Flange hole diameter repair

I mean the bolt hole diameter should be 15.875, but it’s currently 12.7

What you mentioned isn’t very detailed; it’s not clear whether the distance between the holes is correct. Additionally, the central hole in the flange can be blocked with a template, after which the center point can be identified, and the bolt holes can be marked again before further processing. If the distance between the holes is correct, care must be taken to ensure safety during hole expansion, to avoid injuries from a stuck drill bit or other accidents.

I think you’re referring to the bolt hole diameter; use a larger drill bit to enlarge it further

The eye distance is correct; it’s just that the eyes are small

If there’s no problem with the center, just use that large drill bit again to enlarge the hole

The layout of the central garden is fine; the bolt holes can be enlarged from a diameter of 12.7. But drills with a diameter of 15.875 are hard to find; it’s unlikely that this is the correct size here – it should be φ16 rather. The two edges of the drill bit must be ground symmetrically to ensure that the center of the hole remains unchanged.

It can be rotated 45 degrees to re-drill at a position offset from the original hole.

If the eye distance is correct, simply enlarging the holes if the eyes are too small will suffice. Generally, flanges don’t have very high requirements regarding hole diameter – it’s sufficient as long as it meets the minimum requirement for the bolts to pass through

This is a thread with imperial dimensions; for a coarse-threaded 5/8 inch thread, the inner diameter is 0.625 inches or 15.875 mm, while the minor diameter is 0.5266 inches, which is greater than 0.5 inches or 12.7 mm. Therefore, it’s possible to simply use a drill bit to enlarge the hole and then tap it.

For large drill reaming, it is best to drill in conjunction with the correct matching flange.

Use a large drill bit to drill down and align it first, and then expand the hole. In this way, the center of the hole drilled will not deviate much

When such a problem occurs, the first thing to check is whether the center holes on the two flange surfaces are aligned properly. If they are aligned, then drilling can be carried out directly. It seems there isn’t a drill bit with a diameter of 15.875; maybe it was custom-made. There are ones with a diameter of 16. If they aren’t aligned properly, then it’s necessary to check how large the deviation is between the center of the hole you originally drilled and the center of the hole that needs to be drilled. Ideally, the deviation e between the centers of the two holes should be minimal

A diameter of 15.875 mm is indeed a quite high requirement – what kind of flange is this meant for?

“Should the bolt hole diameter be 15.875”? Are there requirements for such high precision in flanges? If such high precision is truly required, it is likely necessary to select a drill bit of the appropriate diameter based on the material of the flange to expand the hole first, and then use a reamer to finish shaping it in order to meet the precision requirements.

Direct reaming – if it affects the sealing surface, it is discarded

Many people have not been exposed to British-style drawings yet; here is an explanation. Since 1 inch equals 25.4 millimeters, a 5/8 inch hole corresponds to Φ15.875; it’s not necessary for the hole diameter to be precise to three decimal places. The purpose of flanges is the same as that of the metric flanges we commonly use. Corresponding British-style drill bits are also available for purchase. This flange can be directly reamed, with little deviation at the hole center, fully meeting general usage requirements. Under normal conditions, it will not affect the sealing surface either. If higher precision is required, drilling can be done on a milling machine. First, use a centering rod or a round rod slightly smaller than the hole to align the center of the hole, and then switch to a drill bit to enlarge it. This post was last edited by oylhupo on 2009-3-31 17:14]

Boring out – is it because you’re worried about the position being off? A template can be created; by being careful during the process, no problems will arise

This post was last edited by yuchenchf on 2014-4-12 07:16: flange repair, on-site machining, boring, journal machining, bolt tightening, bolt stretching, bolt drilling