would you do this

[aboard_epsilon]

Is this normal practice ?

That is... if you were grinding something on both sides

To do the other side ...
turn over ...but also turn end for end to eliminate/cut in half, any wear deficiencies on the machine.

or am i talking daft .

all the best.markj

 

[Dr Stan]

Yes, that is common practice on a machine with a fair amount of wear.

 

[Holescreek]

If you mean to say that by turning "end for end" you are placing the material on a different section of the chuck to spread out the wear, it would be a good idea. I wonder how many give it so much thought?

 

[easymike299]

Is this normal practice ?
That is... if you were grinding something on both sides
To do the other side ...
turn over ...but also turn end for end to eliminate/cut in half, any wear deficiencies on the machine.
or am i talking daft .
all the best.markj

Yes, Markj. The procedure is to grind both sides to an acceptable finish/size, then turn the last side end for end and regrind without down feeding. This then halves any taper/irregularities you may be getting due to wear deficiencies. Your second side then is really not a single plane but rather two intersecting planes (maybe not exactly but you get the idea.) This procedure requires some level of expertise and a pretty good grinder to be of any use. It's used principally when splitting a tenth rather than run of the mill grinding but can be used anytime to reduce glaring irregularities.
Gene

 

[aboard_epsilon]

Thank you guys

Any thoughts on grinding from one side of the work only

by that I mean ..when you've got to the other side winding it back and starting from where you set off ...

I've noticed, that if you grind across ..then come back grinding the other way ...the work is warm on that side ...and it takes more of a cut because of the expansion (I have no coolant).

Setting off from the other, then cool side, stops this .

Also my grinder seems to grind better, from front to back, than back to front .

Another question .........

Is there any benefit ...in when you start to grind the work ..if it has to be done on two sides ...of turning it over, before you've finished full grinding .....eg the work is fresh off the milling machine and covered in scratches... shallow hillocks and valleys ...and could rock on a small scale ....

So one pass one side ..another pass the other ....untill you can see by the grinding witness marks that the work is supported evenly before you start grinding for properly on one side.


All the best...markj

 

[thewskrs]

Markj,
I have great luck grinding front to back only. Just as you describe it gives the work time to cool a bit. I also step dress my wheel from front to back. This allows me to cut .005 on a pass, but each step is only cutting .001. Also keeps a sharp edge on the front side of the wheel for precise shoulders if needed. I regularly cut .090 stainless without problems of lifting.
Whiskers

 

[aboard_epsilon]

either i cant read the dials on this machine or I'm doing something wrong

0.0005 is what i use normally ...no heating up of work piece

0.0007 would be a serious cut ...
and 0.001...would be a stall and skipping of the stone .

thats with the Norton pb 38a46 lvs stone

all the best...markj

 

[easymike299]

either i cant read the dials on this machine or I'm doing something wrong

0.0005 is what i use normally ...no heating up of work piece

0.0007 would be a serious cut ...
and 0.001...would be a stall and skipping of the stone .

thats with the Norton pb 38a46 lvs stone

all the best...markj

Markj
Are you saying that the motor is stalling or that perhaps the wheel is slipping on its mount? These are two different animals. If the motor is stalling you have a big problem. What kind of a grinder are you using? Brand? Size? What size motor?
A .001 depth of cut is not enough to stall any grinder I'm familiar with.
Are you plunge grinding? How are you traversing with the cross feed.
More details please.
Gene

 

[Peter Neill]

Something wrong there Mark.
A 540 will rough at 0.003" (which I was always taught was a large cut) all
day long.

Peter

 

[aboard_epsilon]

must be the belt slipping ..when its skipping .

this is only if i put a 001 cut on a large piece of work ..

example 12" x 6" x 1/2" deep...max is 0.0005 with that

i said normally ...should'nt of ....it's just that Ive been doing a lot of big stuff of late .

if i put on more than 0.0005 on a plate as above

it gets to the half way across and heats up ...and then starts it's antics

must get a coolant system put in ..

I can get away with 002 on small peices.... say ...two inches wide.

all the best.markj

 

[Modelman]

It sounds like he's grinding dry. That's been my experiance that .0005" is a big cut when working across a plate of tool steel when grinding dry. I think the poster who recommended profiling the whheel into .001" steps means to run it with coolant.

Dennis

 

[Peter Neill]

I don't think dry grinding has anything to do with it.
I run an injection moulding business, and we make all our own tools. My business partner runs the toolroom, and has done for the past 30 years, and all of the J&S 540s (18"x6") are run dry. There is no coolant facility on them, and we can still grind accurately down to a tenth.

I bought my 540 (personal home shop) from another business associate who makes progression press tools, with 99% of the punch and dies in D2 or HSS. They run ten 540s and every single one of them grinds dry as well.

Even my previous little Dronsfield Eagle would take a 0.002" dry cut across a tool steel plate without complaining too much.

Definitely belt slip I reckon.

Peter

 

[easymike299]

thats with the Norton pb 38a46 lvs stone

If I'm reading you correctly you are using an l hardness wheel. Entirely too hard. An h or i or maybe even a j would be appropriate but not an l.

Gene

 

[aboard_epsilon]

mmm

its not across tool steel its across mild steel

and it does get warmer as it goes across ...and it does try to grind deeper ...in the end it self perpetuates the heat ...

