Surface grinding attachment WIP

I have no personal experience with the three or four bearing slides, but I did watch a video with a three bearing slide and it was visibly fishtailing. I don't know if it was poorly adjusted or whether the three bearing slides are all that way, but it convinced me to go with the five bearing version.

I wish my progress was a little quicker. I thought making the chuck was the hard part, but that turned out to be fairly straightforward and quicker than expected. What I'm struggling with at the moment is coming up with a good design for tilting the chuck to allow beveling, not just tapering. I'm hoping to get the dovetail slide mechanism completed this weekend and have a design for the taper/bevel mechanism ready for the weekend after. If everything goes well, I might get done sometime in February.
 
Have you looked at the Reeder SGA for the bevel adjustment? I only taper on my SGA, but beveling sure does sound handy.
 
I have watched a Reeder SGA demo video and will probably do something similar for the hinge. On the Reeder, there is very little room between the basplate and the plate that tilts. I want to change that on mine and leave maybe around half an inch in between. This will allow me to tilt both ways, which I think might be useful for taller blades like a chuka bocho. With the geometry I am looking at, there is a height limitation of around 2.75 inches when tilting up before the blade hits the tool arm, so having a few degrees of tilt the other way would overcome that problem. I also think some clearance is a good idea so the plate cannot bottom out on any grit that gets in between. So, I have a rough plan but the devil is in the details. Plus, I am working on a secret plan to add an additional function to the surface grinder that I have not seen done before, and I need to fit that in there as well. I am not sure how well this will work, but I will show my results either way once I get to that point.
 
Sounds like you've got some good ideas for this SGA you're making. As you can tell, I've got this thread tagged so I'm sure to see any posting to it. For sure I'll keep watching and see how it goes. I LOVE making tools - almost more than making knives :)
 
I made a little progress on the feed mechanism today. I did not want to lose any travel, so I cut the supports for the dial indicator back a little to make some room, plus I think it looks good. The hole in the back support is threaded 1/4-20 STI, but I forgot to put the helicoil in before test assembly. There will be a 1/4-20 bolt secured with a jam nut to adjust the range of the indicator at the end of the travel. The hole for the lead screw is threaded 3/8-24 STI and has a helicoil in it. I cut some recesses in the plates to make room for the nuts. I have some nylock nuts, but there is something wrong with them. I tried to get them on the threaded rod, but the plastic is way too tight. So much so that if you try to force it with an impact driver, it strips the threads. I'll take another look tomorrow.

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There is definitely something wrong with the plastic inserts, the opening is a good bit smaller than the minor thread diameter. So, I drilled out a couple of the nylock nuts and made a makeshift tap from a piece of 3/8-24 allthread by cutting four lengthwise grooves into it with a rotary tool. I ran the tap through a couple of nuts so I could finally get them threaded onto the lead screw. There is a bronze washer behind each nut. Unfortunately, the lead screw is bent a bit and I had to leave the nuts a bit loose, so there is a bit more backlash than I was hoping.

I also put the helicoil insert for the dial indicator screw in, but have not put the set screw for the indicator in yet as I could not find any nylon tipped ones (I know they are somewhere, but it's been a while since I've seen them...). I can get the entire range of travel and there is no binding at the near end. I was a bit concerned about how well the holes in the two plates would line up, but they seem to be spot on. I think this thing will work pretty well, but it would be nice to find a lead screw that is not bent. I have some Teflon washers that I will try out to reduce the friction a bit, which might let me take a little bit more backlash out before it becomes difficult to turn. Even with the sloppy way it is adjusted now, the lead screw will move the carriage left to right if I loosen the gib screws rather than moving left to right its clearance hole. I'm hoping the Teflon washers might help, we'll see.

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Is your leadscrew 3/8"X24? doesn't that give about .042" (.0416666" of travel for each turn of leadscrew. I like a 1/2X20 leadscrew since that gives a nice .050" travel for each turn of the screw.

Have you made any progress on the bevel grinding attachment yet?
 
Ken H> said:
Is your leadscrew 3/8"X24? doesn't that give about .042" (.0416666" of travel for each turn of leadscrew. I like a 1/2X20 leadscrew since that gives a nice .050" travel for each turn of the screw.

Have you made any progress on the bevel grinding attachment yet?
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The lead screw is 3/8"-24. I figured it should be plenty strong and the finer the pitch the better. I hope it turns out ok, I really do not want to remake those parts...

I have not made any progress on the bevel grinding attachment, other than digging out a piece of 5/8" thick aluminum from the bottom of the rack. While I was removing the stuff sitting on top of it, I found a small off-cut and thought it would make a nice rise-and-fall indicator, so I've been thinking about how to make one of those. I'll get back to the surface grinding attachment next weekend!
 
Oh, don't worry I fully expect that 3/8"X24 to work just fine. 1/2"X20 worked good for me, and I was planning to engrave the feed knob to indicate each .005". I did that, then later I did some rework and didn't bother with the "calibrated" knob since .005" on the knob never translated to exact .005" off on the pass. Normally in the .002" TO .003" range depending on grit of belt.

