Rapidor hacksaw

I'm repairing a Rapidor hacksaw that's been neglected for a few years.
I don't know what model it is, but the blade is 14" x 1" and several
of the castings have numbers like '3XM3' or '3XM4' on them.
It's in surprisingly good condition under the dirt and leaves (nothing
really seized up) but I'm confused about the dashpot mechanism.
The dashpot itself is straightforward - a piston with holes in it, and
a spring-loaded washer to shut the holes as the piston is pushed into
the dashpot. But there's a length of 1/4" rod screwed into the piston
that runs parallel to the square shaft. It's about 6" long, has a
short knurled length, then just stops, bent and ragged.
The main cam that drives the saw also has some wear, as though a
cam-follower once rode on it. There's an empty boss in the base
casting, directly under the edge of this cam. I suspect there's
something missing here, perhaps a hydraulic lifter that's connected
in some way with that 1/4" rod. Anyone know how it's supposed to
work ? It's a long while since I last used a well-maintained one.
Another puzzle is the vice : when it's tightened, the jaws are pulled
together nicely. But when the crank is loosened, the thread doesn't
drive the jaws apart : instead, the crank winds out of the front jaw
and a tap on the end is needed to move the jaws apart. Is this right,
or should there be a pin somewhere to keep the crank in place ?
-adrian
Reply to
Adrian Godwin
Loading thread data ...
years.
(nothing
Adrian
I have a Rapidor Major in very good condition, and what you describe sounds similar to my saw.
On the Major the blade is angled with respect to the motion of the slide, so that the cutting pressure is maintained as the blade moves forwards. i.e. the frame tends to lift as it moves forward and the blade rides over the work. On the return stroke the descent of the frame is delayed by the action of the dashpot, so the blade is held out of cut. The knurled rod in the dashpot presses against the piston plate, and allows adjustment of the damping rate to suit the speed of cutting. There is no mechanical link between the drive mechanism and the dashpot (though there is a simple prop to hold the frame lifted clear when not in use).
The vice on my Major works exactly as you describe.
Hope this helps
Mike
Reply to
mike.crossfield
OK, I can see how that would work. I presume the dashpot should have oil in it, not just air - if so, how thick should it be ?
However, there's certainly a line of less muck on the edge of the cam. I'm glad I haven't got to build a master cylinder for it, but I wonder what's caused it ? Nothing else appears to rub there, and the boss below doesn't have any obvious function (there are other holes for mounting and draining). Maybe a cam-operated suds pump ?
Yes, I've got the prop too.
Thanks !
-adrian
Reply to
Adrian Godwin
We also have a 14" blade Rapidor, we can do some pic's of specific items if you need them. Our vice also does that!
Peter -- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk
formatting link
Reply to
Prepair Ltd
The one at the bottom of this page ? :-)
formatting link
That's pretty well identical, though I wasn't sure of the size. Except yours has a weight, stand, motor, and has had a lot more elbow grease applied !
I think Mike's sorted out my biggest problem, but a pic of the top of the dashpot would still be interesting, thanks. And do you have a boss (or even just a hole) in the tray directly underneath the cam / flywheel ?
-adrian
Reply to
Adrian Godwin
Mine has such a hole. Since it had a pipe fitting screwed into it I assumed it to be the coolant drain. Whatever; that's what it gets used for.. hth
Reply to
Roland and Celia Craven
Yup, that's the one.
Mad Mick Mills did the work, I bought it from him after he had been over it and sorted it out.
See Roly's reply, but I will check mine as well tonight and take a pic.
Peter
Peter -- Peter A Forbes Prepair Ltd, Luton, UK snipped-for-privacy@easynet.co.uk
formatting link
Reply to
Prepair Ltd
Adrian
I use ordinary 30 grade oil in the dashpot, and it seems to give a sensible range of damping adjustment.
-can't help on the cam you mention. I guess you must have a different model of saw to mine. My suds pump is buried in the base of the unit, and is chain driven
Mike
Reply to
mike.crossfield
Possibly not the same as mine, then - the base casting has a wall just behind the dashpot, and the hole I mean is behind that, only a few inches from the back. This area would tend to collect spilled oil from the mechanism, so is best kept apart from the suds. The coolant couldn't drain to there without also flowing onto the floor. The boss might well be part of a pipe fitting, but I haven't taken it apart yet.
There is, however, another hole just in front of the dashpot : this would drain fine. But on my model, it doesn't have any sort of fitting.
This machine looks as though it was n production for a long while - there must be a lot of variations about, especially in such things as motor mount and coolant pumps.
-adrian
Reply to
Adrian Godwin
Hello Adrian,
The boss in the base under the cam is for a suds pump. Mine is currently siezed...
I can take some pictures of it if you like - let me know...
Cheers,
Jez.
jez[AT]jez[HYPHEN]nikki[DOT]net
Reply to
Jez
Yes please ! Or even just a written description - I can imagine a spring plunger and valve arrangement but approximate dimensions would be interesting.
-adrian
Reply to
Adrian Godwin
I was given a machine vice which had the same problem - there was a slot on the threaded rod, just inside the casing, which I think should have had a circlip on it (or something). I couldn't get a circlip on (not enough clearance for pliers) so I wrapped a couple of turns of thin wire into the groove. It's worked OK for a couple of years now.
Reply to
BigEgg
Hi. I found your reply very useful. I also have aquire one of these lovely old machines. Forgive me for being thick, are you saying that the saw cuts on the forward stroke? Also, just below the top edge of the dash pot, there is a bent and mangled bolt in mine. Any idea of its function? Finally, any clue as to where I might fingers a parts diagram/manual? Thanks in anticipation. Stuart York.
Reply to
Stuart York
Hi. I found your reply very useful. I also have aquire one of these lovely old machines. Forgive me for being thick, are you saying that the saw cuts on the forward stroke? Also, just below the top edge of the dash pot, there is a bent and mangled bolt in mine. Any idea of its function? Finally, any clue as to where I might fingers a parts diagram/manual? Thanks in anticipation. Stuart York.
Reply to
Stuart York
I wonder if the information on the pages starting at:
formatting link

