Broke my compass plane

[andrew_2]

Hi all

If anyone has any advice, that would be much appreciated.

It's a Record 020c.

I was generally scraping rust off and the adjuster knob wasn't turning. I soaked it in WD40 and it ran upwards on the thread after some persuasion and then it wouldn't go down again. I got it to the top of the thread and then had to use some light force with a wrench to get the knob off. I wasn't overdoing it.

I can't see any damage to the thread, but it looks like I've chipped the casting at the beginning of the turn. As far as I can see, the inside screw thread looks fine, but it will NOT go back on again with just hand pressure - about one turn and then it jams. So I reckon I must have warped the casting or bent the casting's internal thread somehow. The threaded rod is straight and all the threads are clean and parallel.

What I'm wondering is whether I can force the knob back on the thread and then paint some grinding paste above and below, screw it up and down the thread a few times until it runs acceptably well? On the basis that even if it ends up a bit sloppy, that would be better than having to bin the plane? Would that work, or can someone suggest a better way of doing it?

I'm not going to be able to get a spare knob or threaded rod without buying a whole plane on ebay, sadly. I don't know of anyone local to me who could tap a new thread into the knob.

Thanks,
Andrew

 

[TRITON]

Get a small file- triangular shape, or maybe thin, knife shape and file into the thread at the top to clean it up and remove any ragged burr. That should clean it enough to get the knob to feed on.

You get this occasionally on threaded rod, there its normal prior to cutting down a length to first screw on a nut, and after cutting you undo it right off which cleans and orientates it.

If you do find or buy a die, you'll need to know what kind of thread is cut into it in the first place. I wouldn't think it would be metric, might even be whitworth.

But in all honesty its a simple thing and should be easily remedied.

 

[Bingy man]

Do you know what size and or type of thread it is as taps are not that expensive. It’s probably not metric but I’d only be guessing. A local engineering firm may be willing to help you out..

 

[Orraloon]

As Triton says use a file on any bits of thread that are out of kilter. Its worked for me on a few things. Cant see enough detail of the thread in the pics but a close visual inspection and feel with the fingers will tell you where to file. If it comes to taps and dies then hopefully someone out there can point you in the right direction as I have never even had a compass plane in my hands.
Regards
John

 

[Derek Cohen (Perth Oz)]

Triton makes good points.

What I would do is find a bolt and nut with the same thread as the existing bolt. You can use the nut to rest the fit.

Then use the bolt to chase the threads in the knob, and the nut to chase the threads in the bolt. Use a little oil when doing so.

Regards from Perth

Derek

 

[J-G]

The resolution of the images posted is too low for me to be certain but I suspect that the thread is ACME. To some extent this would make sense, knowing the purpose of the thread.

The chances of finding a matching 'nut and bolt' without sourcing another same make Compas Plane are vanishingly slim and if the thread at the top of the screw looks undamaged, filing it would have little or no effect. This suggests that the damage is more likely to be in the knob.

Getting a file in there will also be somewhat difficult, as would sourcing a tap.

I would first try to fit the knob the wrong way round - ie. upside down - this would prove whether or not the damage is to the top or bottom of the knob. If it goes on a few turns easily, it may even prove possible to re-form the damaged part. From the looks of it the thread is likely to be steel and the knob a cast alloy of some kind which may well be soft enough to re-form with enough pressure applied.

If that does get the knob down the thread then it may be easy to remove any burr created at the bottom of the knob with a file or maybe a Dremel (or similar) thus cleaning out the damage.

[EDIT]
A further look at the image and I now suspect that it is a Square Thread. This doesn't affect the previous advice.

 

[spanner48]

Why not try turning the knob upside-down, and screwing it down from the top? Then the nut will have all the upper threads to locate it and help you reform the distorted thread at the bottom.

 

[clogs]

there are loads of suppliers of Acme and similar threads on E bay......also used around small cnc cutting machines etc.....
They sell a nut seperately but it's really just a block of metal.....norm used in and around machines.....
so it would be easy to modify the outside shape of said block to to get it to work.....
ALSO,
these nuts are available in BRASS.......not quite pence but pretty cheap....
u just need to measure and find thread type.....is it a square edged thread or does it have an angle......?
If u measure the outer diam and the base thread diam along with tooth shape they'll certainly match ur nut....
easy peasy

 

[Hornbeam]

I have the same plane and just looking at the thread I would say aLmost certainly ACME

 

[okeydokey]

If you cant recut the thread by trying the knob upside down, can you get the stud out and try the knob on that end?
Consider cutting a quarter of an inch off the end of the stud and you have new thread.
Or just get a grip on the knob and wind it/force it through the tight bit after oiling the threads whats the worst it can do?? It will probably go through and job done

 

[Housey210]

I had the same issue on a stanley plane, thread was an oddball size, lucky local ironmonger sourced a new spare.

