How to measure the bottom of a tapered hole

[PaulMakesThings]

[Edit, never mind, stupid question. I should have realized they make inside calipers that small, can't see a way to delete the post]

I need to measure the bottom of a very slightly tapered hole to make a part seal into it. Taper is exaggerated by a lot in my drawing.

The top of the hole is .525. The depth is 2.03 measured to the edge of the bottom. My digital calipers don't have jaws long or narrow enough to get to the bottom of this. My angle gauge is too wide to fit in the hole. The bottom has a 0.25" hole in it and may be funnel shaped.

So I'm trying to figure out a good way to measure the diameter of the hole bottom (labeled D here). It would also be good to get the angle of the sink at the bottom. The crucial thing is that this hole has a clamping element in the side. It's shaped like the curve of the hole, and it can only move inward about 0.010", ideally it shouldn't have to push the plug off center very far. A hole goes through the middle of the plug I'm making, so if the fat part of the plug is too lose it will bend the neck of the tube. I realize I'll need to leave a little slack in the small part of the plug so the clamping doesn't bend it. But without that bottom diameter or the angle of the sides I can't even make it close.



Any ideas? This seems like something machinists would have a trick for.

Thank you!

 

[Mechanicboy]

Use 2 steel ball in difference size + deepth micrometer to find angle of tapered hole. See in page 8-19 in this link: https://books.google.no/books?id=pwnXvLi8plYC&pg=SA8-PA17&lpg=SA8-PA17&dq=To+find+angle+in+tapered+hole+with+2+steel+ball&source=bl&ots=EKiSNv16xK&sig=2uYxxZbs26G3EzKIUlS0cjEA7m4&hl=no&sa=X&ved=0ahUKEwipxsTbuaXKAhVk1XIKHVNlApUQ6AEISDAF#v=onepage&q=To%20find%20angle%20in%20tapered%20hole%20with%202%20steel%20ball&f=false

 

[bazmak]

Can you make a D bit and ease out the hole then make a plug to suit the D bit??

 

[toolznthings]

www.flexbar Has products that can be used to make a accurate " plug " in your case that can be measured after removing from the hole.

 

[Herbiev]

The www.flexbar link doesnt seem to work

 

[abby]

From your initial comment I guess you have internal calipers ?

 

[canadianhorsepower]

this should explain it for further reference

cheers
Luc

 

[toolznthings]

Hi,

Not sure way link won't work. Google " Flexbar Machine Corp. " for the web site
One item is " Facsimile Compound " or one of the very low temp melting alloys would probably work also .

Brian

 

[Swifty]

Hi Luc, you are assuming that the hole goes down to a point, but you have to take into consideration the diameter at the bottom "D". This would make the angle a lot less. The original post gives the large dia and depth but no angle or small dia (which was the one they were trying to measure).

As to the original post, if I was doing this job I would have the topslide on the lathe at the required angle and turn the plug first, then leaving the topslide where it is, set up the mating part and bore it out until the plug was flush with the surface.

Paul.

 

[Jasonb]

It can be done with triganomatry a bit like luc posted bu not quite.

Take a piece of bar smaller than the 0.525 and face it off lets say its 0.500". Insert it into the hole and then measure how far in it goes this will give you the long edge of the triangle, the short edge will be half 0.025" (0.525-0.500) so the angle can be calculated.

You then know the full length is 2.030" and the angle so can work out what the smaller dia at the end will be

 

[Scott_M]

Brians link to flexbar was missing the .com It is www.flexbar.com

Scott

Hey Brian ,I got the lathe all setup and running---Really nice

 

[toolznthings]

Brians link to flexbar was missing the .com It is www.flexbar.com

Scott

Hey Brian ,I got the lathe all setup and running---Really nice

Duh !:
Great on the lathe ! Selling tickets for a tour ?

Brian