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Power hacksaw
| Keith Long | 30/09/2009 20:17:33 |
| 883 forum posts 11 photos | Hello there. Has anyone here made, or had any experience of using the power hacksaw designed by R J Cochrane and detailed in drawing WE54. Just purchased the drawing sheets and construction looks pretty straightforward even for someone who's very out of practice. All comments welcomed. Thank you |
| Flying Fifer | 30/09/2009 23:19:29 |
| 180 forum posts | Hi Keith, I made mine from the original articles in ME. Volume 168 issue numbers 3920 & 3922 & the last part is in Volume 169 issue 3924. I changed a few bits & used some different size gears from the scrapbox (think they were Boxford). Can`t recall any problems during the build & if there were any the sheer pleasure of not having to use a hacksaw has made me forget them!
Any questions drop me an email
 Regards Alan
|
| Keith Long | 01/10/2009 15:59:43 |
| 883 forum posts 11 photos | Hi Alan Glad to hear someone's trodden the path before me! Probably make a few mods myself - Myford change wheels look a suitable alternative starting point to the gears shown for a start and fairly cheap, as well as changing the threads and fasteners to metric as they are much more readily available these days. Only issue that I see at the moment is the manual hacksawing needed to build a machine to do it for me! regards Keith |
| Graham Porcas | 06/10/2009 17:44:11 |
| 6 forum posts | Keith
Interested to find your thread on this, I am also thinking about making my own as I have given up trying to find a suitable secondhand Kennedy or Rapidor, they seem to be like hens' teeth!
I was thinking about the Blackgate kit of castings but it seems expensive for what appears to be a pretty basic design and I am worried about where to get 10" blades nowadays. I don't know the Cochrane design, how substantial is this? If only 1/4 HP then will it cope with say 2" steel bar?
Did you consider any others before you decided to take the plunge?
Regards
Graham |
| Flying Fifer | 06/10/2009 23:56:36 |
| 180 forum posts | Graham,
I use 12" eclipse blades in my version of the Cochrane saw & yes it will cut 2" bar. Largest I`ve cut was 3" dia. OK it wasn`t quick but it beats the hell out of cutting by hand! I`ve got a bit of 10" x 4" U channel which I need cutting in half (across the U ) & I`m currently pondering how to do it. Current thinking is grip 4" leg in vice & cut as far as it can then turn & cut from other side.
See that`s the trouble with powered hacksaws they make you lazy. If I didnt have one I`d probably have sawn it by hand by now!
regards Alan |
| Keith Long | 07/10/2009 00:18:37 |
| 883 forum posts 11 photos | Hi Graham You can usually find Rapidors and the occasional Kennedy on EBay. Most people seem to think that the Kennedy is gold plated from the prices they fetch, and it's a small beast only using half a normal hacksaw blade. Rapidors tend to go for about £200 ish and from the photos of them look as though they've generally seen a hard life, and are usually 3 phase. They are also heavy floor standing machines. I wouldn't like to want to move one about the workshop. The Cochrane design looks fairly robust, the yoke is designed to be cut out of 3/4" m/s steel and the slide arm is 1"x5/8". The saw frame is 5/8" square section, so it's not flimsy by any means. Looking at the drawings there are a few places you could ring the changes as well. As drawn the saw has an 82mm (3 1/4" approx stroke), going bigger would need some mods (possible), and the vice is a bit on the small side at just under 3" capacity, but that is easily altered. 1/4 HP ought to be sufficient, may take it's time, but it's no effort sitting watching it, and as the motor mounts separately to the basic machine, there's no reason why you couldn't use a bigger one. My only concern is that the final drive to the saw is by gears rather than belts. The design calls for a 20dp, 20 tooth bronze pinion driving an 85 tooth cast iron gear, and there doesn't appear to be any guarding over the gears so metal dust from the saw can get in there and mix with any lubricant. I was thinking of using Myford change gears (both cast iron) for the drive and enclosing them in some way, changing the final drive to belts would entail some major reworking of the whole drive. I haven't looked at the Blackgates design as I didn't want to have to buy castings, I prefer to work from basic stock materials. The only other design I've looked at seriously is the one by Vincent Gingery - bought the book. It looks as though it would work OK , and be pretty straightforward and fairly cheap to build but the design and execution of the machine is a bit on the rough and ready side for my liking, and at something like 4 feet overall length, the machine is getting on for double the length of the Cochrane design. I won't be starting building this for some time as I'm still setting the workshop up and still have insulation, flooring and wiring to sort out before I can even start to install my machines. Looks like a busy winter ahead! Regards Keith |
| Ian S C | 07/10/2009 12:32:00 |
 7468 forum posts 230 photos | Before I bought a bandsaw about 12 yr ago I built a power hacksaw,being short of steel the saw frame was suspended on two 150mm links,and swung back and forth by a crank out of a washing machine,It was driven by a 1/3hp motor through belt the gear to the crank,giving a speed of 75 per min,of late I'v thought of rebuilding it,some of the steel has gone to other projects,and the legs have been incorperated in one of my hot air engines,and the motor is driving an old blacksmiths wall drill.No plans used,all materials scrap including ball races on all shafts and the swinging arms,not perfect but it works.IAN S.C |
| Dunc | 29/10/2009 00:35:53 |
| 139 forum posts |
another thought:
There are any number of plans available fro the Google archives of Popular Mechanics
and Popular Science
Once on the respective home page there are articles:
Pop Mech - July 1951, Nov 1969, Feb 1976,
Pop Sci - Jan 1956, Feb 1964.
and probably a few more.
