|Paul Martin||10/09/2020 17:37:15|
|5 forum posts|
My lathe is a 6" colchester student without the quick change gearbox. So i need change wheels, which it never came with.
I've decided one of my first tasks is to make the wheels to produce M8, M10 and M12 threads.
I would like to make them sacrificial for a few reasons, but my question is..
What materials would anyone suggest?? I have just been looking a Tufnell properties after seeing a Youtube video but not sure on performance.
Does anyone have any experience with this or anything else suitable?
|Swarf, Mostly!||10/09/2020 17:51:31|
|544 forum posts|
Hi there, Paul,
First of all, it's 'Tufnol', not 'Tufnell' which I think is a district of London.
I suggest that a surf through **LINK** would be a good way to spend a half-hour or so.
Edited By Swarf, Mostly! on 10/09/2020 17:51:57
|Brian Wood||10/09/2020 18:01:51|
|2271 forum posts|
I have just restored a Churchill Cub lathe from 1947 which is in the same sort of size range as your Student. The larger tooth count wheels that came with it are all made in Tufnol. They run quietly without any of the 'ringing' associated with steel wheels and they are stronger than those made in cast iron in that the teeth will absorb punishment rather than chip or break off. I had metal chips to dig out in several places without leaving significant damage that would interfere with their function..
For a lathe of that size I was surprised to find them to be fine pitched at 20 DP like Myford wheels, albeit a bit wider at 1/2 inch
I would recommend them from about 55 teeth upwards
|1812 forum posts|
I have found Nylatron to be suitable.
1518 forum posts
Also look at the properties for Acetal & Delrin which are a tougher type of Nylon. Would have thought that Tufnol would be best though.
|Dave Wootton||10/09/2020 19:18:58|
|79 forum posts|
I've got a Bantam 2000 and some sizes of changewheel are hard to get and expensive, i've used delrin gears with no problems. not sure about Students, but Bantams have splined gears, I bought some very cheap pattern bantam gears from RDG and machined them away to use as carriers for the Delrin gears, bolted on with four allen bolts and two dowel pins..
i couldn't find the gear for doing 26 tpi i think it was 56T, the thread I use most and it's the one thread you need a different gear for, always the way.
I might do some of the sizes that I have in steel gears as they run noticeably quieter, the 127/100 combination rings terribly, drives me mad.
I got the Delrin gears from ebay and HPC
|259 forum posts|
If you do go the Tufnol route, be sure you understand the different fauna under which it is sold (e.g whale, carp, etc.). For gears, you will need the type that is made like plywood, not the type that is made like a Swiss roll. There has been discussion here on this issue relating to Myford tumbler gears.
I do not know if it allowed now, so read this before it is moderated: there is a UK-based eBay seller with the username of you_engraving who makes various change gears in delrin at very reasonable prices. With Colchester gears, it is often the centre spline that is more difficult to make than the tooth spaces.
|Andy Carlson||11/09/2020 07:39:12|
|296 forum posts|
I use Delrin change gears on my Cowells lathe - a good deal smaller than yours but then the gears are smaller too. I needed to adapt them by opening up the central bore and making a keyway - much easier with Delrin than metal.
Mine came from HPC in Chesterfield but you do need to look at the pressure angle as well as the DP number - my HPC ones are 20 degrees and many lathes came with 14.5 degree gears... although if you use a full set of new plastic ones rather than mixing with old ones then that shouldn't be an issue.
There is at least one other thread on here about Tufnol gears. I can't remember the full detail but the fact that Tufnol is made in both roll and sheet form and with both fabric and paper as the material is something that needs to be considered - some types are better than others for gear use.
I've seen a few folks 3d printing gears recently - interesting but I've not seen any definite reports about their strength and longevity yet.
3869 forum posts
Used aluminium to fix my Drummond-M small backgear cog years ago and the abuse it's taken is amazing
|Nigel Graham 2||21/09/2020 00:44:34|
|748 forum posts|
Tufnol is the manufacturer!
The material itself come in two basic forms, one based on fabric, the other on paper, both bonded with synthetic resin. Within those two classes are a range by grade, each with its own name, according to intended forms of use.
I would recommend anyone planning to use any Tufnol type, to study Tufnol's literature and select accordingly!
This applies to any proprietory materials, so how come so many threads discussing them by manufacturers' names do not suggest the obvious - the makers' own catalogues?
|Alan Charleston||21/09/2020 07:28:46|
|95 forum posts|
I made a set of change gears for my Boxford AUD lathe using Delrin. It works a treat and is easy to cut. I cut them from a 10mm thick sheet rather than having to get a selection of round stock. Luckily the tumbler gears were stamped 20 P.A. so I didn't have to guess the pressure angle. You can get a full set of gear cutters from the Chinese site which dares not speak it's name on this forum for $100 or so.
|Michael Gilligan||21/09/2020 08:50:39|
16411 forum posts
Amen to that !!
Edited By Michael Gilligan on 21/09/2020 08:52:03
|87 forum posts|
Several of my change gears are nylon and they work fine , have cut 6tpi threads in cast iron using a nylon 85t gear no problem at all .
|Jeff Dayman||21/09/2020 14:24:18|
|1896 forum posts|
ANY of the mentioned thermoplastics, Nylatron, other nylon based resins, acetal / Delrin will be FAR superior to any kind of Tufnol for change gears. In my opinion Tufnol is an obsolete and substandard material for any job where a plastic material is needed. Modern thermoplastics are better in every way. Just my $0.02 worth. Got my tin hat on, heading for the slit trench.......
5488 forum posts
Lots of people starting to use printed gears too, even for backgear on a SouthBend. Since the tumbler gears, first 3 of them, don't need to mesh with regular change gears I wonder what improvement might be had by using (printed) helicial gears.
|not done it yet||21/09/2020 20:16:24|
|5031 forum posts|
My Raglan 5” is still going on its likely original tufnol tumbler gears - even though I damaged one a tad while moving it. Replacement would likely be aluminium, acetal or 3-D printed (there are several reinforced filaments available if PLA was ever proven to be unsatisfactory).
|Nigel Graham 2||09/10/2020 23:01:13|
|748 forum posts|
Jeff Dayman -
Sorry but you are very wide of the mark by merely slagging off an entire range of materials and their manufacturer. I have no connection with the Tufnol company but have encountered its products at work and studied its web-site before adding a comment above; so I know that SRBF and SRBP are not "substandard" at all. Adding the company name makes your assertion merely libellous.
Like the other plastics you mention, they have their individual natures that render them suitable for particular purposes but not others, so are made in a variety to cover that. It is up to the user to select accordingly, and if the component fails in service you need establish if that was by choosing the wrong material or by using the right material to a poor design - i.e. the user's not maker's fault.
The Tufnol range is not "obsolete", but is still manufactured so is obviously still in demand; and their main customers are professional engineers of whom many could well be using such materials in costly projects to high specifications. Using them like the acetals etc. and various metals, as right for the specific components in the specific applications.
Or perhaps we should not use copper, tin and bronze either: older than exotic stainless-steels and titanium alloys by several thousand years, so obviously "obsolete".
|47 forum posts|
Bearing in mind the age of some model makers and their supplies, it might also be worth remembering that some Tufnol was asbestos based. I recall contacting the manufacturer about 25 years ago to help with identification and they were happy for a sample to be sent to them. Things may well have changed since then.
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