Taping header bolt hole. What size drill bit?? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jayharrell · 05-26-2008, 09:20 PM

I've got a bolt broke off in my head for my headers.

What size drill bit do i need to run a 3/8 tap??

jayharrell · 05-26-2008, 09:26 PM

NM.. found a chart online.
ttt anyway.

LONGHAIR · 05-26-2008, 09:29 PM

Assuming 3/8-16 (coarse) the chart calls for letter "Q"....but since many guys don't have letter drills, you could probably get by with 21/64" it is just .004" smaller.

But why are you asking about 3/8"? aren't then supposed to be 5/16"?

chrislehr · 05-26-2008, 09:46 PM

tapping > taping

jayharrell · 05-26-2008, 10:10 PM

I'm running a 455 Buick. Little different.

And yeah, its a 3/8-16. A chart i found said a 5/16 bit, but that was google, so i'll go with the Q.

Right now, because i didn't have a bit that would work, i just taped them for 5/16 with a 9/32 bit. I'll have 3 bolts a little smaller then the other 4, but i think i can redrill and tap after i find a decent set of bits.

Sorry, Taping wouldn't do a damn bit of good would it, even if i used 3m tape, would probably melt?? Maybe i should try tapping..... sry.

LONGHAIR · 05-26-2008, 10:48 PM

The 5/16" would work in a pinch...depending upon how deep you are going and what material you are tapping.
5/16" (.312) gives you a 75% thread, which is a little much for steel or iron, it would be ok in aluminum, brass or plastic though.
Letter Q (.332) is a 50% thread, for steel, iron, stainless
21/64" (.328) again only slightly small

PanelDeland · 05-26-2008, 11:29 PM

Next time you happen to be in a supply house that caters to machine shops......they usually have drill/tap charts cheap or free.I have one that's waiting for me to clear out the garage enough to hang.

jayharrell · 05-27-2008, 01:17 AM

Very cool.

YOu think Grainger would have something like that???

PanelDeland · 05-27-2008, 03:44 AM

Possibly.They are really handy.I got mine when I did maintainence in a MS.The supply houses give them to shops to keep their name in the mind of the people ordering the consumables.
I would think someone would make one for sale.Some tap/die sets have one usually stamped or printed on the lid.Some taps have the drill size stamped on the tap next to the tap size.

Senator350 · 08-18-2008, 09:27 PM

TTT for a fun thread.

I'll have to ask after one of those charts next time I'm in the fab shop.

anyway... I found the thread because I wondered what size/pitch normal everyday SBC header bolts are.

I just noticed a set of header studs on CL, and this info will save me a trip off my ass

MrBeast · 08-18-2008, 09:33 PM

Granger will definitely have that, also you might want to get a copy of the machinery handbook. Barnes and Noble carries it, I have a copy, damn good book. Well worth the 60 some dollars it will cost you.

Senator350 · 08-18-2008, 10:00 PM

fer sure... I've got a strange fondness for big reference books, so that might be a future purchase!

I found the chart in the granger catalog... it's on page 132,154,549,008,023 :P

Senator350 · 08-18-2008, 10:00 PM

but oh yeah... what's the size and pitch of a header bolt!

MrBeast · 08-18-2008, 10:01 PM

Quote:

Originally Posted by Senator350

fer sure... I've got a strange fondness for big reference books, so that might be a future purchase!

I found the chart in the granger catalog... it's on page 132,154,549,008,023 :P

Also check out Fastenal, they are often times cheaper than Graingers, and carry quality products as well.

05-26-2008, 09:20 PM	#1
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Taping header bolt hole. What size drill bit?? I've got a bolt broke off in my head for my headers. What size drill bit do i need to run a 3/8 tap?? __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets"

05-26-2008, 09:26 PM	#2
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: Taping header bolt hole. What size drill bit?? NM.. found a chart online. ttt anyway. __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets"

05-26-2008, 09:29 PM	#3
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: Taping header bolt hole. What size drill bit?? Assuming 3/8-16 (coarse) the chart calls for letter "Q"....but since many guys don't have letter drills, you could probably get by with 21/64" it is just .004" smaller. But why are you asking about 3/8"? aren't then supposed to be 5/16"?

