Machinists? Tapping advice...**Updated**

[Eli]

I know there are some mechanical engineers/machinists in here... lol..

I'm going to be tapping something, and I really don't want to break the tap and/or screw up the part.. lol.. So, can you give any advise on which tap I should get.. the speed I should turn it, etc?

The size of the tap is 1/2 - 13NC - left handed thread

The material I'll be tapping is steel.. I have tapping fluid. The operation will probably be done on a lathe.


The spiral point tap is twice as expensive as the normal tapered hand tap.. It says that they're generally stronger. I don't want to spend 20 bucks if I dont have to though.

Any advice greatly appreciated.

 

[duragezic]

Well I'm not a machinist, but I could sell you some taps ... but while working where I do I guess I picked up a little.

I didn't think spiral pt taps were twice as much (I'll look tomorrow, kinda curious myself now that you say), but I do remember some guys coming in and asking for hand taps cause they thought they'd work but they end up back a couple hours later with a broken tap. So although the situations are obviously different, perhaps it wouldn't be a bad idea to go for the spiral point. And it'd probably be a bit more forgiving if you didn't have the optimal speed. But with cutting fluid and it's not exactly a small tap, you should be able to go at a moderate to high speed. I think a 3 flute, plug of course.

That's all I know hah. I don't know where you're buying the tap from, but perhaps the workers there could point you in the right direction also?

 

[Evadman]

I have tapped holes in blocks before with hand taps, and what I found was that if you backed it completly off and cleaned the threads every time you tapped the die "thickness" then the change of a broken tap was about nill.

I would never dream of using a machine on a part I needed. I would test it out on a few scrap pieces first. retrieving a broken tap is not fun. not fun at all.

 

[duragezic]

I looked up prices and a hand tap is $10.84 while a spiral point is $12.28. This is from the book from the manufacturer (reiff and nestor). I don't know why it is twice as expensive where you are buying it from!

 

[jjones]

It's been a million years since I've used a tap but it's really easy and you shouldn't break it, especially since it's a 1/2 inch tap. That's a large enough size that's fairly strong. The one's you need to worry about are 1/4 inch or less.

After every turn or two, just back it up about half a turn; use cutting fluid and you'll be fine. As for a lathe, it's been too long since I've done it that way and I don't have any good advice other than to tell you to turn it slowly and let the tap pull itself in. A lathe is better to use because it'll be aligned properly, whereas by hand you may start out slightly off square.

 

[Eli]

Originally posted by: jjones
It's been a million years since I've used a tap but it's really easy and you shouldn't break it, especially since it's a 1/2 inch tap. That's a large enough size that's fairly strong. The one's you need to worry about are 1/4 inch or less.

After every turn or two, just back it up about half a turn; use cutting fluid and you'll be fine. As for a lathe, it's been too long since I've done it that way and I don't have any good advice other than to tell you to turn it slowly and let the tap pull itself in. A lathe is better to use because it'll be aligned properly, whereas by hand you may start out slightly off square.

Yeah, that's why I'm going to use the lathe.. for accuracy. I'll tap a few holes in some scrap first.. just to get the feel for it.

eagle - Well, I'm getting the tap prices from McMaster Carr's site.. You also have to take into account that I'm getting a left hand tap.. that is, left = tight, right = loose.

I'm changing the gearing on my scooter, and the sprocket is threaded on. The new sprocket has no threads yet.

 

[Johnnie]

i can get ya most any size tap ya need

 

[Ornery]

Originally posted by: jjones
It's been a million years since I've used a tap but it's really easy and you shouldn't break it, especially since it's a 1/2 inch tap. That's a large enough size that's fairly strong. The one's you need to worry about are 1/4 inch or less.

After every turn or two, just back it up about half a turn; use cutting fluid and you'll be fine. As for a lathe, it's been too long since I've done it that way and I don't have any good advice other than to tell you to turn it slowly and let the tap pull itself in. A lathe is better to use because it'll be aligned properly, whereas by hand you may start out slightly off square.

This is the best advice I've seen. I think you're going way overboard using a lathe, though. A simple tapping block should suffice. If you do use it, just spin the chuck by hand and leave the tail stock float free. Any lube on there will be fine. No need for fancy spiral flutes, coatings or anything else. You sure it's 13 pitch? Seems kind of course for that application.

