Thread Sizing Help

[Apache]

Gentlemen,

You know I like throwing you curveballs!

I have a threaded adjustment screw for a Zeiss microscope and the thread is either damaged or corroded. I am going to need the correct tap and die to clean up the threads for the thing to work. They are not in a standard tap and die set. I did buy a book of threads but I'm buggered if I can find it.



I have 3 measurements:

• Diameter of unturned smooth section is 5.96mm
• Diameter of short section between unturned smooth section and threads (little section) 5.36mm
• Diameter measured over the threads themselves 5.85mm

The pitch (have I got the correct term?) gauge matches at 0.5.

Can anyone tell me what size tap and die I need, please? Given this is Zeiss and German manufactured I expect it to be a metric thread - if that helps.

Cheers

 

[Manator]

does this help  https://mdmetric.com/tech/thddat4.htm

 

[ProDave]

M6 by 0.5mm is a standard fine pitch thread size http://www.tap-die.com/contents/en-uk/d345_M6_taps_6mm_x_0.5mm_tap_6mmx.5_tap_M6x0.5_Metric_taps.html

 

[Apache]

Is it really as simple as M6 X 0.5 - that makes me feel stupid!

 

[Lurch]

Is it really as simple as M6 X 0.5

Pretty much for metric pattern threads. Some imperial type threads need some tables to refer to for cross reference but the principle is basically the same.

that makes me feel stupid!

Sometimes Google can be less judgemental.

 

[Apache]

I ordered the M6 X 0.5 tap and die today from ebay. Hope I only need them once!

 

[Marvo]

Yep the thread diameter is within tolerance of M6 and 0.5 is the finest pitch you normally find in M6. Was it stripped or seized/stuck ?

 

[Apache]

There are two of these threaded screws and a third one spring loaded. You are supposed to be able to turn them with fingers to centre the optics (microscope has phase contrast if that means anything to you). Neither would turn with fingers. With mole grips I unscrewed them, cleaned threads (chemically) and lubricated. Now one turns easily with fingers, but the other too stiff to screw back in very far. I suspect dirt or corrosion.

I don't think stripped.

 

[Marvo]

I'd be a bit wary about running a tap into the hole, it's a one way street where you might easily end up with the thread being too large for the screw or you might damage something internal with the tap as it goes in. I'd suggest you persevere freeing it up using fingers and some light lubricant oil on the thread. The screws are stainless steel by the look of it so corrosion is unlikely, it may also be the actual condensor that's sticking. 

 

[Apache]

The condenser is out. Currently the hole I can see daylight through.

I will run the screw down the die. If that goes OK (and things are not improved) then I will risk the tap in the hole.

I've more than persisted using fingers and WD40, surgical spirit, white spirit and finally ether (that gives a good headache!). Something mechanical down there is the only way forward (I'm sure)

 

[Apache]

in M6 X 0.5?

 

[Apache]

I was going to try and use the tap with my fingers - not stick the long handle on and cut a lot of metal. I have half a brain!

 

[Marvo]

Ahh, I thought you might have been thinking of tapping it with the condenser still in, I'm not so worried if you can see all the way through the hole. I'd suggest buy yourself an M6x0.5 stainless steel nut and bolt if you can find them at your local fixing suppliers and try using those first before you use the tap and die. Firstly it will establish whether the problem is with the male thread on the screw or the female thread in the hole and secondly it will reform the existing thread rather than cut a new one so it's less likely to end up with it being too loose.

I thought about a thread dresser and just checked my thread dressing tools and they don't cover 0.5 pitch.

 

[Apache]

The problem is in the hole. I have 2 of these remember - either will go in the other hole and turn with fingers.

 

[Apache]

It does seem a little out of the ordinary. I did have to look to find a suitable tap and die. If I wanted 1/2" UNF I had a million (cheap) options.

 

[kerching]

If going down the tap,route I would be tempted NOT to,use the taper tap as this could kickmthe thread out of kilter. Go first with the second or even better bottoming tap?

Tkae it slower than you 'think' is slow enough, keep,on backing it off and cleaning out the thrake otherwise there could be tears before bedtime and a gnashing of teeth

As said before, try to get hold of a matching nut and bolt. File a threading slot in the male thread to make your own tap

Just saying this is " a proper thread " pun intended

 

[Apache]

Do I need the bolt when the other one of these screws wont go in?

I was looking, but it seems hard to come by

 

[Andy™]

I can probably get you a nut and bolt tomorrow and pst for xmas eve ?

We have a nut and bolt place down the road and they do everything thread wise, let me know

if you are sending it by royal snail, then it might arrive for xmas eve 2016...

 

[Apache]

I can probably get you a nut and bolt tomorrow and post for xmas eve ?

We have a nut and bolt place down the road and they do everything thread wise, let me know

If it's no bother?!

 

[Apache]

All sorted with tap and die - I love been reckless sometimes.