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Tapping Inconel 625

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gregormarwick

Diamond
Joined
Feb 7, 2007
Location
Aberdeen, UK
What's your experience with this? Better form tapped or cut? The holes I'm looking at just now are M6x1.0 16mm deep.

Any recommendations, speeds, oils etc?

Thanks, Gregor
 
I haven't tried forming it but have cut some pretty small threads. I highly suggest taps specific to Nickel-based alloys that most major tap companies have. I have used Prototyp with good success.
As far as coolant I prefer oil for a variety of reasons on Inconels. But, one particular job we were having major thread issues so we tried three different water based coolants and two oils. It didn't have much of an effect on tool life.
 
I've never tried forming in inconel, can't imagine it would work due to the resistance of the material. Definately splurge on the exotic taps, Emuge makes some good ones for tough material. I use Moly-Dee cutting fluid for tough to machine material when tapping. If you are rigid tapping in a cnc, you can program the machine to dip itself in the oil before each hole. You may only get a few holes out of each tap! Price the job accordingly.
 
It will dull taps faster, but I find its not that bad going in. Its that reversing that has to break the chip before it comes back up that seems to want to jam up sometimes, its a pretty tough chip by then. Likely varies with the type of tap used. Figure it all out on some scrap piece before going for the real thing. Unless they're small low cost parts and you can scrap a few.
 
SND is right about the tap reversing. Thread milling is definately a good option. If the hole is blind, I would strongly encourage it. 1 thread mill = the cost of 3 taps, but you might get alot more holes out of it. The last thing you want to do is have to try and bottom taps by hand. If you have to mess with parts by hand you will piss away a ridiculous amount of time. If you do drill and tap, drill your minor out as much as you can get away with.
 
Thanks for all the good replies folks. Assuming we get the job we would be threadmilling all the other threads on this part as they are larger diameters, fine pitch, shallow etc.

I was worried about the depth of this thread, seems like pushing it for a such a small dia. threadmill. You don't think that would be a problem?

SND, if at all possible I will DEFINATELY be experimenting on a cutting first. I'm told the blanks for these parts are over £500 a piece, so I'd be pretty unpopular if I scrapped one...
 
Does your machine have helical interpolation? A solid carbide thread mill IS the answer if you can. Tapping a small hole is usually faster than a thread mill in most situations especially smaller holes, but inconel isn't most situations. It will wear a LOT better, you can control your pitch diameter much better, and if it's inconel, and you break a tap...it's a pricey boo-boo. Very easy to program- most tooling companies can offer you a "fill in the blanks" type of program that will spit out a simple program no problem. PM me, I may be able to help.
 
First crack at inconel 625

Unfortunately won a bid to make parts out of inconel 625. First time ever working with this. We're running a part that needs a .308 hex milled over 1.5 in and has a thru hole going from .170 diameter to .219 and is threaded .25 deep with a 1/4" 28 tap. Initially tried special tooling for inconel such as a coolant fed drill and a custom bb on back side and was recommended to use a micro100 thread bar instead of a tap by a sandvik tooling specialist. Thread bars were a nightmare. Seemed to weak, they would last a few cuts to a part and would snap. Finally went against his recommendations and peck tapped it like crazy 1 packs with spring passes in between and a 10 second pause in between packs. Finally started working great. I am also using an ejector pin to eject chips thru part in sub spindle between passes.
 
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