RobSheffield Posted June 21, 2009 Share Posted June 21, 2009 When tapping to 7/16, what size drill should be used? Is 13/64 correct? Quote Link to comment Share on other sites More sharing options...
Scott Posted June 21, 2009 Share Posted June 21, 2009 What thread? Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 Im sorry, im not sure what detail you are asking for. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 I need to tap a hole to 7/16, and want to know what it needs to be drilled to. I believe the current thread size is M10x1.25 Quote Link to comment Share on other sites More sharing options...
heckler Posted June 21, 2009 Share Posted June 21, 2009 I need to tap a hole to 7/16, and want to know what it needs to be drilled to. I believe the current thread size is M10x1.25 Rob, 7/16 is the diameter, but there are different thread types NPT American Standard Pipe Taper Thread NPSC American Standard Straight Coupling Pipe Thread NPTR American Standard Taper Railing Pipe Thread NPSM American Standard Straight Mechanical Pipe Thread NPSL American Standard Straight Locknut Pipe Thread NPTF American Standard Pipe Thread Tapered (Dryseal) BSPP British Standard Pipe Thread Parallel BSPT British Standard Pipe Thread Tapered There lots more i think too I belive NTP/NPTF & BSP are the most common imperial threads Quote Link to comment Share on other sites More sharing options...
Scott Posted June 21, 2009 Share Posted June 21, 2009 As above bud, if you have a look at the tap it will tell you what the thread form is. UNC, UNF, BSF, BSC, Whitworth and Metric are the norm. Different threadforms need different size holes due to the depth of the flanks etc. Quote Link to comment Share on other sites More sharing options...
Gordon F Posted June 21, 2009 Share Posted June 21, 2009 I belive NTP/NPTF & BSP are the most common imperial threads Most common are UNF and UNC Quote Link to comment Share on other sites More sharing options...
heckler Posted June 21, 2009 Share Posted June 21, 2009 Most common are UNF and UNC oops.... i was just going by what on my car, most the adaptors (egt, oil/water temp) are ntp... besides, i'm an electronics engineer, not mechanical Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 Ahh right, im with you now - thread pitch and TPI etc. Well, its a 7/16 eyebolt i have bought to go into the centre tunnel seat mount point. For fitting a 4 point harness. Quote Link to comment Share on other sites More sharing options...
Scott Posted June 21, 2009 Share Posted June 21, 2009 Probably UNC or whitworth then. Have you bought the tap to do the hole with? You will need to know what thread the eyebolt is before you start Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 I have a set of taps, so ill need to check what thread it actually is, and then find out what thread the new bolt section is. I may do some testing work Quote Link to comment Share on other sites More sharing options...
Scott Posted June 21, 2009 Share Posted June 21, 2009 I have a set of taps, so ill need to check what thread it actually is, and then find out what thread the new bolt section is. I may do some testing work Just hold the 7/8" tap up to the eyebolt thread, have a look at it with a light behind it and see if you have a match Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 Just hold the 7/8" tap up to the eyebolt thread, have a look at it with a light behind it and see if you have a match 7/16 Is there a massive difference between UNC and Whitworth (going on them being most popular) then? Will i be able to distinguish by eye? I imagine one is coarse and one fine pitch or something. Quote Link to comment Share on other sites More sharing options...
Scott Posted June 21, 2009 Share Posted June 21, 2009 7/16 Is there a massive difference between UNC and Whitworth (going on them being most popular) then? Will i be able to distinguish by eye? I imagine one is coarse and one fine pitch or something. UNC is course, UNF is fine. They are all quite different, some threads will screw into different pitches but they won't be ideal. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 21, 2009 Author Share Posted June 21, 2009 Thanks for the advice Scott Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted June 22, 2009 Share Posted June 22, 2009 Hi Rob, The eyebolt thread is definitely 7/16" UNF. Because you want to screw it into a hole already tapped to M10 x 1.25 there is no need to drill the hole any larger (its already a little too big to begin with), just run the correct tap into it with some kind of cutting fluid. When fitting the eyebolt, make sure the parts are grease and dirt free and use some medium strenght threadlock to be sure it won't come undone as you won't be able to tighten the eyebolt a to a massive degree because you are re-tapping a previously tapped hole. Hope this helps mate. Regards, Pedro. Quote Link to comment Share on other sites More sharing options...
Dnk Posted June 22, 2009 Share Posted June 22, 2009 (edited) The eyebolt will be 7/16 UNF which is 20 tpi which is the same pitch as an M10 x 1.25. The thread angle is also the same, 60 degrees. The differance is the o/d as the M10 is obviously 10.00 mm with a tapping drill requirement of 8.75mm if using a 1.25 pitch. 7/16 UNF has an o/d of 0.4375 = 11.112mm so would need a tapping drill of 9.9mm Personally i would try to see if a 9.9 mm drill will go through the M10 thread you have, i doubt it and will need carefully drilling out, if you dont get a great thread in there then i'd get a boss made with 7/16 UNF thread and weld it in place. Can you not get an M10 x 1.25 eyebolt as that would save you some hassel http://www.eye-bolts.co.uk http://www.goliath.com.au/Tapping%20Drill.htm Edited June 22, 2009 by Dnk (see edit history) Quote Link to comment Share on other sites More sharing options...
Tricky-Ricky Posted June 22, 2009 Share Posted June 22, 2009 If its for the Supra, i got the correct thread size eye bolts from Driftworks, they also keep captive nut plates that can be welded onto areas of sheet metal. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 23, 2009 Author Share Posted June 23, 2009 It is 7/16 UNF so thanks folks. Spoken to a few people by PM who said they didnt drill the M10 hole out any further, just ran the tap in and kept it well lubricated. Ill check see if i have a 9.9mm drill though. Only worry is messing it up somehow. Quote Link to comment Share on other sites More sharing options...
Dnk Posted June 23, 2009 Share Posted June 23, 2009 youll soon know if you got a decent thread or not good luck Quote Link to comment Share on other sites More sharing options...
Scott Posted June 23, 2009 Share Posted June 23, 2009 It is 7/16 UNF so thanks folks. Spoken to a few people by PM who said they didnt drill the M10 hole out any further, just ran the tap in and kept it well lubricated. Ill check see if i have a 9.9mm drill though. Only worry is messing it up somehow. Don't drill an already tapped hole to a similar size, the drill will wander like a bitch. Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted June 23, 2009 Share Posted June 23, 2009 One further note Rob, To do the job properly you need two taps, the first tap is called the first taper. Its necessary to use this tap to 'find' your way squarely through the hole. Its easy to spot this tap, it does literally taper off at the end to a threadless blank. Depending on how much room you have behind the hole to be tapped the first taper may be the only one you need. But if you come up against something solid a couple of mm past the hole you'll need a plug tap to finish off the thread. It has cutting thread right to the end of the tap and is usually needed to tap a hole which does not completely pass through the material. Hope that all makes sense mate, you probably know all this anyway. Quote Link to comment Share on other sites More sharing options...
RobSheffield Posted June 23, 2009 Author Share Posted June 23, 2009 No mate i didnt. Im not sure what i have now Quote Link to comment Share on other sites More sharing options...
pedrosixfour Posted June 23, 2009 Share Posted June 23, 2009 Can you post a pic and I'll tell you? Quote Link to comment Share on other sites More sharing options...
Scott Posted June 24, 2009 Share Posted June 24, 2009 Don't worry about that, a plug will do fine since its already got an old thread in place. Tapers are for pussy's BTW Pedro, you missed out intermediate, there are 3 taps to a set Quote Link to comment Share on other sites More sharing options...
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