Tapping threads straight

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Randy3000

Joined
Jun 3, 2017
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I am trying to make a part for a machine and i just cannot get a straight thread. I have tried no less than 2 dozen times over two days, and am getting frustrated. It is two holes in 1/4" thick steel and i have yet to be able to get the screws tightened down tight all the way. The hole spacing is right, and the holes are square as can be, i have checked and checked this. But after running the tap the bolt threads in at an angle.

I am using a $5 tap from lowes and running it with a cordless drill. I am chamfering the holes. The holes are drilled with the bit that came with the tap. The tap was new when i started this project. I have got to have a setup that holds the tap straight. Please help me. What do i need to buy/make/do?
 
DO NOT USE A TAP IN A DRILL EVER. Get a tap handle and use that. On the back of the handle you will see a little cone shaped hole. This is where you use a center. Put a center in your drill press and use the drill press to put tension on the tap handle and turn the tap by hand.
 
Just for clarification... I wasn’t suggesting that he use the motor on the drill press, just the chuck to hold it. Then turn the chuck by hand.

Jt, I’ve never heard of that technique before. It sounds like the way to go. Thanks for the input!
 
I think jt was referring to my post, since i was running the tap with a cordless drill.

I always thought the handle thing was pointless, now i get it.
 
If you have a piece with clearance holes you could clamp them together and use the clearance hole as a guide for the tap.
 
An expedient I use when tapping into something what cant be put into my mill or drillpress. I clamp a heavy nut over the hole to be tapped. The ”clamp” is bar with with a hole thru it what using C-clamps, sandwiches the nut between the workpiece & bar. The tap is screwed into the nut, then on into the workpiece.
Of course it wont work on everything, but makes for a good right angle.
Another variant is dont use a nut, just a drilled hole. Its I.D. the same as the tap O.D. Then clamp that on to guide.
As expedient, nut method is more accurate. The precise O.D. drillbit is never on hand.
 
I was talking about a hand drill. You can power tap in a mill/drill press if you can slow it down enough and stop it on a dime. But it also is a good way to get taps started stright.
 
JTknives said:
DO NOT USE A TAP IN A DRILL EVER. Get a tap handle and use that. On the back of the handle you will see a little cone shaped hole. This is where you use a center. Put a center in your drill press and use the drill press to put tension on the tap handle and turn the tap by hand.
Click to expand...

A.McPherson said:
Just for clarification... I wasn’t suggesting that he use the motor on the drill press, just the chuck to hold it. Then turn the chuck by hand.

Jt, I’ve never heard of that technique before. It sounds like the way to go. Thanks for the input!
Click to expand...

This is what i do. Use the press to drill the hole. Then, not moving anything, chuck the centering cone up in the drill. Use that to push into the cone in the back of the tap handle. Just a little pressure to keep it perfectly aligned with your hole. Then turn tap handle by hand. Voila. Perfectly straight tapped hole.
 
I made a dedicated tool for this kind of work . I use this when I was making my belt grinders......You can tap thread in the middle of the runway on aircraft carriers :)
Drill chuck was removed in picture .....
EpWxE7o.jpg
 
on anything that matters i like to drill the hole in the mill and then at least start it withought moving anything then use a center if i can to keep the tap in line if not just try and be even with the eT handles as i run the tap through
 
Lieblad said:
An expedient I use when tapping into something what cant be put into my mill or drillpress. I clamp a heavy nut over the hole to be tapped. The ”clamp” is bar with with a hole thru it what using C-clamps, sandwiches the nut between the workpiece & bar. The tap is screwed into the nut, then on into the workpiece.
Of course it wont work on everything, but makes for a good right angle.
Another variant is dont use a nut, just a drilled hole. Its I.D. the same as the tap O.D. Then clamp that on to guide.
As expedient, nut method is more accurate. The precise O.D. drillbit is never on hand.
Click to expand...

The nut method may be useful in the future, but how do you get it centered exactly? Do you use the nut as a guide when drilling the hole and then use it again to guide the tap?

By the way, the drill press idea worked thanks everyone!
 
Randy3000 said:
I am trying to make a part for a machine and i just cannot get a straight thread. I have tried no less than 2 dozen times over two days, and am getting frustrated. It is two holes in 1/4" thick steel and i have yet to be able to get the screws tightened down tight all the way. The hole spacing is right, and the holes are square as can be, i have checked and checked this. But after running the tap the bolt threads in at an angle.

I am using a $5 tap from lowes and running it with a cordless drill. I am chamfering the holes. The holes are drilled with the bit that came with the tap. The tap was new when i started this project. I have got to have a setup that holds the tap straight. Please help me. What do i need to buy/make/do?
Click to expand...
1. hole must be straight drilled and right size , the hole itself will straighten the threads.....
2. chamfer the hole before starting to tap it , helps keep the tap straight
3.use all three taps in order ..........
Do this, and you can not miss
lm519at.jpg
 
Randy3000 said:
I am trying to make a part for a machine and i just cannot get a straight thread. I have tried no less than 2 dozen times over two days, and am getting frustrated. It is two holes in 1/4" thick steel and i have yet to be able to get the screws tightened down tight all the way. The hole spacing is right, and the holes are square as can be, i have checked and checked this. But after running the tap the bolt threads in at an angle.

I am using a $5 tap from lowes and running it with a cordless drill. I am chamfering the holes. The holes are drilled with the bit that came with the tap. The tap was new when i started this project. I have got to have a setup that holds the tap straight. Please help me. What do i need to buy/make/do?
Click to expand...
If you do this often you can easy make tool for help .............like on picture.Drill in some square piece of steel or Al different hole to match bolt you will use ...If you have friend with lathe , he can make you tool for several most used tap .........
EsGrA6F.png
 
Last edited:
Lieblad said:
An expedient I use when tapping into something what cant be put into my mill or drillpress. I clamp a heavy nut over the hole to be tapped. The ”clamp” is bar with with a hole thru it what using C-clamps, sandwiches the nut between the workpiece & bar. The tap is screwed into the nut, then on into the workpiece.
Of course it wont work on everything, but makes for a good right angle.
Another variant is dont use a nut, just a drilled hole. Its I.D. the same as the tap O.D. Then clamp that on to guide.
As expedient, nut method is more accurate. The precise O.D. drillbit is never on hand.
Click to expand...
You don t need to ”clamp” nut .Use drill bits to center nut in hole and CA glue will do the job ............
 
Natlek already said it, but an aluminum block 2X2X2" (or whatever you've got on hand) with a hole just the size for the tap to slip thru will allow tapping the hole. I seldom try to tap over 50% to 60% threads in most things.
 
Just as A.McPherson said...I use my cheap old drill press. It’s actually become a dedecated tap guide.

Chuck the tap, clamp the work and hand turn. When I do it, I also preload the tension to force the chuck “down”, then back to normal on removal. Perfectly straight every time.
 
For single tapped holes I use a center in my milling machine and turn the tap by hand. Works great. When doing more than a few holes I mount my Tapmatic in the mill and get to work.
 
I also cannot tap a straight hole. If possible, I drill the hole, change to tap held in chuck/collet and start it in. 1/4 up through holes I am starting to power tap with a spiral point tap. Absent that I use JT’s method and if the work isn’t clamped, I use something like this to get everything straight. The spring tension centers are like 10 bucks to go with it.

https://www.amazon.com/gp/product/B008MPAORO/ref=oh_aui_detailpage_o06_s00?ie=UTF8&psc=1
 
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