Inconsistent results on a Blanchard 20C

billgunsmith · Nov 30, 2020

Howdy, all. I'm having a problem with getting smooth flat surfaces on our old blanchard. i'm finding it doesn't matter if it's steel, cast iron, thick, thin, short, tall, whatever. the issue is that i can run one part and both sides will come out smooth. can run the next part and it will come out rough, though the patter looks perfect. one part can come out exactly to size. the next one? eh, .002 short. the only consistency i'm getting is that just about every part is high towards the middle.
we've focused on the wheel dressing. it hasn't yielded any positive results beyond a part or two. i have no experience with these monsters, and the folks with experience here have only run'em, never dug any deeper. any words of wisdom or ideas would be greatly appreciated. thanks, men

ygolohcysp · Dec 1, 2020

I only have limited experience so far. If the parts are all high towards the middle, you'll want to check both, how flat/true the chuck is, and if the wheel/column is trammed in okay. A straight edge is required to check the chuck surface. As for some parts smooth, some parts rough, I don't know. Unless the different parts are different materials. We are normally grinding hardened steel, and have the segments that are good for that. If we try to grind mild steel, it doesn't break the segments down as well, and leaves a different surface.

J Henricksen · Dec 1, 2020

Set the column in and out first to get rid of taper, then side to side for flat and pattern.
Could be the ways underneath are scored up and need a redo

Mike1974 · Dec 1, 2020

Sounds like the head needs trammed. Are you moving the table in and out during grinding? Ideally you place the table under the head so it grinds the whole part(s) at a one point. Different surface finishes could be wheel segments loading up. Usually a fresh dress (on 36 grit or so) will give you a more pronounced cross hatch with a coarser 'feel'.

billgunsmith · Dec 1, 2020

oh no. i don't mess with the table once the grinding starts. so far everyone has mentioned the head. that's been a suspicion of mine for a while. not even sure we have the wrench for it, poor old machine.

Mike1974 · Dec 1, 2020

billgunsmith said:
oh no. i don't mess with the table once the grinding starts. so far everyone has mentioned the head. that's been a suspicion of mine for a while. not even sure we have the wrench for it, poor old machine.

I don't remember the size of ours, except the chuck was something like 42" diameter. Think we had to make a wrench for the head bolts. Awful expensive to buy in that size!

michiganbuck · Dec 1, 2020

Head tram and table grind are important...

spotters are good: I used to put a piece of tape on my spotter to see .003 high and then watch the blue mark on the spotter itself. but that does nothing for taper just size.

QT: post #2 [A straight edge is required to check the chuck surface for dead flat.}

Qt:[not even sure we have the wrench for it, poor old machine]
Good chance you need to find a Blanchard hand to come in and tram the head. crosshatch tells a lot after you are near tram.

Might advertise on Craigslist for a Blanchard hand...or machine repair shop that knows Blanchards.

It takes a long test bar/parallel to check for a flat table.

And it could be the machine bed is dirty, dry or wore out.

Richard King · Dec 2, 2020

If the machine is old. They used to use greese lubrication on the base ways and the never cleaned the machine and as time went on that grease turned to lapping paste when grit got mixed in it. Eventually the top of base ways got low in the middle. Then the bottom of the saddle started to look like a rocking chair. The table infeed is a rapid in and out and not for feeding. Another issue I've found is the under table ways are run dry and they get galled up. Did the issue just start happening? Or did it gradually get worse?. I am assuming your using the rolling disk dresser ?

billgunsmith · Dec 3, 2020

yes to the dresser. i couldn't say about how long the problems have existed. at least since i've been on it, about 90 days. far as i could figure out the machine's from 64 or 65

michiganbuck · Dec 3, 2020

The material type, volume of parts on the chuck , condition of dress, can have effect on size if just reading off the dial. Spotter use can be a valuable asset for attaining size. Agree variant of .002 is way a lot for a Blanchard if a spark out is made.
A set on the chuck spotter block with a taper bar to be adjusted up and set to micrometer size can get parts quickly to .0002 or so.
I would put a slip of tape on my spotter to eyeball +.003, then dress my wheel and expect about .003 from that spotting, Then with that I would watch my grease pencil mark for first contact.
I had a number of spotters so I could get the most often needed sizes, for an odd size I might double C clamp a bar on a block and use that for a spotter.
The dress at +.003 seemed to make the surface finish more as expected/ consistent.

Richard King · Dec 3, 2020

Also you can check the bottom ways buy setting a precision level on the chuck parallel to the base ways. Start by rapid the saddle all the way back away from the spindle. If you have to shim under one end so it reads level. Then take a mag base and set it against the level and flip it on so it stays put. Then rapid it all the way forward 12" and stop, watch the level, then rapid all the way in, stop read level. Then move it back 6" and watch the level. I bet the level will be so bad, you won't be able to read it. If that happens put a plunger dial indicator and magnet to the bottom of the head and run it in and out. If you have not loosened the 3 head alignment screws for a while, they are probably rusted dead and you will need to squirt penetrating oil around them and you will need a 3/4" or 1" drive socket with along pipe to loosen it. Good Luck.

Here I found this for you. It maybe a smaller machine then yours, but the procedures will be the same.

http://vintagemachinery.org/pubs/4017/24851.pdf

KNR · Dec 3, 2020

Try leveling chuck by measuring from outside to outside, not outside to middle. second let it spart out longer.

CarbideBob · Dec 3, 2020

Given the first part good and second run bad I'm not so sure I'd be chasing column tram or the bottom ways.
If adjusting tram what to do? Make the first part scrap and the others good?
For sure if the bottom ways worn baldly coming in the same position is important but it is rather fixed. I have one with a good .010 dip or curve on the in/out yet it will hold a tenth.
(someday I need to fix that)
Outside of wheel dress and sparkout my first thought would be loss of preload on the spindle bearings.
These machines have a very heavy spindle sitting up and down. You can can have it hanging from the top and it sounds just fine in use and still does a cross hatch.
What goes to shit is size control and sort of skippy marks on the parts.
Bob

EmGo · Dec 3, 2020

CarbideBob said:
Outside of wheel dress and sparkout my first thought would be loss of preload on the spindle bearings.
These machines have a very heavy spindle sitting up and down. You can can have it hanging from the top and it sounds just fine in use and still does a cross hatch.
What goes to shit is size control and sort of skippy marks on the parts.

I bet Mr Bob is right. To be non-repeatable it has to be something that is loose.

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Inconsistent results on a Blanchard 20C

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billgunsmith

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