Thompson Siginaw screw, opinions?

[phantomcow2]

I am very close to buying ball screws for my Z axis frm
http://www.homeshopcnc.com/page2.html
I would like at least a few opinions before i do though, has anybody ever bought from here and ordered this type of ballscrew? What are you experiences with it.
And lastly, is the screw hardened, i know with some screws you need to heat the end you want to machine to anneal the hardening. Is this the case with this ballscrew? Thanks for any replies
-Bernard

[furry]

These are rolled screws and having bought one to try out, they are quite sloppy and rough in their operation. The nut especially has a fair amount of lash in it.

Save and buy a quality ground one, or look into some teflon coated leadscrews with antibacklash nuts.

good luck!

[phantomcow2]

Thanks for a reply.
Its not worth me buying a ground ballscrew for a 300 dollar mill with not a huge amount of travel. So i will keep my eyes open on ebay, but it seems like acme screws are the way to go for now.

[JRoque]

Hi. I have those screws on my 5' x 5' table. They are not great but work ok, especially considering what they cost. I bought two nuts for each screw and have no backlash that I can measure. If I do it again I would get the larger 1" screws instead of the 5/8" since they tend to slop a bit with spinning fast. To help minimize that problem, I applied tension (ie: pulling) from each endmount.

JR

[phantomcow2]

Well considering the longest screw I will need is something like 15", there would be no slop. Either way, im going to try to make some delrin backlash nuts. When this screw wears our (if i have not osld hte machine before), i will look at ballscrews.

[Bluesman]

I worked for Tompson for 10 years I can tell you it good quality and yes on a rolled assembly the are induction hardend all the way from end to end so you do have to aneal them to machine them.
Make sure you are geting class 1screws though,(If they still catalog them that way) rolled threads come in several difrent quality levels.

Blue

[phantomcow2]

Thankyou for a reply BLuesman, can you tell me if the screws on that website i linked are class 1? HomeshopCNC

[furry]

You don't necessarily have to anneal them to machine the ends.. I used an angle grinder mounted on the toolpost to grind throught the case and into the 'soft' stuff

[phantomcow2]

depending on just how hard it is...i would probably just plow through with carbide tooling on the 5Hp engine lathe at my school. I've never seen any material be able to resist that beast. Not sure how well my mini lathe would handle it

[Chivo]

I bought ballscrew (rolled) and bullnut in McMaster.com, They don't givie you the screw's brand in their catalog online. But They are Thompson.
They are very cheap and the acuracy +/- 0.004 per foot.
I bought 48" long 1" OD screw and ballnut for $150

[Bluesman]

Originally Posted by phantomcow2 Thankyou for a reply BLuesman, can you tell me if the screws on that website i linked are class 1? HomeshopCNC

The Ball Screw that is in the picture is a rolled thread screw and a tapped nut, As a matter of fact I wrote the program for the lathe, and set up the cell at Tompson that runs that particular assembly, It is not a precision set at all and is mostly used for power pac acuators. It is primarily for just moving things like satalight dishes or garage doors. I would not recomend it for any precision at all. There are assemblies that use a rolled thread and a Tapped nut but are much more precision. As a matter of fact they have some rolled thread screws that run with a ground nut that are very afordable and prcision too.
Also that screw is carbon hardend in a homocarb and is hard almost to the core, It shouldbe aneald to machine it.
And yes you can plow thru some of the case hardend screws if you only need to turn a jurnal end but for the best results you should aneal first.

Blue

[phantomcow2]

maybe I will try it for my Z axis. Ive got some nice duplex bearings i need to use up, its a good excuse to machine some bearing blocks. The website says it has .004"/ft accuracy. Considering my Z is probably half of that, I can live with that figure.