View Full Version : How do I go about making a tap

06-26-2008, 05:44 PM
I have the need for a 1.0625" 18tpi tap to put threads in the end of an aluminum shaft I am making. The shaft is bigger (2") than the spindle bore on either of my lathes or I would single point it. I don't have a steady rest but making one may be my next option. I really dont' want to spend $hundreds$ for a custom tap

How hard is making a tap? What material would you use? It only needs to do a few parts so can I use some 4340 I have laying around and harden it?

Seems like I could turn threads on a steel shaft. Use a ball end mill to make flutes I would copy the profile of another tap to get the cutting angle right or close. Taper for a clean start and progressive cut. Then harden like Dad tought me to do when making blades for hand planes.

Any help is appreciated.

06-26-2008, 06:00 PM
I made a tap last year using the method that you described. I was trying to tap brass and found that I didn't even need to hardened the steel. I only needed to tap one hole. Make sure that you have a good amount of rake angle by milling the flutes with the work offset in an angle. I just used a regular endmill.

06-26-2008, 06:59 PM
The tap you need is listed in tool catalog for $46.60 . Better than 100s of $. JIM

06-26-2008, 07:08 PM
The tap you need is listed in tool catalog for $46.60 . Better than 100s of $. JIM

I would buy that one, do you have a link? I am not familiar with the tool catalog you are refering to.


06-26-2008, 07:17 PM
Izzy, the tool catalog I quoted is Victor Machinery Exchange. I looked them up on internet (you have it ) Their site is easy to navigate, just lookup thread taps, special thread, 1&1/16 x 18. JIM

06-26-2008, 07:27 PM
I would buy that one, do you have a link? I am not familiar with the tool catalog you are refering to.

Here's a link;
http://www.victornet.com/cgi-bin/victor/productlist.html?subdepartments=Taps%2C+Special+Pi tch%2C+17%2F32+to+1-1%2F8%3A1170%2C596%2C592%2C594%2C507

06-26-2008, 10:17 PM
I've made a couple of taps, pretty much as you describe. They worked, sorta. Good enough, anyway.

A couple of things: when you mill the flutes, see if you can contrive to get any burrs to end up on the trailing edges of the threads, so the cutting edges are clean. I debated the possibility of milling the flutes first, then cutting the threads, to eliminate the burr problem, but I eventually decided interrupted-cut threading probably wasn't a good idea. I don't think I ever actually tried it though.

Keep the lands as narrow as you can, consistent with strength, to reduce cutting friction (e.g. have more, not fewer, flutes).

06-26-2008, 10:25 PM
i`LL GO YOU ONE BETTER TRAVERS Tool / 1 1/16 - 18 thread $37. 27 .

06-26-2008, 10:32 PM
A home made tap might chase a hole fine but tapping new holes is tricky, I find most of my homemade taps needed a whole bunch more horsepower to cut and do an OK job.

1 1/16" - 18 thread is not that rare, you might be able to borrow one local from a shop if you ask and have never been a pain in thier ass. :D

06-26-2008, 11:57 PM
Iíve made them and had them work well. Position the ball cutter such that it puts a bit of a hook on, thatís the positive rake. I used drill rod. The secret, that i learned here, is you have to mill away a lot the thread profile - there should be way more flute that threaded area, else they are darn near impossible to turn. makes senses as its a cutting tool without relief.

06-27-2008, 12:07 PM
Hey all thanks for the help. I ordered a tap this morning from one of the links posted above so that helps a bunch.

Last night I had a quick thread clean up to do in a existing shaft with the same size threads. (which was 1 1/8" x 16tpi so good thing I waited to double check before ordering:D ) These were in a 1 1/4" od steel shaft so I had planned on just single pointing it since I could fit it in my lathe. Turns out the end of the shaft was crushed a bit but the threads were fine. I did not want to just cut away material since it is a fairly important connection. (bottom eye on a fox air shock in a competition crawler) So with taps and threads being on my mind the last few days I grabed an old 4340 stub shaft which was close to the Dia I wanted, turned it to the proper diameter. single point treaded it with a nice 16tpi and then tapered the first 1/2" of it. I didn't cut any flutes cause I was just wanted it to reform the threads. Worked like a charm:D I had to use a little leverage to bend the crushed area back to round but the threads chased fine and a new eye could be threaded by hand.

I will finish cutting flutes and harden it just cause it will be fun and let you all know how it goes. Plus a package should arive soon with a new tap just in case I screw it up.

thanks for the help


Frank Ford
06-27-2008, 12:41 PM
Here's how I made a tap: