Tapping a 6-32UN hole

Tapped a single 6-32UN hole. The real issue was how to hold a large odd shaped part and locate, drill hole, and tap the 6-32 hole. My solution was to use the same fixture made to hold the part horizontally on the mill, to be held vertically in the 6 inch vise on the mill. One of the problems with this was the tapped hole goes thru one of the three 3/8" holes used with Mite-bite XYZ expansion pins that hold the part. I used a small Sherline mill hold down clamp to replace one of the XYZ pins. Also used 2-4-6 blocks to beef up the jaws on the 6 inch mill vise. The other issue was with this setup had very limited Z height with holding the tap and drilling the holes. I wound up using a 6-32 Balax form tap in a Starrett 93A T tap handle with a Fisher micro tap guide. I normally hold the Fisher micro tap guide in a 1/2" TTS end mill holder however that was too tall to fit the limited Z height available. Even using a 1/2" R8 collet didn't clear up enough Z height. I solved this issue by machining a 3/4" low profile 1/2" holder which allowed the Fisher micro tap guide to fit up inside the holder and free up Z height.

Don

Using an edge finder held in a TTS ER 20 holder to locate the center using a 3/8" dowel pin
Attachment 421120

Spot Drill
Attachment 421122

1/8" parabolic flute drill held in a TTS ER 20 holder
Attachment 421124

partial depth hole using #27 drill for clearance
Attachment 421126

6-32 form tap held in T tap handle with micro tap guide
Attachment 421128

Modified 3/4" tool holder with micro tap guide
Attachment 421130

Have you tried thread milling? I've found that it works super great!
The Fusion 360 Thread program generates fine tool paths, once you tune it in.
The two things to pay most attention to is setting the "diameter offset" to the same value as your thread pitch (for standard threads,) and turning on "lead to center" in the linking settings.

Micro 100 has some reasonably affordable single point thread mills. The 100 tool might be about right for 1/8" clearance #6 threads? https://amzn.to/2KdHZx8 Or the 120 tool (TM-120-8) I've used their 180 tool for M6, and their 250 tool for M10 threads. I've also used a Sandvik Coromant M2.5 thread mill, which has multiple teeth and thus can only do exactly 0.45mm pitch, but it cuts nicely, with no special preparation, cooling, or holding solution needed. Tool pressure is quite minimal, too.

Yes, thread mills are more expensive than taps, but I haven't had one thread mill break yet, and if it does, it's smaller than the clearance hole and thus just falls out without ruining the part.

I'm a convert, and big fan :-)

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Originally Posted by jwatte

Have you tried thread milling? I've found that it works super great!
The Fusion 360 Thread program generates fine tool paths, once you tune it in.
The two things to pay most attention to is setting the "diameter offset" to the same value as your thread pitch (for standard threads,) and turning on "lead to center" in the linking settings.

Micro 100 has some reasonably affordable single point thread mills. The 100 tool might be about right for 1/8" clearance #6 threads? https://amzn.to/2KdHZx8 Or the 120 tool (TM-120-8) I've used their 180 tool for M6, and their 250 tool for M10 threads. I've also used a Sandvik Coromant M2.5 thread mill, which has multiple teeth and thus can only do exactly 0.45mm pitch, but it cuts nicely, with no special preparation, cooling, or holding solution needed. Tool pressure is quite minimal, too.

Yes, thread mills are more expensive than taps, but I haven't had one thread mill break yet, and if it does, it's smaller than the clearance hole and thus just falls out without ruining the part.

I'm a convert, and big fan :-)

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Yep I thread mill on threads greater than 1/4 or M6. For aluminum and smaller threads like 4-40 I find Balax form tap in a Procunier tapping head works extremely well for me. Not only are the threads forged and thus stronger there is no chips to deal with. Unfortunately in this case I didn't have the headroom to use the Procunier. BTW I converted a 3/4" SS Vardex insert thread milling tool to TTS.

Don
Attachment 421138

Attachment 421140

Tapping on the 1100 is an absolute piece of cake. I’ve done threads as small as 2-56 on my machine. Heck with that hand tapping crap.

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Originally Posted by Steve Seebold

Tapping on the 1100 is an absolute piece of cake. I’ve done threads as small as 2-56 on my machine. Heck with that hand tapping crap.

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I do it all the time with my Procunier tapping head with the 1100. I have tapped 10s of thousands of blind 4-40 holes really fast with the Procunier tapping head on the 1100 and lots of 2-56 blind holes too. However if one actually bothered read my post I had no Z -axis head room for the Procunier tapping head and hand tapping worked very well in this case particularly since it was only one 6-32 hole.

