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Joined: Apr 2015
Posts: 350
Campfire Member
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OP
Campfire Member
Joined: Apr 2015
Posts: 350 |
I have a new to me vanguard which needs a 6-48 scope base hole cleaned up. I can't get a screw to properly thread without force. I have taper tap, bottom tap and plug tap. I appreciate any advice
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Joined: Nov 2005
Posts: 23,101
Campfire Ranger
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Campfire Ranger
Joined: Nov 2005
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"You can lead a man to logic, but you cannot make him think." Joe Harz "Always certain, often right." Keith McCafferty
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Joined: Jul 2016
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Campfire Regular
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Campfire Regular
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If the hole is a through hole, any of them will work. Blind hole takes a bottom tap as already said.
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Joined: Feb 2010
Posts: 17,820
Campfire Ranger
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Campfire Ranger
Joined: Feb 2010
Posts: 17,820 |
Use a plug tap from which the point has been ground off, that will get you to within 2-3 threads from the bottom of the hole then you can complete tapping with the bottom tap. You need the lead of the plug tap to reduce the pressure it takes to turn the tap thus less danger of breaking the tap. The bottom tap has the least lead of the three and is meant to complete the threads from the lead of the plug tap. In nearly 40yrs. as a Journeyman Tool & Die Maker I did all my tapping with plug and bottom taps, never used a taper tap. In most instances with a taper tap especially tapping blind scope mount holes there is too much lead to allow getting a proper start and you run the risk of stripping the first thread. Anytime you have to force anything that is telling you to STOP there is something wrong, continuing will break the tap, strip the thread or damage the screw. Taps are inexpensive enough versus the cost of removing a broken tap that I nearly always started with a new tap. You can feel the difference in the amount of pressure required with a new tap vs. a used tap. Brownell's sells a tap they call their "premium" tap, the tap is manufactured by Reiff & Nestor a company that has been in business since 1908. R&N has a reputation for producing the best tap in the industry, this due to the fact that they control the tooth to tooth spacing on their taps to a closer tolerance than any other manufacturer in the industry. Try one and you will see the dramatic difference in reduction of effort required to tap a hole. I won't tell you I don't remember ever breaking an R&N tap, but their were very few instances. Some of the parts I made required tapping 80-100 #0-80 holes in stainless steel, I didn't even consider using anything other than an R&N tap.
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Joined: Jan 2001
Posts: 59,162 Likes: 2
Campfire Kahuna
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Campfire Kahuna
Joined: Jan 2001
Posts: 59,162 Likes: 2 |
Use a plug tap from which the point has been ground off, that will get you to within 2-3 threads from the bottom of the hole then you can complete tapping with the bottom tap. You need the lead of the plug tap to reduce the pressure it takes to turn the tap thus less danger of breaking the tap. The bottom tap has the least lead of the three and is meant to complete the threads from the lead of the plug tap. In nearly 40yrs. as a Journeyman Tool & Die Maker I did all my tapping with plug and bottom taps, never used a taper tap. In most instances with a taper tap especially tapping blind scope mount holes there is too much lead to allow getting a proper start and you run the risk of stripping the first thread. Anytime you have to force anything that is telling you to STOP there is something wrong, continuing will break the tap, strip the thread or damage the screw. Taps are inexpensive enough versus the cost of removing a broken tap that I nearly always started with a new tap. You can feel the difference in the amount of pressure required with a new tap vs. a used tap. Brownell's sells a tap they call their "premium" tap, the tap is manufactured by Reiff & Nestor a company that has been in business since 1908. R&N has a reputation for producing the best tap in the industry, this due to the fact that they control the tooth to tooth spacing on their taps to a closer tolerance than any other manufacturer in the industry. Try one and you will see the dramatic difference in reduction of effort required to tap a hole. I won't tell you I don't remember ever breaking an R&N tap, but their were very few instances. Some of the parts I made required tapping 80-100 #0-80 holes in stainless steel, I didn't even consider using anything other than an R&N tap. NO way I could have said it all better myself... Kudos re: that post...
