Tapping Machines

[NormBourne]

I'm aware of quite a few designs and suggestions for building tapping machines, but unfortunately there doesn't seem to be much detail on the holding arrangement for taps.

Taps mount into tap wrenches which are manufactured to engage on the four sides at the end of the tap.

Using normal chucks there is always a problem in getting them tight enough to preventing them turning within the chuck.

So lads, does anyone have any thoughts or any ideas on the construction of a chuck which will engage the tap securely....?

Thanks,

Norm.

 

[mzayd3]

The squares on the end of the taps are standard for each size. Perhaps you could find a commercially made adapter and incorporate that into your design.

 

[Eddyde]

The chuck on my tapping heads has rubber cushioned jaws. Goole search "jacobs rubber flex tap collet" for more info.

 

[Wreck™Wreck]

If you have many parts to do buy a used tapping head that can be used in a drill press, mill or lathe, they are geared and will reverse direction without stopping and reversing the spindle.



Taps are difficult to hold in a drill chuck because they are hardened the entire length, twist drills are not very hard at the shank which makes them easier to hold. If you want to machine tap on the cheap, machine a mild steel tap holder with the largest diameter shank that your drill chuck will hold, drill and ream a hole in one end the size of the tap shank then drill and tap a cross hole where the flat will be, install tap and tighten set screw, you will need to make one for each size of tap.

Prepare to break taps.

As a side note, if the hole that you are tapping does not have a thread fit tolerance call out and is not holding the wings on a passenger plane look at the thread spec's and drill the hole at the upper Minor Diameter size, this makes a world of difference in the amount of torque that tapping requires.

I drilled and tapped about 60-70 holes this week, made the parts in a CNC lathe and tapped them in a small Hardinge Turret Lathe because the Bridgeport CNC lathe does not have a rigid tapping cycle, none of the parts had a thread class call out on the drawings.

 

[NormBourne]

Thanks Fellahs,

It's not that I have plenty of holes to tap, for me the problem has always been, tapping square, which happens regularly.
That's not to say that a project which does require a lot of tapping, won't come up. In any case the advice from you guys is invaluable and it will certainly save me a lot of grief in the future.

Thanks again lads,

Norm.

 

[randyc]

Perhaps this little tip might help. I modified a tap wrench that holds taps up to 3/8 (most of my tapping work is less than 1/2). The following photo isn't all that clear but the modification involves removing the handle and milling three equally spaced flats on the shank.

This allows the tap wrench to be gripped tightly in a 1/2 or 5/8 Jacobs-style drill chuck without slipping.



The following tool is also useful when using the modified tap wrench. At left is an aluminum collar with three tapped holes around the perimeter. The ID of the collar fits over the 5/8 drill chuck in a floor drill press. The three tapped holes are aligned with the holes in the drill chuck normally used by the chuck key.

Three steel rods with external threads screw into the collar. The rods are turned at the ends so that they snugly fit into the chuck key holes in the 5/8 chuck. The rods are backed off while the collar is slipped over the drill chuck and aligned. Threading the rods into the drill chuck holes secures the collar.

For safety the drive belt MUST be removed from the drill press, after which the tap can be lowered to the work and even large holes tapped using the long handles to turn the drill press chuck.

 

[drom68]

Hey Norm,
There are a couple ways to ensure your are square when tapping. These doesn't answer your question of constructing a chuck to hold a tap securely. I try to not hold them too securely as the tap will break much easier when under power.
- When using the chuck, use a slow speed and stop when the tap starts to slip. Keeping the tap in workpiece, remove the chuck. Usually the tap has a great start and is square, switch to hand mode.
- Use a spring loaded tapping pin that you mount in the chuck and it puts pressure on the center of the tap to ensure you are square.
- Turn a rod to a point and use the quill to put a little pressure when you first start out. Once you have a few threads you can free hand
- I have used a piece of drill rod (faced the end) in the chuck to put a little pressure on the tap and then eased up once the tap had a few threads.
- Practice lining up the tap to a vertical object a few feet/meters or more away, make sure you have a two objects 90 degrees. Start slowly and keep looking to ensure you are straight. I have used this a lot and it works well. I have a door frame 3 meters away that I use to line up and I use a bracket on the wall that is at 90 degrees.
- Practice. Both power tapping and hand tapping. I use both.

 

[Bill C.]

I was going to add use a two flute or spiral two flute with a tapping head. Also get a couple of extra taps once they get dull they can break or crumble. Its been my experience trying to power tap with a drill chuck is trying to reverse direction without running out of travel on a knee mill. If you run out of travel you can either pull the part out of the vice or tear the thread out.

I also like a T handle with a spring loaded center.

 

[Smithdoor]

I just use a drill chuck in the mill or drill press
Just tighten the tap so the tap does slip most of time if you over tighten the tap may brake if you hit bottom
This works great for low number of tap hole
If you do a lot setup a taping head. I was taping 3/4 NF buy 1,000's . I setup drill press just for this work and cut the speed down with extra set belts and pulleys.
Today I just use a small milling machine with a set of pulleys for low speed for large tapes and just let the tap slip in the chuck. Note use a old chuck as there will be wear on the chuck jaws

Dave

 

[kingmt01]

I to am glad they slip in the chuck. Else I would break them. If they slip I go the rest of the way by hand. I usually have to remove a tap at least once to clear chips so there is room for more. That is usually what causes my taps to stall.