Member postings for Christopher Churchill

Posted by SillyOldDuffer on 20/11/2021 14:13:40:

Can't comment on the machine or price, but it's collect in person from Boston, Lincolnshire. Is that compatible with 'My problem here is I don't have a way to drive somewhere to pick up a machine I need to have this delivered'?

You would need to discuss shipping with the seller before buying it. Apart from adding to the cost, he might prefer to keep his end simple by only selling to someone who will remove it as well. Nothing's impossible but packaging a top-heavy milling machine for safe delivery by a courier takes a fair amount of effort. Not a problem for the trade, but I wouldn't care to take it on. Some couriers will pack and send: no idea what the costs are but I doubt it's cheap.

Dave

Posted by Ketan Swali on 20/11/2021 13:52:21:

Hello Christropher,

Before you get too carried away, I would strongly suggest you buy and read link: Milling for Beginners written by Jason Ballamy. It is written in plain English. It is based on the SX2.7 mill. It addresses issues on how to use small mills in general, as well as helps you understand limitations.

With regards to rigidity, Andrew is fortunate to have a good old second hand industrial machine, with horizontal attachment to cut gear teeth easily in one pass. To put it into context, the machine on which he is cutting the gear probably weighs around four times or more than an SX2.7 vertical mill. As Andrew stated, gear cutting on vertical mill can be problematic. Even if you tried to bolt the blank onto the rotary table in a similar way to Andrews suggestion, it would be wrong to think that this is the only rigidity issue, and that you will get the same results as Andrew, because to start with the physical weight of the SX2.7 is much lighter than Andrews.

Andrews approach is correct for the type of machine he has. For the SX2.7, Jasons approach is correct, but it is combined with knowledge/experience of how to use a small light weight small mill. You also need to consider what material you are cutting, along with speed, feed and depth of cut more appropriate to any machine you ultimately decide to buy. How things happen on one machine will be different from how they will work on another model of a machine.

Ketan at ARC

Probbly cheaper to visit a scrappie and pick up bits to start with

Pay a pal to take you and bring sacks/old-covers for the metal

Christopher, There's a lot to be said for buying steel that's a known quantity when you're trying to teach yourself.
I, and I suspect many others, have a stock of unknown/scrap steel which we dive into, but the results can be most unpredictable.
It would be very easy to get disheartened with poor finishes when the problem is with the material, rather than the operator or machine.
I'd have a look at your nearest steel stockholders and see if they can supply some free-cutting mild steel.
They may not want to quote you over the phone, but my own supplier(s) are happy enough for someone to arrive, ideally when it's not busy, and buy bar ends etc. for cash.

Bill

Posted by Michael Gilligan on 20/11/2021 10:41:30:

.

Hence my [evidently mis-judged] suggestion that you modify the lathe to make a useful tool.
Wheel-cutting engine / Dividing Head / whatever … Make of it what you will.

MichaelG.

Posted by DiogenesII on 20/11/2021 09:53:15:

Just 'cos no-one else has raised the point, are there specific issues with the lathe that mean things aren't very satisfactory?

..if you are going to be using it to make blanks, arbors to mount them on, etc., the I guess this might be as good a place as any to address any shortcomings?

Some pleasant surprises on the SX2.7 mill, but first

This is a 1MOD cutter mounted on a R8 shank milling arbour. One advantage with these is the overall diameter is smaller than a similar tooth size imperial cutter at 50mm vs 63mm so you gain a bit of room using metric.

Now the usual way most set up a rotary table and tailstock is to have the cutter behind the work and as I said this is going to limit the diameter of gear you can cut. here the gear is 78mm dia and you would be hard pushed to get much larger without hanging the rotary table off the mill's table.

This is as far forward as the table will go

But then I remembered a conversation with Ketan at ARC about how far back some of teh Sieg mills tables will go so thought I would try it that way round. The protective bellows on the column are just retained at the bottom by magnets so can be slid up out the way to gain a bit more room too.

I think you could probably manage 170mm dia gear blanks set up like this and still have the rotary table and tailstock lined up with the middle tee slot.

If doing a gear of this size on the SX2.7 I think I would not use a single central arbour but instead bolt the blank to the rotary table with some suitable length spacers in a similar way to Andrew's photo as it will be a lot more rigid and no risk of the blank rotating on the arbour

The SX2P being a bit smaller may manage 140-150mm dia and with moderate tooth size should cut the mustard. but would be worth checking the available table travel.

Posted by John Haine on 19/11/2021 13:49:22:

Jason, the OP asked what tooth counts and materials I was using. If you profile the gears out of flat plate or on the end of a bar the limits are the usable width of the table (max diameter) and minimum usable size of cutter (minimum modulus). Bigger teeth aren't a problem even for a light mill since the cut width is (say) 1mm and depth 0.25mm even cutting a large tooth. Only feasible with CNC, Christopher is already using CNC on a router and apparently making gears this way.

