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Replacing 3/8" Bristol levers

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Replacing 3/8" Bristol levers

Postby Steve Maskery » 21 Aug 2021, 15:54

I used to have a nice CL3 lathe, but now I have a crappy SIP. It's a big lump of cast iron with sero :) finesse about it and very poor tolerances.
The tool post is held in with a 3/8" x 16tpi Bristol lever. The mechanism is very sloppy and the whole thing is horrible to use. There are two of these and I'd like to replace them.
I can't find 3/8" ones anywhere, even going to posh places like RS and yuk places like AliE, everything is metric. So I'm thinking of trying to retap the holes. I don't have an M12 tap but Cromwell's and BAPP's are both within walking distance and I do have a wrench to put one in. I have twist drills up to 10mm, which is a tad shy of the 10.2mm needed for M12.
Is this doable for a woody like me, or will I simply end up regretting tampering with my machine?
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Re: Replacing 3/8" Bristol levers

Postby AndyT » 21 Aug 2021, 16:12

Presuming that these are UNC not Whitworth, one answer could be to order from an American supplier, or see if anyone can pick some up stateside for you

Do McMaster Carr sell internationally?

https://www.mcmaster.com/clamping-lever ... handles-6/
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Re: Replacing 3/8" Bristol levers

Postby clogs » 21 Aug 2021, 16:16

pls dont mess with it.....
if it were quality iron I'd say yeas....
but that stuff was an old gas cooker/ sash weights etc in a previous life and full of impurity's plus hard bits.....
it wasn't that long ago we used Unf/Unc.....or was it.....hahaha.....
try these....
info@southessexfasteners.co.uk
info@custom-fasteners.co.uk
sales@aitch.co.uk these also do taps n dies.....so used to engineering wants.....
I'm sure these will make a good starting point....
there's also a good machine plus electric tool spares place in Portsmouth but I cant find the number at the mo...must be on the phone and the wifes out with it....
hope this helps.....
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Re: Replacing 3/8" Bristol levers

Postby 9fingers » 21 Aug 2021, 16:41

Are you sure it is the Bristol lever thread that is at fault Steve?
The CI will be far softer than the steel in most Bristol levers.
If you are sure that new levers are what you want have a look at WDS
I'm sure they are in the forum list of useful suppliers aka buyers guide under useful links.

Bob

edit: yes halfway down page six
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Re: Replacing 3/8" Bristol levers

Postby Trevanion » 21 Aug 2021, 16:44

Steve Maskery wrote:I don't have an M12 tap but Cromwell's and BAPP's are both within walking distance and I do have a wrench to put one in. I have twist drills up to 10mm, which is a tad shy of the 10.2mm needed for M12.
Is this doable for a woody like me, or will I simply end up regretting tampering with my machine?


It's an easy job and would be well within your capabilities, Steve. If tapping steel, use some form of oil to lubricate, Brass use paraffin, Aluminium use beeswax and on Cast Iron use nothing at all. Alternatively you could try and find someone to make a couple of M10 to 3/8UNC studs that you could loctite and pin into a female M10 Bristol Lever, but that would probably cost more than just re-tapping. If you're not using too often I'd probably tempted to buy a couple of 3/8UNC bolts and just nip them up with a spanner.

I buy my Bristol Levers from Berger Tools, not the cheapest but the quality is top-notch compared to the cheaper Chinese offerings from Axminster.

https://www.berger-tools.co.uk/Adjustable_Hand_Levers_Clamping_Levers__Tension_Levers/Gn300_Adjustable_Hand_Lever_Male_Zinc_Die_Cast_Steel_Stud/PartCode/GN300-108-M12-32-SW

I bought an Axminster lever last year for my Morticer rebuild, and I bought a bunch of ones from Berger this year for my current project. Axminster M12 Bristol Lever was £4.30 at the time (£5.63 now), Berger Tools equivalent is about £10, more than double the price but it's definitely twice the quality, especially as I had to run a die down the Axminster handle as it had been threaded badly from the factory and wouldn't actually thread into an M12 hole. Had I took it up with Ax they more than likely would've replaced it with no quibbles but the customer shouldn't be the quality control, in my opinion, anyone with a pair of working eyes would've seen that the thread wasn't right.

