[Chriseg1]

I was curious to get peoples thought on this, We have a disagreement in the shop.

Should these be peck tapped, or finished in one shot? About 250 holes for each.

Machine is a TM1-P with rigid tapping

1st:
Vanadium Steel Spiral Point Tap for Aluminum 1/4"-20, H3 Pitch Dia, 3-Flute, 3.150" L O'all,
hole is 0.201" thru, 3/8" 6061.

2nd:
Vanadium Steel Spiral Point Tap for Aluminum 10-32, H3 Pitch Dia, 3-Flute, 2.76" L O'all
hole 0.159" thru 1/4" 6061

[Machineit]

I'd shoot them straight through!

Mike

[Delw]

roll tap them straight through especially on the 10-32

[Matt@RFR]

One shot. If you peck tap things like that, I'd like to bid against you!

[Chriseg1]

Just a bit more info, the tooling is what I have. And the whole peck tap thing is coming from the kid that designed the parts. He is telling me that the holes are deeper than the Dia. of the tap, so they have to be peck tapped.... ? this is what they taught him in school?

[underthetire]

I agree. Straight through, especially if its not a blind hole. Peck tapping is usually for hard materials.

[Machineit]

Just a bit more info, the tooling is what I have. And the whole peck tap thing is coming from the kid that designed the parts. He is telling me that the holes are deeper than the Dia. of the tap, so they have to be peck tapped.... ? this is what they taught him in school?

Ah yes, our great school system!

[KenFoulks]

Straight Through.

Make sure you have:
Good coolant concentration
Good coolant flow
Good drilled hole size

[Machineit]

Please remember the following too:

My version of Machinery's Handbook is #23. Starting on page #1654 there is a chart of "Recommended Hole Size Limits Before Tapping Unified Threads"

It has them listed by Classes, 1B-2B and class 3B. 1B and 2B are in one column and 3B is under another column. The hole sizes are listed in four depths each, To and including 1/3 D, above 1/3 D to 2/3 D, 2/3 to 1 1/2D, and 1 1/2 to 3D. D=the tap size, such as 1/4 inch.

I'll list an example below of class 3B thread holes:

-----------To 1/3 D,--------above 1/3 to 2/3 D-------2/3 to 1 1/2D,-----1 1/2 to 3D
-
-------------Min Max-------------Min Max--------------Mini Max---------Min Max

1/4-20-----.1960 .2013---------.1986 .2040 --------.2013 .2067-------.2040 .2094

As you can see a 1/4-20 tap run in only .400 deep can use a .2094 hole and still be a legal class 3B. It is much easier to tap too.

Using the largest hole possible and also within class limits will make the job a lot easier. This is especially important in tough to tap materials and small taps. We did a lot of 4-40's in excess of .450 deep in stainless and going to the larger hole size saved a bunch of broke taps. Just 1 or 2 thousands makes a tremendous difference in ease of tapping since the root of the tap on a 1/4-20 is larger than .201 inch.

Most of the machinists I have worked with didn't know this, they only used the standard chart for tapping. So every hole for a 1/4-20 was the #7 drill, no matter how deep it was. On your holes just going to .203 for the 1/4 inch tap really relieves the pressure on the tap and has no effect on the strength of the thread.

Mike

[azmachining]

Just give away some what of a trade secret, that's cool (sarcasm)...

[NWSERVICEGUY]

I have trained at many community colleges and must say that few of them actually understand CNC. They mostly teach manual machining with a term or two of CNC. My 17 yo son is wanting to get into the industry. He brought me a community college class schedule and I read through it and was not impressed. I got him a job at a very nice shop that will teach him more in 1 month than 2 years at a community college.

[haastec]

this is what they taught him in school?

Time to school him some more!

[underthetire]

Please remember the following too:

My version of Machinery's Handbook is #23. Starting on page #1654 there is a chart of "Recommended Hole Size Limits Before Tapping Unified Threads"

It has them listed by Classes, 1B-2B and class 3B. 1B and 2B are in one column and 3B is under another column. The hole sizes are listed in four depths each, To and including 1/3 D, above 1/3 D to 2/3 D, 2/3 to 1 1/2D, and 1 1/2 to 3D. D=the tap size, such as 1/4 inch.

I'll list an example below of class 3B thread holes:

-----------To 1/3 D,--------above 1/3 to 2/3 D-------2/3 to 1 1/2D,-----1 1/2 to 3D
-
-------------Min Max-------------Min Max--------------Mini Max---------Min Max

1/4-20-----.1960 .2013---------.1986 .2040 --------.2013 .2067-------.2040 .2094

As you can see a 1/4-20 tap run in only .400 deep can use a .2094 hole and still be a legal class 3B. It is much easier to tap too.

Using the largest hole possible and also within class limits will make the job a lot easier. This is especially important in tough to tap materials and small taps. We did a lot of 4-40's in excess of .450 deep in stainless and going to the larger hole size saved a bunch of broke taps. Just 1 or 2 thousands makes a tremendous difference in ease of tapping since the root of the tap on a 1/4-20 is larger than .201 inch.

Most of the machinists I have worked with didn't know this, they only used the standard chart for tapping. So every hole for a 1/4-20 was the #7 drill, no matter how deep it was. On your holes just going to .203 for the 1/4 inch tap really relieves the pressure on the tap and has no effect on the strength of the thread.

