Canadian Airgun Forum

The #1 Community for Airguns in Canada!
It is currently Fri Nov 22, 2019 9:15 pm

All times are UTC - 5 hours


The Canadian Airgun Forums are a place for people to discuss and learn about airguns and the airgunning sport in Canada. There are lots of discussions about airguns, airgun accessories, reviews, modification and repair information, airgun events, field target and free classifieds!

 

You need to register before you can post: click the register link to proceed. Before you register, please read the forum rules. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload your own pictures, and access many other special features. Registration is fast, simple, and absolutely free! To start viewing messages, select the forum that you want to visit from the selection below.








Post new topic Reply to topic  [ 15 posts ] 
Author Message
PostPosted: Tue Jul 23, 2013 6:08 pm 
Offline

Joined: Sat Jan 12, 2013 6:08 pm
Posts: 117
I need to cut a thread in some chrome moly tubing for a Discovery fill plug ( 13/16-28 tpi thread). I have looked all over, but cant find a tap drill size.
Can someone help out please?


Top
 Profile  
 
PostPosted: Tue Jul 23, 2013 9:14 pm 
Offline
User avatar

Joined: Tue Jun 03, 2008 5:46 pm
Posts: 2815
Location: Canada
http://theoreticalmachinist.com/Threads ... erial.aspx


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 7:34 am 
Offline

Joined: Sun Feb 13, 2011 10:44 pm
Posts: 160
Typically threads this size are single pointed on the lathe not tapped. You can do it of course, I know Joe at HPA (muzzleMack) has this tap. But it takes a manly set of arms. :)
I made one more for chasing out damaged threads on crosman tubes. They are available here for purchase

http://www.victornet.com/tools/Special- ... s/199.html

_________________
Sean


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 12:44 pm 
Offline
User avatar

Joined: Thu Oct 11, 2012 10:41 pm
Posts: 230
Location: Johnstown Pa
bore size is .778 this is for 75% thread which is standard for tapping

Jim

_________________
Crosman 2240 stock
Crosman 2240 highly modded the Changeling
Crosman 2240 polished
Crosman 2240 stubby
Crosman 116
Crosman Vigilante
Crosman shiloh
Daisy 1140
Beeman p17
ruger mark 1
hatsan supercharger 25 in .22
Crosman 2260
Crosman AS2250
Winchester M14


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 1:09 pm 
Offline
User avatar

Joined: Fri Jun 26, 2009 7:42 am
Posts: 4080
Location: Somewhere In Time
Tap Drill Size =

Basic Major Diameter of Thread - ((.0130 x % of Full Thread) ÷ Threads Per Inch)

Example: To Find the Tap Drill Size for a 1/4-20 Tap with 75% Thread:

Drill Size = .250 - ((.0130 x 75) ÷ 20) = .201” = #7 Drill



So...For you

.8125"-((.013x75)/28) = .7777" or 25/32" drill, leaving about .016" of thread p/side (or a 19/50" will leave you with about .022" p/side, but that might be a bit much). I would bore to .777" and start the tap on a lathe, put the lathe in neutral and use the chuck key as leverage to turn the head allowing the tail stock to slide forward as threads engage/cut or have someone slowly turn the drill chuck (that is holding the tap) forward against the tube as you turn the head...

_________________
"Are you guys silly? I'm still gonna send it..."


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 2:13 pm 
Offline

Joined: Sat Jan 12, 2013 6:08 pm
Posts: 117
Thanks fella's some great info and links there. 8)

Sorry for bone questions, but when turning down stock to cut a thread with a die......what is the rule in this case?

Do I turn it down to its major diameter to be correct before cutting?


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 2:45 pm 
Offline

Joined: Mon Sep 05, 2005 10:55 pm
Posts: 6845
Location: Rocky Mtn Hse Alberta
You will not be able to grip the tube in a lathe chuck for tapping that large/heavy.

single point it if you already have the lathe.

Walter...

_________________
Image
Walter


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 3:34 pm 
Offline

Joined: Sat Jan 12, 2013 6:08 pm
Posts: 117
I am a complete newbe when it comes to lathes.....just getting the hang of the basics! To cut a thread using it, quite a way of as yet :roll:


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 3:43 pm 
Offline

Joined: Mon Sep 05, 2005 10:55 pm
Posts: 6845
Location: Rocky Mtn Hse Alberta
what are you building?
what tools do you possess?

