|277 forum posts|
Every now and then I need a tool that is slightly non standard, for example the 0mt on the cowells lathe is essentially half of a standard length 0mt arbor. Now I could buy the arbors from cowells at considerable expense or I could spend a lot of time making them from scratch. Having seen Chinese 0mt arbors for less than £4 around the Web it had me wondering how easy it might be to soften them and then machine them to my requirements.
So my question is, Has anyone ever tried to anneal any Chinese tooling? If so how did you do it? Did it work out well?
|roy entwistle||16/09/2019 10:12:34|
|1104 forum posts|
Are they hard ?
17085 forum posts
I would say they vary from one source to another and maybe even from batch to batch so hard to say. Even if not hardened that much they will have a higher carbon content than the free cutting steels so not so easy to turn on light machines.
I have certainly turned the tapered part of blank end arbors where they poked out further than I wanted using insert tooling but if you only have the cowells to machine them on it may complain.
|Bob Mc||16/09/2019 10:22:59|
|144 forum posts|
I can't give any information for annealing, but I did have a similar problem with my 70 year old Atlas lathe tailstock barrel which was badly pitted and not made of hardened steel.
The original barrel was 1&1/8th inch diameter and I couldn't find an equivalent sized barrel apart from second hand ones which were probably in the same condition as the one I had.
There were straight shank MT2 inner to MT3 outer adapters which had an outer dia of 1 1/4" and I thought of trying annealing it and having a go at machining, The plan was I would cut the MT3 end off and and after annealing and machining to the smaller diameter, fit the part of the old barrel with its acme screw thread to the new MT2 straight sided shank. In the end I didn't anneal it.
Pic below shows the end cut off the hardened steel new part and the badly pitted old tailstock barrel with its acme screw part also cut off.
After much deliberation I decided to grind the outer surface of the new straight sided MT2 shank, I only needed to grind off 1/16" radially, and I fitted a modified chain saw grinder in the toolpost for the job.
The job went quite well and I finished it by lapping with diamond paste, I found that the inside of the new part was not as hard as the outer surface and the finish was just as good as the originally purchased item.
Below....the new tailstock barrel fitted.... it works great and I set it true to the lathe axis using a dti method, it is absolutely spot on. As the barrel was now looking good I fitted a digital readout and partly embedded it in the tailstock casing so it didn't stick out so much.
I know it's not exactly what you were asking but other ideas are sometimes useful.
919 forum posts
Not being familiar with Cowells machines is the shortened taper using the larger end of the 0 morse or the smaller end ?
As far as the hardness of Far Eastern tooling much of it [not all] is not very hard and you may find you can cut it easily, however if it is hard annealing is fairly simple just heat to 700 deg - dull red in subdued light -- and allow to cool slowly it will then be soft again.
Since you are using the taper again it would be wise to use an anti scale medium of some kind, I regularly use Black Lead laid on fairly thick, the stuff used on fire grates etc or Clickspring uses Boric acid mixed to a paste.
Hope this helps John
edit - spelling and some chaps are faster typists !
Edited By JohnF on 16/09/2019 10:33:05
|Roderick Jenkins||16/09/2019 10:42:24|
1815 forum posts
I needed to cut a thread on the end of an ER11 parallel shank collet holder when using it as a spindle in my home made tool post miller. This was too hard to thread with carbide inserts so I warmed up the non-collet end with a torch until it was somewhat hotter than blue but not glowing red and let it cool. Cutting the thread was fine after this treatment. I did wrap some wet rag around the shank to try and stop too much heat getting to the collet end.
3988 forum posts
For four quid, buy one and see how you go with a hacksaw or parting tool to shorten it. Most of the cheap taper arbors are not hardened, from what I have seen. In the unlikely event it turns out to be hardened, an angle grinder or perhaps even a carbide parting tool will make short work of it.
Edited By Hopper on 16/09/2019 11:20:15
|Roger Woollett||16/09/2019 12:03:27|
|110 forum posts|
I think the Cowells uses the short end of the taper. I agree with Hopper - buy one to try. If I am right then you should be able to put the short end directly into the headstock and turn the unwanted large end down to suit your needs. If it is hardened you might be able to use a carbide tool.
|old mart||16/09/2019 13:11:32|
|1101 forum posts|
I have cut the tang off of some Chinese MT2 arbors which have chucks on them, with a hacksaw, and drilled into the small end with no bother. I'm sure they would tap also.
This was to shorten the taper so it would not extract prematurely from the tailstock of my small 7 x 12 Chinese lathe. I got extra tailstock travel for my efforts.
Edited By old mart on 16/09/2019 13:15:21
17085 forum posts
A virgin MT2 and one that is not, as said carbide and a reasonable size lathe was OK, not sure how the Cowells will cope. part of teh taper needed turning down so only the small 1/4" dia spigot remained so the taper would sit just below the level of my rotary table
|5138 forum posts|
I've shortened three tapers from 2 different suppliers and they most certainly were! All the way through too, not just on the surface.
Annealing fully hardened steel is a bit involved. Heat the steel to mid-orange and hold it at that temperature for an hour per cubic inch of material. Then cool slowly at a rate of about 20C per hour. For best results it's necessary to know the critical temperature of the steel rather than guessing mid-orange.. It may be necessary to experiment with unknown metal. Best done with a suitable oven and timer, but for rough purposes you might soften it usefully with a blowlamp, less soaking and faster cooling. Job's still not done - ideally it would be re-hardened after machining.
I couldn't be bothered with all that and chopped mine to size with an angle-grinder.
|277 forum posts|
Thanks for all the replies and advice. I think I will just try it and see what happens. If it doesn't work its no big loss. I do have other bigger lathes (mini lathe and Boxford) but I'd don't have adapters or any means of holding the tiny mt0 arbors. I was hoping to soften the steel enough to turn it in place on the cowells.
17085 forum posts
That one I showed was held in the 4-jaw by the blank end, clocked true and tailstock support used while the middle was turned down to 1/4" dia. I then sawed through the 1/4" and filed the end to finish.
Will depend what you are making as you could not do say a dead ctr that way but you could certainly rough most of it out and then just take a finish skim with it in the Cowells spindle.
|Neil Wyatt||16/09/2019 19:56:42|
17093 forum posts
Or turn your own tapers?
Please login to post a reply.
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.