Tapping Straight Holes With a Hand Drill

We make furniture products with a huge variety of different shapes, sizes, material sizes, etc. Everything gets drilled and tapped for a simple leveler in the bottom. After the base or leg is finished, the holes are drilled and tapped by hand with battery powered drill. We used to use 1/4-20, but due to a number of issues with that, we switched to 5/16-18. There is either a cap on an open tube end that is drilled and tapped, or there is tubing across the bottom that is drilled and tapped. It is all 11ga or thinner.

We never had issues hand tapping 1/4-20 holes straight, however the 5/16-18 holes seem to be causing the drill to twist slightly, causing the tap to run in crooked, which is very obvious when the leveler is installed. Unfortunately switching back to 1/4-20 is not an option. Hoping you guys have some suggestions? I have attached a few pictures of various products so you can get an idea on what they look like.

Drilling and tapping the holes in a mill or drill press prior to welding seems like the obvious solution, but I'm really hoping to find a simple solution that will help the guys drill and tap the holes straight by hand after fabrication. Drilling and tapping the holes first has it's own set of issues and complications for us, but it's not out of the question.

Currently we drill the holes with a 1/4" drill bit, drop a dab of cutting fluid in the hole, and use a 5/16-18 HSS tapered tap.

Econdron said:

Currently we drill the holes with a 1/4" drill bit, drop a dab of cutting fluid in the hole, and use a 5/16-18 HSS tapered tap.

Click to expand...

Try a bigger drill. Standard drill size for 5/16"-18 is .255"

Regards.

Mike

Simple Guide Block?

Piece of steel say 1'' thick with a hole to match the tapping drill, get a start on the punch dot then use the block to maintain a square hole

Same for the tap, drill the block a few thou' clearance on the tap, place block over hole insert tap and wind away.

Although it's worked for me for over 50 years, of course YMMV

+1 on what Mike said, @ .250'' you are making hard work of tapping those holes.

What type of tap are you using? Spiral flute or spiral point? Spiral point will be much easier to run, but will leave chips inside rather than drawing them out.

Are the issues that drove you to 5/8 related to the tapped hole or to the stud? Can you open the hole up even a little bit more than .255 to make it easier.

With a hand drill I've had good luck up to M6 or 1/4. Above that it gets iffy, as you're finding out.

Do you need a tapped hole? Can you plasma/laser/drill a clearance hole and just weld a nut on the backside before you weld on the end cap?

Finegrain said:

Try a bigger drill. Standard drill size for 5/16"-18 is .255"

Regards.

Mike

Click to expand...

I guess I never considered going with a larger drill, I just assumed hand drilling would drill a slightly oversized hole. But I'll try the larger drill and see if it makes things easier.

Limy Sami said:

Simple Guide Block?

Piece of steel say 1'' thick with a hole to match the tapping drill, get a start on the punch dot then use the block to maintain a square hole

Same for the tap, drill the block a few thou' clearance on the tap, place block over hole insert tap and wind away.

Although it's worked for me for over 50 years, of course YMMV

+1 on what Mike said, @ .250'' you are making hard work of tapping those holes.

Click to expand...

I thought of that as well after I posted this. My initial concern was that the twisting of the drill while tapping with the guide block would just cause breakage of the tap. But definitely worth a try if it's worked for you for 50 years!

DanielG said:

What type of tap are you using? Spiral flute or spiral point? Spiral point will be much easier to run, but will leave chips inside rather than drawing them out.

Are the issues that drove you to 5/8 related to the tapped hole or to the stud? Can you open the hole up even a little bit more than .255 to make it easier.

With a hand drill I've had good luck up to M6 or 1/4. Above that it gets iffy, as you're finding out.

Do you need a tapped hole? Can you plasma/laser/drill a clearance hole and just weld a nut on the backside before you weld on the end cap?

Click to expand...

Spiral point. The chips inside are annoying but I can live with that. We actually did try the holes with a nut previously. We had more issues in those cases with the nuts being welded on crooked. Might have just been our process, I haven't revisited that idea since, which was 5 or 6 years ago.

We always drilled 1/4" if we wanted a really good tapped hole with a high percentage thread. We drilled 17/64" if the percentage of thread wasn't critical.


Regards Tyrone.

Not to reinvent your wheel, but have you considered using "rivet nuts" instead of drilling and tapping the hole?

They work pretty well in thin materials.

