Mine have an R8 arbour, but other than that, they look like yours does. I'll post a photo if I decide to try it.
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Tips/Techniques Cutting High Strength Steel Forging
- Thread starter Susquatch
- Start date
Tips/Techniques
Mine have an R8 arbour, but other than that, they look like yours does. I'll post a photo if I decide to try it.
If you have a carbide grinding wheel (usually green) save the munged up end mills. You can freehand grind a workable edge on them, and use them for plunge cuts when dealing with stuff like sheared off bolts down in holes and the like. I would bet that a diamond disk on a dremel could work too, though MUCH slower!
One of the repeat jobs that came in to our shop in Cold Lake was a stainless steel part from a missile rail, that had a helicoil, (stainless too, naturally) and a stainless bolt. These were essentially a perfect recipe for galling followed by corrosion... so lots of them came in with broken off bolts, and needing new helicoils installed. I could take a single scrapped 1/4 inch end mill and get as many as a dozen of the broken off bolts out by simply plunging in at a slow feed on the mill, before I ran out of reach with the regrinding. It doesn't have to be pretty, just has to make a positive cutting edge on each flute.
One of the repeat jobs that came in to our shop in Cold Lake was a stainless steel part from a missile rail, that had a helicoil, (stainless too, naturally) and a stainless bolt. These were essentially a perfect recipe for galling followed by corrosion... so lots of them came in with broken off bolts, and needing new helicoils installed. I could take a single scrapped 1/4 inch end mill and get as many as a dozen of the broken off bolts out by simply plunging in at a slow feed on the mill, before I ran out of reach with the regrinding. It doesn't have to be pretty, just has to make a positive cutting edge on each flute.
I can't save drill bits yet let alone an endmill. It will most likely get the cutting end knocked off and be used as a gauge pin. It is highly unlikely that I would try to sharpen it.
I could also throw it in a bin and drag it out if you ever dropped into Ontario for a visit.....
LOL! Geez man, you sound like some of the apprentices I had, that were sure if they looked in enough drawers, long enough, they would find the tool that made everything easier, instead of just practicing!
Spent long enough in Southern Ontario, and have enough bad memories of it, that Ontario is NOT on my 'happy to visit' list of places! So don't keep the light on,on my account!
ChazzC
Ultra Member
General purpose uncoated: how many of these did you go through?
This comment is probably too late to help
You say the bar was from a scrap bin. Given that it is farm equipment, whatever alloy it is, and whatever hardening technique was originally used, that's probably strain hardened. That makes it more 'tough' than 'hard'. It won't hold an edge if you sharpen it, but it will resist being cut or ground. That's more likely than being something super tough like including molybdenum in the alloy.
From your last picture, it is a large area that needed to be machined down. I would suggest the largest multi-insert shell mill that you have. Something like this. I think that this kind of cutter allows you to keep up your rate of work (progress towards completion) while keeping the rate of engagement of the tool into the piece withing a manageable range for the power available from your mill.
You say the bar was from a scrap bin. Given that it is farm equipment, whatever alloy it is, and whatever hardening technique was originally used, that's probably strain hardened. That makes it more 'tough' than 'hard'. It won't hold an edge if you sharpen it, but it will resist being cut or ground. That's more likely than being something super tough like including molybdenum in the alloy.
From your last picture, it is a large area that needed to be machined down. I would suggest the largest multi-insert shell mill that you have. Something like this. I think that this kind of cutter allows you to keep up your rate of work (progress towards completion) while keeping the rate of engagement of the tool into the piece withing a manageable range for the power available from your mill.
Surprising how far ahead of CL the cutting edge is.
I'm sure thats just an optical illusion. Here's a shot of it from overhead.
Attachments
Hurrah Hurrah!! Let the trumpets blare. Let the temple bells peal!! The @Susquatch shines again!
The other good thing about this kind of cut is that you can hog out the material at a decent rate using shallower cuts. And using lower power through your machine because of the mechanical advantage from a larger cutter.
