3D printing tap guides

You might need to tap holes in a plate for standoffs, or into a heatsink to mount transistors. If you are like me and are a clumsy machinist, then you have experienced the frustration of breaking a tap inside a hole that you are trying to cut threads into because you are not holding the tap handle straight. If you are lucky enough to own a mill, you can position the tap in the mill to hold it straight, but if not, you may have to do it by hand.

So I have designed these 3-D printed parts to hold the tap perpendicular to the surface of the part being tapped. The tap is inserted through the top and bottom hole, and the bottom surface is placed flat against the surface being tapped. These might be used also to help drill the holes straight as well.

This is a parametric FreeCAD model so you can change the dimensions to suit the diameter of the tap being used. I included 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, and 7 mm diameter hole guides already generated with the model. A picture of the 3.5 mm model is included which is usable for 4-40 SAE or M3 taps.
 

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In mechanical engineering metal taps come in three shapes -

Tapered tap to start the thread --this helps to hold it steady .

Intermediate--once a semblance of a thread has been cut by the "start " tap ,this tap is used .

Plug tap --this is the final cut tap .

When drilling the initial hole correct allowance must be made for a full thread otherwise it will be easy to strip the thread.

This correct engineering sequence makes it easier to cut a good thread ---using a plug tap straight away is asking for instability when holding the tap holder and a good chance of a poor internal thread which will --yes brake the tap .

Doing the job correctly to a standard achieves good results.
 
A battery drill/driver makes a great tapping machine.
Torque limited.
Easy to hold still while the motor does the turning.
Much more stable than a tap wrench.

Before you dismiss me as a bodger, commercial tapping machines are used, very similar principle, though mounted on pantograph arms to keep vertical.
 
Its a pity the UK is no longer and industrial power where young people can learn engineering as a trade but that is"progress " .

W.Yorkshire ?-- I did some training several times at a BT school in Otley and know the area including Harrogate & York and a quick look through Leeds , when I was there I enjoyed the food , none of this designer rubbish but plain good food and lots of it .

Does Harry Ramsden still exist I remember the big plate of bread + butter the KIngs pattern cutlery and certainly the fish + chips ?
 
Most home users like myself don't have the resources to invest in a lot of machining equipment or specialized tools. That's why 3-D printers can be a great resource to produce tools and jigs to produce assemblies. Also, the shape of the parts can be distributed on-line to make the tooling widely available. I bought an Ender 3 Pro for under $300 and 2 kg of PLA for about $40, and if one is clever designing around the limitations of plastic parts, there is much that is possible. I looked at even tabletop mills and even a Sherline would have cost $1500 to $2000.


Sherline Vertical Milling Machines – Sherline Products



I like machining and think that the tools and craftsmanship is elegant and beautiful, but having a factory at home is going to change the meaning of production.
 
I had a look at the link , certainly changed days from the Cincinnati vertical/horizontal industrial milling machines of my day I used to repair.

I do realize not everybody is born to be an engineer but its something I still enjoy doing including all my own repairs ( not the roof now ).
 
Tapping machines and attachments have an adjustable over running clutch, it runs free if the tap sticks or breaks.

Using a drill on soft material like plastic is border line, but I would never use it on metal to drive a tap.
And smaller than 3 mm I avoid anyway, too delicate...
 
Its a pity the UK is no longer and industrial power where young people can learn engineering as a trade but that is"progress " .

W.Yorkshire ?-- I did some training several times at a BT school in Otley and know the area including Harrogate & York and a quick look through Leeds , when I was there I enjoyed the food , none of this designer rubbish but plain good food and lots of it .

