Question about tap and drill size

[ANeat]

I use one of these, Brownells screw checker. It has holes tapped in it to double check what fits where, and it has the drill size required.

[giz189]

I use one of these, Brownells screw checker. It has holes tapped in it to double check what fits where, and it has the drill size required.

ANeat, I saw that in their catalogue and meant to order one ...but I forgot when I placed my order. Got CRS pretty bad. What do you guys lube your taps with when taping into aluminum?

[arjacobson]

I like wd40 or kerosene.

[giz189]

I like wd40 or kerosene.

Thanks. I have had some folks tell me to use parrafin wax, but that seems like it would ball up on you to me.

[scb]

+1 on the WD-40 without going to a special tapping fluid.
These plug in formulas seem to be pretty close. The first one does come out a little tight for a 6-48 tho. The second one looks better.

http://academic.evergreen.edu/projec...-tap.htm#pitch

[theperfessor]

99% of the time I use a pre-printed plastic card with tap drill sizes on one side and decimal equivalents of drill sizes on the other. I got them for free from my tool vendor and keep one by each machine in my shop. But sometime you get a non-standard thread diameter/pitch combo that isn't on the chart. The equation I offered is the simplest and easiest to remember version that always gets you close enough to get started.

Thanks for link, I bookmarked it.

[Willbird]

Depends on how close you need the holes. If they need to be dead nuts a rotary table will not cut it..They will get close..........but..

A versa spacer or indexer makes it faster. Faster than a rotary table.

Bill

[El Bango]

Do yourself a favor and get a Brownells catalog,charts,taps,dies,spring stock cerrosafe casenite,Gunsmith Kinks,in short the bible for the gunsmithing trade.

[Bill*]

Yes, it's called a Starrett card.

I just checked my Starrett card--No 6-48 but there is 8-40

[swheeler]

Is there a chart somewhere that will tell you if you are using "x" tap use this "y" size drill bit to drill your initial hole with?

I was just answering the OP, too general I guess

[HollowPoint]

Mathematical formulas have the same effect on me that "Kryptonite" Has on superman. They just throw my brain cells into a state of weakened-confusion.

That little Brownells card that was posted looks like something I could work with.

All this time I've been having to put on my reading glasses then hold my threading-tap up to the light while putting different diameter drill bits in front of it to see which drill bit left just enough threads showing on either edge of my drill bit to be what I was looking for.

Not very scientific but it always seems to work for me; provided I can find the drill bit with just the right diameter.

HollowPoint

[KCSO]

If you look at the front of a GOOD number drill bit box the chart is embossed in the metal front.