Drilling then Tapping in Drill Press

[Iain MarshallParticipant @iainmarshall1]

Guys,

Just getting started with metalworking.

I have a bench drill,vice, some taps / dies etc.

Drilled a nice perpendicular hole in some Alu bar, tapping size for M4. So far so good.

Installed the spring loaded tapping guide into chuck for tapping hole with handle & M4 tap.

Problem is I now have to drop the table down as the setup is too long.

This means I have to mess about having to centre on the hole again.

Any tips for this situation?

I did manage to tap the hole successfully, M4 bolt fitted well, but would like to find a better process.

Thanks

Iain

[Iain MarshallParticipant @iainmarshall1]

[Simon Williams 3Participant @simonwilliams3]

A common, and annoying, situation.

Several ideas for work-rounds.

Ditch the tap guide, clamp the tap in the drill chuck and turn that. The chuck key make a nice tommy bar.

Ditch the tap guide, clamp the tap in the drill chuck and tap under power. (Not without its perils!!!!!)

Ditch the tap guide, don't clamp the tap in the chuck, just hold it loosely so it is held upright. Grind a square on the shank of the tap and fit your tap wrench to the middle of the tap not the usual square on the top end. You need three hands or a quill lock to make this work!

If your drill press has a morse taper, ditch the drill chuck, and hold the tap guide in a morse taper collet held in the spindle. This needs the quill of the spindle to be drilled lengthways as per a vertical milling machine so you can close the collet.

For a drill press without a hollow spindle, make a tap guide on a morse taper. As far as I know there isn't such a thing available commercially, but it's a nice little project.

Attacking the problem from the other end, so to speak, invest in the requisite sizes of long drills so as to make the set-up for drilling the holes equivalent length to the later tap plus guide set-up.

Buy a vertical mill with a dovetail column. This isn't quite as radical as it sounds, it's an entirely logical progression in developing the capability of your workshop. No my wife didn't accept this logic either.

I expect there are other ideas will be along shortly.

Bst rgds Simon

[Anonymous]

If it's not worth setting up a tapping head then I use two methods. One, just put the tap in the drill chuck and make a few turns by hand to start the tap. As a first choice I tend to use spiral flute taps so a few turns gives a couple of turns of a full thread. After that finish the thread by hand away from the machine. Two, just tap the whole thread by hand away from the machine. For free hand tapping I tend to use normal taper taps as they are easier to start nearer the vertical than spiral flute taps. After a turn or so I'll check that the tap is perpendicular to the surface from two directions and then continue turning. To some extent the tap is self-aligning when tapping by hand.

Andrew

[HopperParticipant @hopper]

To help with Andrew's method, you can make a tapping guide by drilling a hole the same diameter as the tap in a piece of thick metal and lay that on top of the job to guide the tap.

Or in the drill press toss the spring loaded guide and use a short point held in the chuck. If you don't have a lathe you can make a point by spinning a piece of round bar in the drill and using a file on it.

[JasonBModerator @jasonb]

As said in the tapping guide thread I don't use the sprung ones and this is one reason why, the simple bit of rod with a point one end and tapered hole the other is a lot shorter. Few stub drills also help but more so in the larger sizes rather than 3.3mm. Wrench on the shank of the tap also acts as a slipper clutch so less chance of tap damage

[not done it yetParticipant @notdoneityet]

in the drill press toss the spring loaded guide and use a short point held in the chuck. If you don't have a lathe you can make a point by spinning a piece of round bar in the drill and using a file on it.

Bearing in mind that drills have bearings which are designed to resist axial loads, not radial ones. Depends on the quality of the drill, of course, but many a drill has been reduced in accuracy simply by using a small wire brush and using the drill like an angle grinder. As it is only for alignment, a short filed wire nail is likely a good enough item for the purpose.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 05/12/2020 07:05:12:

[…]

As it is only for alignment, a short filed wire nail is likely a good enough item for the purpose.

.

Interesting concept ^^^

’only’ is not a word that I would normally expect to use in connection with alignment.

MichaelG.

[larry phelan 1Participant @larryphelan1]

Agree with Hopper, this is the method I use all the time. Not worth the bother of setting up gimmiics unless there is much tapping to be done. I bought a tapping head years ago for a job that required hundreds of holes, worked fine but I have seldom used it since.

