[4]

Performed additional test - B&S surface grinder

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

Technical Ted

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Nov 5, 2016
Messages
682
Likes
675
#1
Right after I refurbished the machine and dusted the chuck I did the 5 block test on my new to me Brown & Sharpe 2B surface grinder and all blocks were within 0.00015" of each other. I decided to do an additional test to help me learn the limitations of my ~1935 well used machine.

I put 2 pieces of bar stock (fairly soft mystery metal) on my magnet and spread them out as far as I dared. They were each 1-5/16" high, 3/4" thick and 12-1/4" long. Most likely much bigger than anything I would ever grind.

I rough ground both sides, dressed the wheel and finished both sides. I didn't take many pains trying to get a perfect finish, just let it spark out on the final couple passes.

I miked the pieces and then checked them with my tenth's indicator on my surface plate. Each individual bar was 0.0002" thicker in the middle than on the ends. One bar was 0.0002" thicker overall than the other one. So, the extreme spread was 0.0004" overall for both pieces.

Hey, it could have been a LOT worse on an old machine like this! For my use and what I have invested I am very happy with the results. If I had both pieces side by side (as in grinding parallels) they would have been within a couple tenths, plenty good enough for me.

Now I have a better idea of what I've got and if the day comes when I need to get things as close as possible I'll have to "play" with things to see how close I can get them.

I know a lot of people would think this is way out of tolerance for them (and I'm sure it is), but for me and my use it's fine!

YMMV,
Ted

IMG_20180925_160608.jpg


Both sides roughed, wheel dressed and ready to finish 1st side.

IMG_20180926_091200.jpg


On the surface plate for inspection.
 

Bob Korves

H-M Supporter - Sustaining Member
H-M Platinum Supporter ($50)
Joined
Jul 2, 2014
Messages
5,872
Likes
6,188
#2
Do they rock on the surface plate or on the unmagnetized chuck? Tap down firmly with a finger on the ends of the bars and listen for a clink.
 

benmychree

John York
H-M Supporter - Gold Member ($25)
Joined
Jun 7, 2013
Messages
2,585
Likes
1,897
#3
Perfection is a relative thing!
 

Technical Ted

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Nov 5, 2016
Messages
682
Likes
675
#4
Do they rock on the surface plate or on the unmagnetized chuck? Tap down firmly with a finger on the ends of the bars and listen for a clink.
I always slide my pieces around when chucking something up to make sure they are seated, but I can't really test rock anything on my chuck since there's too much residual magnetism.

I did check for flatness on my surface plate. I not only listen for the sound but also run my tenth's indicator up and down them while tapping on both ends and both sides to see if there is any rocking. I could not see any movement whatsoever on my indicator on either side on either piece so they are very flat.

Both pieces being high in the middle you would think I should see some rocking with the indicator, but since it's only 0.0002" total or 0.0001" per side that would only be a reading of 50 millionths on each end so I might just not be able to read that with my Mitutoyo tenth's indicator??? While pushing on one end and then the other to see where the pivot point was it was just a touch more than 1/3 of the way in which makes sense since they are both high in the middle.

Ted
 

Doubleeboy

Active User
Registered
Joined
Dec 3, 2014
Messages
769
Likes
439
#5
If you want to read less than a tenth the cheapest way in my experience is find a Euro made .001mm indicator. That is 39 millionths. For some reason metric test indicators go for considerable less on ebay than English ones. Less than a tenth is good enough for anything I do, but it is fun to see how flat you can get a piece of work. The hard part in my experience is make 2 of the same part and get em with in a tenth or less of each other.
 

Technical Ted

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Nov 5, 2016
Messages
682
Likes
675
#7
If you want to read less than a tenth the cheapest way in my experience is find a Euro made .001mm indicator. That is 39 millionths. For some reason metric test indicators go for considerable less on ebay than English ones. Less than a tenth is good enough for anything I do, but it is fun to see how flat you can get a piece of work. The hard part in my experience is make 2 of the same part and get em with in a tenth or less of each other.
Thanks for the tip. I'm not really set up for measuring anything that close... First, you would need an environmentally controlled room. I bought my surface plate used and the last time it was calibrated was in 2004. The sticker says it was flat within 4 millionths then, but who knows what it is now. I do clean it thoroughly with straight ammonia though so I know it's at least clean. And my tenth's indicator hasn't been calibrated in over ten years as well.

I did check my surface plate the best I could with my indicator like they showed on Suburban Tool YouTube and it looked very good. The indicator does repeat very well when checking parts so it's probably close and I could check it with my gauge blocks but have not done so far.

I don't see where I would ever sweat over anything closer than a few tenths and most times, for my work, 1/2 thousandth is plenty close enough. I did buy a new Fowler cylindrical square which is one of the very few new tools I've bought. I plan on checking and dusting if necessary my precision angle plates and 3" grinding vise, but those will be winter projects.

I'm having fun though and that's what it's all about!

Ted
 

T Bredehoft

Active User
H-M Supporter - Gold Member ($25)
Joined
Dec 27, 2014
Messages
2,739
Likes
2,103
#8
Ted, I applaud your realistic view of 'accuracy.' Yeah, .0004 is measurable, but is it meaningful? In a hobby world, No.
 
[6]
[5] [7]
Top