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Measuring and grinding a V block for a suburban master grind

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I purchased a suburban master grind awhile back and unfortunately it didn't come with the v block assembly. I ended up purchasing the v block from suburban and it states when buying that finally fitment is necessary. Okay so I mounted a pin gauge in the V block and did some measuring. Of course every measurement I take has like .0002 variance. I am pretty new to this but from my understanding this thing needs to be perfectly centered within the master grind or whatever you grind will be off.
My questions are am I measuring this the correct way. The V block needs the sides ground only so that's it's centered in the groove of the face of the master grind. The height of block is adjusted by slots on block. Here's my setup for measuring. Tenths indicator pin lightly clamped in V and taking measurements from the sides.
image.jpeg image.jpeg image.jpeg
My problem is the first picture I have .0003 difference from left to right,how do I know if pin is placed correctly in V. I've read that the hold down is touchy when locking down a part ,can shift part.
Now if you take the 1st picture and flip it 180 and measure pin it is .0002 off from 1st measurement which tells me the pin or V in block is pretty dang close to center. I just need to take equal amounts off each side so it stays that way but get it down to near 0.
In the third picture I'm getting a .0002 difference left to right.
I've been able to research and find one person talking of this same task on another forum. A experience grinder was talking about grinding the V block to fit and was getting a .0001 difference when spinning the fixture. Unfortunately you really only get one chance at this. Can't take material from one side and put back on the other.
So what would be the steps a knowledgable person would do to complete this job. Let me hear it. Thanks and this is what it should look like image.png
 

Comments

#2
When you get into tenths, everything matters. Is the surface plate in current calibration? Tell us more about source of the pin and any testing of it for round, straight, and to a consistent diameter along it's length. If the mounting of the v-block in the Master Grind has left to right adjustment, then you could adjust it to center it while holding a high accuracy pin each time you mount it to the Master Grind. You need to verify that with each mounting anyway if you are doing fussy work.
 
#3
I agree on needing to know more about the pin gauge. A class X pin gauge has a tolerance of .00004", and a class XX has a tolerance of .00002", A class Y pin gauge has a tolerance of .00007, a class ZZ pin gauge has a tolerance of .0002", class Z pin gauge has a tolerance of .0001". Depending on the class of gauge you have the difference could be in the gauge itself.
 
#4
Here's is a pic of what I'm dealing with. From what I've read and understand the left to right has no adjustment it should put that V dead center left and right. Only adjustment is sliding the V block within the groove UP and Down to accomadate different diameters. If the block gets ground "short" I think it defeats the purpose of the slot in faceplate of tool. It would be functional but more setup time.
image.jpeg image.jpeg
Thank about the pin grades. I should have known better. That's exactly why I'm asking first before doing anything. I will look into a XX pin gauge. I'm alittle over my head with this project. I've only had the SG for a year now and has opened up a whole can of worms between surface grinding techniques,wheels,materials,setup tooling,on and on. Then the capacity to even measure these kind of tolerances. I'm learning a lot and thankfully have some people to bounce stuff like this off of and get some tips. Thanks guys
 
#5
Cadillac, are you saying that the v-block is oversize to mount to the fixture at it's present width, and you need to center it as you narrow it?
 
#6
Cadillac, are you saying that the v-block is oversize to mount to the fixture at it's present width, and you need to center it as you narrow it?
EXACTLY. from my measurements it’s .0002 off from side to side as it sits which is fine it’s about .100 big right now.
 
#7
Even grinding it to that tolerance (and squareness as well) will be challenging. You will need all your ducks in a row, no guessing. The machines and fixtures you use to do the work will also need to be that accurate, and repeatable.
 
#8
Ive been able to grind a 3”x4” plate 1” thick both sides with both surfaces being flat and parallel to my two different tenths indicators. Now if inspected I’m sure their off somewhere but not to my inspection capability so I feel good about the task. I’ve just come realize that it’s so much easier to make something from on the fly tolerances. Than hitting a known number without any wiggle room and a lot in contention. It will press my limits at this point but should only make me stronger.
 