Econdron said:

Spiral point. The chips inside are annoying but I can live with that. We actually did try the holes with a nut previously. We had more issues in those cases with the nuts being welded on crooked. Might have just been our process, I haven't revisited that idea since, which was 5 or 6 years ago.

Click to expand...

Were you using a weld nut, or a normal hex nut?

Are the tapped holes through or blind? If blind how much can the hole be drilled deeper than full thread depth? If the space allows those combination tap drills are good to use for the tapping operation. The drill end works as a guide when tapping a pre-drilled hole.

Em..
I´ve tapped about 13.000 holes in tool steels using Hitachi lion battery drills.
Mostly M6, M5, M8, some upto M12.

As others said, go up a little in hole size, drills can be had in 0.01 mm increments.
Use a proper tapping fluid.
The thick sticky ones seem to work better.

Use a better drill !
The Hitachi industrial ones are far better than anything else.
Makita lasted 2 months, Hitachi 8 years.
You won´t like the price.

Use the proper tap.
Machine taps with spiral point seem best.

They don´t break in the workpiece, mostly, and tend to be longish.
This is good because it allows them to bend more without breaking.

Spiral flute taps much easier, but also breaks easier.

You might consider double tapping with a loose tap first and a plug tap next.
Needs two machines, but you can run it full whack in and out, takes seconds.
And very little likelyhood of breaking taps.

The hitachi chucks run very true.
This improves results.

I recently started using tap holders, and like them a lot, but only dozens of holes done so far.

My guesstimate is about 40 secs on a deep 5 mm / 6 mm hole tapped about 25 mm deep when running well.
Double tap in about 1.5 minute plus.

Suggest:
If its not a through hole, drill about 6 mm deeper than needed.
This will leave extra room for chips.

I never worry about straightness.
If the hole was straight the tap will always be straight as well.
It´s a bit of skill, but you pick it up in a few days.
You can feel the hole and tap and it will naturally "want" to be straight.

The right speed and pressure comes to You in a few days.
It varies per drill, material, and tap, but after some time You adjust naturally.
The "right" feed pressure makes it run about twice as fast with half the effort.

Since You are making production parts with few variations ..
I would benchmark tap breakagae.
Then simply swap taps for new every x pieces .. x being breakage x 0.7.

Probably get 200 - 400 holes single tapping and 50% more double tapping.
Running flat out and no babying anything.

SNAP-OH S..T... Another bad Idea...Phil

Make some simple jigs out of hardwood. Drill multiple guide holes so you can "retire" each one after a couple of uses. This works for drilling as well as tapping and I've made throwaway drill guides for years.

You might also look into Big Gator Tools as they have several models of tap and drill guides and all models have V-grooves for use on round stock. For production work duct tape all unused holes.

hanermo said:

Em..
I´ve tapped about 13.000 holes in tool steels using Hitachi lion battery drills.
Mostly M6, M5, M8, some upto M12.

As others said, go up a little in hole size, drills can be had in 0.01 mm increments.
Use a proper tapping fluid.
The thick sticky ones seem to work better.

Click to expand...

I've found Rapid Tap to be the best option

hanermo said:

Use a better drill !
The Hitachi industrial ones are far better than anything else.
Makita lasted 2 months, Hitachi 8 years.
You won´t like the price.

Click to expand...

If you end up doing lots and lots of holes, a tap gun is the way to go. Bosch used to make a very nice one, but it's out of production. Fein still makes both corded and cordless versions. Last time I asked, the corded version was a bit over $1k. Tappers | FEIN Power Tools, Inc.

The tap holder is able to float a little bit to align itself with the hole. When you pull the trigger, it spins counterclockwise. When the tap is pushed in, the clutch engages and it starts to turn clockwise. On through holes, you can set the depth stop and when it hits the stop it will auto-reverse. When you have a bunch of them to do, this tool can save lots of time.

For cordless drills, I've always had good luck with Dewalt.

hanermo said:

Use the proper tap.
Machine taps with spiral point seem best.

They don´t break in the workpiece, mostly, and tend to be longish.
This is good because it allows them to bend more without breaking.

Spiral flute taps much easier, but also breaks easier.

Click to expand...

I've had the best luck with spiral flute taps as well.

hanermo said:

You might consider double tapping with a loose tap first and a plug tap next.
Needs two machines, but you can run it full whack in and out, takes seconds.
And very little likelyhood of breaking taps.

Click to expand...

