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Need some help with rigid tapping again. sorry.

Solar71

Titanium
Joined
Mar 24, 2005
Location
Hermosa Beach California
Hey guys.
We are running some SS parts.
12 holes each, Rigid tapped.
10-24 .75 deep.

We are spoting then drilling 0.158 diameter.
We are drilling to about 1.0 inch.

This is mystery stainless BTW. So im going to assume 304.
Tapping at about 300 rpm.
Breaking taps left and right.

We tap to .375 once all the way around. Then tap again to .75
When we tap to .75 the taps are breaking.

So i wanted to try a peck tap cycle. But i cant find one in our machines manual.
We have peck drilling. just no peck tapping. Thats why i tap to .375 all the way around the B.c then again to .75.

I have done this before without any problems. But today we broke 3 taps already.

Can someone help ?

What is the normal peck tapping cycle ? Maybe i can find it.

We use tapping fluid and all that.

Im at a loss. please someone.
 
This is mystery stainless BTW.

I don't mean to be an uptight you-know-what, but why would you do that? If it's customer-supplied, you sort of have to know what he gave you to know how to cut it. If you're sourcing it, I should think you need to conform to the print first of all, but if the drawing just says "SS," then revert to #1 above, you need to know what it is to cut it correctly.

OK, stepping off the soapbox now :rolleyes5: ...

I'm assuming these are blind. What kind of tap are you using? If it's not spiral flute then surely the chips are packing in the bottom and preventing the tap from getting down the requisite 3/4".

Regards.

Mike
 
I had hell with peck tapping until I finally (duh!) figured out that I needed to put an M19 spindle orientation for every hole and step. No more broken taps and I have done some stupid deep holes doing this now.
 
Thank you both.

Yes these are all 100% blind holes.
When i execute the G93 (rigid tap mode) the spindle turns to orient automaticly.
Yes these are spiral flute taps for bottoming (flat bottom, not pointy)

These parts we make are for/from us. Its our product, so we supply the material.
These are just SS rems we had laying around. So its SS but thats all we know.
The prints only call for SS. So there you have it.

PS : This is non magnetic SS.
 
Yes these are spiral flute taps for bottoming (flat bottom, not pointy)

You're running the entire 3/4" with a bottoming tap? That's the problem IMO. The chipload is much higher with the bottoming tap since there's only ~2 pitches of taper, and I bet you're getting chipping at the tips, especially with spiral flute which are extra-fragile at the tips.

Since you're drilling to 1" and tapping to 3/4", I don't think you need a bottoming tap. Use plug, and you should have plenty of clearance at the bottom to still get 3/4" of full thread.

Regards.

Mike
 
The downtime you've experienced this morning would have paid for a couple good form taps. After switching from spiral flute to form taps in 304 (on the advice of the guys here), I'll never run anything else except thread milling.
 
Solar,
I suppose you know that when you break a tap, you never run a new one down a hole that was threaded by the previous tap, due to cross threading. Or if the tap happened to creep in the collet a little bit, it could be significantly out of phase by the time the tap has done 12 holes. For this reason, I'd tap the one hole repeatedly until it was done before I'd move on to the next.
Repeat tapping is no more than calling for:
G84 Z-0.375
G84 Z-0.75
G80

Of course, the controller needs to orient correctly before each poke at the hole.

Spiral flute taps are quite fragile and can chip very easily. Not all tapping fluids are up to the task and the wrong one will cause early tap failure due to chipping of the teeth. As soon as even one tooth is chipped, the tap must work extremely hard to cut the thread.
 
From my expereince - if it is 304 your choices are Form Tap or Broken Tap. Of course there are many on here that don't mind dipping every hole in goop, and you could doo that a WHOLE lot quicker than breaking them!

If 303 and you have that much room, you could prolly try a spiral POINT tap. Doo you need 3/4" full threads, or are you running your tap point to 3/4"? If tip to 3/4 a sprial POINT should werk fine in 303.

Not sure what the defenition of a "plug" means in the previous post? A SP PT is based on the plug chassis, but then so is the "hand" tap. And those would plug up with chips and break on this hole I would think. I [next to] never use a hand tap, and even less likely in a machine app.


-----------

Think Snow Eh!
Ox
 
I don't mean to be an uptight you-know-what, but why would you do that? If it's customer-supplied, you sort of have to know what he gave you to know how to cut it. If you're sourcing it, I should think you need to conform to the print first of all, but if the drawing just says "SS," then revert to #1 above, you need to know what it is to cut it correctly.

You must not read many of Solar's posts, and the kinds of things he has to put up with at his "shop."

;)
 
If it's your own product, why the hell are you tapping a 10-24 .75" deep??

A spec like that usually comes from some dufuss desk-jockey engineer at a customer, not one in your own company!

1.5 to 2 diameters deep is the standard tapping depth in industry...or at least it should be.

So, about .375" deep is more than enough for a 10-24.
 
Solar's shop make replacement parts for machinery. So, it might be a copy of someone else design, or something to fit someone else equipment.

+1 on the form taps.
Also Solar, do you have the M29 in there?
I don't think you want to tap a bunch of holes, and then come back to start over going in deeper. Tap each hole to the bottom and move to the next.
 
Solar, forgot to ask this one earlier. I know your boss is so cheap that you are probably having to use the old way oil and rainwater for coolant, but is your coolant mix good? I have seen some stuff that works great on aluminum but don't even think about stainless (liquid ice). Have you checked your concentration? When I have to do a bunch of stainless I normally take mine to the high side of the mix.
 








 
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