#9
Ive been able to grind a 3”x4” plate 1” thick both sides with both surfaces being flat and parallel to my two different tenths indicators. Now if inspected I’m sure their off somewhere but not to my inspection capability so I feel good about the task. I’ve just come realize that it’s so much easier to make something from on the fly tolerances. Than hitting a known number without any wiggle room and a lot in contention. It will press my limits at this point but should only make me stronger.
It will probably turn out just fine, just nudging you to put on your best game. Even if it is off, it can still be made to work correctly, though maybe not quite as pretty and user friendly as you would like to see.
 
#10
No experience with the Suburban version, but countless hours with the Harig version ( Harig only needs 1 screw to lock the block). Yes you need the new v block to be a .0001/.0002 slip fit in the plate slot at same time it is centered. Rather than worry about the accuracy of any single pin, you need to be checking a range of pin diameters and averaging the readings to figure out how much to take off each side. Dowel pins or drill rod work great if you have them. I would use minimum of 4 pins up to at least 1", with more the better.

Easy to measure the slot width with gage blocks or adjustable parallels, and easy to figure out how wide the v block is now, so know how much to take off. When checking the various pins write down which side needs how much removed (hopefully they will similar) and average the readings. If your block needs .002 removed and pin average is .0004 off one side, you need .0012 off the high side and .0008 off the low side.

We had one Harig with a v block that was about .0005 loose in the slot. It was still east to keep the screw snug and tap the block around to make part run true. Would not loose any sleep if your block ends up slightly looser than intended, just look at is your "fine adjust" feature.
 
#11
I've done a lot of grinding in the past down to the millionths for dies and such . You first need an accurate pin . Reamer blank , deltronic , large gage pin etc . Clamp in your vee and locate off the pin on top of a ground angle plate . Get both sides the same . ( you say you're .0002 off side to side ) which ain't too shabby . Dust the .0002 off the high side and then measure the overall dimension . Split the difference for what your mounting plate needs . Then you're going to need that angle plate to grind it square .


I had to grind a titanium cube for NASA years ago . Space flight material so it had to be perfect . Overall tolerance was .0002 . Perpindicularity was .0002 . Parallelism was .0002 . Bores going thru the 6 sides true position was .0002 mmc .

The job drove me to drinkin ! It tested the inspectors as well as the cmm back then . We finally inspected the cube on one of our Deckel Jig Grinders .
 
#12
Just read what Bob Korves wrote . He is definitely correct . Better have the ducks in a row cuz it's a 1 shot deal . I had my Sine-a-dex down to the millionths . I sold it some time back but I still have gobs of nice grinding accessories laying around . If you could use any of it , shoot me a pm .
 
#13
I think part of my issue is the unknown precision of the tools and tooling I have. Ive bought 90% of my tooling from auctions and stuff. All in really good shape just let say used. I’m gonna need to inspect my toolage and get a little more confident of my measurements.
So what is being suggested is to fasten block to a angle plate than zero part and grind. I originally was gonna put block on mag chuck grind one side then flip. The V block had pretty good support but I was gonna back it with a block to prevent tipping. So that’s how you grind a perpendicular plane is with angle block not just placing on chuck? I’m new
 
#14
You need to grind 1 side of the block parallel to the vee slot first , then grind the other side to match the first . Then you can split the difference for the slot size you need . ;) Correction ……………...parallel ! Fixed .
 
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#15
Or , just for the fun of it ………….grind the block to size to fit your slot , then set up on sine table and re-grind your vee . Food for thought .
 
#16
You need to grind 1 side of the block parallel to the vee slot first , then grind the other side to match the first . Then you can split the difference for the slot size you need . ;) Correction ……………...parallel ! Fixed .
So if sides or one side is already parallel with V then just a matter of getting to final size.
If not parallel to V then I need to use angle plate align V block to zero make one side parallel and then bring to size.
 
#17
Or , just for the fun of it ………….grind the block to size to fit your slot , then set up on sine table and re-grind your vee . Food for thought .
That could be a backup plan thanks for the knowledge :encourage:
 
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