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Minimum stock thickness for Blanchard grinding

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Plastic
Joined
Mar 19, 2010
Location
Canada
I have a production grinding job.

M4 annealed high-speed steel hot rolled plate. 1x1.5" blanks. Starting thickness 0.045. Ending thickness 0.030" +/-.001. Quantity is 5,000-15,000 per month.

I can outsource double-disc grinding. These machines are fabulously expensive used and I have no idea how to run them. Not terribly inclined to buy one, at least not yet. They are likely the machines best suited to this job.

I can buy a used Blanchard grinder for $10k and in-source the grinding. I don't know how to run one of these either but they seem common enough that figuring it out is possible. BUT can a Blanchard grinder reasonably hold material of this thickness? That's what I don't know. Maybe a steel cage 0.025" thick to hold/support the parts?

Automatic surface grinder. Cheaper than the Blanchard, but possibly slower and more labour intensive for the operator.

Any thoughts on this from grinder-hands? I am but a simple toolmaker who's never done any production grinding.
 
at that qty shop hard for the double disc grinding but keep it outsourced, thats not enough to own one, but more than enough to be a good ish customer of some one that does own one! You could probaly double up and ship every two months to and fit all thoes bits in the same parcel easily hence opening up far more distant suppliers as viables. No way are you going to economically do it on a std surface grinder, too slow!! Equally how flat, nothing is going to better the double disc as both sides get ground, unlike Blanchard or surface were there magnetically clamped down to a chuck there not going to end up as flat.

As to gripping thin stuff, google fine pole chuck, its what you need, but even then these bits are small and thin so are not going to grip all that well.
 
Adama, thanks for the reply. You're right that it's a big quantity and good enough to get into some serious bidding for outsourcing. The problem is that we can amortize a blanchard grinder in less than a year if it's usable. Also, we vastly prefer to insource critical work like this. It brings leadtimes down from 1 month to about 1 day, and we have control over finish and sizing.

We're considering grinding down the stock plates and then blanking after grinding. I'm just not sure a standard Blanchard mag chuck can hold .03" sheet/plate material. I might be able to find a local Blanchard grinder company who's willing to try, and for a small fee tell me how they've done it.

I'd love to do double disc in house but even used they're typically over $20k and I can't find anyone who knows how to use one within a thousand km of our shop.
 
I used to grind butt loads of press shims that looked like a horse shoe with about an inch across the legs.

Once I got down to .188" and thinner it was a real pain on the ass to keep them on the table.
The thinnest I can remember were 1/8 finish and we had to lay 1/16 pieces of scrap all around them to help keep them on the table
but just a bit to much down feed and the whole load gets flung off, was a real PITA.

At the thickness and tolerance you gotta have you will really enjoy sending these to people who do it daily.
Just the slightest amount of heat will cause that thin of a part to raise up off the mag and cause a chain reaction ending with
some very F'ed up parts ejecting off the table.
 
A Blanchard will do it but the mag chuck will not hold these.
It's done with a mechanical clamped ring and a kick in the grinding head.
They don't grab my carbide and ceramics either.
You don't spec which type of double disc under consideration.
This part would not be fun to setup and run on a Belsly but dirt simple on a Stahil.
A Blanchard is going to give you about 60-180 pcs per hour with .0002-.0004 flat.
Bob
 
CarbideBob! Many questions:

What's a kick in the grinding head? Perhaps you mean that it's nudged down more slowly than the autofeed is normally capable?

As far as Blanchard fixturing, perhaps a ring around the OD of the mag chuck, thickness perhaps 0.25 (as per the step seemingly on all Blanchard grinder chucks) but protruding above surface of the chuck 0.025"? Perhaps also a disc in the center of the mag chuck .025" thick which provides a channel wide enough for the blanks to sit between the outside ring and the inside disc? Is there a grinding wheel spec which would be most appropriate? We're looking for an Ra32 or better, but to keep the heat down I expect we want a coarse soft wheel?

I'm looking at the Besly type. That seems to be what our outsourcing shop uses. I don't see a single Stahli machine available used and the new ones look fabulously expensive, far beyond our budget.

The higher end of that Blanchard rate you've specified is acceptable. I'm a bit worried about buying one of these machines as an experiment and then not being able to get it going. Expensive and time consuming, even if we can flip the machine for the price we paid....
 
if you have proven demand for 50K+ of them a year is it likely to grow? if it is it might make sense to spend more on the more capable kit.

Kicking the wheel over means a bit like faceing a head on a milling machine, you kick the spindle over a nats so its only cutting on one side of the swing. Like this you reduce the cutting forces a fair bit + you always push the work in the same direction hence it all sits still. Done right, it nearly rubs still on the far side of the wheel and if the spindle is tight - under constant load its so slight it still grinds parts flat damn near as flat as you can measure on bits like your dealing with.
 
CarbideBob! Many questions:

What's a kick in the grinding head? .

Ok, parts on the Blanchard that the magnetic will not hold where the parts are small to the chuck.

You tip the head assembly away from you.
This way the front or entry of the wheel never touches.
All work is done on the back side and it tries to throw the part to the outside of the chuck.

You clamp a ring on the chuck so that there is no way they can move in this direction.
Nailing the kick front to back is a tradeoff.
You want to make sure you never touch the front (entry side) of wheel.
Any kick means you grind a very small arc into the part.

A machine setup this way will never produce a "crosshatch" finish.
If something goes wrong, like a big crash, and one of mine makes a crosshatch it will do very bad things within a day.
Bob
 
The thinnest we will go on our Blanchards/Mattison Rotary is about .060".

In addition your parts LxW is so small even if they were thicker you would have to do major blocking as the parts will not even reach across the poles of the magnet.

As mentioned above either a double disc or fine grinder may be the best way.
 
Would a timesaver be capable of holding these tolerances ???
eighter the parts or the stock plates


Peter from holland

It's a small world sometimes. MN Grinding purchased the original Timesavers building. when Timesavers downsized. Timesavers is still located in MN, just down the road in a smaller building. I used to rebuild their machinery before they down sized. Rich
 
I just spoke to Timesaver, they suggested double-disc. They can't hold the +/-.0015".

I've asked a couple more shops, including Minnesota Grinding, for a DD grinding quote. I've also found a shop with the feed-thru grinder and asked them for a quote.

I'm inclined not to attempt the Blanchard grinding. Too expensive of an experiment given that the consensus here is that it either won't work at all, or will only maybe work :)

I really appreciate your help guys. We'll see what the feed-thru quote looks like but it looks like we're going to farm it out to a DD shop and maybe buy a machine in the future when we can justify the capital.
 
i'd like to see what it cost per pc when subbed out. Even at $1 a part, a double disc grinder would pay for itself in 2 months. (maybe $1 is outlandish???)
 








 
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