Nesting steel square tube

[Lyle]

I am thinking of making an archery bow press, another of my hobbies aside from woodwork.
To do so I need some square steel tube. The smaller tube needs to slide inside the larger tube. A snug, not tight or sloppy fit is required. Tube needs to be about 50mm for the larger tube, with wall thickness of 1.5 to 2.0mm.
I have used some RHS tube but it isn't right for the job. There seems to be a weld line inside the tube which will not give me the fit I want. It either binds or is too sloppy. I've even tried a bushing inside but that is bloody fiddly.

Is there a different brand/style of steel tube I should be searching for. I haven't found anything with my google friend.

Can anyone help with suggestions or suppliers (preferably in Newcastle NSW area).

Thanks
Lyle.

[NCArcher]

Hi Lyle,
Long way to travel for a bit of steel :;
Try Horan Steel (http://www.horansteel.com.au/)in Mayfield
Onesteel in Broadmeadow
Hunter Valley Steel (http://www.hvsteel.com.au/page19858/HoldingPage.aspx)in Rutherford
Southern Steel in Thornton
Cardiff Metal Market in Cardiff
depending on where you are in Newcastle. There are others scattered around.
Are you working off a plan? There are a couple of good ones for free if you do a search on the net.

[BobL]

I have used some RHS tube but it isn't right for the job. There seems to be a weld line inside the tube which will not give me the fit I want. It either binds or is too sloppy. I've even tried a bushing inside but that is bloody fiddly.

How far does it need to slide?

I found I could cut the weld off for a distance of 150 mm from one side and then the other using an 200 mm long HSS wood turning tool. Grind the bevel so it is a lot sharper than that used for wood turning and hold the tool bevel up flat against the weld inside the tube and then just using the heel of your hand you will find you can scrape/cut the weld line off and get it very flat. I do this for 75 x 5 mm SHS and find the 65 mm tube slides very nicely inside it.

[Bryan]

Another trick I've used is to relieve the inner tube to clear the weld by cutting a groove with an angle grinder.

I've never heard of seamless square tube but it may exist.

[Stustoys]

Extruded steel tube used to be available at least in smaller sizes, 30mmSQ as around $40/m 10 years ago.

Could you use Alum?
Know anyone with a shaper?
I like Bobs and Bryans ideas but if they wont work, cut one face of the inner tub off and weld in bridging pieces.(see sketch)

Stuart

[Picko]

Lyle

I'm hopeing there is a PDF attached. Cross fingers!

[Scott]

You should be looking for ERW Tube, most good steel suppliers should stock it. It's most made for the purpose you want (telescoping).

Hope this helps.

-Scott.

[Lyle]

Wow, thanks for the quick replies.
ERW tube and the .pdf, are exactly what I was looking for.
Thanks.

[Lyle]

You're right ncarcher, is a long way, just about as long as the story that goes with it....:U
I must update my profile.
Thanks for the info on places to go.
I'm in Medowie now so Newcastle is closest, unless there is another place. I'm going to Hunter steel in Heatherbrea this arvo. I don't know who they distribute for.
Lyle.

[Dave J]

I went though this when I built my crane on the ute. My fix for the 65 to 50mm problem is show below by welding a plate on the back of the smaller tube and a collar around the front of the larger tube to fit snug around it (more like a ram set up). I ground a small notch out of the plate to clear the weld inside. The other sizes where a good enough fit for what I was using it for.

http://www.woodworkforums.com/attachment.php?attachmentid=171238&stc=1&d=1306464062

On my crane I used 75,65 and 50mm square tube.

http://www.woodworkforums.com/attachment.php?attachmentid=171239&stc=1&d=1306464825

http://www.woodworkforums.com/attachment.php?attachmentid=171240&stc=1&d=1306464825

Dave

[Dave J]

There is also Ezymetal at Raymond Terrace and Hunter metal market at Heatherbrae.

Dave

[nadroj]

I went though this when I built my crane on the ute.

Neat crane, Dave. Do the arms telescope manually?

Jordan

[Dave J]

The crane is a 500kg (my under rating) all manual that I designed around 10 years ago.with manual worm and gear to rotate it around as well. It has lifted a 360 dodge V8 truck engine with all accessories (air bell housing clutch etc) at 3/4 reach and swung it around into a trailer I was towing.
The ram looking tubes are so each extension can be pulled out separately and have pins drilled in them instead of the main arms..
There are 65x35m heavy wall tubes that slide out of 75x50mm just behind the cab to take wind down stabilizing legs I keep in the tool box, and there is a linked handle either side to lock the tray to the chassis when lifting.
I made the custom tray which has remote or in cab control electric hydraulic tipper and was built around the crane design to be strong enough.

I have the parts and the plans in my head for a larger 1 ton crane that will reach 4mtrs and is going to be a full hydraulic knuckle boom crane, but instead of folding like a number 4 as seen on trucks, it will fold up as a single post like this one. Nobody makes one in the 1 ton range or to fold up compact, so it will be a first.

I had an engineering shop interested in buying the design after they had seen it when I was out. I went around to show the boss where they took a few measurements (supposable to work out the steel needed) and I have never heard back from them.

It weighs around 80kg, so it's only like carrying an extra person, but can lift a lot more.

Dave

[mike48]

Hi Lyle

In adition to good info by Picko and others.

BJ Howes has an excellent manual online called "Know Your Steel" with the "telescoping" info and just about all you need to know about steel which is available and sold in Australia, and retailed via Metaland et alia.

http://www.bjhowes.com.au/Know%20Your%20Steel%20Book.pdf

Blackwoods have a table for selecting telescoping SHS and RHS etc in their printed catalogue on page 32-10.

cheerio, mike

[Lyle]

OK, looks like 40 x 40 x 2mm and the nesting 35 x 35 x 2mm will give me a fit of 1mm ( or 0.5mm each side).
I'll start making measurements and re-drawing my plans to suit.

Next search is for the acme threaded rod, acme nuts and a hand wheel.
Then a machinist to cut the press fingers to hold the bow.
The press is coming together in my mind after seeing the steel available.

Slowly slowly.....

Thanks again.