Tapping straight

I’m progressing slowly with my machining. Generally now I get the holes where they are meant to be and straight… dimensions are good.
but I struggle with getting a tap in straight. Leading to wonky studs and such like.
I use a little tapping fluid. But there must be a knack or a trick to getting a tap to thread in straight.
I have a tap handle. I have taps.
what should i do or watch?

As a start, make a tapping block. Adam Savage has a video here which covers the subject.

Rob

Links to https://www.youtube.com/watch?v=XVEww6Ylw5c

The "ultimate" solution is a universal pillar tool, designed by George Thomas and available as a kit from Hemingway.

I use mine constantly.

As an cruder alternative, hand start the tap with it held in a pillar drill chuck if you have one or drill a small block of some material with a clearance hole, rest it on the workpiece and use that as a guide for starting the tap.

Not to teach anyone how to suck eggs, but just in case: taps come in several different types, one of which is a tapered "first tap" which initially sits deeper in the hole making it easier to get it straight. You can start a thread without one of these but it's definitely more difficult!

The other trick that's handy is a spring-loaded tap follower, which holds the tap in your drilling machine and lines it up with the axis of the hole.

The key is to start 'em straight. Assuming you have a drill press to make the holes, you can put the tap in the chuck and turn it slowly by hand for the first few threads, then loosen the chuck and finish with the tap wrench. Many people use a tapping stand which is like a drill press but a hand-operated sliding shaft with a chuck on the bottom and a crank on the top, so you can cut the whole depth with the tap held vertical. Or make some guide bushes that just fit the tap that you press over the hole to hold the tap at right angle as you start it.

Having a mill with a VFD, as far as possible I tap under power at very low speed, haven't yet broken a tap.

If I have a lot of holes to tap I use a reversing tapping head on the vertical mill, fast and accurate. Takes a few seconds per hole. For smaller numbers of holes I put the tap in the drill chuck, after drilling, and start the thread by rotating the chuck a few turns by hand. The thread is finished by hand on the bench. I normally use spiral flute taps for the majority of my tapping. If using hand taps, for freehand tapping, I start the taper tap a turn or so, and then fine adjust the tap to be perpendicular in two planes by eye. In all cases it's a lot quicker to do the operation than describe it.

Andrew

JA

Use a tapping block as listed above for small diameters but as most taps come with a centre hole or tapered end, use a spring loaded tapping guide. (lots of examples on Youtube).

If you do not have a tapping guide use a piece of round bar with a pointed end (or hole to match taps with a taper) and hold it in the chuck of your mill or drill press.. Exert a light downward force with one hand while you turn the tap wrench with the other. If you do not have a DRO to position the hole. tap the hole after you drill the hole without moving the job.

If using a holder like the one above, instead of the tap guide shown, use a round bar with a point. (even a centre punch held in the chuck will work)

Edited By Paul Lousick on 24/03/2022 09:36:09

I converted a cheap and nasty power-drill stand into a tap holder. Can't find a photo, but the principle of the set up is shown here on my lathe.

A couple of spring loaded tap-pushers# are needed to go into the tailstock drill-chuck. Male and female because small taps have a pointed end, whilst big ones gave a dimple. I bought the male example, but had to make the female myself. Not difficult.

Used the converted drill stand until I got a milling machine, which does the same job, as the lathe but can take bigger objects.

A short fat cylinder drilled slightly larger than the tap can be used as a guide.

Dave

Edit: # tap-pusher - is that the right name?

Edited By SillyOldDuffer on 24/03/2022 09:37:53

It's been said ! but make sure you are using a Taper or 1st tap to start with, then depending on the job a 2nd and finally a bottom tap. Make sure you have the right tapping size drill, if the hole is only a few thou small it will make it hard to start and dramaticly increase the force needed to drive the tap and potentially result in breakage ! Good Luck. Noel.

I have small block of steel with many holes drilled to match the range of taps I use. Simple to start the taps, a few turns to establish the initial important threads. Remove the block and continue. Most of my taps are spiral and I can tap almost without looking even down to M2.

