Large Tapped Holes

[TF Leeson]

I have some M20x2.5 holes that need tapped in 2 inch 1018 plate. I've never tapped anything close to this big before in a machine. What sort of rpm should I be looking at to do something like this. Any info helps.

 

Thanks, Jeff

 

[Guest]

Horsepower on that size tap is going to be the key.....

 

That is something I would consider threadmilling

 

I tapped M36 holes 2.25 deep....roll formed them on an old Matsurra 760 gearhead

[jlw™]

If it's not a fitty taper I would only start it. I always start them 1xD deep in the 40 tapers and sometimes just start them in the 50 tapers depending on the job.

 

RPM will depend on the tap and material. However, 24sf is my default number.

[TF Leeson]

50 taper 30 horse spindle. I will start at 24Sf and see what happens. Thanks, jeff

[JAMMAN]

I'm going to second the threadmill suggestion.

[jlw™]

50 taper 30hp I'd tap all day. That's just my 2 cents tho.

[JAMMAN]

Tapping is faster always. But also a host of extra things to go wrong.

[jlw™]

Totally agree. Threadmilling has more to go wrong in my opinion but is infinitely more forgiving.

 

 

I honestly weigh a lot of factors before deciding on tapping or threadmilling. Tapping is definitely faster.

[crazy^millman]

Totally agree. Threadmilling has more to go wrong in my opinion but is infinitely more forgiving.

 

 

I honestly weigh a lot of factors before deciding on tapping or threadmilling. Tapping is definitely faster.

 

Think you meant Tapping there sir. :whistle:

[jlw™]

typo shmypo, you owed me that one!

[Guest]

and on a tap that size and depth, 1 broken tap will throw all your speed out the window....

 

If you're using a cutting tap, I am of the opinion you better be peck tapping. That's too far a distance and too many chips 

 

There are many factors to weigh

[Matthew Hajicek - Singularity]

How many holes?  How tight is the tolerance, and what's the surface finish requirement?

[GoetzInd]

I would thread mill that. Coupled with a pre-setter (allows you to set off the pitch) thread milling basically takes any risk out of the equation.

 

Mike

[jeff]

I have some M20x2.5 holes that need tapped in 2 inch 1018 plate. I've never tapped anything close to this big before in a machine. What sort of rpm should I be looking at to do something like this. Any info helps.

 

Thanks, Jeff

M20 tap isn't that big for a 40 taper, and 1018 makes it even easier. I wouldn't try much larger though.

Get the right tap for the job, and run it 40-50sfpm. 

I do M20 and M24 in my 40 taper mills in 4150pht and 8620.  (1-1/2" thru holes)

[Reko]

Diverse opinions on this one because that size is right on the edge of feasibility for a 40 taper machine, but definitely doable.

 

For just a part or two, I'd threadmill it because I know I can do that without scrapping a part... for a higher quantity, I'd tap them with a good quality OSG Hy-Pro.

[TF Leeson]

M20 tap isn't that big for a 40 taper, and 1018 makes it even easier. I wouldn't try much larger though.

Get the right tap for the job, and run it 40-50sfpm. 

I do M20 and M24 in my 40 taper mills in 4150pht and 8620.  (1-1/2" thru holes)

Roll form of cut? and are you peck tapping the m20's?