Ex- USN (SS) '66-'69 Pro-Constitution. LET'S GO BRANDON!!!
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Joined: Feb 2010
Posts: 17,820
Campfire Ranger
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Campfire Ranger
Joined: Feb 2010
Posts: 17,820 |
I learned a thing or two in 40 years, prolly D&T thousands of holes over that time period. Not only doing my own work in the Toolroom but designing and building machines for production quantity tapping on the manufacturing floor.
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Joined: Aug 2009
Posts: 9,920 Likes: 1
Campfire Outfitter
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Campfire Outfitter
Joined: Aug 2009
Posts: 9,920 Likes: 1 |
Use a plug tap from which the point has been ground off, that will get you to within 2-3 threads from the bottom of the hole then you can complete tapping with the bottom tap. You need the lead of the plug tap to reduce the pressure it takes to turn the tap thus less danger of breaking the tap. The bottom tap has the least lead of the three and is meant to complete the threads from the lead of the plug tap. In nearly 40yrs. as a Journeyman Tool & Die Maker I did all my tapping with plug and bottom taps, never used a taper tap. In most instances with a taper tap especially tapping blind scope mount holes there is too much lead to allow getting a proper start and you run the risk of stripping the first thread. Anytime you have to force anything that is telling you to STOP there is something wrong, continuing will break the tap, strip the thread or damage the screw. Taps are inexpensive enough versus the cost of removing a broken tap that I nearly always started with a new tap. You can feel the difference in the amount of pressure required with a new tap vs. a used tap. Brownell's sells a tap they call their "premium" tap, the tap is manufactured by Reiff & Nestor a company that has been in business since 1908. R&N has a reputation for producing the best tap in the industry, this due to the fact that they control the tooth to tooth spacing on their taps to a closer tolerance than any other manufacturer in the industry. Try one and you will see the dramatic difference in reduction of effort required to tap a hole. I won't tell you I don't remember ever breaking an R&N tap, but their were very few instances. Some of the parts I made required tapping 80-100 #0-80 holes in stainless steel, I didn't even consider using anything other than an R&N tap. NO way I could have said it all better myself... Kudos re: that post... this again
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Joined: Apr 2015
Posts: 350
Campfire Member
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OP
Campfire Member
Joined: Apr 2015
Posts: 350 |
Thank you gentlemen for the advice. All taps are brand new, so I hope all works out......
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Joined: Jan 2001
Posts: 7,988 Likes: 3
Campfire Outfitter
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Campfire Outfitter
Joined: Jan 2001
Posts: 7,988 Likes: 3 |
Would this be a good job for a thread chaser? If you could find one in that size...
Never underestimate your ability to overestimate your ability.
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Joined: May 2003
Posts: 3,284
Campfire Tracker
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Campfire Tracker
Joined: May 2003
Posts: 3,284 |
A thread chaser is normally used for the screw, unless you are talking about a tap for that
+Professional member American Custom Gunmakers Guild
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Joined: Dec 2002
Posts: 32,206
Campfire 'Bwana
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Campfire 'Bwana
Joined: Dec 2002
Posts: 32,206 |
Just curious, but since Howa barrel threads are metric, are the scope mounting holes threaded for the metric equivalent of 6-48?
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Joined: Jan 2001
Posts: 7,988 Likes: 3
Campfire Outfitter
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Campfire Outfitter
Joined: Jan 2001
Posts: 7,988 Likes: 3 |
A thread chaser is normally used for the screw, unless you are talking about a tap for that I've made thread chasers out of matching bolts to clean up a threaded hole and they always worked great. However, never made one as small as a 6-48 so not sure how well it would work out. I've always heard using a thread chaser was safer to the threaded hole as it won't screw up the original threads like a tap possibly can. Bob
Never underestimate your ability to overestimate your ability.
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