Thread chasing a blind machine screw hole

[becker_atc]

I am getting ready to order a tap to chase two screw holes. They are #8-40, this is for the scope mount holes on a marlin leveraction rifle. One hole goes completely through the top of the reciever and the other is a blind hole.

From the looks of it it looks as its just the start of the threads on both holes that is buggered up. My question is will a standard taper tap do the job for both (will for sure on the through hole) or should I also get a plug or bottoming tap to go deeper in the blind hole to make sure all or most of the threads are good to go?

The taps are hanson carbon steel via midway usa or brownells and are about $3 each. Figured they will work fine since the threads are already there just need to clean them up as the screws wanted to start crooked.

Thanks in advance,

J. Becker

 

[Fixnair]

Get the bottom tap. Since you are not cutting new threads you won't need a starting tap or a plug tap.

 

[1953mercury]

They make taps specifically for cleaning out threads. If you use a standard tap bottoming or otherwise, you may remove more metal than you than you want to. Mike

 

[rsanter]

Bottoming tap and chase the blind one upside-down so any debris has a chance to fall out and not block you getting to the bottom

Bob

 

[astroracer]

I make my own bottoming taps... Take a tapered tap and cut off the taper then hollow grind the end until it is nice and sharp. I do the hollow grinding on the side of my 6" carbide grinder cups.
To chase the threads on your blind hole you may want to simply shorten up a tapered tap so it will "start" without bottoming on the point.
Mark

 

[chrisa7164]

I'm with 1953 mercury...get yourself a thread chaser if you are just cleaning up fubared threads.

 

[theknurl]

screw carbon steel taps....

whats an #8-40 bottoming tap going to cost?????

$5?

jig it up right!......gee, all you can ruin is the receiver

 

[becker_atc]

Well, in my search most of the thread chasing tools I see are for wheel studs, spark plugs, and other external threads. I did see a few for internal stuff but nothing that small. Can someone point me in the direction of a #8-40 internal thread chaser??? I knew that chasers exist we use them at work, mostly big stuff like 5/8" and up to 1 1/2" I believe. just never seen any this small.

 

[becker_atc]

Anyone? In my google search I can't find anything this small. Actually I find this thread lol. I have taps ordered but more than happy to look into the right tool IF it is not made of unobtainium.

 

[1953mercury]

I have never used one that small. I use them for cleaning threaded holes in engine blocks and other auto related items. Found this with a quick search under gunsmith/thread repair. (http://www.midwayusa.com/product/153938/sadlak-scope-mount-repair-tap-m1a-m14-12-32-thread) If they don't have it. They may be able to direct you. Might try an Electrical supply place also. Mike

 

[theknurl]

call Nate's Tools 310-325-6262.....

ask for Dan.....tell him I told you to call (Noel)

tell him to get off his *** and walk down down the 2nd aisle to his left

you want an OSG or Royal bottoming tap, I prefer the OSG

......if you want to be funny, tell him his brother Mitch needs to lose weight

 

[becker_atc]

I have never used one that small. I use them for cleaning threaded holes in engine blocks and other auto related items. Found this with a quick search under gunsmith/thread repair. (http://www.midwayusa.com/product/153938/sadlak-scope-mount-repair-tap-m1a-m14-12-32-thread) If they don't have it. They may be able to direct you. Might try an Electrical supply place also. Mike

Actually saw that in my searches. Pretty sure that is the smallest thread chase I have seen so far. Will call nates tool in the AM...

Have a plug and bottoming tap though already coming from brownells. Would like to find a chaser but don't look good as of now.

 

[Kevin54]

If you want to reform or chase your threads without cutting, if you can't find the correct size of thread chaser, use a "roll tap". Be sure to start it by hand or fingers only to insure that you are started into the threads correctly.

 

[gbsmithy08]

Here is a site that has a lot of taps and what you possibly need. A good quality tap. I use these at work a lot.
http://www.mcmaster.com/#standard-taps/=oxdzw4