Drill size for 6-48 thread

[SDWhirlwind]

Can someone tell me what diameter drill I need to use to drill and then tap a 6-48 screw size? I can't seem to come up with a number.

Thanks in advance.

Respectfully,
Dennis

 

[JamesnTN]

Can someone tell me what diameter drill I need to use to drill and then tap a 6-48 screw size? I can't seem to come up with a number.

Thanks in advance.

Respectfully,
Dennis

You need a #31 drill

http://www.lincolnmachine.com/tap_drill_chart.html

 

[SDWhirlwind]

James
Thanks so much for taking time to find and post the chart. I know I have that chart in one of my books but since my darn stroke I cannot seem to remember nor find chit. Gets pretty darn depressing and frustrating!

Have stripped threads on the big thumb screw that tightens to bases on a set of used Redfield 3200 rings I had bought. Want to cut off the threaded portion that is all 1pc and drill/tap a hole into knurled thumb screw portion and Loctite it then thread the end. Using the 6-48 on both ends.

Again, thank so much.

Respectfully,
Dennis

 

[Rustystud]

If you are going to drill an action. I recommend: (1) it be done in a mill, (2) the hole started by a center drill, (3) the hole be drilled with a carbide drill bit.

There are several reasons a gunsmith charges $45.00 a hole. Mills, and carbide tooling is expensive. Proper alignment and spacing is of paramount. In the case the carbide tooling breaks it can be expensive having the piece removed by EDM.

Nat Lambeth

 

[sonofagun231]

Maybe someone here could/would volunteer to help you out?

 

[SDWhirlwind]

Sounds like a good job for you sunnergun, but no you are a paste board potting bench builder.

Geez, some of you guys will argue or insult each other over the darndest crap!!! I wasn't looking or asking for help on doing the actual job, just couldn't remember where to find drill/tap info. Got done what I needed to do except get a 6-48 die to make the threaded portion. Hadn't ordered it until I got the first part done as a die is $25ish bucks and with my prescription costs and other medical costs I cannot afford to buy something and not end up using it to fix what I needed.

So no 'professional' needs to worry about me asking for a 'freebie' etc!

Thanks to those who took time to provide what I needed.

Respectfully,
Dennis

 

[tac284]

Dennis, if you ever find yourself in the same predicament maybe you can remember this formula.

Tap drill size (TDS) = tap basic diameter - pitch

So...... Pitch is 1 / number of threads per inch

1 / 48 is .0208 and your tap diameter is .138

.138 - .0208 = .117

 

[carlsbad]

Dennis,
If you're making both halves, why didn't you use a more common thread so you wouldn't have to buy tooling? --Jerry

 

[Riesel]

I'm a little late coming to this party but I believe Brownells sells a complete kit for something like this or use to. Maybe even Midway.

Robert

 

[SDWhirlwind]

Thanks all for suggestions etc. Thought it would be easier/simpler to use the same thread pitch/diameter as Redfield used. That way screws could be switched or whatever with no worry of crossthreading etc vs. different screw/thread pitch/diameter on 2 different screws. Will post a pic or 2 or what I did and finished product just for giggles.

Ordered the die and some long blank #6 screws from Brownell's and thought they would be here no later than tomorrow and I could have finished over the weekend but an email this morning says my order never shipped until today. Brownell's does have a drill and tap kit for 6-48 no die with it. I had everything but the die on hand and the mental capacity to find correct drill diameter.lol

tac284-Thanks for your info, hasn't really reached the inner parts of my melon yet so don't know for sure if I understand your info fully!

Sincerely thank you all again for your time and sharing info and suggestions. Have a Super weekend.

Respectfully,
Dennis

 

[alintx]

Thanks all for suggestions etc. Thought it would be easier/simpler to use the same thread pitch/diameter as Redfield used. That way screws could be switched or whatever with no worry of crossthreading etc vs. different screw/thread pitch/diameter on 2 different screws. Will post a pic or 2 or what I did and finished product just for giggles.

Ordered the die and some long blank #6 screws from Brownell's and thought they would be here no later than tomorrow and I could have finished over the weekend but an email this morning says my order never shipped until today. Brownell's does have a drill and tap kit for 6-48 no die with it. I had everything but the die on hand and the mental capacity to find correct drill diameter.lol

tac284-Thanks for your info, hasn't really reached the inner parts of my melon yet so don't know for sure if I understand your info fully!

Sincerely thank you all again for your time and sharing info and suggestions. Have a Super weekend.

Respectfully,
Dennis

Wish I would have seen this sooner. I have several dies and would have sent you one por nada. Hit me up next time

 

[kendog]

Dennis, if you ever find yourself in the same predicament maybe you can remember this formula.

Tap drill size (TDS) = tap basic diameter - pitch

So...... Pitch is 1 / number of threads per inch

1 / 48 is .0208 and your tap diameter is .138

.138 - .0208 = .117

Another way is Bolt Diameter minus .975 divided by the pitch
.138 - .975/48
.975/48 = .0203
.138 - .0203 = .1176
That would be for a perfect world and a greater than 75% thread. No reason to go there, unless we are building a space shuttle.
Normal drill size for 6-48's for 75% thread is .120"

 

[SDWhirlwind]

I know this tis almost 2yrs old but wanted to thank those who offered help ect. Got done what I needed and it actually worked the way it was supposed to for once! Again, Thanks.

 

[carlsbad]

I know this tis almost 2yrs old but wanted to thank those who offered help ect. Got done what I needed and it actually worked the way it was supposed to for once! Again, Thanks.

I'm a member of the "it took 2 years club" myself....glad it worked out. --Jerry

 

[fatelvis]

I was told a #32 drill size for the 6-48 tap. If I am tapping a steel receiver, is one better than the other? (#31 vs. #32?)

 

[kendog]

I was told a #32 drill size for the 6-48 tap. If I am tapping a steel receiver, is one better than the other? (#31 vs. #32?)

#31 is the right bit. You would gain very little, if anything at all gong to a smaller pilot hole.

 

[WSnyder]

A #31 is good for 75% thread depth, #32 is probably more than would be needed.