Hercus 9" Model A Nose thread specs.

[Nickon]

There is a thread here that describes a similar problem, but I can't find it at the moment.
I have acquired an early model 9" A. The 2 x 5" chucks that came with it thread on to the spindle fine. There is a smaller 3 1/2" chuck as well. This only threads on to the spindle for about 1/2 of the threads. The threads are 8tpi, but are they supposed to be Whitworth 55 deg threads or American 60 deg threads.
Any info would be appreciated
Cheers
Greg

[nadroj]

. The threads are 8tpi, but are they supposed to be Whitworth 55 deg threads or American 60 deg threads.

The factory brochure says the thread is UNS, which sounds American. Jordan

[MacPuddock]

The catalogue I have says its 1.5in, 8tpi, USS. This is United States Standard, also known as Sellers Standard Thread. Its 60 degree thread.

Hercus Catalogue .jpg

Cheers,

Findlay.

[Nickon]

Thanks for the replies and info. Its a 60º standard thread form then. The special I think refers to the fact that its 1.5" at 8tpi. The standard UN thread would be 12tpi at 1.5".
I'll grind up a suitable tool and see what it wants to do to the threads in the backplate.
Cheers

[pipeclay]

What part of Australia are you in?

[Nickon]

What part of Australia are you in?

In South Australia over by Port Lincoln.

[steamingbill]

I have to do a similar job.

This thread might be useful - discusses various ways of calculating or looking up the initial bore size prior to tapping.

http://bbs.homeshopmachinist.net/arc...p/t-45627.html

Bill

[CliveD]

The Hercus spindle thread is 1.5x8 UNS. A 60deg thread form.
The Boxford spindle is I believe 1.5x8 Whitworth. A 55deg thread.
Could a Boxford catch plate have its thread recut to 60deg ?
I have the opportunity to acquire a Boxford catch plate.
Comments from he experts please.

[pipeclay]

Yes it could,the thread may end up a little loose.
Would be a slow job if retrying to chase on a lathe, the use of a tap would probably easier.

[steamingbill]

The Hercus spindle thread is 1.5x8 UNS. A 60deg thread form.
The Boxford spindle is I believe 1.5x8 Whitworth. A 55deg thread.
Could a Boxford catch plate have its thread recut to 60deg ?
I have the opportunity to acquire a Boxford catch plate.
Comments from he experts please.

Hello,

Am not an expert however am intrigued by the job, hope you dont mind a few questions/comments ?

Would you do it something like this ?

0. Mount the workpiece, centre it

1. Mount a 55 degree bit - in a square hole on the end of a bar - see attached photo - get the point perfectly aligned with the existing thread - engage the thread location dial whilst doing this

2. Remove the 55 degree bit mount a 60 degree bit of exactly the same size- both bits must have the apex of the point in the same place ie exact centre of the bit.

3. Because you engaged the thread locator previously the newly mounted 60 bit will be in perfect alignment with the existing thread and you can now convert the thread, or would you simply not bother with steps 1 and 2 and just poke the 60 degree into one of the vees on the 55 thread ?

4. Do a large scale drawing of the two threads on top of eachother to check for surprises before proceeding

5. Cut a test piece with an internal thread at 55 and convert it to 60, again to check for hidden surprises

Bill

[pipeclay]

Your method may work.

If it was me ( I use reverse to cut threads ) I would sharpen a tool using a thread gauge.

Set the tool square to the job ( set the tool square off a bar mounted in the 3 or 4 jaw ).

Mount a 4 jaw chuck and set your job running true to the spindle and square to your tool post ( sorry but you blokes use terms I don't ).

Set the correct TPI and also set the highest rpm you can.

Engage the half nuts (after you have the tool close to the job )

Turning the spindle over manually either by hand or use of other means,bring the boring bar into the threaded bore.

Using the compound and cross slide adjust the tool so that it sits in the centre of the existing vees or close to it whilst turning the spindle NOT under power.

Once you have it in the centre of the vees or close to it take note of the reading on your cross slide (zero this ) also hopefully there will be no backlash in your compound and you can zero this as well.

Once you feel that you have centred the tool wind the cross slide away return the tool past the end of the job ( if you have reverse just reverse once the tool bit is clear of the thread ) .

If no reverse disengage the half nuts and wind the carriage clear of the job. ( you would need to take note of where you have engaged on the chasing dial ).

NOW place the lathe in the speed you are happy to thread at.

Once you have done either of these things start the lathe and allow the tool to enter the bore,hopefully the tool will just lick the job.

At this point you will need to move the compound or cross slide to cut your new thread.

[steamingbill]

Thanks Pipeclay,

I learned a few things from that.

When you use reverse to cut threads (or any sort of cutting) is there ever a danger of the chuck screwing loose ?

Would there be reasons for using each of the following combinations

Lathe Forward + Travel to Tailstock = LH thread - easier on internal threads - you come out of the workpiece ?
Lathe Forward + Travel to Headstock = RH Thread
Lathe Backward + Travel to Tailstock = RH Thread - easier on a simple external threaded bar - travel away from headstock out of the workpiece ?
Lathe Backward + Travel to Headstock = LH Thread

Made a mess of a test piece doing internal threads today but learned a heap - havent tackled the faceplates yet.

Bill

[pipeclay]

In my opinion if the Chuck has been mounted correctly there shouldn't be any great concern with the Chuck unscrewing,aggressive cutting and feed rates or carelessness may be a different story.

All of my thread cutting is done towards the chuck unless other wise required.

[CliveD]

Your method may work.

If it was me ( I use reverse to cut threads ) I would sharpen a tool using a thread gauge.

Set the tool square to the job ( set the tool square off a bar mounted in the 3 or 4 jaw ).

Mount a 4 jaw chuck and set your job running true to the spindle and square to your tool post ( sorry but you blokes use terms I don't ).

Set the correct TPI and also set the highest rpm you can.

Engage the half nuts (after you have the tool close to the job )

Turning the spindle over manually either by hand or use of other means,bring the boring bar into the threaded bore.

Using the compound and cross slide adjust the tool so that it sits in the centre of the existing vees or close to it whilst turning the spindle NOT under power.

Once you have it in the centre of the vees or close to it take note of the reading on your cross slide (zero this ) also hopefully there will be no backlash in your compound and you can zero this as well.

Once you feel that you have centred the tool wind the cross slide away return the tool past the end of the job ( if you have reverse just reverse once the tool bit is clear of the thread ) .

If no reverse disengage the half nuts and wind the carriage clear of the job. ( you would need to take note of where you have engaged on the chasing dial ).

NOW place the lathe in the speed you are happy to thread at.

Once you have done either of these things start the lathe and allow the tool to enter the bore,hopefully the tool will just lick the job.

At this point you will need to move the compound or cross slide to cut your new thread.

thanks for that Pipelay, that is what I expect do although I hadn't considered running in reverse. I can see that this increases visibility of the cut proceeding, but are there other reasons for this.

[pipeclay]

It's always hard to explain everything in words without leaving something out.

When I refer to reverse I meant when bringing the tool out towards the tail stock for the start of the next cut.

I leave my half nuts engaged when threading rather than using the chasing dial.