Hand Tapping Tool?

[redjr]

Hi all,

I've been fairly successful with the construction aspect of my projects over the past several months. I do have a question to the seasoned veterans here about tapping a hole.

I mount all my PCB on 3mm brass stand-offs. I drill a 2.5mm hole and then manually tap a 3mm hole using the typical t-bar style tapping device. Most of the time I can get a pretty straight hole 90-degrees to the panel I'm tapping. Is there a better way to tap a hole to ensure it's precisely 90-degrees to the panel? Is there some sort of gig that you can use with a manual tap to ensure straight holes?

 

[harperrc]

taprite tool

i have an older version of this that works great
TAPRITE TAP GUIDE - Brownells

or these

http://www.littlemachineshop.com/pr....php?critFast=tapping+guide&B1=Product+Search

 

[DUG]

Block of aluminum with a hole in it.

 

[redjr]

Block of aluminum with a hole in it.

Great idea. Now to find that block of aluminum. I assume you would need to use clamps to secure the the block while tapping. Short of an industrial tooling machine used for tapping in a manufacturing environment, I guess the hobbyist is stuck with doing it the ole manual way.

 

[harperrc]

tapping guide

sorry i misread your post.
go to your local hobby shop and find some brass or aluminum tubing that
will just slip over the outside of the standoff and then cut to length to allow
you to start the tap.

remove the drill you use and replace with the tap and hand turn the chuck to tap

 

[redjr]

I'm not quite sure how this would work. How does the tubing stay in place so that your tap stays perpendicular? The tubing would need to be the size of the drilled hole not the standoff width.

Most of my manual taps work out pretty good, but every once in a while it starts out a little crooked, and an attempt to straighten it up often buggers up the threads. And when you're tapping thru 3-5mm thick panel, you don't have a lot to work with. I also often put a nut on the threads of the standoff once screwed into the panel for extra strength.

I haven't done any real tapping for 20+ yrs until recently, and was more curious if the method of tapping had been improved over the years, or if there were new techniques to use. Tapping has to be done slowly and with oil, so using a drill-press would be out of the question. Right?

PS. I just noticed your other link. I saw this gig on their website. Now this looks like it has some promise for a good perpendicular tap. Maybe it's been around for years. This looks like a perfect solution.

 

[nigelwright7557]

The trick is to drill straight in the first place using a drill press and hold the brass in a vice.

 

[Enzo]

Or simply buy already threaded standoffs. I make a product using standoffs of either brass or aluminum, and I just get them to length with threads already made. Or cut inner threaded tubing to length. McMaster-Carr for starters.


I liked DUG's block of aluminum. Heck, you could do it with a hunk of wood even. Drill a clearance hole for your tap diameter all the way through. Then from one end drill it out larger to fit the standoff stock, deep enough to handle the length of the piece being worked.. Slip the standoff into the wider side, then tap through from the other side, the hole in the block keeps it lined up. Block/slab pieces of aluminum are not hard to find. A local metal or steel company ought to have some, or a welding shop. A piece of scrap would be good enough.

And if you need to, make two holes, one for the drill that makes the hole, and a second to fit the tap.

 

[jackinnj]

Use a drill press -- ergo, i second the recommendation -- i wouldn't use the aluminum block as you want to see whether the tap is torking too much. It's time for the crying towel when you break a tap on a heat sink. I use some oil on the bit as it very much aids the process.

One summer in college i worked on an automated tapping machine in a die casting plant -- scared the daylights out of me so i requested that i go back to just driving a forklift! I did get a boat load of 6-32 taps in the process.

 

[nigelwright7557]

I use some oil on the bit as it very much aids the process.

You definitely need oil or cutting oil or the tap will grip the metal and break.

I learned the hard way after I broke 2 taps !

 

[redjr]

Thanks guys for all the responses. I've learned the hard way both with broken taps and using oil! Now I take it slow. I like the looks of the Hand Tapper here. I think this can go a long way towards 'straighter' taps. Does anyone have experience using this particular or similar tapping gig? It looks like it would still require clamps to tightly hold the material.

 

[natehansen66]

Thanks guys for all the responses. I've learned the hard way both with broken taps and using oil! Now I take it slow. I like the looks of the Hand Tapper here. I think this can go a long way towards 'straighter' taps. Does anyone have experience using this particular or similar tapping gig? It looks like it would still require clamps to tightly hold the material.

