How do you use taps for bolt holes?

Question

How do you use taps for bolt holes?

Answer 1

Use a slightly larger tap than the hole. Example: SAE bore of 5/16" use  11/32" or 23/64" . The trick is to not make the bore too large.

Measure the hole, using a dial caliper, and add, in SAE, 1/64" (in mm, 1 mm).

Cut accordingly.

How do you use them? With care. Make sure, before you cut, that the thread pitch is the same with the other half.

Ream out the bore with the tap. Clean any shavings

Answer 2

I don't think you use that

:)

Answer 3

The tap is designed to route out the metal hol so that the bolt can be screwed directly into the hole instead of passing the bolt thru the hole and placing a nut on the other side.

Find a tap the same size and with the same thread spacing as the bolt you are using.  This should be listed on the sizes.  If you don't have the sizes, hold the tap over the bolt, and then the bold over the tap - they should be the same size.  Then interlock the grooves of the tap with the grooves of the bolt by holding them side by side - they should interlock perfectly showing they both have the same thread spacing.

First you will need to drill a hole thru the metal that is smaller than the bolt.

If you already have the tap, it should tell you the sixe of the hole (pilot hole) needed.

If the tap doesn't say what size hole is needed, select a drill bit that is the same size as the stock of the bolt (the thinnest part of the bolt if the grooves portion was removed).  Yo can find this by holding the drill bits behind the grooved part of the bolt.  You should not be able to see the drill bit or just barely see the drill bit thru the grooves.  If you get down to 2 sizes, use the smaller size first.

Then drill the hole.  Do not route out the hole (move the drill in and out when done) as this may make the hole too big.  Be certain to make the hole perpendicular to the surface - if you are at an angle the tap will want to follow the same angle and the bolt will sit crooked.

Then place the tap in a tool provided forming a "T".  By hand, turn the "T" into the metal lockwise.  If it is a little too tight, go back to the drill and route out the hole a little bigger.  If the tap is way too tight, go to a larger drill bit.

You may need to start, remove, then start the tap again several times to allow the metal the tap is cutting from the hole to be removed.