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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Does a 2"x1/4" mild steel tube slide inside a 2.5"x1/4" tube?
I need to construct something that will slide occasionally inside a
2.5"x1/4" steel tube. I want to use a 2"x1/4 to fit inside a 2.5"x1/4" Do they fit? I've only got piece of 2.5" to measure at the moment. In theory looks like it will. The length is approx 36", and the lenght of slide is only 5-6". I'd like it to be a close fit but not too tight as it might bind. It's going to be part of the frame of a 2"x72" belt grinder. Where the main frame holding the axle will extend or contract depending on the grinder attachments. -Mike |
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I meant 2.5"x1/4" Square tubes.
-Mike |
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mlcorson wrote:
I need to construct something that will slide occasionally inside a 2.5"x1/4" steel tube. I want to use a 2"x1/4 to fit inside a 2.5"x1/4" Do they fit? I've only got piece of 2.5" to measure at the moment. In theory looks like it will. The length is approx 36", and the lenght of slide is only 5-6". I'd like it to be a close fit but not too tight as it might bind. It's going to be part of the frame of a 2"x72" belt grinder. Where the main frame holding the axle will extend or contract depending on the grinder attachments. -Mike I doubt it. Such tubes are welded, and there is a weld bead on the inside, and this is usually the main problem with telescoping tubing. You can buy telescoping tubing, but of course it costs more money than regular square tube, which is itself pretty pricey these days. What I recommend is to carefully fit pads of 1/4" steel inside e.g. 3" square tube, just to make a rim around the inside edge. This can be ground to fit over the bead, and welded on the end, and the pad can be filed or otherwise shaped to just fit e.g. a 2" square tube. The inner member should have a similar pad put on its innermost end, but on the outside. This will make it ride straight, and will keep it from ever coming out. You don't have to fit the pads perfectly in the corners. This is how they make telescoping arms for boom trucks, and it works great. GWE |
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On Thu, 08 Sep 2005 07:30:25 -0700, Grant Erwin
wrote: mlcorson wrote: I need to construct something that will slide occasionally inside a 2.5"x1/4" steel tube. I want to use a 2"x1/4 to fit inside a 2.5"x1/4" Do they fit? In theory yes. In practise, tubing is manufactured to precise outside dimensions. The inside dimensions vary from manufacturer to manufacturer, but are usually within +/- 1/32". It is this 1/32" that determines whether or not they "fit" -- do not assume that they do. I suspect that this variance depends on whether or not the tubing is manufactured in a plant that uses metric measurments for production, where wall thickness is measured in millmeters rather than in inches. You may have to shop around for tubing from different manufacturers to find something that suits your purpose. I've only got piece of 2.5" to measure at the moment. In theory looks like it will. The length is approx 36", and the lenght of slide is only 5-6". I'd like it to be a close fit but not too tight as it might bind. It's going to be part of the frame of a 2"x72" belt grinder. Where the main frame holding the axle will extend or contract depending on the grinder attachments. -Mike I doubt it. Such tubes are welded, and there is a weld bead on the inside, and this is usually the main problem with telescoping tubing. You can use an angle grinder to grind out a notch on the inner tube to make room for the weld bead on the inside of the outer tube. If you don't have much to do, you should be able to clamp the work piece into a vise and do it free hand. For more serious production work, I've seen a jig made for this purpose by replacing the saw head on a Dewalt DW708 Sliding Compound Mitre Saw with an angle grinder and then using it to notch 20 ft. lengths of square tubing. (You'd have to fabricate an adapter bracket for mounting the angle grinder to the sliding rails of the saw frame.) In this case, the sliding rails hold the angle grinder centered on the tubing, while the 12" stroke allows you to work about a foot of tubing at a time without operator fatigue. You can buy telescoping tubing, but of course it costs more money than regular square tube, which is itself pretty pricey these days. What I recommend is to carefully fit pads of 1/4" steel inside e.g. 3" square tube, just to make a rim around the inside edge. This can be ground to fit over the bead, and welded on the end, and the pad can be filed or otherwise shaped to just fit e.g. a 2" square tube. The inner member should have a similar pad put on its innermost end, but on the outside. This will make it ride straight, and will keep it from ever coming out. You don't have to fit the pads perfectly in the corners. This is how they make telescoping arms for boom trucks, and it works great. GWE |
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Grant Erwin wrote:
mlcorson wrote: I need to construct something that will slide occasionally inside a 2.5"x1/4" steel tube. I want to use a 2"x1/4 to fit inside a 2.5"x1/4" Do they fit? [...] I doubt it. Such tubes are welded, and there is a weld bead on the inside, and [...] What I recommend is to carefully fit pads of 1/4" steel inside e.g. 3" square tube, just to make a rim around the inside edge. This can be ground to fit over the bead, and welded on the end, and the pad can be filed or otherwise shaped to just fit e.g. a 2" square tube. The inner member should have a similar pad put on its innermost end, but on the outside. This will make it ride straight, and will keep it from ever coming out. [...] Sounds like you put in pads on 4 sides of each piece, 8 pads total. Also like there could be an assembly problem if the outer tube is closed on the other end. With 3 pads arranged at A, B, and C as below (where = represents a pad, with A and B fastened inside the outer tube, and C on the outside of the inner tube) you could insert the inner tube until pad C hits pad B, then tip the end up to pass B. Vice versa to remove. .. B .. ---=----------- .. -----------= C .. ------------ .. A =-------------- This is for tube walls vertical and horizontal, ie, where the vertical cross-section of a horizontal run of tube is a square. With a diamond cross-section (ie, tube rotated 45 degrees) this idea would work ok with 6 pads. -jiw |
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