I've used those......they're pretty slick for hand-tapping. You do need some way of holding the work though. You could power tap with a drill press, but it would have to have a really slow speed and have reverse as well. Run the tap at the lowest speed in the work (plenty of oil!) then hit reverse when you're at depth. This is how it's done on a nicer drill press or a manual mill/lathe.

It's not a bad idea to chamfer the drilled hole before tapping, the tap is easier to start this way and it guides the tap into the work.

 

[redjr]

Speaking of drill presses...I'm about to invest in one, but I'm not sure it has a slow enough speed for tapping. It's slowest speed is 250 rpm. I've been drilling all my holes by hand, so realize it's time to step up. I don't need a big one, just a small..ish one for these types of light projects. It will make boring wider holes a lot cleaner and easier - not to mention making truly perpendicular holes in the material. For those curious, I'm looking at this one at Harbor Freight. Any thots?

 

[N Brock]

Does anyone have experience using this particular or similar tapping gig? It looks like it would still require clamps to tightly hold the material.

I've used something like this, they work pretty well, keep in mind you have a limited height though. The trick is you actually don't want to clamp the material down rigidly. The end of the tap is pointed to guide it toward the center of your drilled hole. If both the tap and workpiece are fixed and the tap isn't exactly in the center of your hole it will put horizontal forces on the tap (which is why they break). You only need to keep the workpiece from rotating when you turn the tap.

I've also used a clutched auto reversing taping head in a milling machine. It's a dream. Lets you tap 100+ holes/hr. For that you just hold the work piece on the mill table (yes, with your hand) and let the tap find the center of the hole. I wish I had one. It worked just like this http://www.youtube.com/watch?v=_CUGz0jXvWQ.

Best,
Nelson

 

[redjr]

I've used something like this, they work pretty well, keep in mind you have a limited height though. ...

You are right. The maximum height for this particular jig is 3.75". That should work for most all of what I plan to tap now and in the future.

 

[dchisholm]

I like the looks of the Hand Tapper here. I think this can go a long way towards 'straighter' taps.

That tool will work if the hole being tapped is already perpendicular to the surface the workpiece rests on. If the hole is NOT perpendicular, and you clamp everything rigid, you'll still break taps.

Use a drill press . . .

Yes - for BOTH the drilling, and the tapping, using the below procedure. Even the cheapest hobby version will work well if the quill and table are reasonably rigid with respect to each other. It's not even essential that the table is square to the spindle if you do it like this:

1. Mark and center punch the hole location. Secure the proper size tap drill in the drill press chuck.
2. Place the workpiece on the drill press table, align the drill point with the hole location.
   • Usually a good idea to clamp the workpiece, unless it is being held in a drill press vice, or large enough that manually holding it poses no safety hazard.
3. Drill the hole.
   • If you did NOT clamp the workpiece, AND you are paranoid about breaking taps, stop the quill rotation BEFORE withdrawing the drill from the hole, clamp the workpiece to the table, THEN withdraw the drill.
4. Remove the tap drill from the chuck.
5. Release the V-belt from the spindle drive pulley.
   • In most cases there is a lever-operated cam arrangement that releases belt tension when you change spindle speeds.
   • The spindle should rotate freely, without any motor drag.
   • Spinning the drill press motor should not turn the spindle.
6. Secure the tap in the drill press chuck.
7. If desired, apply tapping fluid or cutting oil to the tap and hole.
8. Lower the quill and align the point of the tap with the hole you just drilled.
   • If the workpiece is clamped, this is a "non-step": the hole is still aligned from when the drill made it.
   • If the workpiece is NOT clamped:
     • Place the workpiece in the same general position it had when it was drilled. I.e., don't rotate it, don't flip it over, etc.
     • Gently lower the quill until the tap touches the hole and allow the workpiece to float a little until the taper on the tap point aligns with the edges of the hole.
     • Last chance to clamp the workpiece, if you feel this is necessary
9. At this point the tap should be as close to coaxial with the hole as a mere mortal can achieve in a hobby workshop. (Yeah there's spindle runout, and table flexure, and probably other things that can't be measured with the instruments and skills at your disposal. Only the poor craftsman blames his tools.)
10. Use one hand on the quill advance wheel to maintain gentle to moderate pressure on the tap point. Use the other hand to manually turn the chuck, thus cutting a thread with the tap.
    • The chuck key can be used as a "handle" to turn the chuck if you can't supply enough torque with your hand grip
11. When you feel resistance to turning the chuck, reverse rotation for roughly a quarter turn to break the chip.
    • Depending on the size of the hole, type of material, cutting fluid, and condition of your taps this may not be necessary
12. After the tap has cut the first two threads or so, the alignment is fairly secure and you can remove the workpiece from this setup if it feels cumbersome.
    • While still maintaining the downward pressure, lock the quill advance
    • Loosen the chuck to release the tap
    • Unlock the quill advance and raise the quill
    • Unclamp the workpiece
    • Carefully engage the tap in a standard tap wrench
    • Complete the operation with the manual tap wrench

I don't claim that this procedure is fool-proof, because we fools can be VERY ingenious but it has worked well for me.

