Taping Block

[dlane]

Hi all , made a block to keep taps straight , common sizes 1/4, 5/16, 3/8, 1/2" . Seems the taps are larger od than the hole size , is there a chart with actual tap od sizes , most of my taps have three flutes
Thanks

 

[kd4gij]

I haven't seen a chart , What Size did you drill the holes?

 

[T Bredehoft]

I suspect he drilled the 3/8 hole .375, not oversized which is what the tap measures.

 

[Billh50]

You will have to have the hole large enough for the shank. Once the tap is in a couple threads it tends to straighten up anyway. Most taps under 3/8 only have about 1 inch of thread or less, So if your block is close to that the shank may not fit unless the block is drilled for the shank.

 

[RJSakowski]

Taps are typically oversize, classified by the H or D thread limit spec The number following the H number is the amount of oversize in half thousandths. The number following the the D is the amount of oversize in multiples of .013 mm.

 

[dlane]

I used screw machine drills in a 1" block 1/2, 3/8, 5/16, 1/4 " . Three flute taps are hard to measure , the shanks are useualy smaller than the threads on the taps I have. Most of these taps came from a
GE plant that closed. Guess I'll make a manual tap head for larger size taps I have a proqunier 1-e that needs more collets, there kinda proud of those collets
I was hoping there was somthing that listed the major tap diameter
Thanks

 

[TOOLMASTER]

a couple years ago i bought the tap and drill guides from these guys..very handy

 

[kd4gij]

Here is the link.


http://www.shop.biggatortools.com/

 

[dlane]

Guess some of my taps are oversize

 

[kingmt01]

I read a post the other day where the instructions was for measuring the flutes of a drill or cuter. Chuck a roof of known diameter & use it to set a dial indicator then measure the flutes. This should work for you.

Most large taps have a hole in the back of them to keep them centered. Using a center in your chuck & a wrench on the back of them works well.