Best way to thin .5" x.125 Cold rolled

I need to make some steel inserts (18) to go in a fixture we are building. They need to be .5" x .085" thick x .88" long. I have about a tolerance of about +-.005 on the thickness but they need to all be the same size +-.001 on the width and thickness as they need to be a tight slip or press fit in pockets I will be cutting in the Renshape fixture. Length is about +- .06".

I plan on picking up some 1/2x1/8 cold rolled and making it from this. I only have a knee mill to thin them out to .085" I am not convinced this is the best way to thin them and am thinking of trying to get them surface ground to the right thickness. The problem is I need to get this job done before the end of the year preferably this week. I have no surface grinding experience. How long would it typically take to grind approximately 20" of this stock to .085". If it is pretty quick I will take Cash and hopefully be able to get a favour from one of the shops I sometimes work with.

If I cannot get it ground or if this is prohibitively expensive. What would be the best way to keep the stock that thin flat in the vise while milling? I was thinking a 5/8 4 flute end mill one pass .040" off each side? Pieces about 6" long.

When I quoted this I had assumed I could use a standard piece of CRS or even a piece of standard size of ground stock. I should be able to get a little more for these ground or machined pieces as my quote was budgetary based on pictures before drawings were made. But it is a new customer and don't want to go much more than the budgetary quote.

If 0.88" long is not a typo, I'd do them in longer strips, then cut to length after thinning. (Ah, I see you said 6". Good.) I think I'd do them in width, thickness, length order.

They will need to be flattened after milling or grinding the first sides. When released after doing the first sides, they will look like bananas. If you're grinding, the mag chuck should suffice to flatten out for the 2nd side. If milling, make the strips the length of your vice jaws, and do the traditional support-on-parallels-deadblow-hammer-down thing.

0.085" is not a lot to grab in a vise, so I'd be inclined to grind the 2nd side, regardless of whether I ground the 1st.

If time permits, I'd start with 3/32 x 1/2 low carbon flat stock.
Low-Carbon Flat Stock - MSCDirect.com

Minimal stock removal and it won't warp when ground to size.
Trying to do this with cold rolled on a mill will make you nuts.

I think you're slicing this the wrong way.

Start with half inch CRS, 12 X 3 inches.

Gang mill in a horizontal, and cut them out all at once. Slice to length once you have the
12 inch long strips.

MrWhoopee said:

If time permits, I'd start with 3/32 x 1/2 low carbon flat stock.
Low-Carbon Flat Stock - MSCDirect.com

Minimal stock removal and it won't warp when ground to size.
Trying to do this with cold rolled on a mill will make you nuts.

Click to expand...

Agree.. but would cut the 24 x 1/2 x 3/32 into shorter pieces.. Perhaps 7" or a divide that make an even number with the cut-off amount.. so would not over heat surface grinding. Use a 46 or 36 wheel H through k.. take your time with small take so not to warp..saw cut ..and then grind in rows for length and width..grind wet...about .005 a side piece of cake.

*and don't try to come back on part in a snap but over travel at both ends for cooling time. block the go-side so they don't slide down chuck. Set the part at the front of chuck if chuck is not flat.

QT: [+-.005 on the thickness] so don't take them all the way to size with only .004 take a side for .088 finish.

*Agree a grinder hand should do the job..(I would use a popcorn wheel .. pull .0002 or so full wheel from the grind side..then pause and no-feed pass back.. but that is a trick for a grinder hand only..most guy would burn doing that.)

hire someone with a coolant type surface grinder?

Cold rolled 1018 or whatever will warp like crazy, whether you mill or surface grind down to that thickness. Coolant will help, if that option is available. A magnetic chuck will not grip the part well enough to prevent the part from bowing while grinding. When the part bows, it rises into the grinding wheel and may even stall the wheel, at the same time wrecking the part. As the part bows, it loses contact with the chuck, further weakening the chuck grip. Off it goes, into the outer reaches of the shop. Putting stop blocks of steel around the part will keep it from flying, but that is what makes the wheel grap and stall. I learned a long time ago to not surface grind thin cold-rolled steel.

I would start with annealed O1 or low carbon flat stock, which generally will not warp if you use sharp tools and avoid heating the part. The less material you need to remove, the better, so start with 3/32 stock instead of 1/8 stock.

Larry

l vanice said:

cold rolled 1018 or whatever will warp like crazy, whether you mill or surface grind down to that thickness. Coolant will help, if that option is available. A magnetic chuck will not grip the part well enough to prevent the part from bowing while grinding. When the part bows, it rises into the grinding wheel and may even stall the wheel, at the same time wrecking the part.

