Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder

I needed to resize a piece of hardened shaft for a fixture I'm making so I made a mount for my angle grinder to use it as a toolpost grinder on my lathe. I started with a good sized chunk of 6061 and hogged out the middle to fit my grinder then drilled it to bolt onto the top of my lathe toolpost. I've got a ¾" roughing end mill that's worth its weight in gold and the mill area looked like an aluminum blizzard had just hit when I finished. The mount is nice and rigid when mounted.

Since you can't reverse the grinder rotation the lathe needs to turn in the reverse direction so the surfaces meet in opposing directions. The lathe ways are shielded with some old jeans (wetted with water so they don't catch fire) and the grinding goes slow, never more than .020" off the diameter and feeding very slow, and you reach your target the same way you catch a unique rabbit - unique up on it ☺. The finished part doesn't have a $1000 ground finish because I used the wheel that came with my Hitachi grinder but it is dimensionally accurate and all it cost was the chunk of aluminum.

In action

Attachment 35762

From the backside

Attachment 35763

Great work Crusty.
Cheers
Celso Ari

The shaft turned out perfect and I've already used it to align a series of parts on axis.

A fine better quality wheel would no doubt leave a prettier surface but dimensional accuracy was all that I required. Perhaps with a good quality wheel you might be able to hold to half a thousandth, though that depends on the accuracy of your lathe.

Now that I've got a ½HP DC motor left over after my mill upgrade I think I'll use it to power an actual toolpost grinder with which I can do internal grinding with too.

Crusty,
A unique way to mount an angle grinder fo O.D. grinding.
By the way .020” is a deep cut in one pass with the piece protruding that far out of the chuck.

It's between the chuck and the live center so a bit more stable and truth be told I never actually took more than a .010" cut off the diameter (.005" in on the dial).

I've been looking for a better grinding wheel for my angle grinder hopefully with a finer grit and I haven't found one so far. Any suggestions where to look?

Crusty,
I don’t own an angle grinder so I can’t comment on a grinding wheel recommendation. I believe the wheels normally used are resinoid bonded wheels which are resistant to breaking apart and usually don’t grind cool.

I found a few at MSC that would likely do a nice job (some CBN even) but they're really expensive. It's tough to find a hard wheel that can take the high rpms in my price range. I'll keep looking.

The shaft did get hot so I had to let it cool several times before I hit my target diameter.

McMaster-Carr has 60 and 80 grit wheels for 4 1/2" grinders for right about $6 USD ea.

MSC is insane.

Quote:

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Originally Posted by Crusty

It's between the chuck and the live center so a bit more stable and truth be told I never actually took more than a .010" cut off the diameter (.005" in on the dial).

I've been looking for a better grinding wheel for my angle grinder hopefully with a finer grit and I haven't found one so far. Any suggestions where to look?

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Try McMaster-Carr. They seem to have everything.

Thanks all. I just ordered a couple of 80 grit wheels from McMaster and I'm waiting to find out if the shipping is double what the wheels cost. They look kinda flexible but we'll have to see when they get here.

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Thanks Crusty! We've added your Tool Post Grinder to our Grinding category,
as well as to your builder page: Crusty's Homemade Tools. Your receipt:

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I got those wheels from M-C and I had a chance to try one of them today. I ground down a MT2 arbor into a .625" straight shank. It's right on the money dimensionally and the finish is better than that of the stock wheel I was using.

Hi Crusty,
Great! Glad you found the wheel you you were looking for.

Thanks for the help all. Though I'm still looking for a finer grit this wheel will do for now.

After the upgrade of my toolpost stud my angle grinder would no longer mount onto the compound so today I reworked the mounting scheme for it to attach it to my QCTP using a tool holder. I machined a bar of steel which then bolted to the aluminum block and the bar then goes into a tool holder, so the toolpost stays on the lathe if I want to use it. I reoriented the grinder due to the change in the mount and now it extends horizontally outward rather than upright as before. I was surprised to find that it's more rigid and delivers a nicer finish, even with the 80 grit wheels that I have, and it goes on and comes off the lathe a lot quicker so I'm happy with this transformation.

