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Replacing hardened steel slide rods on Wadkin Radial Arm Saw

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Plastic
Joined
Mar 31, 2020
Location
Canada
Hi everyone. I'm restoring a vintage 14" radial arm saw made in England by Wadkin Bursgreen. The carriage slides on two 1/2" hardened steel rods that are about 29" long (part 42 in attached image). Unfortunately, these rods have some wear in them and I can feel the carriage bump in a few spots. These bumps also transfer to the cut wood as slight ridges.

I can order replacement rods from the UK, but they are £100 each and that translates to more than $400 Canadian. So I'm trying to find a more cost effective way to replace these rods and wondering what the best material would be to use. Half inch hardened steel rod is not hard to find, but unfortunately these rods also have four holes drilled and countersunk in them to accept the 10-32 mounting screws which thread into the arm. So I would need to find a material that can be drilled and possibly tapped if I change the way they are mounted. I think the countersunk holes may be part of the problem and it seems like a bad design to me. I would prefer to insert the bolts from inside the arm into smaller tapped holes in the rods.

I think drilling hardened steel rods with the accuracy required is beyond my capabilities, but I do know someone who owns a machine shop. I don't like to bug him too much, I think he gets asked for lots of favours, but he may be able to help me out with this.

Is it even possible for a machine shop to drill and tap hardened steel or would I need to start with something machinable and have it hardened afterwards?

Any advice on how to proceed would be much appreciated.

Thanks.
 

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What I see here is an opportunity to reverse mount the rods so the clean edges are used.
Or to see if some light grinding can be done.
Modification for a ball bearing slide?
 
Could maybe grab a couple bars of Thompson shaft from McMaster? I think it would be possible to heat the ends with a torch. This would anneal the steel so you could drill the holes.
Unfortunately, each rod has four holes in it about 8" apart. So I'd probably have to anneal the whole rod.
What I see here is an opportunity to reverse mount the rods so the clean edges are used.
Or to see if some light grinding can be done.
Modification for a ball bearing slide?
I have already flipped rods end for end, but they cannot be reversed or rotated 180 degrees because the holes are only countersunk on one side. I'll check again, but I don't think there's enough material left to countersink opposite side. If I'm making new rods I would like to drill and tap the holes and insert the screws from inside the arm. That way I could eliminate the countersunk bores and keep the holes smaller.

Here's a couple pics. Also looks like someone else has already tried grinding or filing the rods in a few spots. 20240119_211253.jpg20240119_211328.jpg20240119_211701.jpg
 
Unfortunately, each rod has four holes in it about 8" apart. So I'd probably have to anneal the whole rod.

I have already flipped rods end for end, but they cannot be reversed or rotated 180 degrees because the holes are only countersunk on one side. I'll check again, but I don't think there's enough material left to countersink opposite side. If I'm making new rods I would like to drill and tap the holes and insert the screws from inside the arm. That way I could eliminate the countersunk bores and keep the holes smaller.

Here's a couple pics. Also looks like someone else has already tried grinding or filing the rods in a few spot
Only the contact line widths have to be clean and not the entire bar.

If there is file work then how hard are those bars?
Have you thought about using some stainless steel type 440C replacements?
Would you br drilling with a drill press?
 
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...If there is file work then how hard are those bars?
Have you thought about using some stainless steel type 440C replacements?
Would you br drilling with a drill press?
Good point about file marks. I shouldn't have said that, I don't know what was used to make the marks I'm seeing. I just tried to file near the end of both bars and the file skated right off.

I've attached some better pics of the marks I'm seeing. Looks more like a grinder or belt sander and I can feel some ridges around these areas with my finger. Most of the marks are around the countersunk holes on one bar. So maybe it's not original.

I hadn't thought about stainless. I'll do some research on it and the Thompson rod others have suggested.

I have a drill press, but no mills or any other metal working machines.

Thanks.
 

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can you grind bevel the holes other side , and then use a flat head?
I'll have to remove the rods to get a better look at the other side to see of that's possible. When I had everything apart I did consider countersinking the other side to accept the original screws, but I don't think there was enough steel left for that.
 
Wadkin made really nice machines, worth the effort to put this back in good working condition. Can you trade some woodworking with your machinist friend? He's in a much better position to get this right having the machines and experience that you lack.
 
It is a beautiful machine, so hopefully I can find a solution that suits my frugal budget.

I'm honestly surprised Wadkin didn't build these saws so the rods could be rotated 180 degrees if they became worn. I did notice the UK supplier actually sells two types of rods, one counterbored like mine and one threaded. The threaded ones could presumably be rotated, so I think Wadkin may have changed the mounting method on later model saws.