05-26-2008, 09:46 PM	#4
chrislehr Engine n00b Join Date: Feb 2008 Location: Austin Posts: 1,031	Re: Taping header bolt hole. What size drill bit?? tapping > taping

05-26-2008, 10:10 PM	#5
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: Taping header bolt hole. What size drill bit?? I'm running a 455 Buick. Little different. And yeah, its a 3/8-16. A chart i found said a 5/16 bit, but that was google, so i'll go with the Q. Right now, because i didn't have a bit that would work, i just taped them for 5/16 with a 9/32 bit. I'll have 3 bolts a little smaller then the other 4, but i think i can redrill and tap after i find a decent set of bits. Sorry, Taping wouldn't do a damn bit of good would it, even if i used 3m tape, would probably melt?? Maybe i should try tapping..... sry. __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets"

05-26-2008, 10:48 PM	#6
LONGHAIR just can't cover up my redneck Join Date: May 2004 Location: Columbus OH Posts: 11,414	Re: Taping header bolt hole. What size drill bit?? The 5/16" would work in a pinch...depending upon how deep you are going and what material you are tapping. 5/16" (.312) gives you a 75% thread, which is a little much for steel or iron, it would be ok in aluminum, brass or plastic though. Letter Q (.332) is a 50% thread, for steel, iron, stainless 21/64" (.328) again only slightly small

05-26-2008, 11:29 PM	#7
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Taping header bolt hole. What size drill bit?? Next time you happen to be in a supply house that caters to machine shops......they usually have drill/tap charts cheap or free.I have one that's waiting for me to clear out the garage enough to hang. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

05-27-2008, 01:17 AM	#8
jayharrell Gettin By on Gettin By Join Date: Jan 2008 Location: Cedar Creek, Tx Posts: 1,033	Re: Taping header bolt hole. What size drill bit?? Very cool. YOu think Grainger would have something like that??? __________________ 69 CST10 LWB 455 Buick 00 S10 2.2 Vin5 76 GL1000 Naked 1bl VW carb "Adios to all the concrete; Gonna get me some dirt road back streets"

05-27-2008, 03:44 AM	#9
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Taping header bolt hole. What size drill bit?? Possibly.They are really handy.I got mine when I did maintainence in a MS.The supply houses give them to shops to keep their name in the mind of the people ordering the consumables. I would think someone would make one for sale.Some tap/die sets have one usually stamped or printed on the lid.Some taps have the drill size stamped on the tap next to the tap size. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil" Last edited by PanelDeland; 05-27-2008 at 03:45 AM.

08-18-2008, 09:27 PM	#10
Senator350 Registered User Join Date: Feb 2004 Location: Albany, NY Posts: 522	Re: Taping header bolt hole. What size drill bit?? TTT for a fun thread. I'll have to ask after one of those charts next time I'm in the fab shop. anyway... I found the thread because I wondered what size/pitch normal everyday SBC header bolts are. I just noticed a set of header studs on CL, and this info will save me a trip off my ass __________________ RN U OVR

08-18-2008, 09:33 PM	#11
MrBeast high-Tech Red Neck Join Date: Feb 2008 Location: Livingston, MT/On my boat WA/BC/AK Posts: 2,294	Re: Taping header bolt hole. What size drill bit?? Granger will definitely have that, also you might want to get a copy of the machinery handbook. Barnes and Noble carries it, I have a copy, damn good book. Well worth the 60 some dollars it will cost you. __________________ "He used to be a pretty nice feller, now he's a welder!"

08-18-2008, 10:00 PM	#12
Senator350 Registered User Join Date: Feb 2004 Location: Albany, NY Posts: 522	Re: Taping header bolt hole. What size drill bit?? fer sure... I've got a strange fondness for big reference books, so that might be a future purchase! I found the chart in the granger catalog... it's on page 132,154,549,008,023 :P __________________ RN U OVR



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