 

[Eli]

Originally posted by: Ornery

Originally posted by: jjones
It's been a million years since I've used a tap but it's really easy and you shouldn't break it, especially since it's a 1/2 inch tap. That's a large enough size that's fairly strong. The one's you need to worry about are 1/4 inch or less.

After every turn or two, just back it up about half a turn; use cutting fluid and you'll be fine. As for a lathe, it's been too long since I've done it that way and I don't have any good advice other than to tell you to turn it slowly and let the tap pull itself in. A lathe is better to use because it'll be aligned properly, whereas by hand you may start out slightly off square.

This is the best advice I've seen. I think you're going way overboard using a lathe, though. A simple tapping block should suffice. If you do use it, just spin the chuck by hand and leave the tail stock float free. Any lube on there will be fine. No need for fancy spiral flutes, coatings or anything else. You sure it's 13 pitch? Seems kind of course for that application.

Nope, I don't know if it's 13 or not. There are really only 2 choices as far as I can see.. 1/2-13NC and 1/2-20NF.. I don't have a thread measurer(lol), so I'm just going to buy a couple of left handed bolts, and see which one threads on.. hehe

For all I know, it could be metric. That would kinda suck. lol.. I'm waiting for my tax return to get here so I can start ordering parts.. In the meantime, I'm just trying to plan it out as best as possible.

Hmm, so you think the lathe is overkill huh.. doesen't it just make it a lot easier? Chuck the piece to be tapped up, set the speed, turn it on and push the tailstock into the part, until it starts tapping, and pulls itself in? shrug. Seems easy to me, rather than trying to do it perfect by hand.. heh.. shrug. I watched my brother tap some parts on the lathe.. Made it seem effortless.

 

[Ornery]

If it's no trouble to get access to a lathe, then fine, but I wouldn't go out of my way to do it. It's only one hole after all! It probably is a fine pitch. You can tell the difference by looking at it. Take a macro picture with a scale by it, I'll tell you from that. If it is metric, that's a different story.

 

[Eli]

Originally posted by: Ornery
If it's no trouble to get access to a lathe, then fine, but I wouldn't go out of my way to do it. It's only one hole after all! It probably is a fine pitch. You can tell the difference by looking at it. Take a macro picture with a scale by it, I'll tell you from that. If it is metric, that's a different story.

Yeah but... but.. It has to be perfect.. if it's off center or anything weird like that, I'd have to buy a new sprocket.. lol..

 

[Moonbeam]

Ta tada ta tada ta tada ta

Ta tata dada ta da ta

Hit it!

 

[Ornery]

Perfect!

LOL, it does not compute... I build furniture using a circular hand saw, rather than a table saw, if that gives you any indication of how fussy I am

If push comes to shove, I can split a thousandth of an inch, but ONLY if I HAVE to! Use the lathe for "perfection", but go slow, like 80RPM or so.

 

[Eli]

Originally posted by: Ornery
Perfect!

LOL, it does not compute... I build furniture using a circular hand saw, rather than a table saw, if that gives you any indication of how fussy I am

If push comes to shove, I can split a thousandth of an inch, but ONLY if I HAVE to! Use the lathe for "perfection", but go slow, like 80RPM or so.

Yeah. The sprocket is only 7/8ths of an inch thick. So I'm not really making that many threads. Hopefully it won't be a problem.

I have another question. Whats the drill size for a 1/2" tap? The bore in the sprocket is already 0.500. Can I tap that with a 1/2" tap, or am I going to have to go a size larger?

 

[tcsenter]

I have another question. Whats the drill size for a 1/2" tap? The bore in the sprocket is already 0.500. Can I tap that with a 1/2" tap, or am I going to have to go a size larger?

The drill bit size for a 1/2" 13NC tap can be between 27/64 and 29/64 for metals such as steel. The internet is a wonderful thing, ask and you shall receive:

Tap and Drill Chart

Another Tap and Drill Chart

Yet Another Tap and Drill Chart

Tapping Speed Guide

You may want to increase the size of your tap and screw if your bore is already .500", unless this application will not require a lot of fixation/tension.

 

[Eli]

Originally posted by: tcsenter

I have another question. Whats the drill size for a 1/2" tap? The bore in the sprocket is already 0.500. Can I tap that with a 1/2" tap, or am I going to have to go a size larger?

The drill bit size for a 1/2" 13NC tap can be between 27/64 and 29/64 for metals such as steel. The internet is a wonderful thing, ask and you shall receive:

Tap and Drill Chart

Another Tap and Drill Chart

Yet Another Tap and Drill Chart

Tapping Speed Guide

You may want to increase the size of your tap and screw if your bore is already .500", unless this application will not require a lot of fixation/tension.

