Need chuck thread cutting Wadkin Bursgreen BZL

Good morning,

I am not an engineer but I am looking for someone hopefully based in or around the Shropshire area to assist my Dad. He has a Wadkin Bursgreen BZL wood turning lathe built in the 1950's and 60's in Leicester.

He has had some trouble getting a thread to fit the outbound/left side, as he wishes to put a chuck on it. We both measured it at 1" x 8tpi (threads-per-inch) with a Left Hand thread, and he had a chuck cut at Axminster to that spec. Unfortunately, it doesn't fit, won't made at all and comes to a hard stop. Because of expansion, they won't be able to do another one until the new year, so I am trying to reach an individual to do the work instead.

The idea being to buy an appropriate chuck with a bored out blank, unthreaded, and have someone cut the appropriate thread for it.

Does that make sense?

At the moment he has the original faceplate for, which could be sent as a reference point. I've tried researching but everything points to it being the regular metric 1x8LH that we ordered, so we need someone who knows what they're doing to help.

I have tried reaching out to several engineering workshops in the Shropshire area but unfortunately none have got back to me. I guess they're all dealing with industrial scale projects and don't have much time for individuals like us.

Would anyone on here be interested in this? And have the know-how?

He is just a hobbyist but is getting a lot of personal enjoyment out of the lathe and just wishes to continue with it. There are a few photos of him using it here: http://www.rharris-images.com/best-coffee-every-morning/

I am basically trying to research possibilities for him at the moment and present them in a few days time.

If there are any questions to clarify what I mean please do just ask.

Thank you!

Hi Richard,

Unfortunately there's more to the specification of a spindle nose thread than the pitch and the handedness. Do you know what threadform Axminster cut?

My guess would be that it ought to have a Whitworth 55 degree thread form, being an old British lathe, rather than a UNC/Metric 60 degree threadform.

Tracy tools sell a left hand BSW tap which I think might fix what you have but it isn't cheap... **LINK**

Looking here the threaded section is quite long by spindle nose standards which in itself might also be a problem... http://www.lathes.co.uk/wadkin/page2.html

Incidentally, I took a look at the photos you linked to. That chap is tall and will get a bad back PDQ unless the lathe is raised - the lathe centre axis should be close to elbow height.

Hope this helps

Jon

Edited By Jon Gibbs on 28/10/2016 11:52:46

Hi Jon,

Thanks for your help. Thanks for your note on the height of the lathe as well, I'll pass this on. He's due to strip down the area and start again as it's a bit of a mess and less than ideal. Tools everywhere. It gives me a headache everytime I look at it . So when he does that, I'll make sure he raises the height accordingly. Would this usually be done with concrete? It's quite heavy.

We've had conflicted research on it being BSW, but it seems probable and makes sense considering the area and location like you say. Would it still not start threading a little if it were 5 degrees off?

This is the exact chuck he had (still has, due to be returned). It's the T04L 1" x 8tpi LH - beyond that, I can't commend. But I assume it's a metric 60 degrees threadform.

Are you saying you could actually run that tap through what we have and it would alter the already cut thread form safely?

EDIT: Interesting observation. The spinde on my Dad's looks the opposite of that - with the larger diameter thread being on the outbound side. I wonder whether this was an optional choice, whether people would turn them around for a reason, or whether it had possibly been replaced in it's lifetime...

EDIT: Here is a rather crude photo I took with my phone last week to demonstrate.

Edited By Richard Harris 5 on 28/10/2016 12:01:12

Edited By Richard Harris 5 on 28/10/2016 12:06:15

Hi Richard,

Ahhh, Axminster T04L will be 60 degree UNC threadform which I think will be much shorter than the thread above. See sizes for T04M which is the standard 1" 8TPI RH thread.

My hunch is that given you have a 1" 8TPI UNC threadform, putting a 1" 8TPI BSW tap through will not need to take a huge amount of metal off to produce a concentric BSW thread.

Jon

Jon,

Amazing, thank you! The shortness (meaning the cutting depth of each thread?) would explain the "hard stop" we found when trying to mate them as well.

This would be really easy to test as well on a piece of scrap hardwood. I'm sure I have some off cut aluminium around as well.

edit: Jon, one other question. If this doesn't work (which hopefully it will work as it seems logical and well reasoned to me), do you have any idea how much it would cost for a shop to cut an uncommon thread side inside a chuck for us?

Edited By Richard Harris 5 on 28/10/2016 12:23:01

That seems odd. Usually a BSW nut will fit a UNC thread of the same TPI and vice versa. And usually headstock spindle threads are machined a bit undersized and loose so that the chuck is free to move a bit and the positive location is on the stepped register collar in behind the thread. So a BSW tap may not be the answer. But you can't know for sure 'til you try.

The thread in your close-up pic looks a bit crusty. Have you tried cleaning the thread down with a wire brush, ditto the register collar, and then with the spindle running, carefully run the corner of a fine file along the thread groove to clean any burrs off the tops of the thread?

How far does the chuck screw on before it comes to a stop? Far enough for the register collar to be causing interference, or before it gets that far? How many turns?

Does the faceplate screw on to this thread OK? If so, have you measured the thread in the chuck, and the register recess, to see if it is the same as the faceplate's? You should be able to measure the inside diameter of the thread and compare, ditto the register recess.

Also, its worth double checking the actual TPI in the new chuck. It's possible you got sent a mislabeled 1" x 10tpi or some such by mistake (T12RL on the above chart?). This might screw on a turn or two then come to a dead stop.

Edited By Hopper on 28/10/2016 14:06:01

Thanks for your thoughts Hopper. It's puzzling us as well - given the miminal difference, you'd expect some mating.

