Home made Tool post grinding

[DPittman]

Hi,

Hopefully the picture will explain alot.

I'm planning on mounting electric die grinder to tool post similarly as many other have. The mounting collar is a piece of shaft that is yet to be bored out. The shaft in the centre now is just an arbor for turning OD. I plan on mounting some flat 1/2" in milled shaft that will then clamp

in tool holder on qctp. The problem is my milled slot is not perfectly in line with the axis of the grinder. I have to do the milling on my home made milling attachment for my little lathe and is it all less than ideal. I included a picture of my set up for giggles.
Will the off axis alignment of the grinder be a serious problem or will simple stone dressing bring things back to where they should be?

 

[DPittman]

I've been thinking.... Even if I did get things milled and bored perfectly, the chances of getting mounted perfectly square would be low. Hence stone grinding... right?

 

[PeterT]

Maybe you are asking about stone 'dressing' where the grinding wheel gets tuned up on a diamond point tool? If so, I made this accessory to do just that. It mounts to the lathe bed & has adjustable height & point orientation. The idea is remove just a bit of wheel so its running true & to expose fresh abrasive if its getting worn or clogged.

Having said that, grinding is messy business. Dressing a wheel is worse because abrasive particles get sprayed & we don't want them on our nice ways or under the saddle or in between the dials.... all those important nooks & crannies. So protect surfaces with towels or whatever & be careful those don't cause secondary problems getting drawn up by the chuck or tangled in your power feed driveline. Some guys kludge a makeshift manifold out of scrap whatever & hold a vacuum to suck up everything possible at the dressing stage.

Depending on your application, if you can dress outside the lathe, better still. Actually (and I am no expert) sometimes folks will dress the wheel to say the longitudinal axis. But then they will cant the compound say 2 deg so that the cutter edge does the work more on its crown. Then as it wears, the contact band extends. Hope this makes sense. If your wheel is only say 1/4" this may not be an issue. But if its say 3/4" long, that surface contact area is actually quite substantial. Things can warm up, sparks can get flying & power forces go up substantially. Be careful, wear a face shield & take teeny-tiny in feeds initially (like 0.0005 to 0.001") to get going. To big a bite or some vibration or deformation, so-so bearings, iffy mounting setup = really bad things can happen in an instant. So treat this operation with respect.

 

[DPittman]

Yes I meant stone dressing not grinding!
Thank you for the tips and info, I will pay heed.

 

[DPittman]

So now I'm wondering about boring the hole out to final diameter with the piece mounted in the holder and on the tool post. If I could do that maybe I could bore the hole in line with how it sits in the holder. Or will my boring bar just follow the existing hole? (which is in straight with the OD of the piece but not the milled out portion)
?

 

[Dabbler]

A boring bar will bore the hole true if your cut isn't too deep. For carbide tooling with neutral rake, around 30 thousandths or less will help true the hole. (assuming the cutter is sharp and has the correct geometry - a tall order if it is an offshore cheapie)

 

[PeterT]

If I understand - regardless of how you bore it, your tool post has a set screw & locking nut for vertical adjustment height. And table moves in Y direction to set relative to work. So the grinder spindle can be tweaked into position as long as the motor housing fits the hole?

Also one thing I learned on my die grinder homebrew chamfering machine - put an accurate dowel pin in the collet, mount the grinder in a vise or something so its stationary & put an indicator on the dowel as you rotate by hand. Mine had some appreciable run out. Just hand grinding it may go unnoticed or feels like a bit of vibration. But when the grinder is locked stationary, any runout transfers to the work. I happened to have another collet that was better so maybe had a dud.

 

[DPittman]

Yes checking the runout is a smart idea but I'm afraid to do that because my grinder is a princess auto special. The first grinder the bearings got so hot from just running I had to return it. The one I got now is unreturnable though because I turned down the casting on out to fit into my holder!

As far as adjusting the tool holder goes...I of course can adjust for misalignment up and down and for left and right but I got my hole crooked vertically so it sets the tool at an angle. That I can not adjust for. (I hope that is clear enough as I had a hard time trying to explain it . Maybe for most grinding that won't matter much but I was thinking it might be handy to be able to drill a small hole on the side of a shaft with the grinder tool?

 

[PeterT]

The way I held my Bosch grinder was a 1/2" thick aluminum plate. The hole is bored say 0.001" over the grinder nose OD like a slip fit. The plate then has a slit that intersects the bore & then a tightening bolt perpendicular to the slit to clamp it. You wont have to deal with these funky angles but just showing as example.

Clamping slits are kind of a weird thing. If the material was steel it would require excessive bolt torque just to close the gap & tighten the nose because the material is stronger. Same deal if the clamping bolt is too close to the bore because of reduced leverage (think pliers). For this reason sometimes you see the slit go through & past the bore into a smaller relief hole so there is more action & less bolt force required. So sometimes this is a good way to hold things & sometimes PITA depending on many variables. Another option is set screws but it will mar your tool nose without other considerations & is really just pushing the tool to one side of the hole which isn't as secure. Hope this helps.

 

[DPittman]

Wow nice set up.
You might laugh at my set up...but I'm learning (I seem to learn by making mistakes first unfortunately)

So I was planning on just having a close fit of the grinder nose (.0001") in the collar and just using loctite to secure it. I have 3" of collar surface area to hold the tool so I don't think that will be the weakest link in my set up. Do you think that will be okay?

I would have liked to use aluminum also but didn't have any and used a horrible chunk of out of round steel I had on hand.

 

[PeterT]

Hmm.. gluing it in would actually pot it quite nicely, but I suspect that would be considered a permanent relationship LOL. The only way to part ways would be heat & force, neither of which would be kind to your grinder or maybe even the holder you put work into. If you had a nice slip fit, how about milling some ever so slight flays so a set screw could just lightly kiss it & prevent rotation. Just in case you need to make other unforeseen mods, you could always back up a step & modify things.