I know, and believe me.. I do do a lot of research on the internet.. But it's nice to talk to people about things sometimes.

Well.. I've decided to do it a totally different way.. although I'll still need the same tap.. lol..

Instead of threading the sprocket itself, we're going to make an extension, threaded on one end, with a keyway on the other. That way I can easily change the gearing, by just slipping different sized sprockets on and off.

Now.. Any advise on drilling a hole directly in the center of something?

 

[Ornery]

Back to the drawing board, eh? Sounds like you're making an "adapter". What kind of stock, round bar? Lathe is perfect for centering a hole up in that. Then you'll need a broach for the key. Does the sprocket already have a key in it? You're going to put one in it? The shaft you're attching to is 1/2"-20, left hand male? Will future sprockets have the same 1/2" hole without a key in them?

Just spent a while trying to find a 1/2-20 left hand Helicoil. See if you can track it down on this Helicoil list. If they make such a thing, you could open that .500 hole up to about .515 and use the Helicoil tap on it. Thread the Helicoil insert in and use it like that. Once you have a few inserts, the tap and inserting tool, you can do as many sprockets as you want later.

 

[Farmall]

One of the easiest ways of getting your hole in the center of the sprocket or anything else for that matter is a indicator with a extension arm. Thats provided you are using a machine to do the drilling.

You will find a indicator wherever you get your tap most likely. You could also use a scale/ruler to find center as well, just measure from different points across the diameter and scribe your center line.

BTW - if you are tapping by hand don't bother with the spiral flute tap, they are designed for machine tapping.

Farmall

 

[Ornery]

Hey Farmall, I know Eli is into small engines, are you into Farmall tractors?

My loose connection to either hobby is my 1986 Wheelhorse 111-5 speed rider. I bought it because of it's ability to store standing on end and the quality Wheelhorse name. The engine died last year and I went shopping for a new rider. Couldn't find a singe machine that could store upright. The oil resivoir has to be at the bottom and the battery has to pivot. Eli is the one who gave me a hand troubleshooting the old engine. In the end, I bought this 12.5HP, electric start from Small Engine Warehouse for only $450.00 shipped. Now I'll get another 15 years out of this old horse! I'd hang out at The Wheelhorse Forum but they don't think much of the lowly 100 series riders!

 

[Farmall]

Ornery,

I have a Farmall M - Has a high lift loader, wide front. The "M" was a pretty powerful machine in its day. I have a fairly lengthy driveway (1/3 mile) it works great for snow removal etc. With the loader its actually a decently versatile tractor. Mine was in pretty good shape when I bought it, had to do the valve cover gasket and added some new lights - not to bad for a old tractor.

Not really a hobby, more of a helping hand so to speak. Someday I want to totally redo the whole machine top to bottom, paint is a bit faded.


Farmall M

 

[Ornery]

Interesting! I built a PC for a friend of my in-laws. He gave me the PC a few years later to tweak and add more memory and I noticed the tractor for his wallpaper. His wife told me he was a fan of Farmall tractors. I think it may have been the "M" series too. I saw a book at Borders closeout store that featured Farmall tractors (and maybe others). It was a huge hard cover book and only $16.00. I should have bought it for his wife to give him for Christmas, but we're not close friends or anything. Funny thing is, I NEVER heard of Farmall before seeing that wallpaper! No doubt I'd seen a lot of those bruisers out in the fields without even thinking about what brand they were.

 

[Eli]

Originally posted by: Ornery
Back to the drawing board, eh? Sounds like you're making an "adapter". What kind of stock, round bar? Lathe is perfect for centering a hole up in that. Then you'll need a broach for the key. Does the sprocket already have a key in it? You're going to put one in it? The shaft you're attching to is 1/2"-20, left hand male? Will future sprockets have the same 1/2" hole without a key in them?

Just spent a while trying to find a 1/2-20 left hand Helicoil. See if you can track it down on this Helicoil list. If they make such a thing, you could open that .500 hole up to about .515 and use the Helicoil tap on it. Thread the Helicoil insert in and use it like that. Once you have a few inserts, the tap and inserting tool, you can do as many sprockets as you want later.

Yeah. An adapter.. lol.. will just use round bar(You know, I never could figure out that term.. "round bar"...)

