Brown and Sharpe Taper Reamer: Straight shaft w/o spinning between centers.

Oh well... Win some, lose some!

Here it is heat treated to RC62 and sand blasted... -and look what the sandblasting uncovered... a fracture. This is what I get for not following the procedure. In this case, I did not normalize the metal before machining it. Everything else was done by the book. Most likely, it had a bunch of internal stress that busted loose somewhere along the line.

The part was slowly brought-up to 1500, held for 10 minutes, oil quenched down to 150 degrees then tempered at 350 for 1 hour. The new piece is now in the furnace getting normalized... I get to do this project over. The crack is so deep, I won't even risk practicing on it in the tool grinder.

Live and learn.

(BTW: It actually tested at 62 RC so that's encouraging).

Heat cracked.JPG

Ray

Heat cracked.JPG
 
This time, I fully normalized the piece at 1600F, 1hr soak and open-oven cool. When turning this, it felt and looked like a totally different metal. The stock I had for this came with certs but didn't specify the condition. It looked to be TGP but no heat condition was specified. Anyhow, I couldn't believe how nicely this machined. ...Wish I could use nice stuff like this all the time...

Take 2.JPG

Ray

PS: As you can see, Frankenfinger is doing incrementally better. Stitches will remain for 2 more weeks and it might need a little more work. LOL, this is probably the only time you'll ever see me with a clean hand...

Take 2.JPG
 
Can you say HOT!

HOT.JPG

Fresh out of the oil bath and first temper. Tempered at 325 for 1 hour. It's still hot.

Remake1.JPG

Second temper and cleaned up. You don't do the second temper until it's dropped to room temperature after the first temper. Second temper must take place within 24 hours of the first. Sooner is better.

Remake2.JPG


I'll check the Rockwell tomorrow. Metal likes to wait a day before it reveals it's beauty...

BTW: No cracks this time. Normalizing helped and I also preheated the oil to 200F.


Ray

HOT.JPG Remake1.JPG Remake2.JPG
 
Ray,did you get a truly hardened reamer quenching in 200 degree oil? What you really need to do is get a proper reamer fluting cutter. It leaves rounded gullets in reamers. Having those sharp gullets is an invitation to crack. Even number or letter stamped impressions can lead to cracking. That's why some marks are made with a series of little dots(ugly as they are).

I make lots of stamps. I never quench the whole length of the stamp's shank. If I do,using W1,it invariably causes the stamp to crack right up the middle. So,I just heat up about 3/4" of a 2 1/2" long stamp. W1 is really treacherous stuff.(I realize you were using 01,of course.)
 
George,

I'll check the Rockwell later tonight.

Yes, I've since read exactly what you are talking about. The books all say that large dimensional changes or machining with sharp angle is a setup for a crack. It is apparently most common during the quench and the suggestion was to raise the oil temperature. Some books say as high as 400 which seems way too high. Other books said 200 and I tried that and at least this one did not crack -so I'm happy about that. I used a large volume of oil so it would soak-up the heat without raising the temperature too much. The oil was 220 degrees when I pulled the part out. From there, I let it cool to 150 then tempered it.

Oh, yes, this is O1 tool steel. I have heard that W metals are very hard to control cracking so I stayed away from it. I only need this tool for hand operation and I made it slightly bigger than needed so I can resharpen if necessary. I hope it will do what I want it to...

Ray




Ray,did you get a truly hardened reamer quenching in 200 degree oil? What you really need to do is get a proper reamer fluting cutter. It leaves rounded gullets in reamers. Having those sharp gullets is an invitation to crack. Even number or letter stamped impressions can lead to cracking. That's why some marks are made with a series of little dots(ugly as they are).

I make lots of stamps. I never quench the whole length of the stamp's shank. If I do,using W1,it invariably causes the stamp to crack right up the middle. So,I just heat up about 3/4" of a 2 1/2" long stamp. W1 is really treacherous stuff.(I realize you were using 01,of course.)
 
It's a hard piece to test but, I got three readings of 59, 60 and 59 at the square end of the shank. I'm guessing (hoping) the cutting edges are a little harder because they would have cooled much faster. The book says 65 is the top-end for O1 and for all practical purposes, 62-63 is what most folks commonly shoot for.

We'll find out how well it works soon enough...

Ray
 
Thanks Ray,
I really enjoyed your posts and learned a few things from your excellent explanation of the setups.
Michael
 
This is bugging the crap out of me... I have two books on heat treating; one costing over $300 and another over $100. These are professional series reference books... So why the heck do I find discrepancies with stated oil preheat temperatures all over the place?

I've decided I really like machining tool steel and want to do more -but it might as well be made of A36 if you can't heat treat it right...

It's only the tool steels where the discrepancies arise... I have a book dedicated to tool steel and even it is different from the other two.


Ray
 
LOL: Because all I had to work with was O-1. Also, the oven is wired with nichrome right now and 1800 degrees is pretty close to it's top end. I have some Kanthal on hand but don't feel like changing-out the coil unless I have to.

BTW, there's really not that much hassle in oil or brine quenching. Matter of fact, it adds to the fun factor. I just wish the books had more consistent recipes.


Ray


O-1 has a complex heat treating process involving, like you stated, oil quenching and so forth.

I'm wondering why you didn't choose A-2 tool steel as the heat treatment for this material is straightforward? A simple oven preheat then a run up to 1800 followed by an air cool down to 150 or so.

The differences in the heat treatment is probably why A-2 is specified for reamers rather than O-1.
 
I make all the punches and dies for our jewelry business from A2,because I want them to last as long as possible. But,you have to carefully wrap A2 in hi temp stainless wrap and seal it well. Also,I'll put a small bit of brown paper in the heat treat envelope to burn out any oxygen in it. Too much paper will burst it right open,and cause the surface of the A2 to decarb and ruin it. I tear open the stainless envelopes with tongs and scissors and hold the part up to a stream of air ASAP. It will harden in still air,but I lie to lower the surface temp as soon as safely possible to avoid de crabbing when exposed to air.

I have found A2 to be much safer than 01 about warping or cracking. The slower the quench needed,the less shock the steel is exposed to. Air hardening steels are the safest in that respect. And,they last longer as tools,too.
 
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