Tap and die thread

[Al Smith]

A bolt thread is a bolt thread .Very seldom will the thread count be anything but standard .SAE threads are given in threads per inch and metric in thread spacing .Most torque specs are given with oiled threads .
A bolt in essence is almost like a spring under tension .You have to put the right amount of torque to literally stretch the bolt .I did this stuff for a living in both setting torque values and measuring same on automated machinery used in automotive engine building .That said tight is tight too tight is broken .BTW I have thread gauges in both SAE and metric plus Acme thread .British Whitworth I don't have .

 

[Bermy]

Excellent information here...confirmed my habit to always change the bolts on my chipper knives every change.

 

[cory]

Alrighty then!!

Al, good stuff. Musta been very cool and interesting to engineer machines that most people take for granted but are actually modern marvels.

09? Sold. I already use anti seize/never seize on the rayco stump teeth bolts cuz those teeth never break and so therefore their bolts stay put a long time. The vermeer teeth break often so most of the bolts get undone and done much more often, hence little danger of them seizing. But yeah, info gleaned, lesson learned.

 

[Tree09]

It's all simply stuff I've had to learn too. Iirc we once talked about rivets actually being stronger, but they switched to bolts for the engineering control. This is exactly what led up to that, the clamping pressure of the bolts, the materials used to prevent galling when torquing (the actual purpose of never sieze, the ease of removal is a nice side effect), the hardness level of the bolt controlling its deformation, e.t.c. I've actually used teflon coated bolts before, it's the step further for different engineering goals. They even have hydraulic torquing machines for large pipe flanges and the like, so they can control it even more. You clip a small hydraulic cylinder on each bolt, pipe them in series so they all exert exactly the same force, pump up to the engineered pressure, and hand tighten all the bolts, and then you're done.

 

[cory]

That is some crazy intense engineering. Smh, humans.

 

[lumberjack]

From what I've seen torque specs can be wet or dry, and the lube specified can be a myriad of things from anti seize to 30 weight. Sometimes it's lubed, torque to 90lb/ft plus a certain number of flats (60* on a hex bolt).


On critical fasteners like connecting rods where both ends of the bolts are accessible, there may be a micrometer to measure the stretch of the bolt a given amount for proper clamping force. Fundamentally that's what the purpose of the torque is for, to stretch the bolt to provide a certain amount of clamping force... too much and the bolt yields (typically breaking), not enough and the joined parts can move, causing wear and potentially failure.

 

[frans]

With an allen bolt you're talking grade 8 which is harder than hammered hell . You'd about need a carbide drill to even touch it .An old trick is to use a prick punch or an old drill bit sharped about like an awl to tap it loose..However if it's jambed tight from bottoming out it about has to be completely drilled out .

Another trick is to use a masonry bit. It is carbide

 

[Al Smith]

A concrete bit would probably work if that's all you could find .Problem would be with an inserted carbide is breaking the insert loose .In my case having worked 29 years in an automotive engine plant I've got quite a selection of solid carbide bits that would be be discarded if after they were resharpened would be too short to be be used in the CNC machinery .Along with drilling out hard bolts they are excellent for things like drilling chainsaw bars .You can break them though .

 

[Al Smith]

The main problem as I see it on chipper knifes is more a chemical reaction with the chips plus the high carbon steel used to make the bolts .If you you don't use some type of anti seize compound they are bound to rust tight .Usually on a grade 8 if you drill the head off once the tension is relieved they back right out .If you wallow out the socket you are just about out of choices .The center of those bolts are much softer than the rest of the bolt .I've also shook them loose using a flat cold chisel and a hammer rather than drill them out .The socket had gotten wallowed out by somebody who wasn't familiar with working on old rusty junk . In short there's a zillion ways to do it but drilling is the last resort .

 

[Al Smith]

Alrighty then!!

Al, good stuff. Musta been very cool and interesting to engineer machines that most people take for granted but are actually modern marvels.

.

To be accurate I did not design them only maintained them .If a change of torque,final angle or sequence it was under the direction of an engineer .I had the knowledge to a point but am not an engineer by any means .

 

[cory]

.I had the knowledge to a point but am not an engineer by any means .

Thank Gawd. You don't want to be one of those guys who designs e.g. oil filters that are basically impossible to access.

. In short there's a zillion ways to do it but drilling is the last resort .

My broken bolt is not seized I'm quite sure, but it is flush on both sides of the pocket, I'll try 'unscrewing' it by tapping on an angle on one side of the bolt to try to get it to turn,

 

[flushcut]

And when all else fails melt the sumbitch

 

[Marc-Antoine]

The torque setting is actually designed to plasticly deform the bolt slightly, stretching it. This provides a hard clamping force that will not come loose. For critical applications, bolts and nuts are discarded every time because of this stretching.

Thanks for the light Kyle. I thought it has to stay in the elastic zone to sustain the use. Makes sens.

Cory, on your first pic, the bolt and the tap don't seem to have the same pitch, like fine and coarse (standard) threads.

Edit, I just had a look in the Machinery Handbook. That takes a lot of time, it's like a rabbit hole as you say.
So, usual pitch for 1/2" bolt is 13 per inch, it's probably your bolt.
The "fine pitch" is 20 per inch.
The die you got is 28, it's in the table of the "extra fine pitch".

That doesn't match at all, no wonder you can't screw them.

 

[Al Smith]

Some engine bolts can be reused and some they recommend not to .With Tom and that old chipper because I had access to them I gave him new bolts .He sold that old thing a long time ago and last I heard he had a self feed Morebark brand .Danged chippers have a lot of maintenance ,something is always broken .

 

[cory]

yeah flush, I've had to do that to a couple rayco teeth that wouldn't budge, hence my use of neverseize on them.

Marc, I have to check it with a thread gauge, hopefully at Home Depot

 

[lumberjack]

I got broken bolts out of pockets by welding a nub onto the flush surface and turning them out. We didn’t use anti seize and it was never hard to remove the broken off portion.

Every normal pocket I’ve seen used 5/8-18 threads.

 

[cory]

That sounds like a good, easy idea, if I had a welder

 

[BlackSmith]

About 90% I get out by welding a nut to the broken bolt and let cool. Drill the threads out of the nut first. If it’s a straight through bolt you can drill through you can torch’em out but ya gotta be steady.

 

[Tree09]

Paraffin wax helps too

 

[lumberjack]

That sounds like a good, easy idea, if I had a welder

Use a normal rotation carbide bit and run them through the other side (Or if it doesn’t work you have a hole for an extractor). It doesn’t normally take much effort to turn them, occasionally I could do it with my fingers.

 

[cory]

It doesn’t normally take much effort to turn them, occasionally I could do it with my fingers.

Agreed, same here. This one is just flush on each side so can't get no purchase

 

[lumberjack]

That’s why Green Bolts have a slot on the tip to turn them out with a screw driver.

 

[cory]

Nice idea

 

[flushcut]

[QUOTE="lumberjack, post: 1004818, member: 21"

Every normal pocket I’ve seen used 5/8-18 threads.
[/QUOTE]
Cory, Carl has it right tap and die size is 5/8"-18. I just measured.

 

[cory]

Thanks, I will check that out