Silvey Rasursharp II grinder redesign and rebuild

A few of you might have seen that I was unhappy with the slide on my used Silvey Razursharp II that I got about a year ago. For those of you not familiar with the grinder they use an aluminum block with a stainless steel slide to move the chain into the stone. This slide has adjustable gibs to change the pressure but if you get any grinding dust in the block it quickly wears and becomes useless. Once a little wear is present it becomes either too loose such that you'll be getting inconsistent beaks on your cutters or so tight you'll have troubles moving the slide and crash the cutter on the stone. Also there is not adjustment to level the slide with the stone so mine was grinding 2-3 degree different on the top plate per side of the chain and there was nothing I could do about it.

I set out to remedy these issues with a new design. It uses eccentrics with small ball bearings on the end to make a linear bearing slide that I can adjust in two planes to be perfectly aligned with the stone. Also I slotted the mounting holes so I can adjust the block in the vertical direction for different chain types or to get more/less top plate angle instead of taking the stone off and changing the stone height on the motor shaft. This will keep me from having to true the stone after each adjustment.

The new design drawn in CATIA.


To make the eccentrics I threaded a hole in a plate and then offset it in the 4-jaw on the lathe. Then just cut down the end of some 3/8x24 UNF all thread and threaded the end to hold the bearing.


The block I made on a cross-slide table on an old delta drill press. If I'm going to make anymore I subbing them out to a CNC shop or I'm buying a decent mill. I took 12 hours to mill the part out since I had to take very small cuts or the slop in the drill press head would cause it to chatter. Also I wasted an hour or two cutting the slot that mounts the block to the original drop piece in the wrong direction.


The final assembly of the slide block.

Here is another view of the block.


The help wasn't very enthralled with the whole project. They just wanted to sniff and eat stuff.

Here is a video of the grinder upside down so you can see how it is all assembled and how it works.


It was much easier to assemble and align the slide when it was upside down. I used a dial caliper to get the stone holders the same vertical distance from the stone. Then I used a square and the dial caliper again to align the slide with the vertical drop piece that it all mounts to. The original Silvey vertical drop piece is not perfectly aligned with the stone center but it was close enough that I'm getting within 1 degree top plate angles side to side.

The grinder is now very consistent where as before your pressure on the chain holder to blow the beak all over. Now it doesn't move even under excessive pressure.

That does look a lot more complicated than it did in that drawing. Let us know how it holds up. I might be interested in one if it will last and be rock solid. Anything will be a step up from the original parts really.

mdavlee said:

That does look a lot more complicated than it did in that drawing. Let us know how it holds up. I might be interested in one if it will last and be rock solid. Anything will be a step up from the original parts really.

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And like the original post, I'm still interested. The workmanship looks great, superior design from the
original and looks like a great upgrade! 12 hours was long, think it would take that long again now that
you know how to make it?

That's a great design and a much superior part which should work well- Proof yet again that there's some kind of insanity going on in your shop.

watsonr said:

And like the original post, I'm still interested. The workmanship looks great, superior design from the
original and looks like a great upgrade! 12 hours was long, think it would take that long again now that
you know how to make it?

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I could only take 0.015" cuts with a 1/2 end mill for the pocket to create the main C shape. 1.25" depth at 0.015" cuts... that took a great while. On a decent mill I could have done it in 4 cuts easy. It would probably take less than 4 hours on a manual and probably 1.5 hours on an CNC machine with an auto tool changer.

Here is a video grinding the first chain with the new block. With the height adjustment I was able to get much closer to the original angles of the RSLHK chain it's grinding pretty quickly. You often opt out of making an adjustment when you have to remove the stone to do it.

srcarr52 said:

I could only take 0.015" cuts with a 1/2 end mill for the pocket to create the main C shape. 1.25" depth at 0.015" cuts... that took a great while. On a decent mill I could have done it in 4 cuts easy. It would probably take less than 4 hours on a manual and probably 1.5 hours on an CNC machine with an auto tool changer.

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What's the slowest speed the drill press will turn?

It's the lack of rigidity with a drill press that makes milling on one with a cross slide an extremely frustrating experience.

BTW, that is a very nicely machined part! I don't have the patience to mill with a drill press, and have a large cross slide table I need to use to make something with as it's been gathering dust for about 10 years.

Looks like it works great.

Metals406 said:

What's the slowest speed the drill press will turn?

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I's a giant old delta, 2hp 3ph motor and has 5 speeds ranging from slow enough you could count the RPM on you hands and toes to winding fast enough to take off. It was really the 0.020" of play in the spindle that was killing me, you could take conventional cut... dial in a .010 cut and not touch a thing on the climb pass. It did really great with a fly cutter but the end mill was too much side load. I might see if I can rebuild the head and tighten it up a bit since the drill press itself is plenty rigid for light milling, it weights in at about 400lbs and only gets moved with the skid loader.

tolman_paul said:

It's the lack of rigidity with a drill press that makes milling on one with a cross slide an extremely frustrating experience.

BTW, that is a very nicely machined part! I don't have the patience to mill with a drill press, and have a large cross slide table I need to use to make something with as it's been gathering dust for about 10 years.

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Thanks, I was surprised how nice the finish came out with the fly cutter. I took the time and dialed in the base of the cross slide table using bolt jacks I put in it such that it was almost perfectly perpendicular to the spindle. I should have taken some pictures of the milling setup but I was always so angry with how slow it was going I didn't want to stop to take a picture.

I also did a quick hand scrape on the ways of the cross slide, it really helped it's rigidity. Straight from china it only touched at the ends so in the middle it would be loose.

my slide on mine is a littlesloppy ,i like your idea there ,i usually dont use the handle underneath and eyeball the cutter pushing from the outsidetorwards the wheel so i can see the tooth being centered right

I use the handle and hold the chain holder with the other hand and usually pull the chain together under the holder so the tooth doesn't raise up much when going across the stone.

mdavlee said:

I use the handle and hold the chain holder with the other hand and usually pull the chain together under the holder so the tooth doesn't raise up much when going across the stone.

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kind of what i do too ,with the little bit of slop in the slide ,have to eyball the cutter make sure in right spot

Mine has a little bit of slop. Sometimes it works to your advantage if you have a short cutter in there so you don't have to adjust the holder for that one tooth.:msp_wink:

I have one hand on the lever and one hand on the tooth to keep it from raising up. I don't have to watch the beak anymore, if the alignment is off it's because of a manufacturing defect in the chain.

srcarr52 said:

I's a giant old delta, 2hp 3ph motor and has 5 speeds ranging from slow enough you could count the RPM on you hands and toes to winding fast enough to take off. It was really the 0.020" of play in the spindle that was killing me, you could take conventional cut... dial in a .010 cut and not touch a thing on the climb pass. It did really great with a fly cutter but the end mill was too much side load. I might see if I can rebuild the head and tighten it up a bit since the drill press itself is plenty rigid for light milling, it weights in at about 400lbs and only gets moved with the skid loader.

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I'm familiar with them old beats. . . It's nice you have that speed adjustment without fabbing a jack shaft.

Wonder if you couldn't install or fab a better quill and spindle to tighten up the tolerance? I also read guys fill up the column with granite concrete to stiffen up the works.

Metals406 said:

I'm familiar with them old beats. . . It's nice you have that speed adjustment without fabbing a jack shaft.

Wonder if you couldn't install or fab a better quill and spindle to tighten up the tolerance? I also read guys fill up the column with granite concrete to stiffen up the works.

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For column stiffness they'd be better off making plates for the top and bottom and running a piece of large redi-rod down the center. Then tightening it up and put the whole column in compression.