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I'm reworking a Deere lawn tractor and want to run a tap through a couple of threaded holes before I put in new bolts. One in particular I had to cut the head off and drill the bolt out. The Deere size is M8x16. Scrolling through the Fastenal site I see about 221 different M8 taps. How do I know which one I need?
Does anyone know of a simple bolt size to tap size chart that lays this out for dummies like me (gawd - taper, plug, bottoming, how many flutes, finish, material??? I didn't know taps where this hard:banghead3).
If any experienced wrenches know of the half dozen or so sizes most used in lawn/garden tractors that would like to share I'd appreciate it.
Thanks for any help.
 

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Ones I use most are 1/4",5/16",3/8",1/2" and 5/8" both fine and course threads...some things are 7/16" and 9/16",like lug nuts and spring shackle bolts..fine thread..

Metric taps get complicated fast..metric has at least 4 types of thread pitch instead of just fine and course like our standards..1.00 ,1.125,1.150 and 2.00 pitch are the 4 I have run across most..certain things on cars use the less common pitch of course,so they cant be fixed easily!..(seems stores never stock those pitch bolts or taps,only macine shop suppliers carry them around here)..

Taps come in many varieties,as you have probably read..a "bottoming" tap has threads all the way to the tip and is to be used to thread a blind hole as close as possible to the bottom of it..AFTER a "starting" tap that has a tapered end so it will start easier is used!..there are other types like a "plug" tap,I think the ones sold in most tool stores are plug type,they are a "universal" type ,good for thread chasing and cleaning threads..

I find once a tap is used a dozen or so times,even if kept well lubed,they get dull--and they will snag and break off a lot easier than a nice new sharp one--so I like to buy a new tap when I have to do a "difficult" tap job,you have a lot better chance of success with a new one..
 

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Ones I use most are 1/4",5/16",3/8",1/2" and 5/8" both fine and course threads...some things are 7/16" and 9/16",like lug nuts and spring shackle bolts..fine thread..

Metric taps get complicated fast..metric has at least 4 types of thread pitch instead of just fine and course like our standards..1.00 ,1.125,1.150 and 2.00 pitch are the 4 I have run across most..certain things on cars use the less common pitch of course,so they cant be fixed easily!..(seems stores never stock those pitch bolts or taps,only macine shop suppliers carry them around here)..

Taps come in many varieties,as you have probably read..a "bottoming" tap has threads all the way to the tip and is to be used to thread a blind hole as close as possible to the bottom of it..AFTER a "starting" tap that has a tapered end so it will start easier is used!..there are other types like a "plug" tap,I think the ones sold in most tool stores are plug type,they are a "universal" type ,good for thread chasing and cleaning threads..

I find once a tap is used a dozen or so times,even if kept well lubed,they get dull--and they will snag and break off a lot easier than a nice new sharp one--so I like to buy a new tap when I have to do a "difficult" tap job,you have a lot better chance of success with a new one..



good info and i do agree ..As i have had to remove many broken taps over the years because i was to darn cheap to buy a new ones..And man are they a pain in the buns to get out once they are broken off.:trink39:..Now i buy them in 2s every time i need one....Easy outs are another one to buy new after a few uses
 

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M8x16, never heard of a metric tap that size. They're spec'd at dia. which is the dia. of the bolt so an 8 mm bolt you'd get an 8 mm tap x thread pitch which is threads per mm. As Tractor-Holic said the most popular pitches are what he posted. Here's a chart http://tinyurl.com/26uf6t2 .
If I'm cleaning out old threads I use a plug tap run down first as it has a slight taper at the start but not as sharp as a starting tap. Less chance of getting buggered up at the beginning as you want to catch the existing threads. Then I'll run a bottomimg tap down to clean it out to the bottom. Make sure you get the chips/rust out once in a while with a blow gun as you're tapping.
You just want a 3 flute strainght hand tap. The spiral cut ones I think are mainly for machine tapping...Mike
 

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I've had numerous taps at my machine shop make hundreds, if not thousands of cycles each. As Robert said, lubrication is key. But a common error, that affects long life, is using whatever lubricant is around. Pick up a small can of tapping fluid. Cool Tool is a good one. If it saves you one or two taps, it's payed for itself. Also when hand tapping and resistance is met, back it out a half of turn or so, and resume tapping. This "clears the chips". Good luck!
 

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Snap-On sells a nice set of tap extractors,that have prongs that fit into the space between the cutting areas on a busted tap--with them you can usually unscrew a busted tap out easily,provided it did not break off way down deep in the hole..

Taps burn like sparklers,quicker than usual steel or cast iron,so a cutting torch will usually blow a broken one out quickly in a shower of sparks if you have to resort to drastic measures--its also possible to chip them away peice by peice with a punch,but wear goggles,spraks will fly off as your chipping and you dont want a sharp tap thread in your eyes..

I dont have tapping fluid handy too often,so I use a penetrating oil or diesel fuel,or Marvel Mystery Oil ...even drain oil is better than nothing!..
 