Mike

Geez, you must be as old as I am, with #23 book
And keep in mind, there are a lot of advances in taps since the #23 book came out, so good reference, but you can get away with a lot more now.

[Machineit]

Geez, you must be as old as I am, with #23 book
And keep in mind, there are a lot of advances in taps since the #23 book came out, so good reference, but you can get away with a lot more now.

Yup, had that book for while, but it is only from 1988. I also have one that a friend gave me that belonged to her father who was in the Navy and it is from 1947. Funny thing is that it is exactly the same size.

yes, taps are better now, but not that much!!!! The bigger issue is the tapping fluids that are available now. Mandating the removal of certain chemicals has made most of them practically worthless.

I was tapping some stainless by hand a few weeks ago and using a good expensive tapping fluid and it seemed way too hard. So for grins I tried some WD-40 and it was easier. That's a real shame.

Some of the people here might remember having really good tapping fluid. I use to go to WESTEC in California for many years and Tap Magic always had their booth and gave away free samples if you did their little test by turning a tap in steel. Then the guy would put a drop of their tapping fluid on it and it was amazingly easy to turn then. Those days are gone.

Thanks EPA!

[underthetire]

Yup, had that book for while, but it is only from 1988. I also have one that a friend gave me that belonged to her father who was in the Navy and it is from 1947. Funny thing is that it is exactly the same size.

yes, taps are better now, but not that much!!!! The bigger issue is the tapping fluids that are available now. Mandating the removal of certain chemicals has made most of them practically worthless.

I was tapping some stainless by hand a few weeks ago and using a good expensive tapping fluid and it seemed way too hard. So for grins I tried some WD-40 and it was easier. That's a real shame.

Some of the people here might remember having really good tapping fluid. I use to go to WESTECH in California for many years and TapMatic always had their booth and gave away free samples if you did their little test by turning a tap in steel. Then the guy would put a drop of their tapping fluid on it and it was amazingly easy to turn then. Those days are gone.

Thanks EPA!

I remember getting those at Westec ! Remember Cooljet with the "go Deep" slogan? Damn political correctness. My book is from'86 so i might have one version older. We were just talking about some tapping paste we had in '87. No one can remember the name, but it was a green almost handcleaner like stuff. Worked great. I still have the old Moly-D i have to break out once in a while.

[Machineit]

I think it was 1,1,1-trichloroethylene that they took out. That ruined the fluids.

Mike

[Delw]

I remember getting those at Westec ! Remember Cooljet with the "go Deep" slogan? Damn political correctness. My book is from'86 so i might have one version older. We were just talking about some tapping paste we had in '87. No one can remember the name, but it was a green almost handcleaner like stuff. Worked great. I still have the old Moly-D i have to break out once in a while.

I remember that green stuff, that was some kick ass tapping fluid. we used it alot in inco's and other nickles.
there was another tapping compound that was in a little bottle back then also. I think it was from hangstafers, I got like 15 bottles of that stuff and finished my last 1 2 years ago.

have you ever tried straight concentrated coolant? I have in a pinch and it works pretty well, even tried the slim off the side of the fadal ( thats gooey crap) thats works too when its like wax.

I think it was 1,1,1-trichloroethylene that they took out. That ruined the fluids.

Mike

Mike, thichloroethylene was a good chemical in alot of products, problem was it was a major safety hazzard. if thats the stuff I am thinking we used to use it to clean ways on machines before we applied turcite. that stuff cleaned everything with out any residue.

Delw

[Machineit]

I remember that green stuff, that was some kick ass tapping fluid. we used it alot in inco's and other nickles.
there was another tapping compound that was in a little bottle back then also. I think it was from hangstafers, I got like 15 bottles of that stuff and finished my last 1 2 years ago.

have you ever tried straight concentrated coolant? I have in a pinch and it works pretty well, even tried the slim off the side of the fadal ( thats gooey crap) thats works too when its like wax.



Mike, thichloroethylene was a good chemical in alot of products, problem was it was a major safety hazzard. if thats the stuff I am thinking we used to use it to clean ways on machines before we applied turcite. that stuff cleaned everything with out any residue.

Delw

Ya, it is supposed to be a carcinogen. We used to have a big tank for cleaning parts at a place I worked at in California. It was about 300 gallons or more and had a refrigerated ring in the tank about half way up. The vapors would not go about that level. Was super for degreasing parts.

Everything is harmful in some way, you just need to use care in working with it. When I went to osha/epa school in California, even water was considered a hazardous substance.

The more we try to protect everyone from everything, the more the people are careless with everything.

No winning!

[Machineit]

Just for laughs I dug out the old Machinery's Handbook. Turns out it was from 1943 not 47.

This should give you a laugh. Under tapping it had a chart for, "Effect of Lubricants and Tap Hole Diameters When Tapping."

They list the power needed to tap without lubricant and with 6 tapping fluids, which I will list below:

Animal Lard Oil

Sperm Oil

Graphite 10%, Tallow 90% combination

Cataract Soap Compound

Mineral Lard Oil

Machine Oil



I guess we don't have it so bad after all!!!!

Oh, and the winner was Animal Lard Oil with Sperm Oil right behind it. Funny thing also, the big looser was Machine Oil, it was worse than dry tapping.

Mike

[Chriseg1]

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