12 x 2 lead screw

Hi all.

I'm hoping to add x-axis power feed to my "nearly new" Sieg SX2PG. It only has one x handwheel, on the right and the lead screw is quite short. I intend to mount the feed assembly on the left and attach it to the left end of the lead screw.

In order to not reduce x-axis travel (and maybe increase it a tiny bit) I want to make a new lead screw. I'd hoped to buy a length, off the shelf and then machine whatever is needed on each end. However, I can't find 12x2 trapezoidal screw anywhere. Every other size is readily and cheaply available but not 12x2.

The existing screw is about 420mm overall, so I'd want at least 450mm.

Can anyone help with a source for the above?

Thanks

Gareth

Hi Gareth. I think tr12 is where it changes from 2 - 3mm pitch. If you can get away with 10mm rs components sell tr10 x 2 for 20 quid a meter. I bought some recently and it's good quality.

Best wishes.

Gareth

Thanks for the reply.

You're right about the step to 3mm being at tr12 but I'd have thought 2mm would be available. If my tiny mill uses tr12 then surely all the larger Chinese hobby-type mills use tr12 or bigger and a lead of greater than 2mm would make for silly increments on the hand wheels.

I'd rather not drop to tr10 as I'd then have to think about a new nut to suit.

Since my first post, I've found some tr12 x 2mm on Ali Express. I've never used Ali Express - is it trustworthy?

Thanks

Gareth

Edited By Gareth Jones 11 on 18/08/2023 12:21:16

Hi Gareth,

A power feed is a great idea, I did this on my SX3. I'm not familiar with your mill - is the leadscrew currently un supported at what will become the power feed end? If so could you not drill,bore,ream that end and fit an extension ? a good fit, Loctite and a cross pin will get you there. It won't increase your travel but do bear in mind that at the extreme of travel the table won't be supported much.

Alternatively you could as Ketan at Arc if the same leadscrew is use in a larger model and adapt it.

Making a leadscrew of that length, pitch and diameter is quite an undertaking as there will be a lot of flex and a trapezoidal profile puts more load on the machine. Longest I have made is ~300mm and that was 22mm in dia. so flex wasn't an issue.

There are companies that would make one for you but I suspect it might cost North of £500 maybe a lot more.

If you search in Germany you can find a few: **LINK** or https://www.walzkraft.de/produkte/trapezgewindespindel.

Niko.

I would be looking at what Tony suggested. When I put a ballscrew on my mill X axis I got one that was a little too short to go all the way along the table based on the fact that at the extreme travel of the table the shorter ballscrew would still be sticking out beyond the ball nut. As I was going to be machining something for the (in my case) right hand end anyway it did not make sense to pay for more length of leadscrew than was necessary and machining a hardened ballscrew did not appeal.. This was for a ballscrew with pre-machined ends so I made an extension to fit on the machined stub of one end.

Martin C

There is no need to change the leadscrew to fit a power feed to the X axis, take the cap off the left hand table end plate and you will see the end of the leadscrew with on convinient slot in it. This can be used to take the drive from the power feed and you can fairly easily knock up a dog clutch so any load from the PF can be removed when using teh handwheel. That is how Mr Sieg does it and it works fine on my X3

If you do still want a longer screw then just get a screw from a long bed X2 machine and use that

Thanks all.

Tony - the screw from a larger machine is a great idea but I've taken the plunge and ordered a length from AliExpress. The lead screw is unsupported at the left end but the minor diameter is only 9.5 mm so there isn't a huge amount of meat to drill and cross pin but I did consider it. I might make the drive motor mount double as a lead screw support on the left.

Jason - I've seen plenty of examples with a slot in the end as you describe. Mine isn't like that unfortunately. No cap, support or slot.

I'll wait for the screw to arrive and get molded and fitted, then order a stepper and electronics and start playing.

Thanks for all the replies.

Has anyone every suggested adding a new 'lead-screw' to a lathe by using a wire wrapped around a drum to pull the carriage along (and back)? It would surely easier in a home workshop to make up a few pulleys and a drum or two, rather than making (or buying) an Acme or simliar screw set-up?

Tim

The closest I have seen to that is the Trend router lathe, used for making spirals on sticks. I think Sears Craftsman in the US also made one (Router Crafter 720.25250) and manuals can be found at vintagemachinery

I have seen a drum arrangement used in the USA to make a tapered shaft for the WW2 effort.

Quick update -

My TR12 x 2mm leadscrew arrived from AliExpress, exactly 2 weeks after placing the order.

It seems to be pretty good quality. I pulled the table off my mill and the new screw is an excellent match to the original nut. Seems better than the original leadscrew.

Very pleased and I've since ordered a few more bits from AliExpress

I simply drilled and threaded a hole in the end of the existing feed screw on my Raglan, then added a drive for the power feed I roughly made to the youtube video by Phil Vandelay.

He used a wiper motor, but I used a 24V (I think) alternative.

Just a thought. Have you checked the length of any scale on the DRO if you have one fitted as twice i have had to sort out this problem when other people slide the bed beyond the scale limits and scraped the reader head.

David

Hi David,

I don't have a DRO fitted yet. It's on my list and I'll double check travel/lengths before I go for it. I'll prob fit a simple Z-axis DRO, ASAP as the standard Z adjustment is just about useless for any level or accuracy.