It,s now one of those things which will "come in handy some day "

Anyone else got things like that ?

[Michael GilliganParticipant @michaelgilligan61133]

Iain

Before it gets lost in the wider discussion …

May I just give you kudos for approaching this exercise so sensibly.

MichaelG.

[Ian PParticipant @ianp]

As others have said ditch the spring loaded widget and use the chuck.

I am fortunate in having a VFD on my Fobco. I set it up so the lowest frequency is 4Hz at which speed it has little torque but I use it for tapping (with the tap in the chuck) from M2 upwards. (I have fingertip reverse switch) I frequently tap scores of 1/4" and 3/8" UNC in 10mm ali plates not clamped down so it aligns itself to the tap.

Ian P

[HopperParticipant @hopper]

Posted by not done it yet on 05/12/2020 07:05:12:

in the drill press toss the spring loaded guide and use a short point held in the chuck. If you don't have a lathe you can make a point by spinning a piece of round bar in the drill and using a file on it.

Bearing in mind that drills have bearings which are designed to resist axial loads, not radial ones. Depends on the quality of the drill, of course, but many a drill has been reduced in accuracy simply by using a small wire brush and using the drill like an angle grinder. As it is only for alignment, a short filed wire nail is likely a good enough item for the purpose.

Actually, most modern drills, especially the cheap Chinese junk that is almost universal today, use standard ball bearings that in reality stand up better to radial loads than they do axial. The old quality drill presses used roller thrust bearings as well to take the axial loads. Not common any more. And still not harmed by radial loads anyway.

So file away and wire brush away without fear.

[Dave SParticipant @daves59043]

There is no need for a spring loaded tapping centre. The quill moves.

Bung a pointy or female centre in the chuck to guide the “free” end of the tap

for M4 you can turn the tap with one hand whilst pulling the quill down to support the back of the quill.

I regularly tap down to M1.6 using this technique.

For M5 and up (M4 if you are careful) a cordless drill makes a good tapping head.

Because it is doing the turning you can use both hands to make sure it’s guided square.

Dave

[Iain MarshallParticipant @iainmarshall1]

Thanks for all the helpful replies, I'm very grateful.

I like the idea of putting the tap in the chuck and turning by hand, possibly with the rod out of the tapping guide as well, as suggested by Jason & Hopper.

A few good ideas suggested. I will try them out & report back.

I hope to get a mini mill at some point, don't know if that will solve the headroom problem though. My drill press is a old Draper one my Dad had.

Iain

[Howard LewisParticipant @howardlewis46836]

The two essentials are:

1 ) Keeping the Tap square to the work

2 ) Not subjecting the Tap to bending. Taps may be strong in torsion, but definitely not in bending!

So use a Male / Female Tap Guide in the chuck, and rotate by hand, preferably with a Tap Wrench, or grip in the chuck, and by pull the spindle round by hand, following down with the feed handle.

The only time that I tap under power is with a spiral flute tap.

Howard

[not done it yetParticipant @notdoneityet]

1 ) Keeping the Tap square to the work

Howard is spot on with that one. If only the very minimum of threads in the workpiece one may get away with it but as the tap will be aligned by the first couple of threads cut (after which it will continue in that same direction) deeper threads will be successively cutting more on one side of the hole than the other, if initially mis-aligned

The tap will eventually break, or jam, unless it manages to emerge from the hole before breaking, but leaving a mis-aligned threaded hole for the subsequent fixing.  Taps are for cutting threads, not drilling🙂 .

Edited By not done it yet on 06/12/2020 20:32:44

[Iain MarshallParticipant @iainmarshall1]

NDIY,

Keeping the drill & tap square to the work was my primary objective in this exercise.

I succeeded, despite some faff with having to adjust table height.

I'm a bit confused though about the need, or otherwise, of keeping the vice secured to the table.

👍🏼

Iain.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, although you should keep the tap square, they will tolerate a little out of squareness, but may be a pain getting studs/bolts in without faffing about with corresponding holes.

Regards Nick.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Iain Marshall 1 on 06/12/2020 20:43:29:

[…]

I'm a bit confused though about the need, or otherwise, of keeping the vice secured to the table.