Shortcut: If you have several holes to tap, you can first drill all the holes then tap them individually without losing very much of this technique's effectiveness. The key is Step 8, above, where you return the workpiece to the same orientation it had when the hole was drilled, before starting the tap. If you pay attention to this detail it won't matter if the spindle and table aren't exactly perpendicular to each other. For that matter you could even tilt the table relative to the spindle if you needed to tap a hole at some crazy angle.

I use some oil on the bit as it very much aids the process.

I use turpentine - the genuine stuff, made from real pine sap, not the synthetic substitute imitations. (Ever notice that folks who make genuine butter never advertise that it "tastes as good as margarine"?) It seems to work especially well with mild steel - I have almost no experience with brass. It takes a little practice to get the feel of turning the tap forward until you feel it just start to bind a little, then backing off a quarter turn or so to break off the chip down at the cutting edge.

An old machinist showed me this trick decades ago. I have sometimes wondered why it works, since turpentine is quite volatile (and flammable - take appropriate precautions!), low surface tension, and doesn't feel the least bit oily or slick. The best theory I have is that it has a tiny bit of resin dissolved in it, and the liquid flows into the tiniest gap, right to the cutting edge of the tap. At that point the heat of the cutting action vaporizes the liquid, leaving the resin behind as a solid lubricant.

Dale

p.s. It might be possible to trace the decline of Western civilization to the day they took shop classes out of the Junior High and High Schools . . .

 

[redjr]

Great reply Dale. So you're saying use the press to drill the hole first and continue to use the chuck manually with your hand to start the tapping for 2-3 threads. Remove tap and material and finish the tapping by hand with a t-bar. Does that pretty much sum it up?

 

[dchisholm]

Speaking of drill presses... I'm looking at this one at Harbor Freight. Any thots?

No experience with that one that I know of. I'm sure there are home shop and hobby machinist forums (similar to DIYAudio, but different topic) on the net where you could get some honest opinions. I think many of those import tools are turned out at a common factory, then different paint and nameplates are applied depending on whether it's sold by Harbor Freight, Sears, Lowes, etc - so you might find a user experience with that machine even though it's called by a different make and model number.

Over the years I DID have experience with some inexpensive import drill presses. Many incarnations ago an employer had one from Taiwan that favorably impressed me by how well-fitted everything was, all the sections moved smoothly, very low vibration, couldn't be made to chatter, etc. I saw another at a Thresher's show a few years back marked "Free to Good Home" - no motor; you could feel the chuck flop around when you grabbed it with your hand; and then you noticed that the chuck had a definite eccentric wobble as it rotated. The guy giving it away said the spindle was loose when he got it, but at some point it was drilling a workpiece that broke loose and the torque apparently bent the spindle shaft.

Asking for personal experience and reviews, as you're doing, is probably the best way to sort the durable ones from the scrap iron - you probably can't tell much by looking at them in the retail showroom, though a smooth operating "feel" (if you can touch the thing), visual check of overall component "fit", and attention to cosmetic details might be clues to the underlying design and manufacturing quality.

(My drill press is a cast-iron floor model from Sears, circa late 1970's, and I have no reason to replace it.)

Dale

 

[dchisholm]

Great reply Dale. So you're saying use the press to drill the hole first and continue to use the chuck manually with your hand to start the tapping for 2-3 threads. Remove tap and material and finish the tapping by hand with a t-bar. Does that pretty much sum it up?

That sums it up nicely. (I hope you didn't think I was insulting you with the details - I didn't know how much experience you had, or who might stumble upon the post in years to come.)

Almost all the tapping I do is in pretty easy-to-tap materials (aluminum, acrylic, steel panels or chassis up to about 1/8") so I usually complete the entire hole on the drill press table. By the time I get the tap started into the first few threads, the job is half done so why bother changing to the T-bar? The exceptions are workpieces that are too large, or too small, to comfortably and easily hold on the drill press table.

Dale