Match Drilling and Tapping Holes

[rgsparber]

When you must drill two or more holes to attach two parts together, the alignment of the first hole is easy. Getting the second hole to align can be difficult if you want close-fitting clearance holes. It only gets worse from there. The problem is solved by using the procedure illustrated in this article.

If you are interested, please see

https://rick.sparber.org/MatchDrillingTappingHoles.pdf


Your comments are welcome. All of us are smarter than any one of us.


Thanks,

Rick

[Paul Alciatore]

Rick, you present some interesting techniques there, but it seems like a lot of trouble to avoid just throwing the parts in a mill-drill and using the handwheel scale (or DRO) to simply locate the two holes the same distance apart. No need to even scribe the locations, although I probably would just as a reality check.

And as for the set screw trick, that would work but it would need to be replaced every time the bolt holding the two parts was loosened. Perhaps that will not ever happen, but there is an easier way to maintain alignment. Just drill a small hole through both of them while they are aligned and then install a spring pin. Two spring pins, one on each side of the bolt would maintain complete alignment. And drilling the two holes is a lot faster and easier than tapping the one. This is an age old technique that probably predates even the advent of the roll pins.

Oh, and the roll pins are a lot better way to align all of the assemblies. With them the holes and bolts holding the two pieces together can be done with more clearance so they would go faster. Pins for alignment and bolts to fasten them together. Each has it's own job.

[rgsparber]

Rick, you present some interesting techniques there, but it seems like a lot of trouble to avoid just throwing the parts in a mill-drill and using the handwheel scale (or DRO) to simply locate the two holes the same distance apart. No need to even scribe the locations, although I probably would just as a reality check.

And as for the set screw trick, that would work but it would need to be replaced every time the bolt holding the two parts was loosened. Perhaps that will not ever happen, but there is an easier way to maintain alignment. Just drill a small hole through both of them while they are aligned and then install a spring pin. Two spring pins, one on each side of the bolt would maintain complete alignment. And drilling the two holes is a lot faster and easier than tapping the one. This is an age old technique that probably predates even the advent of the roll pins.

Oh, and the roll pins are a lot better way to align all of the assemblies. With them the holes and bolts holding the two pieces together can be done with more clearance so they would go faster. Pins for alignment and bolts to fasten them together. Each has it's own job.

Paul,

My goal was to explain how to match drill. It is not a universally known procedure.

Although I do own a mill/drill, many people do not. It would be interesting to learn what the members of homemadetools.net have in their shops.

I admit that match drilling for screws might be overkill because you can always go with a larger clearance hole. But if I was going to install dowel pins, I am positive my skill is not good enough for the alignment needed by independently drilling and reaming the holes.

You may have noticed that I did take the assembly apart to take the picture and then reassembled it. Didn't have any trouble screwing in that setscrew the second time.

I did look through my parts bin for a short roll pin but had none. Going to the hardware store is not an option so I went with what I had - a short set screw. I wasn't going for alignment, I just didn't want the block to turn. There wasn't much material around that screw for flanking 1/8 inch holes. Remember, I had two set screws going horizontal through that block.

Rick

[DIYSwede]

-Thanks for yet another well-written document, Rick!

The neat magnet trick for hands-free horizontal alignment of your work with the vise jaws particularly caught my eyes, so simple and yet operative!
Finally a use for some Microwave Magnetron 3" donut magnets I've had in the shop for a coupla years.
Just gotta check them on the surface plate for flatness first.

"Dang- why haven't I ever thought of THAT!"

Cheers, Johan

[DIYer]

Thanks rgsparber! We've added your Match Drilling and Tapping Method to our Fastening category,
as well as to your builder page: rgsparber's Homemade Tools. Your receipt:

Match Drilling and Tapping Method by rgsparber

tags: tapping, drilling