.

The vice [or whatever] should be secured to the table when drilling … This is for safety.

[ exceptions ‘prove the rule’ but let’s not go there ]

With the machine un-powered, it’s entirely optional and, in the present example, probably depends upon how likely you are to accidentally nudge the vice and break the tap.

MichaelG.

[VicParticipant @vic]

I do nearly all of my drilling and tapping on the milling machine using a spring loaded tapping guide most of the time. Of course it’s easy to raise and lower the table to suit without losing registration. Sometimes if Z height is tight I use a small dowel with a point on the end instead as a guide.

[HopperParticipant @hopper]

When I use the aforementioned short point for tapping in the drill press, I put a bungee cord on one handle of the drill press to pull the quill downwards so two hands can be used for tapping.

And I have the vice bolted down securely so the the hole does not move out of line with the drill spindle. It all stays nice and straight.

As Michael said, bolted down vice is essential at all times when drilling, for safety. Even a 2mm drill bit can grab into the job and fling a loose vice across the workshop, with disastrous results for whatever gets in its way, whether the family jewels or the freshly chromed petrol tank of your restored Brough Superior.

To get around the clumsiness of drilling small holes in precise locations etc the vice can be loosely bolted to the drill table so it can be moved around into the desired position by hand but if the drill grabs, the bolts will prevent take-off.

[Iain MarshallParticipant @iainmarshall1]

Thanks Guys!

Iain

[Iain MarshallParticipant @iainmarshall1]

As a follow on to the above.

Last night, drilled Alu bar 5mm, tapping size for M6. Tapped it M6.

M6 bolt screwed in nicely.

I noticed that the bolt was able to deflect from vertical about 2- 3 degrees.

Measured bolt and it was 5.85mm.

Is this normal spec for an M6 bolt?

Might it have been better to drill a smaller hole?

Thanks

Iain.

[Clive Brown 1Participant @clivebrown1]

Screw thread tolerance is always metal off. Your bolt seems to be within the largest, "free fit " tolerance of 0.18mm according to my Machinery's Handbook.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Iain Marshall 1 on 11/12/2020 09:50:03:

…

Last night, drilled Alu bar 5mm, tapping size for M6. Tapped it M6.

M6 bolt screwed in nicely.

I noticed that the bolt was able to deflect from vertical about 2- 3 degrees.

Measured bolt and it was 5.85mm.

Is this normal spec for an M6 bolt?

…

Probably! Fasteners come in various fits. Nuts & bolts for ordinary use are generally on the loose side because it makes them quicker to fit, less likely to cross-thread, and cheaper to make. The steel is unlikely to to be anything special, and tolerances are generous. Space may be left for galvanising. DIY store & cheap online fasteners are bottom of the range, liable to be slack. Acceptable for general-purpose use, but not when strength is important and/or the thread is subjected to vibration.

Most of the time, ordinary fasteners are fit for purpose. Over specified fasteners are a waste of time and money. However, under specified fasteners are dangerous. Plans normally highlight the need for anything unusual in a build.

Almost everything done in Model Engineering has a 'general purpose' strength requirement, but a particular project might demand a good fit, strength or look. If you don't know it matters, ordinary loose fitting nuts and bolts should be OK. But beware components subject to shock loadings, vibration and heat, or anything causing injury if it breaks.

More highly specified nuts and bolts aren't difficult to buy. Car-engine fasteners are likely to be a tighter fit and made to resist heat. Safety critical bolts used to secure seats and belts are made of an extra strong steel. Top of the range in terms of strength and small tolerances are used in aerospace, and considerable care is taken fitting them. If better than normal is needed, check the specification and if necessary find a specialist engineering supplier.

I wouldn't try and compensate for a loose bolt with an undersized tap drill. It throws a lot of stress on the expensive tap, they wear quickly, and are prone to snap in the hole. Better to replace the bolt! Most hobby engineering books recommend deliberately reducing thread engagement as a way of improving tool life, and reducing breakages. Slightly bigger tap drill and a slightly reduced rod diameter. Moderate looseness doesn't reduce joint strength much, but tapping into a tight hole massively increases stress on the tap, much worse if the tap isn't new sharp, and the material is difficult.

Dave

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