[How do I?] Drilling tapered holes

[keeena]

How critical is that taper? How close is a standard off the shelf taper reamer? Drilling and reaming is the best way. use a depth stop to get your final dimension hole on one side. Good luck getting it 100% on the other.

I have no idea what taper difference would translate to functional difference. RJ above suggested going for a larger taper (6* included angle) and think that makes sense. I don't think the hole size isn't as critical because the indexing pin is on a sprung plunger and could take up minor differences in hole size.

@RJSakowski - it was a bit tricky to measure. I used gage pins but I don't have the "feel" experience to pick the best pin which starts to fit but doesn't go too deep and thus throw off the measurement.

@Nutfarmer - The taper does result in a really nice feel; solid locating and taper likely wears better? This is for a Walter HU-80 dividing head:


And these are the plates I need to make. I'm debating getting these laser (?) cut and just doing the finish work myself; still need to find a price to see if worth going that route. But I'd still need the taper tooling to finish the job.

 

[pontiac428]

The taper would certainly preserve the nice feel of your high end dividing head. Luckily, the tolerance for taper in dividing plate indexing holes would be loose, since it is the location that is important (then again, how many seconds of a degree in index tolerance does it take to actually ruin the function of that part?). I think pre-drilling and then reaming with a chucking reamer and a depth stop would make the work go quickly enough.

 

[Nutfarmer]

Nice dividing head. Can understand why you are making the missing plates. Finding them used would be a stretch. My instructor at college made a set for a Cincinnati off of separate set using a transfer punch. They turned out great. I didn't think it would have been accurate enough ,but you couldn't tell the difference. Good instructor ,now owns S and S Machine. Make sure and show us the finished plates.

 

[NortonDommi]

Looking at the photo's of that dividing head I can tell you I am a slightly darker shade of green. Machinery's Handbook lists American Standard Self-holding Tapers one of which may come very close to what you want and the fit will depend on what the pin is. Page 914.