Damaged 60 1/2 block plane thread - replacement?!

[Fergie 307]

I'm not sure about this, but those threads look like a different size to me as already said. They also look the same pitch, but the steeper helix angle implies a double start thread. It does actually look like that, but can only really be ascertained by examination. It makes sense in the the parts would move apart when the thread was turned. It also complicates things for anyone making one. Certainly not insurmountable, but just more complicated. Any maker would need to examine the whole plane preferably to take sizes and threads off it.

I think chai latte is correct, it looks as though they are different threads simply because, although the pitch may be similar or the same the different diameters make it appear different.
From my point of view, if I have the parts in front of me then replicating them is easy. I don't really need to know anything more.
If it was a case of making a missing part from scratch, then I agree you would want the whole thing to be able to understand how it is supposed to work.

 

[Corset]

not sure thats worth the effort of repairing, lots of poor ones go cheap on ebay and just take the part of another one. thats a personal view but i have restored 50 or so over the years and certain things just arent worth the effort.

 

[Fergie 307]

not sure thats worth the effort of repairing, lots of poor ones go cheap on ebay and just take the part of another one. thats a personal view but i have restored 50 or so over the years and certain things just arent worth the effort.

Oh agree entirely, depends on the quality of it, or maybe sentimental value.

 

[Amplidyne]

I think chai latte is correct, it looks as though they are different threads simply because, although the pitch may be similar or the same the different diameters make it appear different.
From my point of view, if I have the parts in front of me then replicating them is easy. I don't really need to know anything more.
If it was a case of making a missing part from scratch, then I agree you would want the whole thing to be able to understand how it is supposed to work.

I was simply thinking that if I were making the whole thing, I'd want to be able to try the threads for fit. Especially if they are non standard.
In my mind, the threads are near enough so that a similar pitch on a different diameter wouldn't show that much difference in angle on the helix. Also if you try to follow the threads round, they look as if they don't match a single start. Also how does the thing work?
However as I've said, I may hopefully be wrong.

 

[Fergie 307]

I am coming at it from the assumption that the tool has been used by the OP for some time, and worked correctly until the threads stripped?
If that is the case then a new part or parts with intact threads should get it back into use.
Two things I don't understand.
1 why the different diameters? If they were significantly different, say 1/4 and 7/16, then I could understand, although would still be interesting to know why. But when they are so close it just seems rather pointless.
2. The female part appears to be brass. If that is the case then I am struggling with how a brass nut can do that much damage to what appears to be a steel thread. I wonder if there is something else going on, is it rubbing against something for example?
Ok ignore point 2 having looked at a video of one being stripped down I can see it is steel.
This is a still, not very good quality but can't make my mind up if the larger thread is actually left handed, which would make much more sense.
Someone on here must have one, this video is of a Stanley, which appears to be identical to the OP's.

 

[Fergie 307]

I was simply thinking that if I were making the whole thing, I'd want to be able to try the threads for fit. Especially if they are non standard.
In my mind, the threads are near enough so that a similar pitch on a different diameter wouldn't show that much difference in angle on the helix. Also if you try to follow the threads round, they look as if they don't match a single start. Also how does the thing work?
However as I've said, I may hopefully be wrong.

Not disagreeing with you. But if they have to be posted from Scotland, where the OP is, then sending the whole thing a tad pricey.
I can make a replacement to the exact dimensions to within pretty tight tolerances, so ought to be ok.
But I agree it would definitely be better if he could find someone locally, and take the whole thing in.

 

[Fergie 307]

Looking at the Stanley site not clear if the one they sell now is exactly the same. Maybe worth contacting them.
Or look on e bay USA loads of them on there, if you contact one of the big sellers of them they might have spares.
The guy refurbishing it in the video says the damage you have is very common, so I dare say someone must supply parts.
As to how it works, given that the movement required is tiny it maybe that they are both right hand threads. If one were a slightly finer pitch than the other then they would move relatively by a very small amount, which is all that is required. No idea without seeing it in the flesh.
I'm guessing this design came about because the low blade angle doesn't leave enough room for the yoke type you see on bigger ones.

 

[BillHoughton]

They're effectively different pitches, and the screw advances the cutting iron as it screws into the body. I've never quite understood the physics, or why Stanley chose that over a simpler method, but it works quite controllably.

 

[ChaiLatte]

They're effectively different pitches...

You mention physics and then write a meta-physical statement.

They are either different pitches or they are the same pitch. No 'effectively'.

The physics, if you wish to call it that (I am more humble, and would say mechanics), is encompassed by the term "differential screw".

 

[Fergie 307]

They're effectively different pitches, and the screw advances the cutting iron as it screws into the body. I've never quite understood the physics, or why Stanley chose that over a simpler method, but it works quite controllably.

I think it was the chosen method because the design doesn't leave room for the yoke or similar used on bigger ones.

The use of two slightly different pitches is going to lead to a very small relative movement of the connected parts, in response to comparatively large movements of the knurled wheel. It enables a very fine adjustment, which makes perfect sense.

It's a shame they chose to make the female part from a piece of folded steel. Looks like penny pinching on what is a relatively expensive tool.

The chap in the video mentions that on older ones this part was more substantial, and cast iron. A much better idea but more expensive.
As someone else has mentioned it's a good idea to partially release the clamp before making the adjustment, just to reduce the strain on the threaded parts.
Any way if the OP can't find a replacement it is easy enough to make one. But if it is as common a problem as the chap in the video suggests I would be surprised if no one supplies the spares.

 

[Limey Lurker]

That is good to know.

However, that leaves us with an issue that requires explanation (I am using now using terms aligned with those used by jsjwilson above): if the threads are the same pitch (and same hand), the metal clip will not advance relative to the iron base when the knob is turned.

You can prove this to yourself if skeptical: put two nuts onto a bolt. hold the nuts steady and turn the bolt. The bolt moves relative to the nuts, but the distance between the two nuts stays constant. Hence, you might need to propose a way that the blade is advanced with this setup.



Making judgements based on the helix angle could be misleading because it is a function of diameter. If you put a 1mm pitch thread on a 6mm dia. rod, it will look steeper than a 1mm pitch thread on a 10mm dia. rod.

If we see the thing assembled, we can work backwards from the fact that the arrangement must allow adustment of the blade. That will circumscribe possiblities for the threads.

The further thread, if the opposite hand, MUST be smaller than the other.

 

[Homeless Squirrel]

Pretty sure same thread pitch just two sizes and one screws into body while other thread brings blade in and out