My plan is to buy a 1 foot length of this round bar.. I'll cut a section say about 1 1/2" long.. in one end, I'll drill a hole for the 1/2"-20 threads(I think I confirmed.. There is only about 1/4" of threaded shaft left after cutting the old sprocket off(was welded), and there are 5 threads in that 1/4"..).. The only thing I'll have to do to the other end is mill a keyway for the sprocket. The sprocket will have a 1" bore with keyway. Actually, the sprocket could be a few different bore sizes.. 5/8, 7/8, 3/4, and 1"..

Thinking about it, I probably don't want the adapter to be a whole half an inch bigger in diameter than the shaft. I don't know, I'm not a machinist. I just want everything to be nice and solid, and with only 1/4" of threads.. I hope the whole assembly is strong enough. Is the metal that I chose going to be strong enough to withstand the stresses that will be encountered? heh.. Maybe I'll get 3/4" round bar, that will leave about 1/4" of a sidewall on the threads.. Wonder if thats thick enough? Questions, questions.....

That way I dont have to deal with all that sprocket threading business, and it will be very easy to change sprockets if I want/need to.

 

[Farmall]

Eli,

How much torque is going to be put on that sprocket? I am no machinist, but I am a moldmaker and do quite a bit of tapping, drilling, milling etc. Seems to me that a 1/4 inch of thread would just barely be enough, granted you are using 1/2-20 threads. Will the shaft 1" or whatever it is you bought hit against the area the old sprocket was mounted on once its threaded on? If it can that will make the thread issue a lot less of an issue. I would drill the hole for the 1/2-20 thread slightly undersize to get a higher % of thread in the hole, the 27/64 drill would be about right its actually used for the 1/2-13. The tap drill sizes are figured for 75% thread in most cases.

the bar stock you are planning to buy will work fine.

One other question, what is going to hold the sprocket on the keyway? Will there be something else outside of the sprocket to keep it in place once you slide it on the key? One thought might be to thread both ends of the stock and use a lock washer/cap screw combo to hold it on. I might have missed something along the way, so that may not make sense.

 

[Eli]

Originally posted by: Farmall
Eli,

How much torque is going to be put on that sprocket? I am no machinist, but I am a moldmaker and do quite a bit of tapping, drilling, milling etc. Seems to me that a 1/4 inch of thread would just barely be enough, granted you are using 1/2-20 threads. Will the shaft 1" or whatever it is you bought hit against the area the old sprocket was mounted on once its threaded on? If it can that will make the thread issue a lot less of an issue. I would drill the hole for the 1/2-20 thread slightly undersize to get a higher % of thread in the hole, the 27/64 drill would be about right its actually used for the 1/2-13. The tap drill sizes are figured for 75% thread in most cases.

the bar stock you are planning to buy will work fine.

One other question, what is going to hold the sprocket on the keyway? Will there be something else outside of the sprocket to keep it in place once you slide it on the key? One thought might be to thread both ends of the stock and use a lock washer/cap screw combo to hold it on. I might have missed something along the way, so that may not make sense.

Well, the engine develops 2.31ftlbs @ ~4500rpm.. The primary gear ratio will be(12/30) 2.5:1 So.. yeah. Well, maybe I'll get like.. 7/8" round barstock. I was looking at some shafts at http://www.mcmaster.com... I could get a 6" length of 7/8" case hardened, precision ground 1566 steel for $7.39. Would I have trouble milling a keyway and drilling/tapping such a hard metal? Would the stuff I linked to on OnlineMetals be straight enough? Yeah, I plan to have the adapter screw all the way on until it hits the raised area of the shaft just after the threads. I'll probably use stud locker on it.

The sprocket has setscrews. I'll loctite them, too.

 

[Farmall]

Case hardened steel is not hard all the way through, it is only about 1/32" thick or a bit more on the outside.

If you are using a lathe use a carbide cutting tool to face the end of the stock and you will have no trouble drilling and tapping into it, use cutting fluid though.

Far as milling the keyway get a carbide cutter or you will have a tough time getting through the case.

I think if you are not going to bore the diameter in the sprocket its hardly worth getting precision ground stock. You can turn the cold roll material you linked earlier to whatever size you want and it will be perfectly straight and true to the hole you drill/tap in it provided you do them both in the same setup.

Its probably not a bad idea to turn the diameter anyway so you can match that dia. to the bore in the sprocket more closely.