Ax on the left, Berger on the right.

Image

The Ax handle has quite harsh, square edges to it.

Image

The Berger by comparison is quite well-rounded and is comfortable to lock off.

Image

The Ax is quite crude, it would be for the price of course, the zinc casting finish also seems cruder than the Berger, possibly of inferior grade zinc as well. The handle has a lot of play in it, on a machine I can see it making a bit of racket if it vibrates at all.

Image

The Berger is definitely a higher quality item (It should be at twice the price), everything is finished better and there are many more locking positions on the locking lever as well as having more contact between the steel and zinc casting so it should be less likely to wear out compared to the Ax, there is next to no play in the handle.

Image
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Re: Replacing 3/8" Bristol levers

Postby Woodster » 21 Aug 2021, 17:07

I wouldn’t touch the lathe either. You wouldn’t get far using a 10mm drill bit to cut an M12 thread anyway. I’m sure someone in the UK will sell you a 3/8” UNC locking lever - at a price. I’m disappointed Axminster don’t sell them as many of their wood turning lathes have imperial fasteners.

Here you go, about £4 each. They have other types/colours.

4E2C1526-FC62-4E1F-87AE-0B1E82F4E0E4.jpeg
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Re: Replacing 3/8" Bristol levers

Postby Doug » 21 Aug 2021, 17:52

Could your engineering mate not sort it for you Steve? I can do it if you are struggling but I’m isolating next week as elder son contracted the dreaded lurgy last week.
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Re: Replacing 3/8" Bristol levers

Postby Steve Maskery » 21 Aug 2021, 17:53

Thank you all. I'm off out now for a Garden Party, ha-ha, but I'll follow the links later.
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Re: Replacing 3/8" Bristol levers

Postby Dalboy » 22 Aug 2021, 10:43

The other alternative is to buy a metric female lever and get someone to make you a stud with metric one end and the thread you need on the other loctite this in with a strong hold type.
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Re: Replacing 3/8" Bristol levers

Postby 9fingers » 22 Aug 2021, 10:49

Dalboy wrote:The other alternative is to buy a metric female lever and get someone to make you a stud with metric one end and the thread you need on the other loctite this in with a strong hold type.


Excellent suggestion Derek, as although Steve is yet to comment, I suspect the weakness is the female thread in the CI part.

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Re: Replacing 3/8" Bristol levers

Postby Eric the Viking » 22 Aug 2021, 10:52

Don't drill + tap the cast iron for a new metric lever. Two reasons:

1. as discussed, cast iron is soft. Cheap Chinese cast iron is like bread flour ground on an old mill - lumps of hard who-knows-what in it (and I like my teeth as they are, thanks!).

2. You'll make it the only metric thread on the thing (probably), which will be a PITA for anybody following on, including you if you forget you did it.

But if you really must, get a Helicoil kit for it instead.

They are surprisingly simple to use, and crucially, the new thread will be excellently strong (actually stronger than the original). Choose the size carefully, and use the drill press to align the tap while you hand tap it (OK in cast iron at that size - or at least it should be). You should be able to find a kit for a suitable metric oversize, but a better idea would be to Helicoil it back to 3/8" and use the original Bristol lever. As suggested, the steel threads are likely to be undamaged and you will be giving it a good-quality steel-on-steel thread.

A Helicoil kit usually comes with:
  • the correct sized drill (usually not a standard series size!),
  • a tap. This isn't a bottoming hole, I expect. If it is, you might need to grind some of the tap nose away if it's not a 'bottoming' profile, but don't go bezerk (the ones I've had for Helicoil kits ARE bottoming profile though). As a general rule, if four turns engage fully, the thread is as strong as it will ever be. So you probably need less thread than you think, and anyway, the helicoil will be stronger than the original, if done right.
  • the installer tool. The bottom end of the uninstalled helicoil goes has a sharp bend, taking it across the diameter, and the tool engages with it; you "pull" it in by driving from the bottom end of the helicoil (it's obvious when you look at the kit), and when it reaches the end of the new thread you can wiggle the installer tool to snap off the diametric piece (it's pinched to facilitate this).
  • usually quite a few actual helicoil inserts of the correct size.
There's a lot of YouTube videos on Helicoiling, to see best practice. As I said, best to use the drill press both to drill out, then, with the belts removed, the quill will guide the tap, keeping everything aligned.

