Tapping Small Holes

When tapping small holes, breakage invariably occurs because of flexing the tap sideways causing it to jam (well for clumsy me it does).

I now do all my small holes with the rig below using a cheap 1/4" pin chuck as a drive.



I slip a 1/4" socket spanner over the hex shank (because I actually need a round shank) - hold this lightly with the drill chuck I just used to drill the pilot hole (so its bang on aligned) - release the chuck slightly - its now free to turn and float but impossible to bend.

Using only finger power (I did say this was for small taps) you get a good feel for the applied torque.

Haven't busted a tap since.

Ken

That's a good method. I use a similar method, but found that with a small Sherline mill, with a rotory table under the part, I don't have enough room to use a drill chuck. So, I made a handle that mounts directly to the tap and I use the tap itself in the mill chuck as a guide. Small stuff is fun, but sometime it's a pain. Tapping 2-56 in the photograph.

I have been using Balax Thredfloer forming taps, including down to 1-72, and find them much better than the conventional cutting taps. You must be careful to match the drilled hole perfectly to the tap size, adjusting the hole size to the hardness of the workpiece. Takes a little practice, but no more backing up every 1/4 turn. Try em.

Russel said:

That's a good method. I use a similar method, but found that with a small Sherline mill, with a rotory table under the part, I don't have enough room to use a drill chuck. So, I made a handle that mounts directly to the tap and I use the tap itself in the mill chuck as a guide. Small stuff is fun, but sometime it's a pain. Tapping 2-56 in the photograph.

Click to expand...

nice one. Copying you. How do you secure the knurled wheel on the tap? brass tipped set screw?

take care,
tom in MA

My take on the subject...

http://www.homemodelenginemachinist.com/index.php?topic=464.msg2829#msg2829

Hi Marv,

I followed your link to see the small tap guides you've made. Nice work. Are the collets you mention more like bushings with a flat to allow the clamp screw to contact the tap shank?

Regards,

Chuck

kuhncw said:

I followed your link to see the small tap guides you've made. Nice work. Are the collets you mention more like bushings with a flat to allow the clamp screw to contact the tap shank?

Click to expand...

Yes, exactly. I chose that approach, rather than a true collet, because I assumed that there wouldn't be much standardization of tap shank sizes and I would need to make a bunch of them so the simplest design was in order. As it turns out, I was correct - I have a whole pillbox full of vari-sized bushings.

Thanks, Marv. I have a piloted tap wrench that I bought, but I'm getting tired of changing taps all the time. I believe I'll copy your idea and make several.

Regards,

Chuck

Marv, love your tools - mental note for future.

My post was simply about using stuff to hand that might not be imediately apparent.

Regards,
Ken

I have one of those cheap chucks,and I wouldn't trust it to drill a straight hole,let alone tap a thread with any kind of precision.
I lucked into an old drill stand,and converted this into a tapping stand.It uses a chuck of a similar size,but a quality old english type.Never broken a tap since,even M2.

Russel said:

That's a good method. I use a similar method, but found that with a small Sherline mill, with a rotory table under the part, I don't have enough room to use a drill chuck. So, I made a handle that mounts directly to the tap and I use the tap itself in the mill chuck as a guide. Small stuff is fun, but sometime it's a pain. Tapping 2-56 in the photograph.

Click to expand...

ttrikalin said:

nice one. Copying you. How do you secure the knurled wheel on the tap? brass tipped set screw?

Click to expand...

The thumbwheel is secured to the tap using a steel set screw. The tap is quite hard and the set screw doesn't need to be very tight to be secure, so the set screw doesn't mark the tap.

Sorry I took so long to reply!

Ken I, I hope you don't mind that I add a little more to this thread. I don't really think my addition merits starting a new thread, so I tacked it on to this one.

In the second post of this tread I posted a photo of a simple tap driver that I made to help tap a bunch of 2-56 holes. I recently needed to tap a bunch of 10-24 and 10-36 holes (very common with Sherline machining equipment) and made a couple more tap drivers. This time I figured that I would take the time to learn how to make spokes with my rotary table.

First here is a photo to illustrate the limited room when using the Z axis of a Sherline mill as a guide. Note: the drill chuck is not tighten on the tap, it is simply close, acting as a guide. When working with a rotary table instead of a milling vice, there is even less space. That is why I've made tap handles (or drivers) that don't require any additional space above the tap.



Here is a closer shot, using the first tap handle I made with spokes to tap the set screw threads on the second one.


A photo of the tap handles, the four spoked one is my first attempt at spokes and came out a little crude. The one on the left is after applying the gray matter between my ears a little more.


And a couple photos of the better looking tap handle with a 10-32 tap in it.




It took me a little time to figure out the geometry for machining the spokes. I was surprised after I got it figured out how simple it really is. Also, I've got to credit Google for providing Google Sketchup free, which I used to calculate the angles needed for the machining.

Pretty nice!
I use the same concept but not near as pretty.

Agree, very pretty.

I'm definately going to copy that idea but mine will be a knurled blank without the pretty "flywheel" holes.

Thanks for sharing.

Ken