mark roberts
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I used brass strips on one of mine
- Thread starter brewdexta
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Jaeger_S2k
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brewdexta
The biggest tool in the box
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I bought a couple of pairs of bronze castings from @mark roberts a few years ago for the PK saws. This for the quadrant or double mitre, they are normally cast iron and usually go missing or get broken. This is what they should look like, I believe this is probably one of Mark's renovations.
This is one of the two sets of castings that I bought
Given they are not cheap, and my neighbour is a toolmaker that works at an aerospace company that has many rather large machines, I cheated and got him to machine all the major dimensions. I had a drawing of one of the two castings plus Mark posted a pair of machined castings to me so we could take dimensions. We also worked off the bed of the table saw to get the various pivot points, slots and retaining pin holes aligned so that the quadrant did what is was supposed to do. from a geometry perspective. this video shows what they should do, the quadrant appears about 4:50 in,
My neighbour did all the major milling and returned them to me, they then needed a few holes drilling and tapping, plus lots of filing around the pivot to allow the two parts to rotate around the pivot.
I don't have any parallels at the moment, they are on my Christmas list, so just used the clamps to lift them off the mill base
They are awkward shapes to drill, for the next one I had to get the "Yorkshire" parallel out
and for tapping
After that it was filing time, I used lots of sharpie to show me where I was filing to keep it square
Plus I used more Sharpie when fitting the two together, this time it showed where the two components were catching when pivoting so I coud remove just the right amount
Eventually it pivoted sufficiently so I could check if the machining was correct. We were pretty confident but decided to mill one pair at a time in case we screwed up.
The pivot, handle-clamp and pin are just temporary, not the finished article, the handle just happened to be 1/2" BSW
Continued.....
This is one of the two sets of castings that I bought
Given they are not cheap, and my neighbour is a toolmaker that works at an aerospace company that has many rather large machines, I cheated and got him to machine all the major dimensions. I had a drawing of one of the two castings plus Mark posted a pair of machined castings to me so we could take dimensions. We also worked off the bed of the table saw to get the various pivot points, slots and retaining pin holes aligned so that the quadrant did what is was supposed to do. from a geometry perspective. this video shows what they should do, the quadrant appears about 4:50 in,
My neighbour did all the major milling and returned them to me, they then needed a few holes drilling and tapping, plus lots of filing around the pivot to allow the two parts to rotate around the pivot.
I don't have any parallels at the moment, they are on my Christmas list, so just used the clamps to lift them off the mill base
They are awkward shapes to drill, for the next one I had to get the "Yorkshire" parallel out
and for tapping
After that it was filing time, I used lots of sharpie to show me where I was filing to keep it square
Plus I used more Sharpie when fitting the two together, this time it showed where the two components were catching when pivoting so I coud remove just the right amount
Eventually it pivoted sufficiently so I could check if the machining was correct. We were pretty confident but decided to mill one pair at a time in case we screwed up.
The pivot, handle-clamp and pin are just temporary, not the finished article, the handle just happened to be 1/2" BSW
Continued.....
brewdexta
The biggest tool in the box
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Next, check both pieces are aligned correctly
There are marks on the bed to align the faces of the quadrant, see mitre below
and again.
Bang on 90 degrees
And now with a Fordson Dexta mud guard below it
We had already checked the single mitre was at 90 degrees to the blade when the 90 degree hole was selected so we were happy with the machining.
Now more filing, and more filing
This is typically how the unmachined bits were
After a bit of effort, more to do.
and then filling, I took off the high spots with a burr first then some dolphin glaze.
only a thin coat, just enough to fill any major holes and the pores in sand marks in the castings
You can see I finished filing. There are some small inclusions in the castings so you have to stop at some point.
Both finished ready for paint
continued.....
There are marks on the bed to align the faces of the quadrant, see mitre below
and again.
Bang on 90 degrees
And now with a Fordson Dexta mud guard below it
We had already checked the single mitre was at 90 degrees to the blade when the 90 degree hole was selected so we were happy with the machining.
Now more filing, and more filing
This is typically how the unmachined bits were
After a bit of effort, more to do.
and then filling, I took off the high spots with a burr first then some dolphin glaze.
only a thin coat, just enough to fill any major holes and the pores in sand marks in the castings
You can see I finished filing. There are some small inclusions in the castings so you have to stop at some point.
Both finished ready for paint
continued.....
brewdexta
The biggest tool in the box
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Two coats of epoxy primer by brush. once this has hardened I'll give it a light sanding, top coat may wait until I have the other two castings fettled
There's a bit of fettling to do, but only a little.
There are a few tweaks we will be making to the other two castings during machining, only minor.
Next step is to get on with making the pins out of 303 stainless, I'll wait for the other castings first as the pin length will depend on the final machined height.
Now back on the tractor for a while.
There's a bit of fettling to do, but only a little.
There are a few tweaks we will be making to the other two castings during machining, only minor.
Next step is to get on with making the pins out of 303 stainless, I'll wait for the other castings first as the pin length will depend on the final machined height.
Now back on the tractor for a while.