Attachment 37720 Attachment 37719

Attachment 37728

Here's a test grind. Accurate within a few tenths on the diameter (.4989 - .4993).

Just remember to wash the pants before putting them back on :-P

Do the bolts in the AL block just clamp onto it or do they thread into the grinder body? While trying to make a much simpler guide bar for mine I discovered the threaded hole I was using it attach it was not perpendicular to the axis of the shaft but canted up a few degrees...grr

The bolts go through the block and thread into the handle holes on the grinder head, then nuts on the bolts fasten the block to the grinder head.

If you look closely you'll see that my bolts are tilted to match the grinder handle holes and it was a challenge machining that block of aluminum so that it all fit, working from measurements that I made of the grinder. It's plenty solid but if I were doing it again I might try to hold the grinder using clamps on the body, or perhaps adapters that fasten into the handle holes and then some sort of attachment to the hopefully parallel adapters.

I don't have to worry about the pants, they're not mine. ☺

A smaller(115mm disk) grinder + a external speed control and you could use all kinds of stones/disks that weren't angle-grinder specific and if the grinder spindle run-out was low enough you would have a tool-post grinder capable of everything a much more expensive and made for the purpose tool-post grinder could do, I even think they make collet chucks(Aliexpress/bangGood etc.) that can be screwed on a grinder spindle and used with bits for internal grinding..

A different grinder won't fit the mount - it was custom made for that specific grinder.

I have plans in the works for building a more traditional TP grinder that can mount a variety of wheels and cutters, and can even be used as a TP drill.

Quote:

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Originally Posted by Crusty

I have plans in the works for building a more traditional TP grinder that can mount a variety of wheels and cutters, and can even be used as a TP drill.

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I have just made a cross slide grinder as opposed to a TP grinder. This eliminates the TP and top slide from the chain of flexibility, so the mounting is much more rigid. The only disadvantage is that you cannot grind tapers with the compound, of course you can still use the tailstock offset method. My needs are more for accurately sized parallel shafts and so the taper grinding is not important for me and I have other methods of doing that anyway.
Mine mounts on the back side of the cross slide, that is not essential but it does mean that the headstock can rotate in the normal direction, which is best for those with screw on chucks.

Prior to making this grinder I had fitted a ball screw in place of the cross slide Acme style screw. This has no discernible backlash and makes it easier to set very small infeed increments.

Sounds intriguing, Tony - any follow-up posts with pics, per chance?:)
Any data on the ball screw cross slide enhancement would be much appreciated, at least by me...
ATB
Johan

Quote:

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Originally Posted by DIYSwede

Sounds intriguing, Tony - any follow-up posts with pics, per chance?:)
Any data on the ball screw cross slide enhancement would be much appreciated, at least by me...
ATB
Johan

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Johan,

I do plan to make posts on both of those subjects and also another recent job, I converted the screw on chuck mounting to a Bayonet type. This provides for a quicker chuck change, a more accurate chuck change and the ability to run backwards. Here are some teaser pix.

Attachment 37847 Attachment 37851

Attachment 37848 Attachment 37849

Attachment 37850 Attachment 37852

Grinding tapers using the compound was one of my objectives so that drove the design along with budget. I wish I had a better chuck mounting system but the two setscrews on the neck of my screw on chuck do a reasonable job of keeping the chuck on when run in reverse. I do check that it's staying tight periodically though.

That's good stuff Tony and I'd appreciate it if you continued it in another thread focused on it.

Quote:

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Originally Posted by Crusty

I'd appreciate it if you continued it in another thread focused on it.

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Don't worry I would start new posts for any original work as I always do. I have no intention of hi-jacking your post, I was simply responding to you in my first post and Johan in the second.

When I first joined this forum I asked about the policy for responding to posts and whether it was the done thing to stay strictly on topic as some more rigid forums insist on. I was told in no uncertain terms by several established members that is was quite usual and appreciated to wander off topic as some of the most interesting threads had formed in that way. The wider the topic spread in a thread the more attention is drawn to the original post.

