Replacing gibs on a mechanical hacksaw

[scottmk1]

I Have a Qualters & Smith LDS 6 mechanical hacksaw. I have just re cut the dovetail slides on the over arm that the bow runs on & they have turned out quite good. The gibs or wear pieces whatever the correct name for them is on this application, well one is quite worn, so I could mill it back so that it is the correct shape, but then I'd have to make a spacer to go in behind & re drill the mounting holes in the bow. So, if I was to make new ones what would be the preferred material? The originals are some kind of steel, but obviously I don't know what type?

 

[gordon stephenson]

I would recon Key steel or even mild steel, keep both well lubricated

 

[scottmk1]

Thanks Gordon. It has an oil bath that wicks through felt pads, unfortunately they were pretty gummed up when I took it to bits, I'm going to wash them out & make sure the channels are clear. What about gauge plate? I have a big enough bit to make both of them.

 

[gordon stephenson]

I recon gauge plate will be fine.

 

[scottmk1]

Ok, well I've nothing to loose. That's tomorrows job sorted then.

 

[MrFluffy]

Should be cast iron in larger piece, brass or bronze in small ones, cast iron has a very low co-efficient of friction and will wear out sacraficially before the surface in sliding contact with it and the graphite helps with marginal lubrication.
You can buy durabar or grey cast iron bars as a raw material for this, or if you search about sometimes you can find a off the shelf pre-made gib thats suitable.
I have this job to do on the knee of my mill in the near future as it locked up the other week and when I got it free there's some very ugly marks on the gibs :-(

 

[mr migwire]

is this a certain saw from the fife area scott or did you manage to pick one up elsewhere? just being nosey...

 

[scottmk1]

Hi Mark, it's a different one. I did get in touch with your man & he said he would give me a shout when he is ready.

 

[mr migwire]

ahhh cool mate, ive not seen him for a good while, anyway back to the topic, do you have pics of this project as we all love to see refurb jobs you know....

 

[scottmk1]

Just for you Mark. Here is the offending item, the old Qualters & Smith LDS 6.

The saw ran nice & quiet when not under any load, but as soon as you took a cut it was crashing and banging like no ones business. I tries making some adjustments to the gib, but that just made it too tight. So I stripped it down, and upon checking contact between the gib & dovetail ways on the overarm well there wasnt very much contact at all. So I set it up on the Bridgeport to re cut the dovetail ways on the overarm.

After the first cut you can see the worn area in blue.

And after taking off 0.75mm

The same was done to the other side, but that needed a bit less taking off. Round about 0.5mm iirc.
The re cutting of the dovetails left the inside corners very sharp as can be seen here.

So I set up the Quillmaster attachment for the Bridgeport with a ball nosed 3/32" endmill to reach in there & put in a radius undercut.

Cut the radius undercut on both sides, and thats the milling work on the overarm finished, just needs a real good clean to get rid of all the cast iron fillings.

The next job is to make 2 new gibs. I could re cut the originals but that would mean re drilling mounting holes etc & I have a nice bit of gauge plate to make the out of.