Here's a pic of the saw after most of the restoration was done.20231129_001858.jpg
 
In my earlier days I have built and crafted some very fine things with just a radial arm saw. Because it was all I had. As I progressed the radial saw was used to chunk stock to smaller lengths for processing on other machines. Rough mill type stuff.
But looks like the Wadkin is a fine machine and Thomson rods will be fine if you start with a solid setup and carbide tooling to get through the "crust". But also be aware that tweaking that old machines bearings with the eccentric screws can sometimes make them run very close tolerances, and the arch bearings may get stressed enough to split. Some do not have an arched outer race, just a pressed on sleeve.
It can be quite an experience to watch the carriage start to fall off as the arched bearing splits. It you are sharp you can deal with it before it comes off the track and climbs up your chest (lucky for me, I did).
 
McMaster sells the shafts: https://www.mcmaster.com/6061K79/

As previously mentioned, the shaft is case hardened, meaning it has a hard shell and soft center. The case hardening depth is around 0.030 IIRC all around, which you have to get past it on both entry and exit.

In a previous life, I modified these on a Bridgeport by cutting flats with a carbide endmill to get past the case, then drilled/cbored normally.

On the exit of the drilling, I used a carbide tipped Hiroc drill. https://www.mcmaster.com/2973A22/

If you try to exit the material with a standard HSS/cobalt drill, it will destroy the tip on the very first hole.
 
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Do you have means to estimate how hard the existing rods are?
If they are not actually fully case hardened, with your available equipment you might find it easier to deal with "Turned-Ground-Polished" (TGP) 4140 prehard which is about 28 - 34 RC. Quite hard compared to annealed or "normal" mild steel. But still easy to drill and tap with HSS tools.

Link provided for description of material.
There are certainly other vendors who may or may not be more cost effective or easy to deal with for retail customers.

 
Wadkin made really nice machines, worth the effort to put this back in good working condition

Completely agree, but if there is nothing missing, that is a really poor design.
It bothers me that the bearings are only contacting at the centers, too; especially despite obvious wear on the wheels.
I would expect the wheels to bear on a line on both sides, with the center not contacting the rod. Of course that method is more sensitive to proper adjustment to reduce forces on the bearings as Scruffy notes can sometimes be a factor. But i really think something is wrong in that picture unless Wadkin made some lazy brained, willfully ignorant design decisions i was not aware of. Do you have any set-up information or specs for the stock design? Is there a spacer between wheel halves (as a possibility) that should be accounted for? Having the contact circumference of the wheel directly rolling over manufactured pot-holes is abysmal.

smt
 
Stephen makes a good point! Here's a link to a brochure on OWWM, not the same model but a good illustration and description of their rail/roller system on page 4. Note that they mention adjusting to rollers to take up wear on the rods.


I'd advise going to OWWM and searching or posting a thread, there's usually someone there who's dealt with the usual machine problems. It's always my first stop for woodworking machine info.
 
I have the manual from OWWM. I have followed the instructions there and adjusted the two of the bearings that are mounted on the eccentric pins. This eliminates any play in the carriage and should help with consistent wear up and down the length of the rods, but I don't think it does much to help with intermittent low spots, rough patches, or the pot-holes as Stephen called them.

I haven't posted a thread on OWWM, but I did ask a question on a Wadkin user group on Facebook. One member there said he had his rods remade years ago and copied the original design with the counterbored screw holes. He said his carriage doesn’t bump as it traverses the holes.

I was looking at mine a little closer the other night and I think it may just be the grind marks around the holes on the one rod that are causing the problems. I rotated the rods without inserting the screws and moved the carriage back and forth gently. It felt a better, but the eccentric bearings were also loose, so hard to tell for sure.
 
I rotated the rods without inserting the screws and moved the carriage back and forth gently.

I still think there is something amiss, given the wear pattern on the wheels.
(edited) OK. i was probably mis-seeing the evidence of what i was describing as wear on the wheels. Is the center of the wheels relieved? rather than being a wear artifact? So the wheels are bearing to each side of the potholes? That would be a lot better, especially if the potholes were narrower.

That said, can you rotate the rods 90 deg, shift them, say 1/2" lengthwise, and try drilling and tapping them?
 
Is there a spacer between wheel halves (as a possibility) that should be accounted for? Having the contact circumference of the wheel directly rolling over manufactured pot-holes is abysmal.

smt

The bearings are solid with no spacers between the two halfs. Here's a link for replacement bearings with some info about them. It describes them as running on "½ inch Silver steel rods". Not too sure what "silver steel" is.

 
The Brits tend to call "silver steel" what we call "drill rod" - a catch all term for low alloy high carbon steel, usually normalized (soft), that has been ground to close tolerance and sometimes polished. Originally "silver steel" was simple water hardening steel. Maybe sometimes oil hardening. Like drill rod, the term may have expanded to encompass some slightly higher alloys. But the point is, if it is stock standard "silver steel" rod, it is probably not very hard. The designation alone does not imply any type of heat treatment; and while there is a legitimate British spec for "silver steel", common usage of the term does not always adhere to materials of that spec, so long as they are round, accurate diameter, high carbon, and mostly shiny. :)

with the rods off your machine, try filing with a sharp file, or possibly starting a new split point drill somewhere in a non-functional area.

smt
 








 
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