Are these available off the shelf, or did you have them made?

hanermo said:

I never worry about straightness.
If the hole was straight the tap will always be straight as well.
It´s a bit of skill, but you pick it up in a few days.
You can feel the hole and tap and it will naturally "want" to be straight.

The right speed and pressure comes to You in a few days.
It varies per drill, material, and tap, but after some time You adjust naturally.
The "right" feed pressure makes it run about twice as fast with half the effort.

Click to expand...

What I've found best is to not try to control the drill too tightly. Hold it gently and let it follow the hole. If you try to hold it firmly, you better be dead on coaxial with the hole.

Wolfcraft has a coupe of drill attachments that could help with hole alignment.

Drill guides

Tbaroletta's suggestion of using Rivnuts has merit. A tapped hole of 1/4 or 5/16 size has very little strength in thin material.

Have you considered a Flow Drill? On thin materials the displaced material goes inside the material and allows several more threads. Used with a form drill there are no chips to worry about.
Flow Drilling - Friction Drilling - Form Drilling. Basically, you create your own inserts. - YouTube

What was somewhat interesting is I started digging into this a little more, some of the products have all the holes perfectly straight, while most of the other products have all crooked holes. It seems to be there are a handful of employees here who can tap a straight hole, while the rest are tapping crooked. I'm actually now leaning more towards the view that people are just running the tap in crooked. Maybe a simple guide block is the way to go.

Tbartoletta said:

Not to reinvent your wheel, but have you considered using "rivet nuts" instead of drilling and tapping the hole?

They work pretty well in thin materials.

Click to expand...

We actually use rivet nuts quite a bit on bolt-together assemblies, I would personally love to use this option for all of the leveling inserts, however many of our customers for whatever reason often choose to NOT use the leveling feet, they like the look of the metal directly contacting the floor. The rivet nuts add about 0.08" or so, so it's not much, but it's enough that we would get complaints about the "awkward" protrusion on the bottom when not being used with levelers.

ratbldr427 said:

Have you considered a Flow Drill? On thin materials the displaced material goes inside the material and allows several more threads. Used with a form drill there are no chips to worry about.
Flow Drilling - Friction Drilling - Form Drilling. Basically, you create your own inserts. - YouTube

Click to expand...

Can you use Flow Drills in a hand drill? Last I checked, I seem to remember seeing that a 5/16 Flow Drill needed a lot of force, like a quill handle on a Bridgeport may not be strong enough to force it through.

Econdron said:

What was somewhat interesting is I started digging into this a little more, some of the products have all the holes perfectly straight, while most of the other products have all crooked holes. It seems to be there are a handful of employees here who can tap a straight hole, while the rest are tapping crooked. I'm actually now leaning more towards the view that people are just running the tap in crooked. Maybe a simple guide block is the way to go.

Click to expand...

I am sure this is your problem. With 1/8 wall tube you can drill at an angle and tap straight or drill straight and tap at an angle.
Can you pre drill and tap the pieces on a mill or drill press to make sure they are all straight.
Get a tapmatic head and dont look back.

I would make some simple guides and switch to drilltaps.

Econdron said:

We actually use rivet nuts quite a bit on bolt-together assemblies, I would personally love to use this option for all of the leveling inserts, however many of our customers for whatever reason often choose to NOT use the leveling feet, they like the look of the metal directly contacting the floor. The rivet nuts add about 0.08" or so, so it's not much, but it's enough that we would get complaints about the "awkward" protrusion on the bottom when not being used with levelers.

.

Click to expand...

Tell them they forgot to put the self stick felt on the bottom


I don't think I could deal with doing shippable product with a hand drill.

I keep thinking I would spin one of the heads on my WWII 4 head drill press around and drill them with that

A drill jig is the right answer.

A pair of drill bushings in a 2 inch thick block of aluminum will last years.

The reason the bigger taps are crooked is they take more force to start and turn, lean on the drill, it gets crooked

The jig for tapping will be slightly more clever than the drill. Perhaps a block with a tap shank sized drill bushing at the top and clear hole through, so you don't wear the cutting edge of the tap. Probably becomes captive on the hand drill.

Econdron said:

We actually use rivet nuts quite a bit on bolt-together assemblies, I would personally love to use this option for all of the leveling inserts, however many of our customers for whatever reason often choose to NOT use the leveling feet, they like the look of the metal directly contacting the floor. The rivet nuts add about 0.08" or so, so it's not much, but it's enough that we would get complaints about the "awkward" protrusion on the bottom when not being used with levelers.

Click to expand...

Would a Pem nut be a good option?