The Acme Thread Explained

What is the Acme Thread all about?

In a large number of projects, acme threaded rod is used. If you know the proper method to cut an Acme Thread, constructing the entireacme threaded rod would be very easy. Generally, 2 – 10 acme threaded rod is used, hence, this article teaches you how to construct an acme threaded rod of this size.

Materials you would need:

•    An ACME threaded gauge inclined at an angle of 29 degrees.

•    A standard thread pitch gauge.

•    An HSS tool bank. It depends on the size of the thread you want to make.

•    Steel pieces of 8 inches.

Tools you would need:

•    A Lathe machine (Make sure that the lathe has threading gears).

•    A Bench grinder.

•    A sharpening stone.

Image of the Acme ThreadSteps to Follow:

Step One: Grind the Threading Cutter

For simplicity, you can use a standard cutter which would be at an angle of 60 degrees. Also, for achieving the results fast, you can use quick change tool post. This would also reduce the effort that needs to be applied. Use a horizontal bit cutter and make sure that you do not misalign the horizontal position of the cutter. In case you use tool post that is of rocker type, then you might have to adjust angles as per the requirements.

Once you have made all the adjustments, you can proceed to grind. Start from an angle of 4 degrees between the grinder and the tool rest. Also, keep in mind that the work centre and the wheel centre must coincide.

From that position, move up to an angle of 14.5 degrees and grind from either side by holding the HSS tool bit. Keep on repeating the process till you get the correct shape. And, as soon as the correct shape is achieved, do not stop there but keep on making corrections so that minute distortions are eliminated and a perfect 29 degree angle is obtained. This is important because just a little distortion might affect the entire setup.

Finally, check the gauge to be sure of the work. You can check it by noticing the gaps between cutter and gauge. If there are no gaps, everything is right and if there are gaps, you would need to make corrections. To see better, you can take help of a white card and hold both the things in front of it.

When everything is done, set the tool rest at an angle of 10 degrees and as soon as it fits the 10 mark on acme gauge, you are done.

Some Tips:

•    Spend time in the grinding process. If you do things fast, optimum results might not be achieved.

•    Do not let the piece get overheated. As soon as you sense that overheating has occurred, quench the piece.

•    Do not apply too much pressure on the piece. It would either discolour the piece or it might burn your fingers

Step Two: Lathe Setup

This is the next part. Start by putting a 0.5 inch piece in the chuck. Make sure that it faces the end. This would provide a tailstock support. The piece should then be extended up to 7 inches.

Now, level the tool and using a tool holder and adjust its height as per the requirements. Now, the compound also needs to be adjusted to a specific angle. Adjust it to 14 degree angle. Side by side, you should square the tool bit using your gage.

The procedure from now on is similar to normal threading. You would need to run back the compound and cross slide should be moved forward. Now, choose the length of the Acme Thread rod and make a mark so that you can stop at the right time.

Time to time, the material gets away from the spring. Hence, once a few cuts have been passed, take a cut without feeding anything further. This would make sure that the shape remains good. Cut using the slowestspeed of lathe as it would give you time to correct error. Thread pitch gage can be used to check the correctness of pitch.

Repeat the process till you get the desired depth. At the end, you would have the perfect acme thread.