Nice work Tony, I am particularly interested in your bayonet chuck mounting conversion. I have long thought of a way to convert my screw on chucks while keeping the original mandrel (plain bearings) judging by the marks on your mandrel it would appear to be the original. I am thinking modern adhesives may provide the answer but any ideas would be well received.

Quote:

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Originally Posted by olderdan

Nice work Tony, I am particularly interested in your bayonet chuck mounting conversion. I have long thought of a way to convert my screw on chucks while keeping the original mandrel (plain bearings) judging by the marks on your mandrel it would appear to be the original. I am thinking modern adhesives may provide the answer but any ideas would be well received.

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Alan,

I'll make a post on that topic separately. When I got my lathe it came with a spare spindle with a bit more meat at the chuck end. So I was able to still use the lathe for preparation of the other.
BTW Did you get my email from a day or two ago?

Seemed like it deserved it's own thread rather than being panned over here in this one.

I didnt because my email address has changed,I will PM you with my current one.
Regards
Alan

Nice Tony! I’m kind of confused by the term “bayonet”. It kind of looks like the beginning of a Long style or “D” type taper mount. Or were you referring to sumptin else?

Your ball-screw conversion, as well as your very unique thinking for the mount, deserves its own post. Very much looking forward this work.

Quote:

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Originally Posted by Saltfever

Nice Tony! I’m kind of confused by the term “bayonet”. It kind of looks like the beginning of a Long style or “D” type taper mount. Or were you referring to sumptin else?

Your ball-screw conversion, as well as your very unique thinking for the mount, deserves its own post. Very much looking forward this work.

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As I said in my original post here. I shall be doing dedicated posts on on each of the three things mentioned, but to answer your question briefly. My preference is for the long nose taper style but that would have required making a lot of swarf from big lumps of steel or CI for the chuck backplates, whereas the D style or bayonet only needed a minimum of work modifying the existing backplates. "Bayonet" is not my term it is a recognised standard. The taper dimensions etc. are mostly the same as a D type. There will be full details in the dedicated post. Meanwhile

Attachment 37919

Opps! . . . I was thinking of the Nikon, Pentax, etc., bayonet lens mounts requiring a twisting motion. Totally forgot the term applied to the lathe tapered mounts I used years ago. Age and cross-culture technology. . . sometimes an unfortunate mix! LOL

I’m very interested in converting my screw thread Sheldon lathe so will be watching with interest. Many thanks for the dimensions.

Quote:

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Originally Posted by Saltfever

Opps! . . . I was thinking of the Nikon, Pentax, etc., bayonet lens mounts requiring a twisting motion.

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It does require a twisting motion, not the chuck but a holding ring (the bayonet??)

https://youtu.be/3Eo_GvDGP-g

There is a reason why pond scoops were invented.

Takes a little longer but you never even have to get your machine in the mud, for that matter a pond scoop can be used in standing water.

I'm talking about this...Attachment 37935

Not a 3-point hitch rear scoop.

I guess that works on a drag line.

I think in the case above access is the big issue since it's in an established neighborhood and an excavator on mats was the only way to get equipment in there that would do the job without tearing everything up. Then again they said it was a rental so it might be that a track hoe was the only thing that the property manager knew about.

I've seen a video of that same recovery operator cleaning a bigger pond which was worse and he didn't get stuck so skill is a big factor in success.

It is a drag line, it can also be pulled by a horse or mule, or a tractor running on higher ground. the side tubes take handles like a wheelbarrow which are used to control depth and to steer it to some degree.

I have a pond that is silted in on one end, and a vehicle will bury itself within 50 feet of the bank most of the year. I have seriously thought of using a pond scoop to dredge the shallow end.

The fish stocked in the pond have tied for state records in the past so I really don't want to risk a kill off by lowering the level just to dredge one end.

I have considered suction dredging, that's a story for another day....