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I dont have tapping fluid handy too often,so I use a penetrating oil or diesel fuel,or Marvel Mystery Oil ...even drain oil is better than nothing!..
Funny you should say that. Most of my tapping is done on the CNC's now. So the taps are lubricated by the cutting/coolant mix. Years ago I bought a ton of tapping fluid at a fire sale. Well, I been living with those cans for years now. I mean how much can you use right? Maybe I should reach out to the Chinese.................
 

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The "16" in M8x16 is 16mm length. You can take a bolt you know fits the threads to NAPA and they can find out which M8 is right.
I had to do that just the other day on a stinkin' Buick!
 

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My Tap & Die set from HF included a pitch gauge. It looks kinda like a feeler gauge, but each 'leaf' has notches in its side that line up to the proper pitch on a bolt or in a nut. You just visually guess close, then hold it to the threads, if it meshes correctly you've found the right pitch.
 

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My Tap & Die set from HF included a pitch gauge. It looks kinda like a feeler gauge, but each 'leaf' has notches in its side that line up to the proper pitch on a bolt or in a nut. You just visually guess close, then hold it to the threads, if it meshes correctly you've found the right pitch.
They are extremely handy.
 

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Snap-On sells a nice set of tap extractors,that have prongs that fit into the space between the cutting areas on a busted tap--with them you can usually unscrew a busted tap out easily,provided it did not break off way down deep in the hole..

Taps burn like sparklers,quicker than usual steel or cast iron,so a cutting torch will usually blow a broken one out quickly in a shower of sparks if you have to resort to drastic measures--its also possible to chip them away peice by peice with a punch,but wear goggles,spraks will fly off as your chipping and you dont want a sharp tap thread in your eyes..

I dont have tapping fluid handy too often,so I use a penetrating oil or diesel fuel,or Marvel Mystery Oil ...even drain oil is better than nothing!..


next time the snap on man comes to the shop i think i am going to get me a set of them tap extractors
 

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Got to love the big white truck.
Know they love our $$$$$
but they are the best in my opinion......
 

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Got to love the big white truck.
Know they love our $$$$$
but they are the best in my opinion......


yes i do agree there lol ..I used to buy cheap tools ..when i worked the the wrecking yard as they took a nasty beating from time to time ..What made me change was i was buying ratchets non stop all the time ..so i decided to try a snap on one out ..I still have it to this day and use it everyday...Most of my stuff comes from the big white truck or mack ..depeding on what it is ...My air gun is from blue point and it will still snap wheel studs and its 8 years old now
 

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I just got a set of Blue Point ratchet wrenches a couple weeks ago.
My delux tap and die set has the extractors included.
 

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Discussion Starter #17
Metric taps get complicated fast..metric has at least 4 types of thread pitch instead of just fine and course like our standards..1.00 ,1.125,1.150 and 2.00 pitch are the 4 I have run across most..certain things on cars use the less common pitch of course,so they cant be fixed easily!..(seems stores never stock those pitch bolts or taps,only macine shop suppliers carry them around here)..

QUOTE]

Shazam, that's what those numbers mean. Many thanks, though I suspect Deere has some machine in the back room that cuts a special pitch and I'll never find the right tap.

Thanks all for the quick response and feedback.
 

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I ran into a new "thread" recently..."FORD" thread!,,thats right--FORD has exhaust manifold studs with a special pitch,all their own!..NOTHING else is even close,they almost look like lag screw threads...since my friend got them out without breaking them,he decided to see if they had them at the Ford dealer..they did..they were 8 bucks apeice,and the nuts were not included,they were another five bucks each almost!..

My friend was ready to drill and re-tap them to 7/16..I would have if it were my car--or better yet,use a bolt and nut instead,that can be cut off in two seconds and replaced with no fuss or expense!..it amazes me what lengths car manufacturers go to,to ensure repairing them is expensive and difficult,for no good reason..
 

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That means there will be some new expensive taps for them...

Yeah those wrenches are really nice with the adjustable angle ratchet head.:fing32:
 

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Metric taps get complicated fast..metric has at least 4 types of thread pitch instead of just fine and course like our standards..1.00 ,1.125,1.150 and 2.00 pitch are the 4 I have run across most..certain things on cars use the less common pitch of course,so they cant be fixed easily!..(seems stores never stock those pitch bolts or taps,only macine shop suppliers carry them around here)..

QUOTE]

Shazam, that's what those numbers mean. Many thanks, though I suspect Deere has some machine in the back room that cuts a special pitch and I'll never find the right tap.

Thanks all for the quick response and feedback.
AND! Those numbers stamped on the head of the metric bolts are the "grade". The higher the number the harder the bolt. 8.8 seems to be the most common and is about equivalent to a "grade 5 SAE", 9.8 is roughly equivalent to a "grade 8 SAE"

Roger
Old, Tired, and Grumpy from putting several Snap-On dealers kids through medical school
 
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