_________________
Image
Walter


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 4:10 pm 
Offline

Joined: Sun Feb 13, 2011 10:44 pm
Posts: 160
Threading is quite easy once you understand the basics

Tubalcain (MrPete222) does an amazing series of machine shop instructional videos

Here a link to the index. If you watch the series on threading you should be up and running.

http://www.hobby-machinist.com/showthre ... (MrPete222)-videos

_________________
Sean


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 4:18 pm 
Offline

Joined: Sun Feb 13, 2011 10:44 pm
Posts: 160
lanky94 wrote:
Thanks fella's some great info and links there. 8)

Sorry for bone questions, but when turning down stock to cut a thread with a die......what is the rule in this case?

Do I turn it down to its major diameter to be correct before cutting?


It largely depends on the quality of your dies but if you turn your stock to 1 or 2 thou under the major diameter you should have no trouble. Don't forget to put a decent taper at end(<minor diameter) to start the die

_________________
Sean


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 4:24 pm 
Offline

Joined: Sat Jan 12, 2013 6:08 pm
Posts: 117
SMP wrote:
lanky94 wrote:
Thanks fella's some great info and links there. 8)

Sorry for bone questions, but when turning down stock to cut a thread with a die......what is the rule in this case?

Do I turn it down to its major diameter to be correct before cutting?


It largely depends on the quality of your dies but if you turn your stock to 1 or 2 thou under the major diameter you should have no trouble. Don't forget to put a decent taper at end(<minor diameter) to start the die



Thanks Shaun


Top
 Profile  
 
PostPosted: Wed Jul 24, 2013 8:34 pm 
Offline

Joined: Fri Nov 10, 2006 12:02 am
Posts: 1076
If you want to thread a chrome moly tube for a 13/16''x 28tpi the tds is 49/64''. This fits the Disco fill assembly very well. If you can;t thread this on the lathe the tap works very well. I have threaded a couple dozen with a tap and they work just fine. I find this method easier then trying to make internal threads using a boring bar. I just chuck the tube in a 3 jaw and lock the tap in a chuck in the tailstock. I start the tap into the tube by hand then remove the tube and lock it in a vise between 2 hardwood blocks with a 3/4'' hole into the 2 pieces of hardwood. Clamp the tube in a big vise use lots of cutting oil and a big tap wrench and go to it. Works like a charm .



George.


Top
 Profile  
 
PostPosted: Thu Jul 25, 2013 12:02 am 
Offline
User avatar

Joined: Sun Jul 15, 2012 10:49 am
Posts: 6029
Location: Victoria, BC and Clarkston, WA
SMP wrote:
lanky94 wrote:
Thanks fella's some great info and links there. 8)

Sorry for bone questions, but when turning down stock to cut a thread with a die......what is the rule in this case?

Do I turn it down to its major diameter to be correct before cutting?


It largely depends on the quality of your dies but if you turn your stock to 1 or 2 thou under the major diameter you should have no trouble. Don't forget to put a decent taper at end(<minor diameter) to start the die


Hehe! I use an M24!

_________________
-Rick
Pardini K10
Brocock Concept .22
3 Custom Crosman 2260
Benjamin Discovery .22 w/Joe Hickey stock!
Crosman 150 pistol .22
4 Crosman MK 1 pistol .22
Mrodair CP-1M .22 and .177


Top
 Profile  
 
PostPosted: Thu Jul 25, 2013 4:00 am 
Offline
User avatar

Joined: Fri Jun 26, 2009 7:42 am
Posts: 4080
Location: Somewhere In Time
magnumair wrote:
If you want to thread a chrome moly tube for a 13/16''x 28tpi the tds is 49/64''. This fits the Disco fill assembly very well. If you can;t thread this on the lathe the tap works very well. I have threaded a couple dozen with a tap and they work just fine. I find this method easier then trying to make internal threads using a boring bar. I just chuck the tube in a 3 jaw and lock the tap in a chuck in the tailstock. I start the tap into the tube by hand then remove the tube and lock it in a vise between 2 hardwood blocks with a 3/4'' hole into the 2 pieces of hardwood. Clamp the tube in a big vise use lots of cutting oil and a big tap wrench and go to it. Works like a charm .



George.

X2

Like I said in my earlier post. Cant see why this wouldnt work...

_________________
"Are you guys silly? I'm still gonna send it..."


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 15 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 0 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
News News Site map Site map SitemapIndex SitemapIndex RSS Feed RSS Feed Channel list Channel list

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

phpBB SEO