Problem with a model I am building

Spotface is usually meant to provide a flat surface for the bolt or nut, and only enough metal is removed to provide a suitable area for a flat seating.

Measure the diameter of the nut or bolt head or washer, and spotface 10 thou larger in diameter until you have a formed circle only, don't take it down deeper than is necessary to give a circular faced area.

Stud is presumably the same as the 8BA thread you are putting in.

Should get a few replies on this from the others who may be more technically able than you and I... :-))

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Hi,

Thanks Peter, this is what I thought, but with the wording, made it a little unclear. Looks like I should spotface to 2.3mm then drill a hole all the way through for 8BA but 3/16" under??? Does that mean drill a 3/16" dia hole on the underside of the fixture or drill the spotface for 3/16"?

BTW. I was an apprentice trained precision mechanical and production engineer a number of years ago, but I came out of engineering to follow another career path (RAF) about 15 years ago. It is amazing how much you forget... but apart from that, the drawing is not too intuitive with the way it tries to describe the holes.

Best regards, Dave. ~~ Customise your internet experience

Difficult to interpret a drawing without seeing it :-)) I'm on our CAD computer at present, doing a large cabinet drawing for our metalbashers, and interpretation is the bane of drawers and readers alike.

If you have a scanner, scan the part you are unsure of and email it to me, that way I canb get a better feel for the problem.

I don't think you forget, but sometimes it can be a problem remembering the detail if you haven't used the knowledge for a while. Swapping between electronic and mechanical CAD packages gets my grey matter exercised sometimes!

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Without having the drawing to hand this is my interpretation of it.

Drill through 2.3mm, spot face on top to suit 8BA and spot face on the bottom 3/16" [possibly for a washer and nut ]

A spot face is a flat slightly recessed surface for a washer or bolt head to sit, you usually go just deep enough to clean up and form a slight recess.

Reasoning behind this. If t was a tapped hole you wouldn't need a bottom spot face and the drawing would say tap as in the later example you have posted. If it was a blind hole, again no need for a lower spot face and it would have a depth.

Is there a General Arrangement drawing [ GA ] that shows what goes thru this hole?

Drill 4 holes with an 8BA tapping drill 5/32" deep and tap, Fit an 8BA stud into the hole that's 1 3/16" long over all. Again does the GA show any of this ?

You often have to piece this together on drawings by adding various dimensions up.

Hope this helps.

-- Regards,

John Stevenson Nottingham, England.

Hi,

Thanks John and Peter,

(Whoops John, I clicked reply, which replied direct to you rather than reply to group, so I have just copied to group now.)

I have looked further through the series to see what it is...

In vol 4, page 147, there is a drawing which shows this hole in use, but it is still not quite clear. Page 148 shows the actual item. This is a control shaft pedestals. These look like they support a shaft just underneath the entablature.

The assembly drawing shows that there is a nut on the top side, the pedestal underneath, shoving through, so I guess Johns interpretation is correct. Drill large enough for 8ba to pass through (2.3mm) and mark the top and bottom surface, top large enough for a mating surface for a nut and bottom

As I don't yet have any 8ba nuts or the shaft yet, I will leave this hole un drilled, though I have put a mark in place with a center drill so that I can easily return to it later.

Thanks. Dave Colliver.

BTW. John, whereabouts in Notts are you? I am in Kirkby-in-Ashfield. ~~ Customise your internet experience

I worked out that the stud must be 8BA, what I meant when I was asking is why do I need to know what length the stud is, at this stage, after all, I am only drilling and tapping an 8BA. The stud length is irrelevant as far as I can see, so why put it on the drawing, unless there is a meaning to it. (With the drawing I have got, there is no meaning to it.)

Regards, Dave.

Guessing ?? Possibly because the stud isn't on the drawings as a separate item ??

Dave, I'm 2 junctions down the motorway at long Eaton

-- Regards,

John Stevenson Nottingham, England.