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Blanchard, lapping machine or double disk? Options to make hard steel parts flat?

Garwood

Diamond
Joined
Oct 10, 2009
Location
Oregon
I just had a product line explode on me. I need to ramp up and dial stuff in.

One component I have troubles with is carburized mild steel about .130" thick and 1.5" x 3.5"

When these come back from carburizing some "potato chip" a bit. Some get a small twist to them. I have to rotary tumble to remove the heat treat smut then I sort them on a surface plate. I probably discard 20% from some batches. That's a lot of parts.

These parts seat against machined surfaces and can go in either way. Both sides need to be flat within a few thou, but paralellism does not matter at all as long as the part looks good to the eye.

I'd like to replace the sorting out the twisted ones with a process that makes every part a winner.

I think I want a small Blanchard, but I hear from one of my customers they are incredibly messy and I run on a 60HP phase converter. It would suck to get one and not have the Pixies to run it.

Can lapping machines get aggressive? Can they remove .015" or more in a reasonable time?

I live in knife country (Benchmade, Leatherman, Gerber, CRKT, Kershaw, etc) and always hear that double disk grinders are worth more than gold by weight. Are there any lower cost similar processes?

Anything else that might do it with, say, sub-10HP so I could run it while running everything else and I could break into for under $10k give or take a few grand?
 
I'd go double-disk. The part size is perfect for a smaller machine, and no worries about distortion due to magnetic clamping as on a Blanchard.

But I also wonder if changing over to a different steel with a more uniform hardening process might be better. Something more expensive for material, but less process/post-process costing, perhaps like a 17-4 SS sheet that you can harden yourself with a good furnace, then just Scotch-Brite when done as it shouldn't move much.
 
I'd go double-disk. The part size is perfect for a smaller machine, and no worries about distortion due to magnetic clamping as on a Blanchard.

But I also wonder if changing over to a different steel with a more uniform hardening process might be better. Something more expensive for material, but less process/post-process costing, perhaps like a 17-4 SS sheet that you can harden yourself with a good furnace, then just Scotch-Brite when done as it shouldn't move much.

I can't change the steel. This is very much a low price high volume item.

How do I determine what I need in a double disc grinder?
 
I think you will have a hard time removing .015in. with two 30hp spindle motors in one pass.

You will also probably have a difficult time finding a double disc grinder with small enough spindle motors. The 60hp phase converter will be somewhat limiting in your search.

Now if you do it in a couple of passes, more doable. Do not forget that you will need a coolant filter and a chiller system to run this and hold size for any length of time part run.

You will also have the cost of setting up the part holding disc when setting up the double disc grinder.

The double disc grinder is a great way to get flat parts at size but they do require more fixturing to get setup.
 
I can't change the steel. This is very much a low price high volume item.

Not knowing what the part does I can only guess at the best way to go. It does seem odd to me that the balance of cost is in favor of lots of process time over a to-size, single shot machine/harden/use.

How do I determine what I need in a double disc grinder?

I'd start by checking out what's for sale used and working out what has wheels big enough for the parts. Whether you fixture axial or radial will matter, as will (as mentioned before) if you want to grind in one shot or multiple passes.

Frankly, I'd be really tempted to just outsource the part to a sheet products specialist. Let someone else deal with the "hows", and just integrate the finished part.
 
I don't have much experience with DD grinders other than to know one will be pretty expensive by the time it is making good parts.

If your part was 1" thick a Blanchard would eat it for lunch and not even burp. But at .130, getting the warp out will be a painstaking process involving lots of shimming and flipping. Then, no matter how well you think you have them blocked in, occasionally you will throw the whole batch off the chuck on the last pass.

You might talk to your heat treater or find another heat treater. The fact that some parts come back flat shows it can be done. You probably have to pay more for the heat treatment, but it will be a lot cheaper than a DD grinder.

A timesavers belt finisher may also produce an acceptable part.
 
Not knowing what the part does I can only guess at the best way to go. It does seem odd to me that the balance of cost is in favor of lots of process time over a to-size, single shot machine/harden/use.



I'd start by checking out what's for sale used and working out what has wheels big enough for the parts. Whether you fixture axial or radial will matter, as will (as mentioned before) if you want to grind in one shot or multiple passes.

Frankly, I'd be really tempted to just outsource the part to a sheet products specialist. Let someone else deal with the "hows", and just integrate the finished part.

As well... OP, have you done a somewhat comprehensive time study? I think heat treating a toolsteel (or in-house for whatever..) would be cheaper than carburerize and harden, but I've been out of that game for a while now.

If you took something stable, like A2, S7, heat treat, no/little warpage, and straight from heat treat into the assembly, surely the time and labor costs savings makes up for the difference in material costs? And at high volume (if a known stable product) you could bargain with different suppliers for a better "bulk" price...?

ps. Don't know anything about DD grinders, but a blanchard would be alot of work as someone mentioned for .13" thick parts...
 
