So I've been doing a heap of fabrication with RHS from 20 to 40mm lately, and starting to go nuts managing distortion for every single join, tacking, checking square, belting/breaking tacks to correct, welding out then discovering unexpected movement...
So I decided to get me a nice angle clamp. Wandering around the local Total Tools I see a stack of them for $60 each. Can't argue with that price, so I get one, take it home, wipe the grease off and stick 2 bits of 30mm RHS in it only to discover they ain't square. Seems odd. So I go back to the shop and armed with a square, unpack a whole bunch of the angle clamps on the counter, checking each for square - they're all out.
In the end, I take the least worst one with the idea of taking it across the road to my neighbour who has a mill and get him to square it up. However, with my 2 bits of RHS clamped in it, I suddenly realise that in addition to being a bit out of square, the 2 pieces aren't lining up flat - they're out by 0.5mm or more. Talking with the neighbour, he observes that the hollowed-out casting of the base has left the bottom surface only about 5-6mm thick, so if he runs an endmill over it to get it flat, it'll be down to maybe 5mm or worse, and with no guarantee it wouldn't twist or warp, and in addition, it didn't actually sit flat as it was.
So I returned it for a refund and went next door to Gasweld, taking my bits of RHS to test in the shop. Sure enough, both units on offer were not flat (I didn't bother testing for square), making them next to useless (how can they sell these things?).
The final option was the more serious industrial supply shop (where you find Kemmpi & Hypertherm etc.) - they can do the Hare & Forbes stuff, whose clamps looked mighty similar to Gasweld's and therefore a risky proposition. However they also offered stuff from Strong Hand, claiming they're the ones the "professionals" use. So I ordered one, which arrive the next day - they're made in China, but do come with a testing report, showing the measurements for various critical faces against the allowed limit.
More to the point, it's square and flat, just as you'd expect such a clamp to be. Turns out you need to pay 3 times the price of the Total Tools unit to get that.
So I decided to get me a nice angle clamp. Wandering around the local Total Tools I see a stack of them for $60 each. Can't argue with that price, so I get one, take it home, wipe the grease off and stick 2 bits of 30mm RHS in it only to discover they ain't square. Seems odd. So I go back to the shop and armed with a square, unpack a whole bunch of the angle clamps on the counter, checking each for square - they're all out.
In the end, I take the least worst one with the idea of taking it across the road to my neighbour who has a mill and get him to square it up. However, with my 2 bits of RHS clamped in it, I suddenly realise that in addition to being a bit out of square, the 2 pieces aren't lining up flat - they're out by 0.5mm or more. Talking with the neighbour, he observes that the hollowed-out casting of the base has left the bottom surface only about 5-6mm thick, so if he runs an endmill over it to get it flat, it'll be down to maybe 5mm or worse, and with no guarantee it wouldn't twist or warp, and in addition, it didn't actually sit flat as it was.
So I returned it for a refund and went next door to Gasweld, taking my bits of RHS to test in the shop. Sure enough, both units on offer were not flat (I didn't bother testing for square), making them next to useless (how can they sell these things?).
The final option was the more serious industrial supply shop (where you find Kemmpi & Hypertherm etc.) - they can do the Hare & Forbes stuff, whose clamps looked mighty similar to Gasweld's and therefore a risky proposition. However they also offered stuff from Strong Hand, claiming they're the ones the "professionals" use. So I ordered one, which arrive the next day - they're made in China, but do come with a testing report, showing the measurements for various critical faces against the allowed limit.
More to the point, it's square and flat, just as you'd expect such a clamp to be. Turns out you need to pay 3 times the price of the Total Tools unit to get that.
0 commentaires:
Enregistrer un commentaire