Fit on Calibrated bolt

[Gorpomon]

Hi,

I am trying to make a calibrated bolt to the following print, but I can't determine what the fit on the pin inside the bolt is. Press fit, slip fit? Also there is at the top what looks like a threaded plug holding it in the head? Any advice on what's being called out would be greatly appreciated. The bolt and pin are item 7 and 8 on the print.

Thanks

 

[MikeHalloran]

It appears that the pin is welded at and to the head, and is otherwise a clearance fit inside the bolt.

Items 9,10,11 appear to be an adapter that holds a dial indicator (shown in phantom with no balloon) such that its pointer rests on the pin, and its shank rides with the tip of the bolt. I.e., the indicator shows bolt stretch.



Mike Halloran
Pembroke Pines, FL, USA

 

[Gorpomon]

Thank you so much Mike,

Since the pin dimensions is given as 3.0mm (one decimal place) is it fair to assume I would use the standard machinist tolerance of +/- 0.2 for the hole?

 

[MikeHalloran]

No. It does not follow that the hole dimension would be related to the pin, except for a short portion inside the bolt head.

Maybe I'm reading too much into it, but I'd expect the hole geometry to be a little fancier than what is shown on the drawing, and if it's indeed 'calibrated', something other than default tolerances.

... of which, there are none. The drawing does not define a standard tolerance, or give any indication of how one is to interpret it. Perhaps that's intentional, to discourage homebrewing. Perhaps it's incomplete, e.g. there is a separate set of fab drawings for the details.






Mike Halloran
Pembroke Pines, FL, USA

 

[unclesyd]

That hole has a large L/D in a somewhat hard material. The problem is going to be keeping it straight.

As posted by MikeHalloran it is an effort to emulate a micrometer measurement by making it work like a direct tension indicator bolt.

The title says steam test where does the steam enter the chamber?

http://www.vfbolts.com/maxbolt.htm

http://www.smartbolts.com/

 

[Gorpomon]

The drawing is from the Fluid Sealing Association Standard FSA -NMG-204-02 "Standard Test Method For Performance of Non-Metallic Flat Gaskets In High Pressure, Saturated Steam"

The standard is given complimentary from the FSA.
Here's a link:

http://www.fluidsealing.com/pubimg/204-02.PDF

The test rig is just two flanges, one a sealed weld neck, the other a blind flange and the weld neck is filled with 125ml of water. The flanges are put in an oven and heated until saturated steam forms. The calibrated bolt is used to determine how much loss in stretch the bolt undergoes after a testing cycle, to get creep relaxation.

To my knowledge there is no set of related drawings, what you see is what you get.

This was my issue exactly, I had no clue how to interpret this drawing, no indication is given. I posted here however, because it's been about year since I've really had to look at any drawings, so I figured I might be missing something.

 

[unclesyd]

Appreciate the heads up.

 

[MikeHalloran]

The FSA standard also mentions a commercial source for the assembly. It might be worth buying one, just to make real fab drawings from it. If the source is sensible about their pricing, it would make commercial sense to just buy all the assemblies you need from them.





Mike Halloran
Pembroke Pines, FL, USA

 

[Gorpomon]

I did initially contact them, it was approx. $1000 dollars for it, and they really haven't made them in some time. Making these bolts will be expensive it seems (approx. $100 each), but the rest of the accessories were obtained much more inexpensively, making total cost somewhat less.

 

[SnTMan]

Gorpomon, ASME PCC-1 has drawings for similar indicating bolts. For 7/8 thru 1 1/4 (no smaller bolts in the table) it calls for 1/8 dia. rod and drill size of 0.1875 +0.002 / -0.000. As you can see, not an especially close fit. It calls for "free-fall" fit before welding. It also calls for machine grinding the indicating end, perpendicular to the CL within 0.001.

Rod material for B7 bolting is called out as UNS N10276 nickel welding rod, I assume for similar COTE's.

Regards,

Mike

 

[Gorpomon]

Thank you so much for the reference to PCC-1. To think, I read it a few months ago but completely forgot that was in there, the drawing in that is exactly what I need.

As you said, PCC-1 calls out for using UNS N10276 (C-276) for the rod in the center or any material "having essentially the same coefficient of thermal expansion", while my print from the test spec just says carbon steel.

Looking at the C-276 material on matweb, it was a 6.78 microinch/in CTE. So what range would you consider a similar CTE?

This last question is just to more firmly understand these calibrated bolts, I intend to get some C-276 rod.

Thanks so much for all your help everyone.

 

[SnTMan]

Gorpomon, Sec II Part D is giving me as average COTE, to 500 F., 1 Cr - 1/5 Mo (B7) = 7.3 x 10^-6, N10267 = 6.9.

I would think CS would be fine, as it would be in the same material grouping as B7 in Table TE-1.

Regards,

Mike

 

[Gorpomon]

Mike, I noticed in PCC-1, the calibrated bolt drawings had the hole for rod .0625" bigger than the diameter of the rod.

1/8" rods used a .1875" hole
3/16" rods used a .25" hole
.25" rods use a .3125" hole

.0625" is 1.5875mm, or approx 1.6mm, looking at the initial print of the bolt from the Fluid Sealing Association, the fillet weld call out on the print is 1.6.

Is this how they specified the fit of the calibrated pin on the print?

 

[SnTMan]

Gorpomon, as noted by MikeHalloran, the drawing is incomplete, don't really know what the pin or hole dias. are. If you follow PCC-1 in general, you should be OK, the pin just needs to be a free fit in the hole.

Regards,

Mike

 

[unclesyd]

Do you know what stress values that are going to be used when tightening the bolt?

I would talk to someone like Guhring about drilling the through hole. They have a relatively new drill point, RT 100 x, for large L/D holes. Make sure you abide by the suggestion of drilling a pilot hole before using the deep drilling bit. This applies to anyone's drill bits and it needs to be a very good hole.

http://www.guhring.com/Catalog/Drills.htm