Tool Post Grinder

[Susquatch]

I've always been leery of putting a tool post grinder on my lathe for fear of messing up my ways with grinding grit. But others here don't seem to be afraid of them so I may just swallow my fears and make one.

I've seen lots of videos about how to do that from mounting a Dremel attachment to a CNC drive motor.

Anyone here ever make one?

Favorite approach?

Any advice regarding do's and don'ts, etc.

Lathe is a 14x48 with BXA Series 200 tool holder.

Love to hear what others think.

 

[combustable herbage]

Dremel 395 Mount for MPCNC using Universal Tool-Mount Plate... by dintid

Mount for Dremel Multipro 395...for a MPCNC using the Universal Tool-Mount Plate I also made for it.With/out -SupportThe version with support in the filenames is with build-in supports. The other version is if you like to print without or use your own support systemPartsThere is the Dremel Main...

www.thingiverse.com

I found this one on thingiverse you probably want something a bit more robust but with the drawing one could probably fashion something out of aluminum or help with the footprint. I have been thinking a bit about this one a bit as well but I wasn't sure the dremel would be robust enough but maybe lighter grinds it would be ok.

 

[Susquatch]

Ya, I think I mentioned the Dremel approach someplace. But I share your view of it. My Dremels are not all that great - especially as they wear and get older. I think the Dremel approach is just an easy way to go.

I'm kind of favoring the cheaper cnc spindle drive motor approach.

 

[combustable herbage]

Yes I had looked at some of those as well it maybe a better long term idea this one I had found has an er11 chuck.

Machifit ER11 Chuck CNC 500W Spindle Motor with 52mm Clamps and Power Supply Speed Governor

Only US$69.99, buy best machifit er11 chuck cnc 500w spindle motor with 52mm clamps and power supply speed governor sale online store at wholesale price.

www.banggood.com

 

[Johnwa]

The workshop practice book Spindles by Harprit Sandhu is a good read whether or not you want to build one from scratch.

 

[gerritv]

Dremel's suck. Go for Proxxon instead. They have a proper mounting boss on the front.
https://www.proxxon.com/en/micromot/handheld-power-tools-12v-and-transformers.php

Gerrit

 

[RobinHood]

Stefan G has a 4 part video series on making a TPG starting with this one:

Ca Lem also made his own TPG here:

 

[PeterT]

Sorry for cross referencing to another forum, but in the best interests of my typing fingers skim through these in particular for more links, resources & opinions to digest.

Grinding spindle.

Hullo, I looking for ideas really. I retired from precision engineering, college workshop technician and 30 years in a shipyard and now have a small Colchester student and similar size vertical mill. I have been making the Quorn t/c grinding machine, which has been a challenge but...

www.homemodelenginemachinist.com

Toolpost (or other) grinding in the lathe

I thought it might be beneficial to share information & experiences on this subject because it seems to come up often. The typical reason behind grinding in general is to achieve a high degree of accuracy as well as surface finish. Personally, I am interested in what you have achieved with...

www.homemodelenginemachinist.com

I'm not being critical of Dremel type assemblies because IMO they have a role in hobbyist tool arsenal. But its important to set out what you want to achieve: A) making something 'shinier than a machined finish' is very different than B) hitting a tight tolerance with appropriate finish. In A) lots of reasonable options exist. In B) the spindle assembly, bearings (under load & temperature), machine stability, vibration, measurement feedback... all factor significantly & typically cost more. Also depends on what kind of mass you are working on. Small objects can get away with low HP. Bigger objects & higher removal rates can be power hungry.

 

[whydontu]

Dremel is kind of useless, unless all you want is what I want, which is something to do final polishing.

Here‘s my rig. Flex shaft, boring bar holder, a insert machined to fit the barrel of the flex shaft. Dremel make a Forti Flex with a metal barrel. ( the photo shows my regular Dremel flex shaft without the insert, my Forti Flex is at a job site.

 

[Susquatch]

Wow! I love it all guys! It's looking like this project will be a LOT of fun!

I'll prolly have more questions shortly, but I feel like I have way more to chew on for right now than I ever anticipated. Please give me a while to do that.....

 

[Susquatch]

Ok, so I've researched the crap out of this. I think I'm going to go with @combustable herbage suggestion but upgraded to a brushless motor. It has an ER11 Chuck, comes with a 1/8 collet to take Dremel size bits and is variable speed w a controller and best of all, can be easily adapted to my quick change tool post. There were too many complaints about overheating of the brushed version.

I have not ordered it yet, so last minute concerns are welcome.

[CA$173.21 47% OFF]Machifit 400W 12000rpm ER11 Chuck CNC Brushless Spindle Motor with Driver Speed Controller and Clamp Machine Tools & Accessories from Tools on banggood

https://banggood.app.link/zSH1wXtAVlb

A leading alternative is a compressed air die-grinder......