are of any help to you?
Alan
Reply to
Alan Dawes
Hi. Thanks Alan, the site you mention has details of the Rapidor saw, they are asking a lot of money, and I'm reluctant to purchase as there's no real indication of the quality you get for your money. I was hoping a fellow enthusiastic rebuild had a parts list/ diagram they might share. Thanks for taking the time to reply. Stuart
Reply to
Stuart York
Hi. Thanks Alan, the site you mention has details of the Rapidor saw, they are asking a lot of money, and I'm reluctant to purchase as there's no real indication of the quality you get for your money. I was hoping a fellow enthusiastic rebuild had a parts list/ diagram they might share. Thanks for taking the time to reply. Stuart
Reply to
Stuart York
Stuart
As I explained in my original message, when properly adjusted the damper holds the blade out of cut on the back stroke. The blade must therefore be set in the frame so that the teeth cut on the forward stroke.
HTH
Mike
Reply to
miked.crossfield
Hacksaws normally do.
I remember my school metal work teacher having a funny demo to teach this, along with using an initial 'back stroke' to mark the line of cut.
The Japanese use some pull saws in woodwork but I've not seen them in metal saws.
Jigsaw blades cut on the up stroke but the blade is only supported at one end.
Reply to
Brian Reay
Hi Adrian fellow Rapidor restorer. I have just finished what I believe is a 1952 Rapidor Manchester Hacksaw with the same similar issues your having. I think the vice mechanism is how you see it. Mine is exactly the same. No pin to hold it from coming out of the release jaw, but at the very back of the lose jaw on mine there is a screw hole but whether that held a plate or somethings to be guided on the threaded bar. I don't know, there is no sign of it on the machine when I was taking it apart. The piston you described is exactly the same as mine. What the little bar does on the side Once again I do not know. The only thing I can think of is that it could of operated a water cooling pump. On the older versions its got a lit cover on it and shaft is free to move through it but no sign of a water pump. The code number how ever I think mine is 3mx or something but after that all in the same line its got 1952 . So 3MX1952 and that's all I have to go on with regards to its age. This machine looks great. I have painted it with a dark green Japlin colour and a red wheel in memory of Frank Hornby, Meccano. The main Cam is perfect with no ware on it so again I cant comment on that. The problems I have had is the motor was Three phase so I have fitted it with a single now. I have one last problem and that the release handle with the looking handle I am not sure how the spring mechanism works I cant find any literature on or with regards to the machine specification at all. There's is lots of lovely Youtube videos on seeing them operational which is great, but not much use when you are restoring them. Only other issue it heavy ha ha. If you know of any literature with regards to the spring mechanisms I would greatly appreciate it. Good luck Adrian hope it all works well.
Reply to
Peter Noden

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.