A couple things ... carburizing shafts, if you quench them end-on as opposed to the long ways, they distort a lot less. Quenching these end-on in some sort of rack might work. I'm guessing this is one reason you get a variety, they go into the quench at random.

Also, you didn't say whether you were making them out of plate, I am guessing yes but if they could come out of bar, the grain would run the other way.

And 8620 might distort less than 1018 but still give you a hard case, softer core (if that's why you are carburizing.) Machines just as good, doesn't cost much more.

And you might try a facing cut across each side, then normalize, then finish. That should help relieve any internal stresses.

All of the above is more work but should deliver better than a 20% scrap rate.
 
I have a #11 Blanchard with a 15hp motor in my little shop that runs on a 20hp phase converter without any issues. It’s not anymore messy than anything else in the shop. Not sure about your area but you can find them in good shape around here for about $5k.
 
Emanuel is correct. This is a heat treat problem. You are going through great effort and expense to correct their problem. Parts need to be spaced equally in a Special rack oriented vertically before going into the carburizing furnace and later quenched in that position. There must also be sufficient agitation in the quench tank to assure even cooling of all the parts in the batch. If any of this is missing you will get potato chips. Can’t know what your heat treater is doing but in my experience most of them are hacks that can’t be trusted and must Therefore be instructed.
 
I will have a meeting with heat treater. I know they hang every part by wire currently. It's so cheap I can't believe they make any money at it.

I like the timesaver idea. A good friend has a nice one.
 
Not sure such a small part will work in a timesaver. Mine has the hold down rollers a few inches back from the belt so wouldn't the part need to be at least as long as the distance between the two hold down rollers to keep it from spitting out? I only do long parts on mine so dont have any direct experience with little parts. Do they need to be in a carrier that staggers them so they dont get a tapered edge from the belt ramping up to the top of the part. Put sacrifice parts at the begining and end of the carrier.
 
Can’t know what your heat treater is doing but in my experience most of them are hacks that can’t be trusted and must Therefore be instructed.

I this really everyone else's experience?

I sure hate it when a prospective client tries to instruct me. On the other hand it's hard to keep my mouth shut when I watch tradesmen working on my house...
 
I this really everyone else's experience?

I sure hate it when a prospective client tries to instruct me. On the other hand it's hard to keep my mouth shut when I watch tradesmen working on my house...


I use one of the big heat treaters in the Portland area. Happens the owner is also a friend of a friend. We've had lunch many times. I can't fathom knowing any more about what they do than they do. I expect I'm just not asking the right questions or explaining my needs correctly.
 
You can always start by presuming competence . Sit down, show him the good and the bad, and give him an idea about the level of occurrence. Ask what he thinks he can do to improve it.
 
I use one of the big heat treaters in the Portland area. Happens the owner is also a friend of a friend. We've had lunch many times. I can't fathom knowing any more about what they do than they do. I expect I'm just not asking the right questions or explaining my needs correctly.
Possibly the parts are just too close together, so you're getting unequal quench in different areas. Have you mentioned it to him, and asked about possible things to try ?

You could also try straightening, which could be something of a bitch but if it's only 20% and you scrounged up an Eitel press or similar, it could go pretty fast.
 
I this really everyone else's experience?

I sure hate it when a prospective client tries to instruct me. On the other hand it's hard to keep my mouth shut when I watch tradesmen working on my house...

Ok that is a normal reaction. No one wants to be told what to do by a customer. But what if that customer has the experience with dozens of suppliers on a large range of products totaling A million parts/year Over many years? Now suppose that these are all safety related components where nothing is ever allowed to go wrong. Damn straight that customer will be telling you what to do and making sure you have procedures, equipment and Capability to do it.

Heat treaters may know very well how to do their job but usually are small shops with limited experience. Beware of parts they have never seen before.

In this case the op is not in a position to instruct the heat treater but as was just said in another reply must have the conversation noting that there is a problem and changes are needed.
 
I sure hate it when a prospective client tries to instruct me. On the other hand it's hard to keep my mouth shut when I watch tradesmen working on my house...

I had a friend I would do occasional work for and he'd preface his remarks with "I'm not trying to tell you how to fuck your goat, but ...."

And I know about the tradesmen. I had a re-roofing job years ago and they also replaced the wooden gutters. It made some sense since there was overlapping flashing etc. All good until it got to the ends where they just snipped the tin and hammered it down. (Woodwork is now rotted out from continuous moisture.) I knew he must be a good roofer because he sure wasn't a sheet metal worker.
 
Have you considered clamping them between plates and stress relieving them. That is done at a much lower temperature than hardening. You could do it in a kitchen oven.

Bill
 








 
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