Lathe Tool Post Grinders

What is a Tool Post Grinder?

Tool Post Grinders are a type of cylindrical grinder that is mounted on the tool post of a lathe.  They provide you with the ability to do precision grinding without all the cost of a separate cylindrical grinding machine.  The downside is that grinding is a messy business and lathe are precision machines.  Any time you use a cylindrical grinder be sure to cover your lathes ways to protect them from any grit thrown off by the grinder.

When Would You Use a Lathe Tool Post Grinder?

Lathes are often called on to work with more precision than mills.  Round parts are often used in rotating machinery which demands higher precision than many other applications.  Grinding can achieve higher precision than turning in many cases, although a modern CNC Lathe has eliminated a lot of the advantage of grinding.

You use a Lathe Tool Post Grinder when you’re having trouble achieving the required tolerances with normal turning operations.

Homemade Tool Post Grinder Ideas

There have been several times when I’ve wished for a tool post grinder to finish a shaft just right and to close tolerances. I debate whether to buy a used Dumore or Themac on eBay or try to fabricate one as a project. Simple ones are really easy to make and just involve lashing a suitable Dremel or hand grinder to the post in some way. More complex versions involve fabricating a spindle and replicating the style of the commercial TP grinders. I am really tempted to work on a spindle for one. It would be a good warmup should I ever choose to make a more ambitious spindle, perhaps for a lathe or a mill. Meanwhile, I am collecting photos of TP Grinders others have made for ideas.

Several designs ranging from simple to fancier are pictured below:

This is a very slick example using an air grinder and QCTP adapter…

Router-based TP Grinder: A Bit Heavier Duty!

Router-based TP Grinder Again…

Sewing Machine Motor TP Grinder…

TP Grinder from a Makita Trim Router…

A tool post grinder with a slightly larger die grinder. Note the cam action atop for turning on the grinder…

Yet another die grinder-based tool post grinder…

DeWalt Zip Tool is a Heavy Duty Dremel-Compatible Machine…

Nice one from RCPlanebuilder on HMEM

Spindle parts. Note the knurling on the shaft–original cut too small. Knurling raised it to fit the bearing better!

Drive components.

Electric motor is an RC Plane starter. It proved marginal according to the builder…

Nice Cartridge Spindle Project from Mad Modder

And the TP Grinder that goes with that spindle is here.

3/16″ Redthane Belting…

Pulley made with a 3/16″ endmill and a 4th axis/indexer…

Cartridge spindle and sewing machine motor…

Squaring up to the backplate…

Pilot…

Line boring the spindle holder plates. Nice way to do it on a lathe!

Upgraded to a more powerful router motor!

Adapter to mount Dremel wheels…

Now remade to use a pin chuck–much more accurate than the Dremel chuck!

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