 

[andrew_2]

Thank you all very much for your replies and advice.

It is indeed an ACME thread. I measured it as 12.2mm, 8TPI, which doesn't seem to fit any chart I can find, so no chance of getting some rod or nuts to play with off ebay. I reckon Record must have copied Stanley, and I read that Stanley made their screw threads obscure on purpose so you had to buy their spares.

Filing the rough ends hasn't made any difference - It goes on a turn and a bit before seizing. It's too small to get anything serious inside the hole and a thread file costs more than the plane is worth!

Turning the knob upside down is a no as well. It wants to go on skew. I don't really understand how it managed to get so knackered - it's the kind of tool I only use once a decade. I really didn't use much force to get it off, and it was only lightly rusted on the sole anyway. Very bizarre. Can cast alloy warp by itself over time?

So I'm going with J-G and okeydokey. A bit of gentle brute force on the basis that the knob ought to be softer than the steel rod, so if I don't break it more, that should be good enough.

Best regards
Andrew

 

[williams1185]

hang fire i had one with a broken casting i will look in my workshop tomorrow and let you know , ian

 

[J-G]

At 12.2mm OD that is likely to be a ½" nominal (12.7mm) - regrettably the 'standard' ACME would be 10 tpi - though ACME 'Standards' are somewhat loose because it's essentially a specialist thread often designed with specific criteria in mind.

If Ian comes up trumps you wont need to concern yourself with damaging the knob but if you have a lathe, it might be worth mounting the knob and machining a chamfer into the top before trying to screw it on.

 

[cowtown_eric]

any sign of hammering on top of the threaded post.....which could cause slight mushrooming

you cold use a sharpie pen or engineers blue layout die on the thread to see where it's binding.

if it is binding,some light filing of the top few threads could ease you pain. Rinse and repeat.

I'd also take as close a look as possible on the female threads on the knob ,just to rule out the possibility that somebody didn't try to run an inappropriate tap thorough it. -I am assuming that this plane is new to you

Eric in Calgary

 

[andrew_2]

Ian, thank you that would be briliant, so I have fingers crossed.

J-G, no, no lathe I'm sorry to say. Ironically my neighbour used to be a machine parts maker, but moved away years ago. There is an engineers supplier nearish to me, but they say all the toolmakers have gone from round here. I don't think the local garages would make their own parts any more. But there is a proper motorbike shop down the road (lightbulb moment)

Eric, no I bought it brand new back in the 90s, can't remember for what reason, so it's never been mistreated, just left on the shelf. That's why I don't understand why it's decided to seize up. I'll have a go at the sharpie idea though.

Regards
Andrew

 

[Astrobits]

You could try locating a local model engineering ( trains? ) club. They might have some people with expertise and tools to sort you out.
Nigel

 

[williams1185]

had a look at my spares mine is an older version yours appears to be more modern im thinking the threads should be the same the adjuster on yours is like a knob in shape mine is like a large knurled nut for some reason i cant access my pics if you do a search for compass planes you will see what i mean yours is the 020c mine is the earlier model 020

 

[david.tamlaght]

i'd tend to rule out the threading on the bar first with a matched ordinary nut as its rare to damage cast threads so easily on the turn wheel.
if all seems well on the threaded bar ,you'll need to retap the thread on the wheel but go gentle and use a bit of cutting oil as you go .
cast can be a bit brittle

 

[Dee J]

As an economic position I guess this is a good benchmark to set the value of fixing it:Record No 020c Compass Plane - Free UK Postage | eBay
But as an interesting engineering challenge that's a different matter. Then it's time to change gear and get forensic. It's a chunky half-inch thread, not some tiny watchmaker scale thing - so any fault, corrosion, distortion, galling should be visible - especially if the problem occurs on the first turn or two. External threads can generally be cleaned up with small files, but for the internal thread of the nut (without a matching tap) then maybe make a right angled scraper. A thin file, bent hot to a right angle at the tip and ground to the thread form should work. Or a small piece of high speed steel set into the side of a mild steel rod - in the style of a lathe boring bar.
In hindsight, is there any chance that it was something more than corossion stopping the removal of the nut? Had the thread been staked or punched the limit movement to a safe range of adjustment so as not to over-bend the sole?