I have a new project

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What i believe he is refering to is the actual tip of the tool. make it so the outside edges are higher than the inside. if you looked at the tool standing on its tip from the rear you would have a cave under there with an opening only to the rear. basically a three sided 7 deg cutting edge. it takes the pounding stress out of the tool. as he stated though you have to be careful not to try to cut going backwards. you can also cut in a V with it sloping so that the front of the tool is higher if you cant grind the three sided cut.

Roy

on review it doesn't take the pounding out it spreads the pounding over a longer time and reduces the initial shock.
 
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JOSHUAZ2 said:
What i believe he is refering to is the actual tip of the tool. make it so the outside edges are higher than the inside. if you looked at the tool standing on its tip from the rear you would have a cave under there with an opening only to the rear. basically a three sided 7 deg cutting edge. it takes the pounding stress out of the tool. as he stated though you have to be careful not to try to cut going backwards. you can also cut in a V with it sloping so that the front of the tool is higher if you cant grind the three sided cut.

Roy

on review it doesn't take the pounding out it spreads the pounding over a longer time and reduces the initial shock.
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Exactly, although I thought it was a punch. Sorry sometimes language barrier is tall for me to explain.
 
With 2 1/2" stickout, and milling 1 3/4", you will find that on that small a bar, you will need to provide additional support. Even if you could only stick out 1 3/4", it would still need support. And climb cutting produces less push off than conventional, not more. But as everyone knows, if you have uncontrolled backlash, that can be problematic.

If you can handle the M2, it should provide a good tool. You might consider some of the hot work tool steels too. They are used for shears and punches as well.
 
As always, thanks to everyone for sharing their knowledge. :tiphat:

I found time to mill a prototype (pics attached). The shorter (broken tip) punch is a $110 commercial. Overall, mine came out fairly well. Of course, form is only half the battle. Hardening and sharpening will determine how well it functions.

The annealed M2 was reasonable to machine. Not much more difficult than mild steel. All cuts were side milled with a used, 4 flute, 7/16", HSS, TiN end mill. It doesn't appear to have suffered undo wear. A new one should give a smoother cut.

As Tony predicted, I did get some chatter / stock deflection. You can see chatter marks on the rear photo. It wasn't bad once I reduced the DOC and my next one should be better. That was with conventional milling. The front face was climb milled and turned out smoother. If I had been smarter I would have made a fixture to clamp the stock at both ends. I could have milled two bits at once (tip to tip) and had less chatter. Maybe next time.

The rear of my punch has a step near the middle. Some commercial punches do, others don't. I believe it's a reference for mounting the punch to the correct depth. It doesn't seem necessary and I may eliminate it.

Syaminab, it was me who used bad terminology. I called them bits. You are correct. They are actually punches. My bad.

I believe I understand the 7 degree grind now. I'm not sure how you would actually accomplish it. Maybe using a narrow, small radius wheel and grinding in three directions. That one may be beyond me, but I do get the reasoning. With the equipment I hope to use, the V grind might be achievable.

Tony, you have far more experience than me, but I'm going to disagree on something. Maybe it's a terminology thing or maybe I need some of that good learnin'. When you are conventional milling, I believe the forces on the end mill are larger, but they are mostly parallel to the cut. The end mill deflects mostly rearward. With climb milling, the overall forces are smaller, but they are more perpendicular to the cut. That can cause the end mill (or part) to deflect sideways and give a less accurate cut. And of course there is the backlash issue. Am I wrong on that? Oddly, I did get more chatter with conventional milling in this case. There is a nice diagram of the forces at this link.

http://www.cnccookbook.com/CCCNCMillFeedsSpeedsClimbConventional.htm

Phils69, thank you much for the grinding offer. For now, I think I'll pass... unless I don't come up with a grinder soon. I kind of want to learn this... and then there's your steep $0.99 fee.