Does Harry Ramsden still exist I remember the big plate of bread + butter the KIngs pattern cutlery and certainly the fish + chips ?
I'm aldo resident in the UK, I work in a town that employed 1,000s in heavy engineering, now all gone. I recently asked our company buyer to get me a whitworth tap, I was told when it came it was the last in the country. We sent an apprentice on a course, and he was the best in his class, but he can't even use a ruler for imperial.
Anyway, enough of the grumpy tirade, and back to threads, if I've got a difficult thread to tap I sometimes start with a taper, the go in a little way with a plug, then taper - I keep alternating to reduce the torque. I also regularly sharpen taps and dies. If I had to drill/tap a hole without a drill press or milldrill I'd stick the workpiece in a vice, pop a drill in the hole to check the angle and tap accordingly. I tap holes daily, I've used the same 10 taps ( different sizes, taper/plug ) and haven't broken one in a least 10 years. I like to get a lot of use out of stuff.
 
Whitworth tap ?--nearly brings tears to my eyes hearing that again - British through and through now its all decimal system .

I always went by my post in post # 2 during my 5 years apprenticeship as a factory maintenance/machine tool engineer /millwright that was provided by the factory , I have to be honest its taken me a long time to get used to using decimal tools although my old Rabone steel ruler had decimal measurement somewhere on it , I still am inclined to use eights of an inch -16,s etc .

AFAIK the USA still uses the old system -never get my head around European speedometers in kilometers and their high numbers in relation to MPH.
 
Here we get Metric, BSW, BSF, BSP, UNC and NPT...the fun starts when the people mix them up and say oh ho.....

I have to keep or arrange different taps for molds which are sent in by clients.

For cooling, we use 1/4" BSP or more commonly 1/2" BSW 12 tpi, nipples are easily available, it is the ones in metric threads which are hard to find.
We have to be bilingual - Metric and Imperial here, plates in Metric but taps in Imperial, at least for cooling holes.

And yes, Allen wrenches in both series, and a few BS spanners.
 
I've just been down to our new bolt store room ( ie bolts that are commonly used ), there's predominantly metric, but also BA, Whit, BSF, UNF and possibly something else if I looked long enough. I the old, old bolt store there's wrought iron bolts with square heads. I sometimes come across some weird thread ( about 100 to 150 years old) that doesn't match anything. Sometimes I have to extend a thread and the only way is a needle file. A few years ago someone wanted a left hand thread on a grub screw, after I had screw cut it on a lathe a young'un remarked " I didn't know you had screw cutting tips ", I just told him I ground a piece of HSS, these young'uns don't have a clue.
 
Nostalgia ? this is day to day stuff, I daily use hand turning tools on bronze ( ie like a hand held wood turning tool but with braze carbide tips ), the traveling head shaper has just had a Bridgeport head fitted to bring it up to the last century; at least I wont hear the damn thing groaning away, it used to sound like a donkey, but with rattly gears, " eeeeee- orrrrrrrr rattle rattle eeeeeeorrrrrrr rattle rattle ". We came across the problem of replacing a flat ( leather ) belt for a off hand grinder, in my previous occupation ( sock machine mechanic ) 97% of the machines were driven by ( floor mounted ) line shafts and flat belts, and they still have spare belting and the joining device - possibly worth it's weight in gold now. They also have a weird mystery block of stuff that you hold against the moving belt to get it to grip better, very health and safety.
 
As an apprentice one of my first jobs was starting up the large line motor - the "weird mystery block " to help the belt grip was ---RESIN -I know because I used it .

Health & Safety ? -- didn't exist one turning machine operator got jammed in the belt of his machine --lifted him up to the Main Drive shaft -- body parts -- you know what I mean.

We had one guy all he did was repair the belts and a piece of gut to hold each end together.
 
Before my time there was an an unfortunate game of hide and seek involving a stone crusher, not so much " body parts " as red mush. When I started I was asked to " feed a casting ", poking a steel rod into a riser as the metal solidified. No problem, apart from this was done whilst standing on a plank, itself supported on trestles. Behind me was a ditch, after the casting the crucible was emptied of the spare metal into this ditch, so there I was standing on a plank, on trestles with a river of molten metal behind me. I declined the offer to repeat to experience.