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Black Forest
10-18-2011, 02:58 PM
I need to make a bolt for my John Deere tractor.

It is a .250 diameter bolt. The closest mm thread is a 1.25mm.

Can anyone tell me what the "normal" TPI would be for a .25 inch bolt?

strokersix
10-18-2011, 03:05 PM
1/4-20 or 1/4-28

20 tpi should be real close to 1.25mm pitch.

TexasTurnado
10-18-2011, 03:06 PM
NC - 1/4 x 20
NF - 1/4 x 28

TexasTurnado
10-18-2011, 03:07 PM
1/4-20 or 1/4-28

20 tpi should be real close to 1.25mm pitch.


You beat me to it :D

Black Forest
10-18-2011, 03:10 PM
Danke!

Now I just need to figure out how to setup my lathe for 20 tpi. It is just a matter of turning a couple of knobs so it shouldn't take too long.

john11668
10-18-2011, 03:44 PM
For 1/4 would you not be better to run a die down it :p

Black Forest
10-18-2011, 03:48 PM
If I had a die of that size of course that is what I would do. But I don't so I would have to order a die. I need the tractor tomorrow so I will single point a rod supported with a center by the tailstock.

Highpower
10-18-2011, 05:20 PM
For future reference:

http://www.icscuttingtools.com/calculate/metric-conversion.htm

A 0.9mm pitch would be closest to a 1/4 - 28 thread.
:)

Rich Carlstedt
10-18-2011, 06:57 PM
The correct pitch in metric for the 1/4" bolt should be 1.27mm
( .050 x 25.4 )

Black Forest
10-19-2011, 12:29 AM
The correct pitch in metric for the 1/4" bolt should be 1.27mm
( .050 x 25.4 )


I guess that is why my pitch gage of 1.25 was the closest.

J Tiers
10-19-2011, 08:40 AM
If it is truly a "bolt", that is, it has a nut on it, then it should not matter what thread it is...... so long as you have or can make a nut.... I'd be tempted to use a 6mm screw, and if it had to be a close fit, wrap a shim around to make up the extra 0.35mm.

If the thing screws into a tapped hole, as I suspect it does, then you are stuck, unless you want to drill out and re-tap larger.

Depending on the depth of threads, and on how critical the part is, you could go with 1.25mm pitch and it would likely fit. Many parts on a tractor are pretty non-critical, and farmers are not known for being fussy when there is work to be done but the tractor is not working. Whatever fits is likely to be pounded, stuffed, or cross-threaded into place in that case.

vpt
10-19-2011, 09:09 AM
Just grab a metric bolt and impact it in there! Thats what lots of people do.

gary350
10-19-2011, 09:24 AM
If it is a 1/4" bolt it will have a 1/4" thread, 20 or 28.

If it is a metric bolt it will have a metric thread.

Black Forest
10-19-2011, 11:34 AM
I had a great time making a .750 inch long bolt today!

I pushed a button and changed my DRO on the lathe to inch.

Then I turn a hex head 8mm bolt down to .245 inch.

Turned two knobs on my lathe that set it to cut 20tpi.

Cut the threads and installed this work of art in the tractor and off to work.

I didn't want to fudge too much on the bolt because this bolt holds a clip in place that holds a pin in place that is critical for the steering!


Thank you for the info on the TPI.

My wife is worried about me. I was so pleased with myself that I made a bolt.

john11668
10-19-2011, 02:36 PM
Mine was very pleased with me !
I made her a batch of screws to replace broken plastic ones which adjusted the soft closers on the kitchen cupboard doors :D

Black Forest
10-20-2011, 01:41 AM
J Tiers, question. What do you call a metal thing that has threads with a hex head on one end that threads into a hole on a machine and not a nut? I/we always called them bolts. A screw to me always has a point on one end. Or is driven in with......wait for it......a screwdriver!

The Artful Bodger
10-20-2011, 02:08 AM
J Tiers, question. What do you call a metal thing that has threads with a hex head on one end that threads into a hole on a machine and not a nut? I/we always called them bolts. A screw to me always has a point on one end. Or is driven in with......wait for it......a screwdriver!


I was told that a bolt which has thread right up to the head is called a screw.:cool:

Mike Burch
10-20-2011, 02:50 AM
I'm not fluent in American (though I can often make myself understood), but in English something with a thread all the way up is a machine screw, and something with a thread only part way up is a bolt.
Either may be hex-headed, countersunk or whatever-headed.
To a layman, they're all called bolts, but to an engineer, they differ.

Black Forest
10-20-2011, 05:52 AM
So Mike, is this a bolt or a screw?
http://i853.photobucket.com/albums/ab91/burnandreturn/screwbolt.jpg

rohart
10-20-2011, 06:37 AM
There's the term setscrew too. Some use that for a caphead screw.

The window frame doobrie is a screw in the carpentry world, but what BF has just made is a screw or a setscrew in the metal world.

Just remembered. I think the difference between a screw and a setscrew is whether there is any plain shank, in which case the setscrew is the one with the plain shank.

George Bulliss
10-20-2011, 06:47 AM
There is an entire section in Machinery’s Handbook titled, “Differentiation between Bolt and Screw” (in the Fasteners section).

The first few lines:

A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torqueing a nut.

A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread and of being tightened or released by torqueing the head.

It goes on from there, but that’s the basics.

George

Black Forest
10-20-2011, 07:00 AM
Screw in inches?

So I made a screw not a bolt. But my tractor runs now!

vpt
10-20-2011, 08:22 AM
The way I look at it is this. If the bolt has a flat on the end of the threaded side it is a bolt. If it comes to a point it is a screw.

J Tiers
10-20-2011, 08:35 AM
Cap screw...... probably originally "bearing cap screw"...... threads into solid material. A 2 piece bearing has a 'cap" half that is secured with screws.... i.e. short threaded items that look just like a bolt.

Bolt.... something with a nut on it (does that make a motorcycle a bolt?). Typically longer, and may have an unthreaded section.

I have no real idea why there is a distinction.

a) The unthreaded section may be the key difference other than the nut.... a bolt then is capable of taking "shear", while a screw is only for tension, holding something down with mo location function.

b) Alternately, the "bolt" has standardized threads within a specific spec, while a screw is potentially identical without meeting the thread specs.... according to this "internet legend" site....
http://euler9.tripod.com/bolt-database/boltdef.html

Frankly the second makes sense, ... as it neatly includes wood "screws" and sheet metal "screws" within its definition without needing any further explanation.

lakeside53
10-20-2011, 10:47 AM
The way I look at it is this. If the bolt has a flat on the end of the threaded side it is a bolt. If it comes to a point it is a screw.


But is it made from billet?:D :D :D :p


sorry.....

vpt
10-20-2011, 03:57 PM
But is it made from billet?:D :D :p


sorry.....


Only the expensive ones. ;)

The Fixer
10-20-2011, 04:11 PM
Your tractor is screwed! :)

Black Forest
10-20-2011, 04:18 PM
Tomorrow I go look at new tractors. I think I will buy a German made tractor. I don't want a tractor that is screwed together!

Really, I go look at a Fendt tractor tomorrow.

Mike Burch
10-20-2011, 06:53 PM
Black Forest, that is clearly a screw.
I suppose I should have made it clear in my previous post that I was referring to machine threads, not self-tappers or wood-screws, but I thought that we could take that as a given. Sorry about that.