Question: Using a thread die in a drill press

[Douglas Robinson]

I am working on a project where I have to thread a 1 1/2" diameter hole in 1" thick maple. I drilled the hole using a 1 3/8" forstner bit on my drill press, soaked the hole with linseed oil and then used the hand die to thread the hole. Unfortunatley I must not have had the die perfectly perpendicular to the wood and I threaded the hole at an angle. :mad:

Before, I joint and glue up more boards, does anyone have advice for or against mounting the thread die in the drill press to ensure that the hole is threaded true?

Is there a risk I should know about?

It the speed of the drill press a problem?

Thanks

Doug

[Jim Becker]

You could put the tap in the DP, but you HAVE to turn it by hand...not an easy thing to do. Threading requires you carefully turn the tap, back it off to remove material, and repeat until you are done. It's not a continuous process, like drilling...ya can't use the motor.

[Dan Mages]

I agree. The drill press motor is way to strong to do any die tapping.

Dan

[Jim Becker]

The drill press motor is way to strong to do any die tapping.

Dan, it's not a matter of "strong", it's a matter of control. You can turn on a DP and only get one or two revolutions, etc., to simulate the method needed to use a tap. A CNC controlled milling machine might be able to do this, but not a DP.

[Jamie Buxton]

I agree with Jim. If you mount the tap in the drill press, you shouldn't use the motor. You'll need one hand to advance the drill press, and probably your other two hands to rotate the tap.

Another way to assure perpendicularity is to use the drill press to bore a guide hole through a thick block of wood. The guide hole is the outer diameter of the tap. Clamp the guide block to your workpiece, drop the tap through the guide hole, and tap away.

[Douglas Robinson]

Jamie:

What a great idea. I would never have thought of using a second block with a 1 1/2" diameter hole to guide the tap. :)

I might do that or use the DP by hand. Don't know yet.

Thanks for the advice.

Doug

[Jim Becker]

I really like Jamie's idea for the guide block. It's simple. It's functional. It's a heck of a lot easier to use than the tap in the DP!

[Dar Lounsbury]

UNPLUG the drill press first. An accident here could, no, would be bad. Take care, good luck.

[Dean Baumgartner]

I don't know how much guiding you'll get out of a hole the same diameter as the tap, still a lot of potential to tip in the large hole. Maybe an upper section tight to the shaft of the tap to guide it would work better.


Dean

[David Rose]

I tap holes in steel all the time using my drill press. It makes a great guide. Pop the cover and turn the spindle with the pulleys on top. The machine I do this with is a 35 year old Craftsman with the cone shaped pulleys. I haven't tried it with newer dual belt machines. When you get a feel for it, the momentum of the weight of the pulleys and motor armature help. The part has to be clamped of course, as one hand is holding down the feed handle while the other is rotating the pulleys back and forth.

After years of doing this (not continuously :rolleyes: ), I have hit the power a time or two before feeding in. Fortunately I've never had the tap catch the work with such a faupax (sp?) before I shut it down. Think about what would happen with that big tap. What do you have, maybe 6 threads per inch? At a low speed of say 180 rpms, that is 3 revs per second. In way less that 2 seconds all kinds of "stuff" is gonna break loose! The tap will feed in doing (with no reversals to clear chips) all kinds of distress to the poor board will all kinds of stress on the DP. When the tap hits the table something has to go somewhere. I can't picture it very pleasantly. :eek:

David

[Keith Outten]

Below is a (very poor) picture of a tool I made in a local machine shop while I was in high school. In those days every machinist had to make these tools as they weren't available to purchase. I believe that you can buy them now at most machine supply stores.

The tool is chucked in a drill press, the bottom point sets into the end of your tap. A spring in the outside cylinder of the tool keeps the proper pressure on the tap and the tool will maintain a perfect alignment while starting the tap. The small hole in the cylinder is threaded for an insert that rides in the machined slot in the center cylinder which keeps the spring from ejecting the center cylinder. You use a standard tap handle to turn the tap, the tool simply holds the tap perpendicular to the center of the hole being threaded.

If my description of how this tool works isn't clear I would be glad to install it in my drill press and take another photo of the setup.