a couple of years ago I got a cheap Metz shrinker / stretcher off ebay
http://www.ebay.co.uk/itm/261620178141
and then saw some lazze videos about using a deep shrinker / stretcher to create compound curves like this one
so rather than buying one, I thought I'd make a new body for one, as the jaws on the standard and deep shrinker stretchers are the same.
so here are a few pics from me building it.
the sides of the body were made from 12mm thick steel plate, I decided that that it was a bit thick for cutting out with hacksaw and file, so decided to cut the shape out in my milling machine, using 6mm carbide slot drills. the holes in both plate were drilled at the same time (both plates clamped together), then the plates were separated and the slots were cut (like doing a dot to dot with a milling machine). the bolts and washers in the slots on this pic are to clamp the centre being cut out
and one plate after being drilled and one with the slots cut out, I guess it could be done quite cheaply by other methods but took a few hours moving the plates about,but the carbide cutter was only £3.00, and time is free to me.
I then had to mill the recesses for the shrinker/stretcher jaws, I wouldn't have needed to do this if I had used 10mm plate (I wouldn't have needed to make new pivots if I'd used 10mm plates too) its not an issue with a milling machine but without one I would have been stuck. ohh and I'm using large lolly sticks for packing to save the milling machine table as the plates are hot rolled plate.
then it was time to weld the two sides together, with 4 plates in stategically located places, I already drilled some holes in the corners so the plates could easily be aligned using studs and nuts
and the welding completed, showing my poor attempt at tig welding (we all have to learn by practicing), but its not structural so it should be ok. there is also a plate on the base with the mounting holes and a small plate on the back too.
then first assembly of jaws and operating lever.
I had already decided that if I made some new levers and pivots I could use the old body for the stretcher (and saves having to keep changing jaws which can be a pain). At this stage I was wondering why they were so hard to use as I'm not the world strongest person, but then realised its all about the leverage, so thought that if I moved the point of contact with the shrinker jaws back towards the pivot hole, I would need to use less force, with a smaller jaw opening which is a trade off I can live with, so on my new lever I cut some slots so that I could use some round bar to change the leverage ratios. so here are my new and old levers. Im not sure how long mine will last as the old (black) ones are definately tougher, so I may need to case harden mine.
and the completed assembly. the cover that holds the shrinker jaws together was just cut in two and and a couple of extra mounting holes were cut in both halfs
and a test piece shown in front of the new body. I'll still be hand operated instead of foot operated. I started of with a 20cm dia disk of 1.0mm zintec, after shrinking its 160mm dia at the base and 45mm high. the finish is a bit rough though, but its a start
so he is the new body I've made on the left with shrinker jaws in and the original body with stretcher jaws in. the body in the background is one that I made earlier and turned out to be a failure due to being to flexible. it was made from 250 x 250 x 6mm sides (this was cut with a hacksaw and filed by hand), so when I made the one with 12mm sided I started out with plates that were 200 x 200 x 12mm. the hole in the middle was smaller too to help increase rigidity.
I've started using BEJ steel for material, as I cant get to the local steel suppliers as Im working (so have it delivered to a relative who lives close by. they also have more items on ebay, but you can email them by their site they will send you a paypal invoice which works out cheaper than buying through ebay, and the combined postage prices help too if you have a few items
http://bejsteel.co.uk/
http://www.ebay.co.uk/sch/steel2go/m.html
http://www.ebay.co.uk/itm/261620178141
and then saw some lazze videos about using a deep shrinker / stretcher to create compound curves like this one
so rather than buying one, I thought I'd make a new body for one, as the jaws on the standard and deep shrinker stretchers are the same.
so here are a few pics from me building it.
the sides of the body were made from 12mm thick steel plate, I decided that that it was a bit thick for cutting out with hacksaw and file, so decided to cut the shape out in my milling machine, using 6mm carbide slot drills. the holes in both plate were drilled at the same time (both plates clamped together), then the plates were separated and the slots were cut (like doing a dot to dot with a milling machine). the bolts and washers in the slots on this pic are to clamp the centre being cut out
and one plate after being drilled and one with the slots cut out, I guess it could be done quite cheaply by other methods but took a few hours moving the plates about,but the carbide cutter was only £3.00, and time is free to me.
I then had to mill the recesses for the shrinker/stretcher jaws, I wouldn't have needed to do this if I had used 10mm plate (I wouldn't have needed to make new pivots if I'd used 10mm plates too) its not an issue with a milling machine but without one I would have been stuck. ohh and I'm using large lolly sticks for packing to save the milling machine table as the plates are hot rolled plate.
then it was time to weld the two sides together, with 4 plates in stategically located places, I already drilled some holes in the corners so the plates could easily be aligned using studs and nuts
and the welding completed, showing my poor attempt at tig welding (we all have to learn by practicing), but its not structural so it should be ok. there is also a plate on the base with the mounting holes and a small plate on the back too.
then first assembly of jaws and operating lever.
I had already decided that if I made some new levers and pivots I could use the old body for the stretcher (and saves having to keep changing jaws which can be a pain). At this stage I was wondering why they were so hard to use as I'm not the world strongest person, but then realised its all about the leverage, so thought that if I moved the point of contact with the shrinker jaws back towards the pivot hole, I would need to use less force, with a smaller jaw opening which is a trade off I can live with, so on my new lever I cut some slots so that I could use some round bar to change the leverage ratios. so here are my new and old levers. Im not sure how long mine will last as the old (black) ones are definately tougher, so I may need to case harden mine.
and the completed assembly. the cover that holds the shrinker jaws together was just cut in two and and a couple of extra mounting holes were cut in both halfs
and a test piece shown in front of the new body. I'll still be hand operated instead of foot operated. I started of with a 20cm dia disk of 1.0mm zintec, after shrinking its 160mm dia at the base and 45mm high. the finish is a bit rough though, but its a start
so he is the new body I've made on the left with shrinker jaws in and the original body with stretcher jaws in. the body in the background is one that I made earlier and turned out to be a failure due to being to flexible. it was made from 250 x 250 x 6mm sides (this was cut with a hacksaw and filed by hand), so when I made the one with 12mm sided I started out with plates that were 200 x 200 x 12mm. the hole in the middle was smaller too to help increase rigidity.
I've started using BEJ steel for material, as I cant get to the local steel suppliers as Im working (so have it delivered to a relative who lives close by. they also have more items on ebay, but you can email them by their site they will send you a paypal invoice which works out cheaper than buying through ebay, and the combined postage prices help too if you have a few items
http://bejsteel.co.uk/
http://www.ebay.co.uk/sch/steel2go/m.html