Thread: Yet Another Norris Question

Bob, mine is a post-WW2 model, and it has a 7/16" screw, and a tad more than 14 tpi by my count. The thread is also quite steep, my rough measurement is 60 degrees or slightly steeper.

Cheers,

Thank you Ian.
I was under the impression, and I could be miles off, that the screw thread form was square. I was planning on cheating anyway and using an 29 degree Acme thread - for two reasons. I've never cut a square thread and I have a cutter I ground for the Acme thread.

Bob.

Hi BT,

Peter is the guy to answer this question properly, the thread pitch is important to get the right amount of clamping force.

I take it as being implied in your question that you aren't going for the traditional Norris adjuster?

And yes, I think square is the traditional profile... Peter did a write up on making a square tap somewhere?

Regards
Ray

Hi Bob, nice body your doing, I was told that you were doing this , first view I've had of it though.
Machined out of solid, wo !!

Have you been getting out for a bit of Sushi over there? like we did when you were here?

Cheers Rob.

Originally Posted by RayG

Hi BT,

Peter is the guy to answer this question properly, the thread pitch is important to get the right amount of clamping force.

I take it as being implied in your question that you aren't going for the traditional Norris adjuster?

And yes, I think square is the traditional profile... Peter did a write up on making a square tap somewhere?

Regards
Ray

I haven't abandoned the adjuster Ray.

I had been going to adopt Jim Kingshott's 40tpi single thread idea but for some reason the traditional 32 tpi RH /40 tpi LH adjuster has more appeal. Could be because I'm lazy and there is a bit of effort involved in making a slop free junction between the adjuster shaft and the plane iron screw cup if Jim's idea was used.

I know the general consensus is that the adjuster is a dead loss. Just happens that I like the look of it.

I'll contact Peter.

Originally Posted by auscab

Hi Bob, nice body your doing, I was told that you were doing this , first view I've had of it though.
Machined out of solid, wo !!

Have you been getting out for a bit of Sushi over there? like we did when you were here?

Cheers Rob.

Hello Rob,

It's great to hear from you. I often think about your workshop, your work and that beast of a lathe out the back.

Sadly, my wife is not a Japanese food aficionado. I haven't easten raw fish since the time with Peter, Matty and you. Maybe next time I'm in Melbourne.

The pretend plane has been a bit stop start. I'd been bogged down trying to finish something else. The something else is now finished. If you are interested in how the ersatz 50 has taken shape, then here is a link - https://www.woodworkforums.com/f65/ad...4/#post1292677 and another https://www.woodworkforums.com/f65/ba...2/#post1444073

There is an early reference to the "fat 13". It's my mill.

Bought a Hercus yet?

Regards
Bob.

No Hercus as yet Bob, I'm out of space.
I still have a little way to go on the lathe out back, Ive been working on the cutter for it the last few weeks.
I will have a read of the links you provided , thanks.
And yes, next time your over, another tool talking sushi night will be good

Rob

Bob,
the cast iron 51 I have has the standard 7/16 in Whitworth, 14 TPI. Just got some planes out of boxes after moving house.
14 TPI was an "industry standard". Like ALL those makers, I find it just the right thread for that lever screw....Goldilocks principle.
The early square threads were about 12mm, curiously, and 14TPI on Mathieson & Spiers, and 11.5 - 11.6 on early Norris planes, again with 14TPI.

http://petermcbride.com/temp/images/norris51_a.jpg


Regards,
Peter

Originally Posted by lightwood

...the cast iron 51 I have has the standard 7/16 in Whitworth, 14 TPI...

Peter - is the plane you looked at a pre WW2 model? I didn't put a thread gauge on the screw of mine when I checked it the other night, but I would have sworn the thread profile was a bit steep for Whitworth, but given my eyesight & haste, I could easily be mistaken. I will revisit it in the cold light of day.

I wonder if any great 'research' went into the thread size/pitch for the lever cap, or if it was just a convenient size that happened to work!? It is a happy choice in that it locks securely with little finger-pressure, but limits the force that could be applied if a finer thread were used. I'm too lazy to work out the thread 'ramp angle' for that diameter, but it must be less than for a 1/4" Whitworth (20 tpi).

Funny - I never gave any thought to thread size/pitch on locking screws until I struck a minor problem using the brass knurled-head screws from LV for some marking gauges. You need to make a conscious effort to clench the screw down, or risk having it loosen in mid stroke. Without doing the arithmetic, I have assumed it is because of a steeper ramp angle to the thread, but I guess I should do the sums before being too confident that that is the reason. I can report that switching to 6mm metric (25 tpi) makes a very worthwhile difference, though.

Cheers,

Originally Posted by lightwood

Bob,
the cast iron 51 I have has the standard 7/16 in Whitworth, 14 TPI. Just got some planes out of boxes after moving house.
14 TPI was an "industry standard". Like ALL those makers, I find it just the right thread for that lever screw....Goldilocks principle.
The early square threads were about 12mm, curiously, and 14TPI on Mathieson & Spiers, and 11.5 - 11.6 on early Norris planes, again with 14TPI.

http://petermcbride.com/temp/images/norris51_a.jpg


Regards,
Peter

Hello Peter,

I thought you might have been snowed under with your move. Thanks for the reply.

I had a close look at the photos of your now gone 50G this morning. Looks mighty BSW -ish. I have a set of 7/16" taps and a die so no more excuses.

Regards
Bob.

Hello Bob,
Good to see the plane project back up and running,
I will follow with interest as the lever cap screw I have has a brass knob and steel thread. Not a fan of the steel thread, I am interested in a one piece brass lever cap screw. So will follow your progress.
Cheers Gerry