Don

I didn't have to read your post to understand that :). Both types of T.C. units that Tormach sells will not work either from what I was seeing, and a Procunier head is even bigger. I like the collar on your single pass multi point threading tool. Been thinking about buying a couple 3/4 inch shank 1 to 4 insert endmills and put collars on them. Tormach's Sheer hog system is priced a little rich for me. I also use a spring loaded tap guide mounted in a TTS Holder. Tapping tough materials and only a few holes, imho there will be far less drama and pucker factor involved.

If you have, and can fit, a Procunier, it's a great option, especially if the tapping isn't part of an elaborate multi-tool-change flow.
My point is that a thread mill gives you more vertical space, and doesn't need any customer workholding (ER20 works fine!)
(Also, mine is a 440, so I can't even reverse the spindle, which also limits my options ...)

I use the ER16 T/C tapping head. I’ve developed a problem that allows me to tap holes as small as 2-56 on my 1100 and the T/C tapping head takes up a lot less room than the Procunier tapping head.

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Originally Posted by Steve Seebold

I’ve developed a problem ..

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Is this something you'd like to talk about???

Sorry, I just couldn't resist :)
Step

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Originally Posted by mountaindew

I also use a spring loaded tap guide mounted in a TTS Holder. Tapping tough materials and only a few holes, imho there will be far less drama and pucker factor involved.

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Exactly. That's what I just did tapping a 4-40 hole in a SS part. Had plenty of head room this time but since this is a one off part and difficult SS material I used the Fisher micro tap guide in a TTS 1/2" holder with Starrett 93A T-handle tap holder to hand tap. Brought out my special ingredient for tapping SS (in addition to a new Brubaker 4-40 cutting tap) the Old Tap Magic with 1,1,1-trichloroethane. I use my Tormach for both prototyping and limited production. With the shuttle jog controller prototyping on the Tormach is just like using a manual mill with hand wheels. And if I have a one off part that is quickly made by hand tapping that's what I do. BTW I only use the old Tap Magic using plenty of ventilation i.e. shop door open.

Don


This is the view yesterday from in front of my Tormach with the shop doors opened. BTW it snowed last week. This week perfect.
Attachment 421314


Special Tapping ingredient for SS
Attachment 421312

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Originally Posted by Don Clement

Exactly. That's what I just did tapping a 4-40 hole in a SS part. Had plenty of head room this time but since this is a one off part and difficult SS material I used the Fisher micro tap guide in a TTS 1/2" holder with Starrett 93A T-handle tap holder to hand tap. Brought out my special ingredient for tapping SS (in addition to a new Brubaker 4-40 cutting tap) the Old Tap Magic with 1,1,1-trichloroethane. I use my Tormach for both prototyping and limited production. With the shuttle jog controller prototyping on the Tormach is just like using a manual mill with hand wheels. And if I have a one off part that is quickly made by hand tapping that's what I do. BTW I only use the old Tap Magic using plenty of ventilation i.e. shop door open.

Don




This is the view yesterday from in front of my Tormach with the shop doors opened. BTW it snowed last week. This week perfect.
https://www.cnczone.com/forums/attac...d=421314&stc=1


Special Tapping ingredient for SS
https://www.cnczone.com/forums/attac...d=421312&stc=1

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The old formula tap magic brings back many memories, in the late 60's early 70's thdey wouldnt let us have it in the dairy any longer, this was the best SS tapping fluid ever!

Edit: I looked it up on Wikipedia and one of its uses is as a solvent for circuit board resist, I may have about a half gallon of that stuff still left over from my circuit board days, I'll have to check that out..............

Set the WAYBAC to the 1980's when Westec was held every year in DTLA at the convention center with the gigantic night sky star map inlaid on the ground floor. Tap Magic had a demo where one could try one's one hand using Tap Magic for themselves by hand tapping in SS before use and after. (must have been before CARB). The effect of using Tap Magic in the demo sold me. This is when Tap Magic include 1,1,1-trichloroethane. I have a gallon of reagent-grade 1,1,1-trichloroethane and think I will use that when my supply of Tap Magic runs out try using that. BTW I was told this story about a machinist who keep a small bottle with eye dropper of 1,1,2,2-Tetrachloroethane and would put on a drop when tapping really difficult materials. I would use a respirator under a hood using that stuff.



Don