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6-32 Roll tapping into Cast - Speed & Feed


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Hi guys,

 

Here's what we need. a 6-32 tapped hole thru cast 1/4" thick. Thread minor has to be .109 to .112. Hole is made with .125 carbide drill. The roll tap give a nice minor dia, but were eating thru the taps like no tomorrow. The operator has been going thru about 8 taps a shift. Originally the program had the tap rpm set to 1000 with a feed of 37.5. I thought that was way too fast. the first couple flutes on the tap would get burned up in no time. So i slowed the S&F down. But I dont think I slowed it down enough. Currently its set at S750 F23.4375. I was reading thru some of these forums and many people said that the max rpm for small dia tapping was around 200-250 rpm. If I need to slow the tap down to prolong its life, then I guess thats what i have to do. Only thing that will affect is longer cycle times. :(

 

What are your thoughts on this issue? Could I start with a smaller hole and use a plug tap? Is it the coolant? What variables am i missing?

 

Thanks,

 

Matt

post-48725-0-49186700-1375278936_thumb.jpg

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we tap 0-80 to 10-32 all the time in anything from alm to ti 6al-4v.

with the small taps i never go over 250 rpm and it usually runs pretty good.

for tap life look to coated taps.

and if you can try and open up the hole size.

with a form tap this can be a pain but doable i have some times reamed the hole to open it up a bit.

i think emuge has some new taps and coatings you might want to look at.

 

 

HTH Ken

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Cast 80/60, TiNc coated, coolant...have no idea, but ill look into it.

that is cast iron and mostly seems to be categorized as a ductile iron.

at 3% elongation i can't see how it would be considered ductile. headscratch

 

1st 6-32's are a tough combination for tap breakage.

2nd form tapping relies on the ductility of the material to form the minor diameter. a metal with only 3% elongation would be my last choice for form tapping. but if you are drilling oversize and it is forming correctly, who am i to argue..

 

try plug or starter rype cut tap to spread the wear over a larger area.

2 cents

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  • 2 weeks later...

Thread Mill a 6-32 hole! LMAO! Thanks for a good morning laugh!

 

Im going to try a plug tap on a smaller hole. These operators continue to break the roll taps. I changed the speed to 250. Seems to be lasting longer, but its the coolant that I feel is the issue. Training the guys to point the coolant line ON the hole to be tapped is common sense, but second shift just doesnt seem to care. I wonder if the coolant has anything to do with the lubricity of cutting as well... I gotta find out what kind of coolant and the concentration.

 

Thank You all for your input in this.

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you may want to have a mo so the operators can blow the chips out of the hole prior to tapping them , maybe there leaving crud in there and helping to kill the life of the tap ??? just a thought

HTH

 

That and maybe some Moly-D

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that is cast iron and mostly seems to be categorized as a ductile iron.

at 3% elongation i can't see how it would be considered ductile. headscratch

To form/roll tap you really want a minimum of 5% elongation, to get a 'good thread'.

You can get a 'good looking thread' at less than this, but it will usually be either a mall formed root, or even worse brittle so will fail way before it should...

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We are still having issues with this. I ended up changing from the TiN coated roll taps to TiAlN coated. In other words we bought the Widia Tin taps, and sent them out for TiAlN coating. The tap is lasting much longer. We used Oerlikon Balzers Futura Nano.

 

Question 1. Is it wrong to double coat a cutter? They said it was fine.

 

Question 2. I set the rpm of the tap to 250. Could that still be too fast/slow? opinions?

 

Question 3. What comments do you have about this? Heres the drill and tap prog.

 

T12M06(.120 DRILL STE#1139)

(4 HOLES )

T17M62

G00G40G17G80G90

G54.1P25X.4750Y-.365M08

G43H27Z2.030M03S6324

G90G98G73Z1.455R1.83Q.05F9.0

X-.475

X-3.2059

X-4.1559

X-6.8874

X-7.8374

X-10.5685

X-11.5185

G00Z2.690

X-11.5185Y-1.785

G90G98G73Z1.455R1.83Q.1F9.0

X-10.5685

X-7.8374

X-6.8874

X-4.1559

X-3.2059

X-.475

X.475

G00Z5.0

G80

M05

M09

G28G91Z0

M1(REMOVE CHIPS OFF DRILL)

 

T17M06(6-32 ROLL TAP STE#3006)

(RIGID TAP 4 HOLES)

T7M62

G00G40G17G80G90

G54.1P25X.4750Y-.365M08

G43H28Z1.950M03S250

M29S250

G99G84Z1.430F7.8125

X-.475

X-3.2059

X-4.1559

X-6.8874

X-7.8374

X-10.5685

X-11.5185

G80Z3.040

X-11.5185Y-1.785

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.04

X-10.5685

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.04

X-7.8374

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.04

X-6.8874

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.04

X-4.1559

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.040

X-3.2059

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.040

X-.475

Z1.950

M29S250

G99G84Z1.430F7.8125

G80Z3.040

X.475

Z1.950

M29S250

G99G84Z1.430F7.8125

G00G98Z5.0

G80

M28

M05

M09

G28G91Z0

 

(I hope I dont get yelled at for this and If I do, I WILL NOT post a prog again.)

 

Again, any help/opinions are appreciated.

 

Thanks.

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  • 3 weeks later...

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