The chuck doesn't start at all, won't being screwing on at all. Nothing. It comes to a hard stop immediately. We tried multiple times. He did clean it up a little bit and even lightly filed what he thought was a slightly rounded first thread. But nothing...

Axminster took two months to cut the thread due to a backlog. I haven't measured the chuck thread in great detail but counted 8tpi and the diameter as the same.

The faceplate screws on perfectly - it's the original one. Aluminium. I haven't tried checking the thread difference. I am out of the area for the time being but could try and get my dad to measure the inside diameter differences between the original faceplate and the chuck - I guess that would also give us an indication of the threads are metric & BSW as well? If the BSW has a 'deeper' thread form, compared to metric?

Thanks again for your thoughts.

edit: this was another crude photo I took. You can't judge much by it, but it's the inside of the axminster chuck which doesn't fit... the thread measures an inch down (more or less), so you can just about count 8 threads.

Edited By Richard Harris 5 on 28/10/2016 14:36:51

Just a thought but Axminster havent cut a right hand thread by mistake??? I would have expected it to go on at least one or two turns at least.

I used to have a BZL and it had a 1 3/8" x 6 unc thread but that was the larger spindle nose thread.

I have problems with getting stuff to fit my south bend lathe as despite bxoford being similar the thread form is different and boxford made stuff will only go on a few threads then jam. BSW as opposed to UN.

Thanks Mark. From my infrequent research it seems there is some variation on the threads on the BZL spindle, or at least in which way they're laid out. I can't rule out the spindle being replaced, for one reason or another, on lathes that are 60 or so years old as well.

Well, in terms of the part number and what it says on the chuck itself, it's meant to be the Left Hand thread version. There is a photo of both the spindle and the inside of the thread above... do they both seem Left Hand thread to your eyes?

The photo does give me the impression it may be a RH thread

Neil

I've just got my Dad to measure the thread differences. They are as follows.

Original Faceplate Diameter: 22.78mm

New Chuck Diameter: 22.16mm

Spindle Outside Diameter: 25.44mm
Spinder Inside Diameter: 21.95mm

What do you make of this?

The original faceplate has a deeper cut, which relates to it possibly being a BSW thread. I should note it's aluminium and old, so perhaps there is some wear in there as well...

Edited By Richard Harris 5 on 28/10/2016 16:46:54

I keep staring at the photo but it's difficult to see. I just asked my dad to double check and he says it is indeed left hand...

Richard

If all else fails if you can have a trip over to sheffield with your spindle and offending chuck i can redo it for you i'm used to cutting large lh threads for my graduate lathe1.5" 6tpi ...that's if you can take the spindle out..i'm happy to do it whilst you or your father waits

Ian

What an exceedingly nice gesture - just goes to show that forums can be friendly places.

As a temporary measure, try screwing in a piece of soft wood such as spruce or balsa to the chuck. It will take on the form of the thread. Then compare it to the end of the spindle for pitch, diameter and thread form.

Neil

Well let's stick to Imperial measure as that is what the thread is, either BSW or UNC.

So your original faceplate thread has an inside diamter of .897"

The new chuck thread ID is .872".

That is a pretty massive difference of .025".

The spindle thread is 1.001", so a tad oversized. It would normally be something like .990" to allow a bit of clearance. Therein lies another problem.

The minor diameter of the spindle thread, measured presumeably with calipers so not 100 per cent accurate as the jaws may not be right on the bottom of th thread, is .864". This is actually the correct core diameter for a female 1" UNC thread. Male thread should be .846" core diamter. Whitworth would be .840. ( the difference in thread depth between UNC and BSW is .076" and .080" respectively. So not very much.)

Nonetheless, the spindle minor diamter as measured is .008" smaller than the ID of the chuck thread, so even though the chuck thread is smaller ID than the old faceplate thread, it is still greater than the minor diamter of the spindle thread, so should fit.

You might want to look at spinning the spindle under power and running a fine file over the tops of the threads on the spindle to clean it up and get it down a bit below 1.000", or a standard UNC or BSW will never go on there. The thread may have been distorted or burred over the years by screwing on the faceplate etc. .

I can't tell from your photo if that chuck has left or right handed thread. Easy enough to tell if you look at teh chuck in person and follow the spiral from the start of the thread and see which way it goes. But if it were a right hand thread, the chuck would not jam up when you try to screw it on because the RH thread would not even start on the LH spindle thread. It would just turn around and around with a click once per turn as the ends of the two threads passed each other but did not engage.

Edited By Hopper on 29/10/2016 03:02:50

Questions about re left and right handed threads. Presumably the other side is the same size thread? So easy to check?

Thanks extremely kind and generous of you to offer Ian, thank you! I haven't yet done all the research for my Dad but will contact you directly if this is the route we need to take. Out of curiosity, would there be a way in which you could do it without having the spindle with you? Also, would you be able to do this from the current chuck - which has some sort of 1 x 8 LH metric thread cut - or would it need to be a 'fresh' chuck which is yet to be threaded at all?

Could you elaborate on what you mean by the other side?

edit: but for all intents and purposes, my dad has confirmed the chuck was cut to a LH thread.

Edited By Richard Harris 5 on 29/10/2016 13:03:15

Thank you Hopper, that makes sense.

The only thing I'd add is that when I measured the spindle OD at various parts my average was 25.22mm, which is 0.99291339 - so reasonably undersized?

But you are right, the spindle should fit. It is confusing. I'm reluctant to tell me Dad to take a file to it because he can be somewhat heavy handed... Maybe I'll suggest he gives it a fresh cleaning over with some wire wool and checks the start of the threads first. Difficult when you're a good 4 hours drive away...