 

[PeterT]

I was looking at the 500 or 600w cousin of that (same brushless) for light duty messing around. If I recall, the higher watt versions have same/similar motor can diameter & ER#, so similar form factor with more power. I was fully expecting the bearings might be dubious quality, so just expect to upgrade and/or replace often. That's cheap & easy fix, treat it like a 'kit' etc. Attached video of brushed motor is a bit revealing. ~3:30 he shows the end bell disassembly with a rubber thingy to <ahem> centralize/float the bearing? Not good.

So I'm not sure if the brushless and/or larger motor assemblies mean a better bearing system? Really there should be no correlation brush/brushless motor to bearing layout other than maybe the latter might be more predominant in hobby cnc machines? The end bells looks a bit meatier, maybe thicker can, maybe wishful thinking on my part. I've even seen encouraging runout claims in hobby CNC spindles. But haven't seen as many teardown/inspection links to see what's under the hood - if they have any kind of compensation. My gut feel is light duty; don't run it long/hot/hard. But if that fits the bill, its a cheap experiment. I had a bailout plan to use in a rudimentary pantograph but that project is far down the list.

 

[gerritv]

The fact that he expects to do milling with a drill chuck, esp. mounted as it is on that shaft, tells me to ignore this particular video altogether.

Gerrit

 

[Johnwa]

The motor on my little CNC router looks very similar to that one. Mine came with an ER11 chuck already mounted.

 

[PeterT]

>The fact that he expects to do milling with a drill chuck, esp. mounted as it is on that shaft, tells me to ignore this particular video altogether.
I didn't even pay attention to that. I was just referring to the rubber bearing support washer on that particular model.

Most of these hobby CNC motors look like they have an ER collet fixture that slides on the output shaft & retained with a set screw. Some are package deals where you can add the power supply if needed, select between different ER#, with/without clamp.. etc. Note, some power supplies are N-Am/Euro AC-IN voltage switchable, but some are dedicated one way or another, so check the fine print. Some of the brushless controllers look a bit different so maybe some variation to investigate.

FWIW, most of these max at 12-15K max rpm which might seem high but in reality on small wheels works out to low-ish SFPM typically recommended for grinding (say 4-5K SFPM according to literature). Commercial TPGs can spin 45K for <1" wheels, but usually require wheels to step up the motor rpm. I'm not sure if these surface speeds are more for efficient material removal that we could overcome with patience & more/lighter passes, or if finish or heat is also factored. Precision grinding can be pretty specialized. I suspect these TPG add-ons is more like messing around but can still serve a hobby purpose.

GRINDING FEEDS AND SPEEDS

We need to convince Gerrit to put his cnc VFD motor in the lathe with a wheel!

 

[Susquatch]

All good stuff guys. The job at hand is a toolpost grinder.

Today, I confirmed that the motor OD will work on my toolpost. I'll just need to dedicate and modify a BXA tool holder to the task for ease of attachment, and may have to overhang the compound for clamp clearance if needed.

 

[DPittman]

Here is what I used for a tp grinder. I wanted a more powerful and hopefully sturdier one than what I thought the little electric or air die grinders are so I bought a 700 watt variable speed electric die grinder from princess auto.

I'm not sure yet how successful the grinder will be as I have only done a bit with it and the 1/4" shank stones I've bought ate terrible.

I really like the stones that @PeterT picture posted above. Where did you get those done? I think that is what I need.

 

[Tom Kitta]

I frequently just slammed one of these pencil air grinders into the tool post and ground away. For small tiny stuff it works great. Not sure how "accurate" that is but I bet that once nicely dressed it is no more then few tenths.
This is not to remove a lot - just few thou runout on say chuck jaws or similar.
I do have large tool post grinder but no belt. I finally have to take the stupid expensive thing out and add a belt to it. On the other hand this thing is massive so maybe I sell it and buy or make something more "tiny" with say 100w motor just to do little cuts not hog on things with its 1/2 hp or more motor.

 

[RobinHood]

the 1/4" shank stones I've bought ate terrible.

It’s probably the bonding of the abrasive that is bad.

I would look for “mounted stones” online and go with a reputable name like a Norton, Radiac, Dumore, CGW, etc (not affiliated). You should also have a diamond dresser to true them up before use.

 

[DPittman]

It’s probably the bonding of the abrasive that is bad.

I would look for “mounted stones” online and go with a reputable name like a Norton, Radiac, Dumore, CGW, etc (not affiliated). You should also have a diamond dresser to true them up before use.

Yes the stones vary quite a bit on quality and some of them glued in so crooked they wouldn't be adequate in a hand drill. I did dress them all with a diamond dresser but the worse one practically were ground down to nothing and were so unbalanced until then. I did buy a couple of mounted stones from kbc and they were not so bad. The worse of the bunch I had were called 1/4" shank but were actually 6mm shank and of course unusable in a 1/4" collet.