That will give you a much smoother and stronger thread, and within reason you can choose imperial or metric.

I'm pretty certain Chronos or one of the other model engineering suppliers will carry the right kits.

E.
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Re: Replacing 3/8" Bristol levers

Postby Woodster » 22 Aug 2021, 10:58

Dalboy wrote:The other alternative is to buy a metric female lever and get someone to make you a stud with metric one end and the thread you need on the other loctite this in with a strong hold type.


What’s the point when the correct lever is available?


Eric the Viking wrote:a better idea would be to Helicoil it back to 3/8" and use the original Bristol lever


Steve’s already said the original lever is horrible:

Steve Maskery wrote:The mechanism is very sloppy and the whole thing is horrible to use. There are two of these and I'd like to replace them


As the correct levers are readily available I’d just buy two of them, much easier. ;)
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Re: Replacing 3/8" Bristol levers

Postby Eric the Viking » 22 Aug 2021, 14:25

Woodster wrote:
Eric the Viking wrote:a better idea would be to Helicoil it back to 3/8" and use the original Bristol lever


Steve’s already said the original lever is horrible:

Steve Maskery wrote:The mechanism is very sloppy and the whole thing is horrible to use. There are two of these and I'd like to replace them


As the correct levers are readily available I’d just buy two of them, much easier. ;)


I got the impression from the conversation that at least part of the problem was worn thread in the cast iron.

Horrible possibly, but I would still replace it with a better imperial-threaded one for consistency, AND helicoil it to be on the safe side - far better than having the tool rest (or an actual cutting tool if it lets you use one) come loose. As I said, properly made helicoil threads are stronger than the originals, particularly so in cast iron or aluminium, I think mostly because of the increased thread diameter.
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Re: Replacing 3/8" Bristol levers

Postby Steve Maskery » 22 Aug 2021, 16:06

Hi all
Sorry, I've been indisposed for the last 24hrs.
First of all, thank you for all the very helpful suggestions.
The problem is with the levers themselves, rather than the threads. The meshing mechanism is all over the place, it's like trying to stir porridge with a paper spoon.
Buying two new Bristol levers (it seems tht everyone is calling them Clamping levers or Locking levers these days) looks like the way to go. I got a bit of a shock looking at that American site, the first one I clciked on was $57, just for 1! But it was solid stainless stell, which accounts for quite a lot. There were others quite a lot more reasonable.
I don't do a lot of turning, not least becasue I'm lousy at it, but when I do, I want to be able to use the lathe with ease, not fighting it all the time. I'll keep you posted.
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Re: Replacing 3/8" Bristol levers

Postby Steve Maskery » 22 Aug 2021, 16:43

OK, I've ordered 2 from WDS. But they are not £4 each!:
wds order.png
(23.36 KiB)


It's really galling to have to pay more in delivery and VAT than the damn things themselves cost.

But thank you all very much.
Last edited by Steve Maskery on 26 Aug 2021, 00:20, edited 1 time in total.
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Re: Replacing 3/8" Bristol levers

Postby Steve Maskery » 25 Aug 2021, 11:06

Off with the old, on with the new:
bristol.jpg
(500.02 KiB)


The new ones are bigger, which makes them easier to operate but maybe they will get in the way a bit more. I can shorten the thread easily enough.

But operationally they are most very excellent. Compared to the originals they are like night and day, chalk and cheese, my ex-wife and normal women.

Thanks for the advice.
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Re: Replacing 3/8" Bristol levers

Postby Woodster » 25 Aug 2021, 17:03

They do look very smart! :D
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