Metric Acme thread question.

[mark costello 1Participant @markcostello1]

I want to make a nut to fit a Metric bolt. It is for the adjusting bolt on a H/F tubing roller, will be used as a positive and repeatable stop. The O/D is 26mm. The pitch is 3mm. the form seems to be Acme. Anyone have any dimensions or point Me in the correct direction. Past experience has shown that the gents here are most knowledgeable about the variety of threads. Suck up mode off. Thanks, Mark.

[mark costello 1Participant @markcostello1]

[Keith LongParticipant @keithlong89920]

Mark – sounds as though it's not a standard metric thread, bolts are normally 24 or 27mm dia around there with a 3 mm pitch, 26mm would be an oddball. There is a M26x3 TRAPEZOIDAL thread used for lead-screws, hopefully this link will give you the details

Edited By Keith Long on 09/01/2016 23:22:43

[Chris Evans 6Participant @chrisevans6]

Mark, take a look at Automotion Components web page. The thread will be Trapezoidal, they should list a nut at a price low enough not to bother making one. I have just ordered a 1000mm length of 16 diameter x 4 pitch left hand lead screw for <£14 plus vat and delivery. I also ordered a pair of bronze nuts but the do them in steel cheaply.

[Chris Evans 6Participant @chrisevans6]

Just looked on Automotion site, only 26×5 listed price for hex steel nut is <£8.

It may be worth looking at other lead screw suppliers for your size. Chris

[David ColwillParticipant @davidcolwill19261]

This method is worth considering **LINK**

I followed this and it proved quite painless and has no detectable backlash.

Regards.

David.

[Marcus BowmanParticipant @marcusbowman28936]

Assuming this is a 26mm x 3mm pitch 30 degree Metric trapezoidal thread, 26mm is "second preference" from BS 5346:1976.

The basic pitch diameter should be 24.500mm

Fundamental deviation is zero for the internal thread

Other dimensions depend on the class of fit, but ….

On a thread of this diameter, the easiest way to cut the nut is to use a full-form carbide threading tip and use the existing screw as the gauge. That way you don't need to worry too much about measuring to achieve a particular the class of fit. If you are really picky, you will need a proper thread plug gauge (jolly expensive, but the proper way to do the job).

I'm not sure if that helps, but the full-form tip will certainly allow you to do the job accurately.

Marcus

[mark costello 1Participant @markcostello1]

I am across the pond and shipping from the empire would probably make me hyperventilate. I have cut my share of threads, just did not know about the dimensions of Metric (or Chinese Metric). I have not made a Acme thread that small yet, all have been bigger. Needed the thread angle so I do it right and don't take a room at the Bodgers Lodge. Thanks all.

[Author]

Posts