Thread pitches on small parts.

I tried google but it just shows howto measure thread pitches which i know.

But i need to check the thread pitch on a small part that measures 2.48mm diameter. Some of you may think thats huge and easily done but I am struggling to see how you do it accurately.

I have thread gauges but at that small size it has me stumped. My gauges go low enough but its the reading of them that puzzles me.

I marked the item and gave it 2 full turns, but only had the digital caliper to check it. It closed up by 0.78, divided by 2 turns = 0.39 so probably a 0.4 pitch? Wrong way of doing it?

What do you use to accurately check that is correct?

Thanks.

projecting microscope would be a good way to do. Niko.

Try measuring over more threads and then decide if the context makes it more likely to be metric, imperial or BA. At the moment you seem to be mid way between M2.5 coarse and fine, and a bit off 7BA. Too thick for #2-56UNC or #2-64UNF and a #3-56UNF has got to be rather unusual.

Nope not connected with the seat motor, this is the shaft from a dial gauge. I 3D printed a holder to help level the printers bed but the plunger is not long enough. Silly me for not checking.

Rather than try another design thats lower yet clears the drive belts i thought about extending the plunger instead.

Checking more threads is difficult, only 3 turns to remove it. Can you rig up a projecting microscope quickly in blue peter fashion? Or would that me more stuff to order and another project onto my list?

Its 2.4mm diameter not 2.48 that i put previously.. Not sure how i got that? If i keep rotating it then a low spot will give 2.38, but the rest is 2.4 Maybe i put 2.4 and then measured again and added the 8 on?

So with the right information does that put me closer to anything?

Thanks.

Is it an old or new dial gauge as this would give some idea of what the thread may be, a new far eastern import is probably metric M2.5. An old English one probably 7BA or 8BA, Amereican will be UNC or UNF.

Is there any plain shanlk beyond the thread as that could also give a clue as it will eliminate any overcutting of the thread.

Edited By JasonB on 11/06/2016 07:34:38

Try your local CFE.  Most decent 'A' level, and above, science departments might have a travelling microscope which they would pull out of a cupboard - well, the one I worked at twenty years ago did.

Edited By not done it yet on 11/06/2016 10:50:02

YOu have the perfect instrument to mesure the pitch right there. Set the plunger shaft tip on a flat surface, with dial gauge suitably bolted down. Set dial to zero. Mark the shaft. Rotate shaft tip one turn so that the thread unscrews. Read the pitch off the dial gauge dial.

Its a fairly new and cheapy gauge, Tool Zone one.

Local CFE? I contacted the Campaing for the Farmed Enviroment and they didnt know what i was talking about

CFE? College for Engineering? Do we have them these days? Wont that be dangerous for students? Electicity and moving machinery etc. Should that not be banned? My daughters school didnt have a metalwork room and the woodwork one only had hand tools.

Measure the pitch with the gauge, I will give that a try but dont hold your breath My answer maybe worse than the one i got with the digital calipers

Thanks.

I am also trying to do the same as you, but for a different reason, making an adaptor to set timing on a two stroke motor cycle engine.

I am getting same sort of readings as you i.e. 2.42 mm major thread diameter.

I have poor eye sight and not able to compare thread with a thread pitch gauge, even with the aid of an illuminated magnifier.

I have 7BA and 2.5mmx.45 taps and these do not fit the thread in the DTI shaft.

Edited By Chris Shelton on 11/06/2016 17:11:38

OK i set the gauge up and took a reading of 6.8mm, Unscrewed one turn and it showed 7.2mm.

0.4? Measured the thread diameter with the micrometer and its 2.42mm.

Do these tally?

Thanks.

PS, just found my M2 0.4 taps and the shaft is too small, so 2.5 appears to be right.

Cannot be certain of the thread pitch but it appears right. Need a microscope..

Edited By Dave Smith the 16th on 11/06/2016 17:41:01

Edited By Frances IoM on 11/06/2016 17:48:10

Edited By Frances IoM on 11/06/2016 17:51:23

This is the offending article.

I do not see the problem, why do you want to know the pitch with 3 digits behind the decimal for such a short thread, be practical, M 2.3 has a pitch 0.4 mm. Make the type you want and if it fits it fits. I have done the same for the one I have. Niko.

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For this job ... The easiest 'Blue Peter' solution would probably be to use a manual-focus webcam ... slightly butchered, you shoud be able to unscrew the lens far enough to focus pretty close: Good enough for checking the pitch of a thread this size.

MichaelG.

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P.S. This page from Long Island Indicator may be of interest.

Edited By Michael Gilligan on 11/06/2016 19:06:53

The original one has a diameter of 2.44 mm, I used M 2.6 for the one I made certainly not the correct thread but it has a much better fit than the original one and that without forcing it. Niko.

I have one of those digital ones on order, 1" travel so that should sort my problem as long as the shaft is 8mm..

Nothing i want to do is ever straightforward All this to get ABS prints to stick to the glass bed on the 3D printer..

PLA prints without any issues. Not had a failed PLA print in a very long time. Added the glass bed on the top of the table and heat it to 65 degrees and use a pritt stick just before the nozzle is at full temp. A quick wipe with it and done.

This would would well with a shadowgraph if you could get access to one. Buying one(and having the room for) would probably be way too expensive, it would be for me anyway. 

Michael W

Edited By Michael Walters on 11/06/2016 21:11:14

CFE. College of Further Education. The place where many went to learn a bit more after leaving school. I worked there. Uni's (where you might get a full time degree) are another option. Many of us with a science degree have used these instruments for a range of scientific experiments.