I built the Pop Mech Feb 1976 one - slightly modified to use scrap box stuff & to accept longer blades. Cut like a charm. I used power hacksaw blades, not hand ones (were 12 inches long by about 1 inch high) . Sold it & bought a 4x6 horizontal / vertical bandsaw. Only problem these days I think would be getting the power blades I used but bi-metal hand hacksaw blades are easily found & cheap. Maybe I will just build a mark 2...
Edited By David Clark 1 on 17/07/2012 16:13:05 Edited By David Clark 1 on 17/07/2012 16:14:14 |
| Ian S C | 29/10/2009 11:15:37 |
7468 forum posts 230 photos | The drive arrangment on my swinging arm saw was belt drive from motor to jack shaft,then gear drive to the crank,can't remember the ratios,but if you get between 60-80 your not too far off spot on.IAN S C |
| Geoff Theasby | 29/10/2009 15:12:42 |
| 615 forum posts 21 photos | I bought a power hacksaw from eBay, said to be by Blackgates Engineering, but it differs from their current design.
It takes hacksaw blades which need notches ground in the blades to fit, as they are shorter than normal. However, this is an easy process, if you have a bench grinder.
Pressure is applied by a weight, and the blade clamps reciprocate on square section slides. The motor drives a pulley via a V-belt, and then by gears to a crank.
After the lathe, it is my most useful tool! Saves hours of hard, boring, repetitive work, and produces lovely, parallel sided offcuts, with a fine finish, so they scarcely need any further attention.
Regards
Geoff
|
| Bizibilder | 08/01/2010 15:53:41 |
 173 forum posts 8 photos | I have made the Cochrane saw myself and it works extremely well! The only mods I made were:
Instead of welding the frame I made side plates and fitted bolts in each of the top corners - No problems.
Second I used the motor from a Warco small bandsaw (The bladesnapper!!!) which I believe to be 1/3 HP - it works fine. I have cut 2.5" round in under half an hour.
I mounted my motor "behind" the machine - so the whole thing is about two feet "long" so I made a cupboard underneath to hold my steel stock and add some mass and stability to the saw.
The gears were from the ME exhibition the large one is CI and the small one is steel I think they are 85 and 21 teeth - chosen to provide a "hunting" tooth count.
Bizibilder (I have some pics but can't seem to post them!!) |
| Les Jones 1 | 08/01/2010 17:55:46 |
| 2292 forum posts 159 photos | Hi Bizbilder, To insert pictures you have to upload them to the site first using the "My Photos" option at the top of the page. Once they are in there you can insert them into your message. It took me a long time to work this out at first. Les. |
| Bizibilder | 17/01/2010 14:37:38 |
173 forum posts 8 photos | Thanks Les!
I've put some photo's in an album called "Power Hacksaw" (What else!!) I anyone wants more details then please ask.
Bizibilder |
| Martin Cottrell | 17/01/2010 20:44:18 |
| 297 forum posts 18 photos | Hi Bizibilder,
Looks like a nice job you've done there! Are plans still available for this hacksaw, I've had a quick look in the plans section on here and can't seem to find any?
Regards, Martin. |
| Rob Manley | 18/01/2010 14:48:18 |
 71 forum posts 14 photos |
Ive always wondered if the home built power hacksaws are heavy enough in the bow. I bought a rapidor from a garage the was 'modernising'. It was under £100 and a single phase motor cost less that £20. It wasnt clapped out (it was actually extremely good) and now ive put castors on it slides under the bench when needed very easily. Unless you like making machine tools, which I doo but have far too many other projects on the go, don't rule out finding a nice one
Oh, but nice work - looks too good to be a hacksaw.
Yes you need a permanent workshop with a strong floor, yes you will need help shifting it, yes you will be cutting stuff up for the sake of it but this is the god of hacksaws - had one at work and would go through 10" (not that we need it too) easily. (nothing to do with me)
You can search Ebay for hacksaws.
Edited By David Clark 1 on 17/07/2012 16:15:32 |
| Ian S C | 19/01/2010 09:54:29 |
7468 forum posts 230 photos | The 'bow' on my home made saw was made of 1 1/8" sq steel barFairly rough stuff),and that needed a bit of extra at times,that was using a 12"x1" industrial blade with 16tpi.Ian S C |
| oilcan | 20/01/2010 20:02:48 |
| 34 forum posts | I'm thinking of building a power hacksaw myself, but before sending of for the plans of the cochrane does it have backstroke relief of the blade and /or dashpot control? I remember many years ago seeing some articles in model engineer about modifying a shop built saw with these features. does anybody know the year? Our main library has most volumes in the reference section so I can always look them up. But theres an awful lot of years to trawl through! If the features are not on the cochrane design they are something that i would like to build in. (too mean to buy new blades!) |
| Bizibilder | 20/01/2010 20:14:53 |
173 forum posts 8 photos |
I don't have relief on my saw and the blades seem to last forever! There is a stop that you can set (carefully) so that the "drop" at the end of a cut is minimal. i also built a retractable pin to hold the saw in the "up" position.
There were some articles by Duplex many years ago - I think these went with the Duplex machine. There was also an article in MEW about some sort of damping device for a hacksaw.
If you download the ME and MEW indexes:
you should be able to search for the articles that you want. (Excel spreadsheets)
Bizibilder
Edited By Bizibilder on 20/01/2010 20:17:50 Edited By David Clark 1 on 17/07/2012 16:16:30 |
| oilcan | 21/01/2010 16:02:11 |
| 34 forum posts | Thank's for the link to the index archive. For anybody interested some articles on hacksaw blade relief for powered machines appeared in volume 142 year 1976 (although not been down to the library to check them) but ,as you say, if the blades last forever why complicate life? |
| Flying Fifer | 24/01/2010 23:15:20 |
| 180 forum posts | Hi
Relieving device is in Vol 142 issue 3456 starting on page 957.Author Ian Bradley who was I think part of the Duplex team.
Regards Alan |
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