IE ...half way across plate getting hot..... expanding ...grinds deeper .gets hotter .expands more .grinds deeper still...

this grinder came with a conveyor type coolant system ...

it has the guards and the attachments for it .

but its in a poor state ...chain conveyor is rusted up ...and it needs a spool for the filter paper ....and is of an open design ......which may lead to problems of condensation in my workshop

i was just looking at this on ebay ...

http://cgi.ebay.co.uk/Axminster-Coo...ryZ11705QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

don't think it will last very long with grinding dust in it though ...what do you think ?

 

[aboard_epsilon]

If I'm reading you correctly you are using an l hardness wheel. Entirely too hard. An h or i or maybe even a j would be appropriate but not an l.

Gene

thats what j&l recommended to me ...
looks like they advised wrong..


i will not be grinding any tool steel on it ...just mild ...


all the best.markj

 

[Peter Neill]

mmm

its not across tool steel its across mild steel

and it does get warmer as it goes across ...and it does try to grind deeper ...in the end it self perpetuates the heat ...

IE ...half way across plate getting hot..... expanding ...grinds deeper .gets hotter .expands more .grinds deeper still...

Still don't think it's that.
Steel expands at 0.00000636" per inch/per deg C, so if the entire 12"x6"x0.5" thick plate - not just the top surface - increases in temperature by 200deg C, it will only grow thicker by just over half a thou'.
And even at half a thou' increase in 'height' the wheel should still plow though it.

Can't hurt to fit coolant though, if you live with the mess.

Peter

 

[aboard_epsilon]

Still don't think it's that.
Steel expands at 0.00000636" per inch/per deg C, so if the entire 12"x6"x0.5" thick plate - not just the top surface - increases in temperature by 200deg C, it will only grow thicker by just over half a thou'.
And even at half a thou' increase in 'height' the wheel should still plough though it.

Can't hurt to fit coolant though, if you live with the mess.

Peter

yup

that's the theory ...
but it's not what happens in practise ...in my case ..

it's expanding ...that means its cutting more half way across ...its a messy looking cut then ...and you have an inaccurate grind ....

then you have to start again .and take it more easily .

even a 0002 finishing cut can chuck up the same problems if you don't let a plate that size cool down .

like i said once it gets warm ....its bigger .then it gets warmer ...and bigger .then hotter ..and bigger...and on...

i want to finish the grind .not plough thru it and start again .

think coolant is the only cure for the big stuff .

must have a look at that belt as well ..

i take it..it should just be twistable thru 90 degrees along its length

small stuff is no problem to grind dry

all the best.markj

 

[Troup]

If the skin across the top heats up more than the rest (as you'd expect), couldn't the workpiece be bowing up slightly in the middle?
There's no way the magnet would resist the forces involved

 

[CarbideBob]

How much infeed per pass?

Sounds like the wheel is glazing over and loading up.
You can change the effective hardness of a wheel 3 or 4 letters when grinding flat parts by changing your dressing technique. Try taking your last dressing pass as fast as possible and at least .001-.002 deep. Dress one direction only.

Faster table speeds will also help prevent wheel glazing. This places more load on each grain which causes the grains to fracture or fall out rather than dulling.

Problem is most likely not the part getting too hat and expanding but the wheel getting too hot and growing. Commonly known as "sucking up" because it seems like the part "sucks up into the wheel". Actually the wheel is getting hot because the grains are dull and it expands. This removes slightly more stock which heats up the wheel even more. Now the wheel is rubbing, not cutting and the part gets hot too, Part will end up slightly thinner in the effected area.

Many people run into wheel glazing and burning problems so they slow down. This makes the problem worse. If your wheel is cutting freely at first but loads up when grinding you need to push it harder. When you go back to redress the leading edge of the wheel should be noticeably worn. The back section should touch the dresser before the front does.
You should not need coolant with less than .003 per pass unless you are trying to hold micron level tolerances.

Aggressive dressing and faster table speeds make the wheel act softer, slow fine dresses or slower table speeds make the wheel seem harder.

One thing to be aware of when grinding both in and outward. Many small grinding spindle bearings are spring loaded, notably Harigs and such.If you pull outwards on the grinding wheel on a Harig it will pull out of the spindle .040 or so unloading the bearings. Very bad if this happens while the wheel is spinning. This is documented in the Harig manuals as a method to check for fretting in the spindle housing. This is also why you should never grind up to a shoulder with the back side of the wheel on these small machines. It does take a fair amount of force, 20-30 lbs or so, to overcome the preload spring so if you take it easy you're ok to feed from part front to back. Harig offered a higher preload spindle for slot grinding.

Bob

 

[aboard_epsilon]

Thank you Bob ...
you are indeed right .

learning one of these beasts is a case of many hundreds of hours ...

sucking up etc...all new knowledge to me ..

i need many more hours on this grinder before i work out the techniques and understand the feedback from IT...Telling me ...what I'm doing wrong.

I've done some more ...and I'm beginning to get it ,....

It's a huge learning curve ....bit like welding properly ...
you do it one way ..see your mistake and try it another way ...

I'm beginning to listen to the thing ...
I can now hear when the wheel is blunt or loaded with crud ...

yep earlier on ..I leaned that slow travel wasn't a good thing ...

You need to put all your senses into understanding what's going on with these machines

The machine is always set on its fastest travel on the lever ..left to right ....but seems to be slower left to right than my pal Alwyn's. js540..aprox...half the speed of his ...must be another adjustment somewhere on the hydraulics to get it going faster ...

it slowed down a bit more when i replaced the piston rings and seals on the ram ..

The machine is set to travel across the work front and back at .03 increments ...is this too slow.

and what's the right wheel for grinding the cast iron magnetic chuck .....

and whats your opinion on magnet off or on for grinding of the chuck .


all the best..markj