I have small block of steel with many holes drilled to match the range of taps I use. Simple to start the taps, a few turns to establish the initial important threads. Remove the block and continue. Most of my taps are spiral and I can tap almost without looking even down to M2.

Me too!

I do virtually all my tapping on the milling machine using a spring guide like those shown. If I didn’t have a mill I’d do it on my bench drill. Failing that I’d use a block to keep the tap straight.

I use the tapping block method a lot, especially with small taps. For motorbike sized 1/4 and 5/16" etc diameter threads, it is a block of steel 1" thick with holes drilled in it at each tap size.

For the tiny stuff, like model engines using 1.5mm diameter threads etc for stud holes, I have cut a few small pieces of key steel about 10 or 12mm square and maybe 20 to 40mm long and drilled one hole in each to guide either 1mm, 1.5mm 0r 2mm etc taps. They work really well on the small model stuff.

On rufty tufty Harley Fergusson sized stuff using 5/16" and upward taps I will often drill the hole in the drill press than hold the tap in chuck and hit the start button, then the stop button and bring the quill down to "bury" the tap into the hole while it is still spinning. Usually goes in a couple of turns, which is enough to set it straight. I can then finish it off in the vice. (Drill press vice must be bolted down for this one of course!)

Another way, the official way apprentices used to be taught, is to hold the job flat and square in the vice and use a small try square to check progress from two directions as you go. Once you get started, a quick sight to line the tap up with a door frame or window frame etc in the distance behind it is a quick check.

Spring centre for the lathe and drill press as described by above posters is brilliant too.

Edited By Hopper on 24/03/2022 10:23:17

Edited By Hopper on 24/03/2022 10:24:00

I too have problems tapping totally by hand.

If appropriate, I tap in the mill using my VFD with fingertip speed and direction control. In the lathe I make use of the spring-loaded tap-wrench guide mentioned above. If neither of these methods are appropriate then I use a tapping block. Take an appropriately sized piece of metal - a short length of 6 or 8mm thick bar is suitable. Drill and tap it the required size (best in the mill or drill-press), partially insert the tap, position it on the hole you want to tap, and proceed with the process of tapping your hole. Works for me.

Tap them while the work is still in position after drilling the hole thus making use if the spindle or tailstock to guide the back end of the tap.

I simply use a short bit of 6mm rod, pointed at one end and ctr drilled at the other so you can locate either a tap with ctr hole or pointed top end. Light quill pressure as you tap, release pressure if you need to back off the tap.

Tap wrench on the shank of the tap so it does not foul the guide and that also allows the wrench to slip before you apply too much force to the tap.

Don't use taper, second or plug much these days, a single spiral flute tap will do in 95% of cases

Further to earlier, probably THE handiest thing related to straight tapping I have made is a spindle crank handle for the lathe. It means that when you use the srping centre to keep the tap wrench straight, you are not at the same time wrestling with turning the chuck back and forth with the chuck key etc. Crank handle makes it sooooo easy to whiz that tap in with the requisite backing off along the way.

Worth making the spring centre to go with it too. And the sliding die holders are worth their weight in gold.

The only caveat is DO NOT LEAVE THE HANDLE IN THE SPINDLE AND START THE MOTOR!!! You will only do it once. It makes quite an impression with all that off centre weight trying to do 800rpm. I have since attached a large DO NOT START tag to the handle that is put on the lathe switch every time the handle is installed.

As you are using a wrench to stop the tap rotating why not also use it to turn the tap?

Agreed. It is quite exciting

My choice is the pillar tool. The castings came in the large box of bits when I bought my lathe.

Rod

Hi, I agree yes you only leave the Mandel handle in once....!

Roderick, the George Thomas pillar tool and drill attachment is like mine. A fantastic bit of kit, normally used mainly for tapping but the sensitive drilling attachment is very useful.

A great project and well worthwhile in the time it takes to construct

Regards

Derek