That's important to _me_ because my machine has a very low power (1HP). But probably can be useful to you and others too
That's important to _me_ because my machine has a very low power (1HP). But probably can be useful to you and others too
<sigh> LOL!
We tried!
Gonna suggest, aside from the option to use a carbide concrete drill with a little judicious sharpening work being done to it, you could do worse things than to read up on the Cole Drill, and how and why it works where a lot of other machines won't. Basically very slow turn rate, VERY high pressure to the tool, allowing HSS or carbon steel drills to punch way over their weight class, as it were. the main effect is that the drill does not move fast enough to create a bunch of heat.
Otherwise, I think this job might have to wait until you source a decent carbide insert drill bit of the correct size.
ChazzC
Ultra Member
Then you’re ahead on cost of end mills (and your time is free, right?
)
Then you’re ahead on cost of end mills (and your time is free, right?
They agreed to pay for consumables plus my time.
Ya, that part is over.
It's possible. But judging by how poorly the chop saw grinding wheel worked, I'm not sure an angle grinder would really have been much better.
I'm not looking forward to drilling today.
I've started calling it the drawbar from hell.
Cool trick. Wish I understood the science there.
I can run my mill at 3 rpm (even less if I really want to), but I'm not sure a lot of quill pressure is a good idea.
My plan is to drill it with a 1/4 carbide drill first, then 3/8. Then switching to a sharpened 1/2" concrete drill. Then switching to a carbide insert boring bar.
I dreamed about this last night and my dreams were all nightmares. If I have to wait for an insert drill, my client is NOT gunna be happy......
Well, some of that learnen been done! A little more to go. I am not sure what to tell you about the drilling. I have noticed when drilling stainless, that skipping the step drilling seems to work better, and sometimes the same for unknown steels. It seems that the wider the land/cutting edge engagement, the better. Many times just a clearance hole for the drill tip works way better then step drilling. Many times just to get past the edge/corner of the clearance hole will be a bear, the loading in one concented spot often destroys that part of the cutting edge, leading to failure of the drill bit, and work hardening of the metal being worked.
This leaves the corners of the cutting edge of the drill bit to try to finish the hole to size. The failures there are many also, to say nothing of material breaking off the drill bit and lodging in the metal being drilled.
Many times I have ground the cutting edge nearly to no rake to make the edge stronger, and removed some of the heel to reduce rubbing and heat build up. Some bits are ground somewhat this way from the maker.
I am sure you know a lot/all of this, but hard to say.
Anyway good luck, will be thinking of this while at the meet.
This leaves the corners of the cutting edge of the drill bit to try to finish the hole to size. The failures there are many also, to say nothing of material breaking off the drill bit and lodging in the metal being drilled.
Many times I have ground the cutting edge nearly to no rake to make the edge stronger, and removed some of the heel to reduce rubbing and heat build up. Some bits are ground somewhat this way from the maker.
I am sure you know a lot/all of this, but hard to say.
Anyway good luck, will be thinking of this while at the meet.
Drilled ok with 1/4 inch carbide drill. Went real slow and put lots of pressure on it.
Also set a depth stop to prevent messing up my vise on breakthrough with all that pressure.
On a suggestion from @thestelster I used the OLD endmill (now more like a plow mill LOL) to plunge cut that to 1/2. Worked GREAT!
But boring bar still doesn't fit.
So, per @trevj , I sharpened an old 7/8 concrete bit to shank OD at 3/4 and very low cutting angle - again with lots of pressure. Noisy and scary, but it worked.
Time for lunch then a long session with a boring bar this afternoon.
So far so good!
Also set a depth stop to prevent messing up my vise on breakthrough with all that pressure.
On a suggestion from @thestelster I used the OLD endmill (now more like a plow mill LOL) to plunge cut that to 1/2. Worked GREAT!
But boring bar still doesn't fit.
So, per @trevj , I sharpened an old 7/8 concrete bit to shank OD at 3/4 and very low cutting angle - again with lots of pressure. Noisy and scary, but it worked.
Time for lunch then a long session with a boring bar this afternoon.
So far so good!