I would start with annealed o1 or low carbon flat stock, which generally will not warp if you use sharp tools and avoid heating the part. The less material you need to remove, the better, so start with 3/32 stock instead of 1/8 stock.

Larry

Click to expand...

^^^^^^ everything about this ^^^^^^

MrWhoopee said:

If time permits, I'd start with 3/32 x 1/2 low carbon flat stock.
Low-Carbon Flat Stock - MSCDirect.com

Minimal stock removal and it won't warp when ground to size.
Trying to do this with cold rolled on a mill will make you nuts.

Click to expand...

That will be my approach as well. One or more strips on the magnetic chuck and coolant.
Another fast way is to use rolling mills. I do it often, especially with non ferrous materials. No material waste and easy to control the thickness.

I would consider using 13 gauge steel sheet. As small as your parts are, finding an area of the sheet within .001” would probably not be difficult.

I was about to say sheet steel as well although at .085 you are right between 13 and 14. You need to find some offcut size like 13 that's too thin. We get weird stock sizes all the time from Metal Supermarket especially 16Ga that actually is almost 17Ga. We would waterjet and mill to size but band sawing should be fine. Otherwise tool steel and grind. Cold rolled warps in the most unbelievable ways.

If time and your suppliers align, I agree with those saying get 3/32 flat ground stock. You will be frustrated, tired, and angry by the time you take 1/8 cold rolled down to thickness. If I absolutely had to do that job, I'd first anneal the material, even if I had to do it freehand with a torch.

If a grinder was out of the question, I'd follow Rozen's suggestion. Put a piece of 1/2 thick stock in the mill and cut off pieces of the appropriate thickness with a slitting saw. Air blast or coolant for chip control and the parts will be usable off the mill.

I'd rather make the parts sawing slices from 1/2" stock with a good bandsaw and a mill or surface grinder than start with 12 gauge cold rolled.

I'd have the whole damn stack on the 48" Blanchard I ran, one shot.

qty (1) hour floor to floor.

And than includes flipping them over.

digger doug said:

I'd have the whole damn stack on the 48" Blanchard I ran, one shot.

qty (1) hour floor to floor.

And than includes flipping them over.

Click to expand...

I love the sound of shims hitting the waterguard in the morning. (as long as someone else is the operator)

I had not thought of being able to get 3/32" stock. I had to go to 3 places to get 3/32 stock and the place I got it was surprised that they had it. I did not have a lot of luck getting someone to surface grind it Today or tomorrow in the first 2 places I tried. I spoke with my customer and they approved using the 3/32 ground stock as it is only .004 /side. That is quite a relief I just had to adjust my model for the slot these are fitting into.

Pattnmaker said:

I had not thought of being able to get 3/32" stock. ...

Click to expand...

You are a victim of progress. Up until computers and the Internet took over the world, tool sellers mailed out thick paper catalogs showing thousands of items, with price, weight, pictures and sometimes even helpful application info. I used to read them for entertainment and learned a great deal about machining in the process. As I gained cash and space, I bought stuff from those catalogs, often stuff that I had decided to buy years before while reading catalogs.

These days, it seems you need to know what you want or need before you go shopping on the Internet. You also need to know where to look. Even Google requires you to at least have a clue what search words to use.

Now that you have been made aware of O1 and low carbon annealed ground flat stock, there is another thing to know. The tool steel variety comes in precision (made to nominal size to close tolerance) and oversize (to allow some excess stock for final grinding after heat treat). In other words, O1 flat stock 3/32" thick might not be 3/32" thick, so you need to read the label or mike it.

Larry

Pattnmaker said:

I had not thought of being able to get 3/32" stock. I had to go to 3 places to get 3/32 stock and the place I got it was surprised that they had it. I did not have a lot of luck getting someone to surface grind it Today or tomorrow in the first 2 places I tried. I spoke with my customer and they approved using the 3/32 ground stock as it is only .004 /side. That is quite a relief I just had to adjust my model for the slot these are fitting into.

Click to expand...

So, was the original .085 dimension an arbitrarily selected number or the result of other factors?

It is the distance between 2 parts that are getting assembled. However the model is made from scanned data and they felt the .008 was within the room for error on the scanned data. I am pretty sure the tolerance on the distance between the 2 parts is pretty loose.

The old fixture is aluminum but I wonder if the original was done the same way I am doing this one where a pocket is cut and a steel piece inserted. An island of .085x.5" .6 high would vibrate quite a bit while being cut.

At some point I would like to try Doug's suggestion but I am under the gun on this one.