A rise 'n fall indicator is really nice for making slipjoints. They're not hard to make and really make it easier.
 
No machining today, just 3D printed a knob. This was only meant to be temporary until I make a real knob, but it's nice enough where I think that will be a while...
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Finally, some progress! I received the 200x75mm wheel I ordered from aliexpress. It was not supposed to arrive until early April, so I was quite surprised when I got the package. I had ordered the wheel with 20mm ID bearings (6204) and the only option for those was shielded, not sealed. So I was not really disappointed when the wheel came with one damaged bearing, as I had planned to replace them anyway. The machining on the wheel is pretty poor and there is a small void in the casting on the inside, but overall it seems pretty decent.

I machined a shaft for the wheel today and it fits very nicely with no play at all. While I was turning the shaft on the lathe, I used one of the shielded bearings that came with the wheel to get the fit right and then put the wheel with the new bearings on the shaft to test for run out. I did not put an indicator on it, but at least it looks like it runs pretty true.

I am waiting on some material to arrive to finish the rest of surface grinder, but it looks to be at least three weeks out before it gets here. There are a few odds and ends I can work on in the meantime, but it will be a little while yet before I can complete the project.

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Another installment in the "How to build a surface grinding attachment in six months" series... I machined the top plate that the chuck attaches to this weekend. It turned out pretty decent aside from some surface finish issues. There will be two hardened inserts that go in the back side for adding spacers to the built-in sine bar which I still have to machine on the lathe.

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I milled the slot by drilling a few holes using coordinates I had calculated and the DRO, then used an end mill to drill the same coordinates and the points in between. To finish the slot, I used a shoulder bolt through a piece of 18mm Baltic birch plywood as a pivot and a couple of mini Kant twist clamps as stops. I initially just used the quill to drill more holes with the end mill, then offset the x direction by 3 thou and rotated the work piece to clean up the edge of the slot. I did this in four passes per side using conventional milling. This worked a lot better than expected and took less than half an hour, including the time to build the jig. The picture below shows the setup and the slot I had made with the DRO.

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To clean up the surfaces and mill the insert flush, I really needed a machinist jack to reduce vibrations. I should really build a proper one for next time. For this project, I just made a makeshift jack from a grinder wheel, a bolt and a nut. This worked really well to reduce chatter.

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It looks like my chuck has picked up a bit of a warp. Not sure how visible it is in the picture, but there is a pretty large gap between the surface plate and the chuck in the center, I'd guess at least 20 thou. I think I'll try to straighten it a little bit with the hydraulic press and then machine it flat before mounting.

The chuck was made from cold rolled steel, I wonder if this issue could have been avoided by stress relieving the steel.

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Bummer on the bow in the chuck. Sounds like you've got a good plan, and the finished chuck will ALWAYS require finish flattening with the grinder. And perhaps from time to time a touch up might be required.
 
Hubert S. said:
It looks like my chuck has picked up a bit of a warp. Not sure how visible it is in the picture, but there is a pretty large gap between the surface plate and the chuck in the center, I'd guess at least 20 thou. I think I'll try to straighten it a little bit with the hydraulic press and then machine it flat before mounting.

The chuck was made from cold rolled steel, I wonder if this issue could have been avoided by stress relieving the steel.

CEBzkNG.jpg
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Yeah it most likely warped when after you unclamped it when you milled all the slots in. CRS is terrible about turning into a banana when you take a lot of material off one side and not the other. You should be able to straighten most of the warp out then grind it flat once assembled.

Looking really good otherwise!
 
Ken H> said:
Bummer on the bow in the chuck. Sounds like you've got a good plan, and the finished chuck will ALWAYS require finish flattening with the grinder. And perhaps from time to time a touch up might be required.
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Yeah, I'm not too worried about the front of the chuck, that will get ground flat anyway. It won't be too bad machining the back flat again, but I am not looking forward to cleaning up the mess it makes. I really wonder how I did not notice this earlier. The first time I noticed a gap was last week when it was sitting on a workbench. At that time, I thought the table had the bow and was a bit surprised since that bench has a torsion box on top that was pretty flat when it was made.

I think I will skip the bevel hinge for now. I ordered some steel in February that I was planning to use for the wear parts and it still has not shipped. It was part of a larger material order and there are supply shortages for some of the stuff. I made the top plate so it will not interfere with the hinge if I want to add the bevel capability in the future, and the chuck will just need a new set of mounting holes to get to the right height. With just the tapering capability, all I need to finish this thing is drill rod and aluminum which I already have.
 
Contender Machine said:
Yeah it most likely warped when after you unclamped it when you milled all the slots in. CRS is terrible about turning into a banana when you take a lot of material off one side and not the other. You should be able to straighten most of the warp out then grind it flat once assembled.

Looking really good otherwise!
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Thanks!
 
I machined the backside of the chuck flat and started on the mounting plate. The two pins for the sine bar are not pushed in yet, I'll do that after I drill and tap the mounting holes in the bottom of the plate. The threaded studs are removable, they will be fastened with Loctite during final assembly. The one for the hinge has a very tight fit, there is no play at all. The inserts for the sine bar are still missing, but I am getting really close now.

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