Posted by Martin Connelly on 19/11/2021 13:11:26:

If you look at used mills and a round column vertical mill is available do not dismiss it out of hand. The ability to rotate the head around the column allows the spindle to be further away from the table centreline for larger diameter gears.

For example if you had a Ø70 cutter and a Ø100 gear blank you need at least 85mm between the spindle centre line and the dividing head centre line. With a square column mill this may be hard to achieve without having the rotary table hanging over the edge of the table.

Martin C

That's the very minimum I think you could probably get away with.

I think close to almost impossible on a generic Mini-mill sized machine. It is not just the large diameter of the gears but also think about the size of the teeth. Unless you want to cut several hundred small say MOD1 size teeth around those big diameter gears then you will need to use cutters that produce a larger tooth and they need more power and rigidity in the machine which you won't get on the smaller ones.

You have not said what material you will be using for these gears, if something like birch ply or a plasticic then that will be a lot easier to cut than metal.

I'll mock something up on an SX2.7 tomorrow to give you an idea of the size that could cope with but won't be until late afternoon.

.

Dare I suggest that you might convert your sucking Chinese mini lathe into a wheel-cutting engine ?

Have a look at J. Malcom Wild’s masterwork for inspiration : **LINK**

http://www.j-m-w.co.uk/contact.html

MichaelG.

if you do indeed mean radius rather than diameter then you will struggle with the smaller mills. certainly a (mini-mill) won't do it and even the Sx2P sized machine will struggle This is because you can't bring the table far enough forwards to get the cutter into the right position behind the gear blank.

Even the next sizes up like the SX2.7 and SX3 size machines will be hard pushed to accomodate a 200mm dia gear and rotary tables for that size will be a lot more than the figure I mentioned earlier, you could possibly get away with a 6" rotary table packed up but front to back movement may still not be enough.

A DRO is nice to have but may be more economical to buy separately and fit yourself. Power feed less so

As for measuring tools a half decent 150mmdigital calliper will do to start with and cover most of the gear sizes you are thinking of. Dial test indicator and a magnetic base will get your work and th rotary table set true and an edged finder to locate the work

Big jump from woodwork to cutting gears ! How come ?

Posted by John Haine on 18/11/2021 07:10:26:

Do you mean jobbing, or just cutting?
John Haine

Posted by JasonB on 18/11/2021 07:14:45:

I suspect you mean gear cutting as to do hobbing properly you really need a gear hobber, it can be approximated with home made tools but you would also need a lathe to do that.

An idea of the size (diameter and tooth size) of the gears as well as what material you want to make them from would give members a better idea of what machine to suggest.

You will almost certainly need some form or rotary table or dividing head to increment the blank around 1 tooth at a time so allow 250-300 euro for that. And easily the same again for some other basic tooling to go with the mill such as an arbor to hold the gear cutter, the cutters themselves, measuring tools to set the job up, etc.

Welcome to the forum.

My recommendation is to look at this the other way around. If you haven't already done so, first get a copy of the Workshop Practice series book ' Gears and gear cutting '. It will cost less than a tenner from on line sources and will tell you what type of kit you need and how to use it. This may save you making an expensive mistake and buying equipment that is not fit for purpose.

Are you intending to make gears for a specific purpose?

Edited By Mike Hurley on 18/11/2021 10:16:49

Welcome!

If you are going in for gear manufacture, do buy Ivan law's book on "Gears and Gear Cutting" No.17 in the "Workshop Practice Series", as Mike Hurley has already recommended.

You will find it a great help. Study it well before starting to cut metal.

If need be make your mistakes on some trial pieces, to gain experience, before embarking on the final product,

It may help to bear in mind that gear cutters are numbered in the reverse order between Imperial (DP ) gears and Metric (Module ) gears.

You are also going to need a Dividing Head or Rotary Table, (With Tailstock ) and a 4 jaw chuck to hold the mandrels on which the gear blank will be mounted for machining.., The mini lathe will come into its own to make the mandrels on which to mount the gear blank

I prefer using Division Plates on a Rotary Table, to calculating the angular divisions and setting them on the vernier scale.

Since gear cutting involves a heavy cut, although at a very slow feed rate, you will need the Tailstock to support the mandrel on which the gear blank is mounted.

This also implies that the milling machine needs to be fairly substantial and rigid, if your gears are going to be made from steel. You can do small work on a large machine, but not so easily the other way round.

A larger, heavy machine will be more rigid, so an aid to quality, so buy a little larger than you initially anticipate

New machines will be Metric, so you will need a calculator to make the settings for Imperial gears...

If you do not have it already, you will need measuring equipment to measure diameters, and to ensure that the work is held concentric in the chuck.

Howard