Precision Grinding a Hardened Shaft with an Improvised Toolpost Grinder

[DIYer]

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:

Tool Post Grinder by Crusty

tags: angle grinder, tool post

[Crusty]

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.

[old_toolmaker]

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

[Crusty]

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

[Crusty]

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.

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

[bruce.desertrat]

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

[Crusty]

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. ☺

[MasterMaker]

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..

[Crusty]

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.

[tonyfoale]

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.

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.