-mk3-surface-grinder-rebuild.96469/page-6

[Roy BirchParticipant @roybirch29994]

Many thanks to all of you who have replied

The Capco does not have a removable spindle for balancing so I am not sure how to achieve this, I am starting to think down the lines of Chris Crewe and the belt slipping as I have noticed the grind wheel will stop quite easily if a heavy cut is taken especially with a wider wheel and the motor is on the end of adjustment.  The Capco is a MK3 with the 25″ bed which will grind just on 24″ in Length, it is also a 240v machine so no converter in line.

 

Kind Regards

Roy

[Neil WyattModerator @neilwyatt]

That finish does look coarser than I would expect, but a surface ground finish can be flat and still show a noticeable texture.

You say you can’t ‘feel’ any unevenness, is the surface flat enough for your purposes?

Neil

[Roy BirchParticipant @roybirch29994]

It is flat enough but I would like the finish to be better, I now believe it is a combination of wrong wheel choice and belt replacement, I cannot find any thing that tells me the correct belt for this machine as the capco did not seem to have any documentation provided originally.

 

Kind Regards

Roy

[Tony Pratt 1Participant @tonypratt1]

Balancing the wheel and also dressing is important, to balance the wheel it will need to go on a separate arbor and then on to a balancing fixture [basically 2 knife edges to eliminate friction], but first is the wheel hub fitted with balancing weights, if not you can’t correct any imbalance.

Tony

[noel shelleyParticipant @noelshelley55608]

The Brierley has a circular dovetail and 2 opposed holes to put 1/4″deep x roughly3/8″ wide cones tapped 1/4″ whit with grubscrews. Very neat ! If You want more info let me know.  Noel.’

[Roy BirchParticipant @roybirch29994]

Is that the one sold by Chester Machine tools? is this a way to balance the wheels that you are talking about?

The reason I want to get a better finish is because I want to re surface the magnetic chuck and would like a smooth finish.

 

Kind Regards

 

Roy

[Howard LewisParticipant @howardlewis46836]

It is normal practice to balance a wheel on an arbor on knife edges.

The wheel hub has a circular dovetail slot into which are inserted one or two small dovetail weights which are positioned to balance the wheel, and locked in position with grubscrews.

With a properly balanced wheel, a well dressed wheel and bearings in good conditiuon, you might still get slight patterning, because the machine is powered by a single phase motor. Single phase motors do not produce such constant angular velocity as three phase.

Also, a poor or swollen joint in a belt, or pulleys with run out in either plane might cause patterning.

Howard

[Roy BirchParticipant @roybirch29994]

I do have the Jones & Shipman balancer but it would not be any use on a Capco as I cannot take the arbor off easily to balance, I am leaning to replacing the belt initially and then trying a new wheel, I did clock the spindle at the front and the back and it is running true with no deflection, this Capco is unbelievably quiet when running but I am using the wheels that came with it.

 

Kind Regards

Roy

[Roy Birch]

On Roy Birch Said:

Is that the one sold by Chester Machine tools? is this a way to balance the wheels that you are talking about?

The reason I want to get a better finish is because I want to re surface the magnetic chuck and would like a smooth finish.

 

Kind Regards

 

Roy

I struggled with doing that job on my little Herbert; the chuck that came with it id 5″x10″, but the travel is only 4″x8″.
I managed to get the full 10″ by swapping the traverse lever for a handwheel, but can only het the width of the table by moving it, which is far from ideal.
I thought about trying an overly wide wheel, but even that is pushing it.
The final cure was to get a top magnetic transfer plate, which is smaller.
None of that is likely to affect you of course, but for me, one thing which improved the finish on the chuck was a mist oil cooler, using a synthetic grinding oil/water mix.
Also an absolute minimum depth of cut to minimise local heating; again the water cooling helped with this, I just surrounded everything with paper towels, as it’s a dry grinder.
Suburban Tools has a good video

p.s. check your chuck instructions, some need to be energised, others left off.
From my Eclipse manual

Bill

[Roy BirchParticipant @roybirch29994]

 

Hello All

Thank you for the advice, the pictures above show my finish now having taken the advice, This morning I took a look at the belt and it was flopping about all over the place at the back of the machine so I cleaned the pulleys and re aligned them, I then changed the wheel to a more open freshly dressed wheel, I noticed with a heavier cut it no longer stalls but burns. I think the above finish is good enough for the magnetic chuck unless anyone disagrees.

 

Kind Regards

Roy

[Pete RimmerParticipant @peterimmer30576]

I think you can be happy with that, what an improvement!

For grinding your chuck use an open wheel and try to cobble up some coolant even if it’s just a mist spray. You can raise a burn on a chuck very quickly. You need to get right across the chuck in one dressing so that you still have some wheel left to spark the last bit out then you know that the chuck is flat. Check your gibs before you attempt it, or stick a sensitive level on the chuck beforehand and run it end to end on the travel. If the level moves significantly from fully left to fully right you’ll grind the chuck convex.

[Howard LewisParticipant @howardlewis46836]

Looks like your actions have solved the problem

Good!

Howard

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