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Tips on purchasing a toolpost grinder

dakeddie

Plastic
Joined
Jun 24, 2008
Location
Canada
I have a TOS S28 lathe which is something like a 13x30 and I think has a 5hp motor. Going from memory here. The distance from the compound slide to the spindle centreline is ~1.125".

I want to get a toolpost grinder for it, but having never used one before, would like to get some tips on selecting one.

My budget is small, less than $400, so it'll have to be a used item and probably a smaller HP item. I've been looking 1/14hp and 1/5hp Dumore grinders as well as the smaller Themac grinders.

I plan on using the grinder for OD, ID and face grinding. My first task with the grinder would be to make an adapter to mount a 4 jaw chuck on the universal plain backing plate on the lathe... so some face grinding.

I'm pretty confident all the grinders I've been looking at will do the OD/ID stuff without problems. Might I expect any issues with face grinding? Should I look for a grinder that comes with a cup stone? Or can you face grind with say a regular 2" wheel?
 
Themac or Dumore

One thing to consider...

You must take extreme precautions with any toolpost grinder to ensure that the lathe is protected from abrasive dust. If that gets on any bearing surface it can destroy the finish in short order.

A couple of brands are highly regarded:

1) Themac - they invented toolpost grinders
2) Dumore - very popular

Check either of their websites to get an idea of models available and sizing.

Be very careful when using one of these. The wheels can turn at up to 30,000 rpm.

- Leigh
 
My Logan is less than 1", and I had to play some games to fit a Dumore, specifically make an adapter that goes in place of the compound. You probably won't have that problem. Be aware that many/most of the less expensive Dumores on eBay can have bad spindle bearings, so plan on spending some additional money unless you can get a guarantee of good bearings. If you can get one with a 5T-200 spindle, it will take interchangeable quills, making ID and OD work a snap.

Conrad
 
Ditto on the ebay spindle bearing issue. I have yet to get a "good bearings" spindle with good bearings :angry:. Proper ABEC 7 bearings can cost more than you pay for the used grinder so beware. There is a yahoo group on the dumore grinders. I have a 1/2 hp model 57 I have yet to get working so I can't be of any help on the actual use of it.
 
As Leigh said.. Be careful. It is easy to get mixed up on pulleys, and overspeed a larger wheel.. I knew of a shop where a guy was killed using a Themac grinder.

If you plan on face grinding with a cup wheel, you will need a micrometer stop, and/or set the compound at an angle to get a fine infeed.
 
Regina- I was able to get decent grade ORS bearings for my spindle very reasonably from the local bearing dealer. I specified them oil filled for high speed, though I would have preferred Kluber high speed grease. You might investigate that route- about $35 each. I did have to make up tools (custom pin spanners) to get the spindle apart.

CH
 
As Leigh said.. Be careful. It is easy to get mixed up on pulleys, and overspeed a larger wheel.. I knew of a shop where a guy was killed using a Themac grinder.

Eddie;

I'm going to repeat it again. Lathes kill more machinists than any other machine in the shop. Tool post grinders account for a significant percentage of these deaths.

I took pictures after a tool post wheel explosion. The machinist didn't get hit but the damage to other objects made it obvious he would have been killed.

Learn the equations. Double check your setup. Clear the blast area before you turn it on.


Doug
 
The 1/14hp Dumores are too small for anything other than painfully slow grinding. I have one that works great but it bogs down very easily.
 








 
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