I'll be making at least one more prototype. Unfortunately, my muffle furnace thermocouple took a dive. It will be a week or more before I can harden them.

Any suggestions on a brand of universal grinder or what to avoid? What do I need to look for... or look out for?

Bottom.jpg Top.jpg
 
Just to be clear, I'm not looking for a true, $3 million dollar, universal grinder. I'm looking for a 150 lb bench top universal cutter / grinder (and not a double ended carbide grinder). Something like model 426245 from Northern Tool. I'm still reading, but I believe that style grinder (Deckel SO) will do all I need.

http://www.northerntool.com/shop/tools/product_200414732_200414732

I'm not sure about buying NT equipment. I have usually done better buying good, used, US equipment. I'm just not familiar with these grinders or the manufacturers. [TABLE="class: long"]
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I use to operate three different, a cincinnatti #2, a Jhones Shipman and a Parker Majestic. The most precise and versatile was the Jhones Shipman, but on the cincinnatti you could bite 0.020" a pass.
The Jhones Shipman had all kind of nice attachments, holders, fixtures and dividers. You could grind anything in shape. On it, our toughest assingment was to grind off a 42 deg. Angle of a sealing surface of a poppet valve for Diesel engines for CAT, we missed the job because we where at four micrometers of runout consistently, A brand new Okamoto was doing it under two microns.

By the way, what you are buying, we call a tool sharpener, far from the versatility of a universal grinder like this

http://www.ebay.com/itm/Jones-Shipm...894?pt=LH_DefaultDomain_0&hash=item2323e6933e
 
Can't help with machining advice but re hardening, why not just send them out to a professional heat treat shop? The shop where I work does that all the time... A2 stuff we do ourselves but for other alloys, we send it outside, then do the finish grinding after we get them back. That lets us use some pretty exotic alloys that few machine shops have the ability to handle in house.
 
Thanks for correcting my terminology. As you can see, I am often bad about that. I do believe I am looking for a "tool sharpener"... of some type. In my defense, it seems every manufacturer calls their grinder something different.

Send it out for heat treatment! Blasphemy! "jawdrop: If I were a professional shop, I agree that would make perfect sense. However, I'm doing it for fun... and maybe a new grinder. Since I already have the furnace and materials. There's no reason not to do it myself... except maybe to avoid that burnt oil smell. :))
 
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No burnt oil smell. HSS is air hardening. If you make up a bunch of those at once,it would really make sense to send them out as the price per piece would drop,you'd get optimum results,making your cutters more durable,and you'd save money on energy,too.

I harden my own stuff,but we're talking HSS here. The foil is bothersome and expensive,too, and easy to cut your fingers on!! But,suit yourself. You do want your cutters to last as long as the ones your customer is using now,if you want to keep getting the business.That has to do with the correctness of the heat treating.
 
I'm going to vote for outsourcing the HT also.

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  • Soft-annealing 850°C – 900°C / 1560°F – 1650°F, slow cooling 10°C / 18°F/h to 700°C / 1290°F, hardness max 260 Brinell.
  • Stress relieving 600°C – 700°C / 1120°F – 1290°F, approx. 2 hours at temperature, slow cooling to 500°C / 930°F.
  • Hardening with preheating in two steps 450°C – 500°C / 840°F – 930°F,
    850°C – 900°C / 1560°F – 1650°F and austenitizing at
    1050°C – 1220°C / 1920°F – 2230°F. Quenching to about 550°C / 1022°F then air cooling down to room temperature.
  • 2 temperings at 560°C / 1040°F are recommended (maintaining at least one hour each at temperature).
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My position is unchanged regarding the climb vs conventional cutting. The other terms used are "up" milling and "down" milling. Depending on just how sharp your tools are, conventional or "up" milling is more stressful on both the part and the tool. And there is the material to be considered. I don't think a blanket statement can be made that covers all the variables, but climb cutting is generally preferred. Except for the exceptions, of course.:))
 
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