Thread Mills

[Big B Sprint88]

I am trying to threadmill 1/4-20 threads in 304SS. .400 deep. Do you guys recomend starting at top and going down or start at the bottom and mill up? I generally have more luck starting at the bottom of the hole and climb milling out, but I have never done anything this small. Any suggestions?

[robk]

Why thread milling something that small? Tapping is much quicker with shorter code for that size... Yet if you have to, definitely start on bottom and work your way up.

[Toolfab]

Bottom up, counterclockwise, absolutly.

 

Are you using a solid thread mill or an indexable one?

[Tim Johnson]

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Are you using a solid thread mill or an indexable one?

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Are there indexable 1/4-20 thread mills? If so could you tell me where to find them?

[Keith Graydon]

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If so could you tell me where to find them?

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Ka-Ching! another sale for Paul!

[Toolfab]

I dont know anything about indexable thread mills, that is why I asked. We make solid carbide ones, so I didnt want to give any info that wasnt accurate.

 

@ Keith

[Big B Sprint88]

the reason for threadmilling is that i am pushing the envelope for the number of good threads needed compared to the depth of hole that i can drill. i am also talking about 160000 holes that need to be done and i feel much better about thread milling this project. I did try taps with verry little lead, but i was constantly breaking them and really diddnt get deep enough anyway. I am using a solid carbide mill. thanks for your help!!

[g huns]

I have had great luck w/ solid carbide thread mills (TiALN coated) even in 56 RC S-7 tool steel. We always start at the bottom and go up. I would love to try #10-32 threads but the cutter costs about double what the 20 tpi one does. We always have lots of hardened steel laying around from the wire burner and it's way cool to be able to get threaded holes in them to make something useful.

[Threept82]

Always climb.

Bottom up.

[McRae]

Hole size is important. I always use a next nominal larger of on the tap drill chart for stainless - nobody is going to miss that 0.0075" off the crest of the thread that is now radial clearance that I am giving myself (except for those pesky #0-80 holes...)

[Shawn Wentzel- Wenteq Inc]

On external threads is it better to start from the top or the bottom?

[jeff]

External threads I don't think it matters,since there would be no problems with chips.

[Shawn Wentzel- Wenteq Inc]

So chips are the only problem?

[M. Anderson]

Big B Sprint88,

 

Just a thought - but for 1/4-20 - have you tried or thought about roll forming the threads?

 

We do this quite often with 304ss. We mostly use OSG's but have used some Greenfield's. Usually get 200+ holes on one tap - but that is about the extent of our runs, so don't know how long one tap would really last?

 

Oh-yea, run very High coolant concentration levels, (double normal) this makes a very big difference with the SS stuf!!!

 

HTH's

 

Later,

 

Mark

[Guest CNC Apps Guy 1]

Bottom Up, if you want to tap, Peck Tapping is the only way to go. :twothumbsup:

[crazy^millman]

Yep I would Roll from it and look at a Carbide drill for the holes problay chaning it ever 1000 to 2000 holes or so depedning on what my pin gauges and finish looked like might get 5000 holes just depends. The hole is the key for roll forming and can hit class 3 tolerance with no problem if done right again the holes is the key. If threadmilling is you final decision get a air blast to help flush as well as the coolant.

 

HTH

[Fig sign]

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Peck Tapping is the only way to go. :twothumbsup:

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For peck taping you must have rigid taping option available :wingsspread: