D-bit grinder work head swap

[pontiac428]

The spin slide fixture from Shars has worked for me in the past, but I totally destroyed two "scrapped" end mills that I wanted to reduce diameter on just day before yesterday. I failed once because the friction was all messed up, so I took it apart, cleaned, and repeated both my effort and failure to obtain anything close to an acceptable grind. All my head-scratching only led me to think the thin sliding shell tube bulges when tightening the collet. That might explain why it didn't work to install fitted sleeves. Out of the box, it worked great, but maybe I was doing something different with collet tension.

 

[petertha]

That is an interesting observation. Last night I was using the 5C version on a metric shank countersink. It seemed like I was in between sizes. It was a bit tight on one collet, which you are not supposed to exceed nominal, but next smaller seemed like collet had to collapse quite a bit & required extra tightening. These are 1/64" increment so I figure I have the range covered. But that may not be entirely true. I have this same issue on occasion in my lathe where there are certain size gaps, typically on metric stock. I was almost warming up to getting a metric 5C set for that reason.

One of my ideas was to use an ER-16 shank with smaller nut & basically make my own spin work head from block of metal. I really could do no worse than the 'kit' I now have, in fact can visualize many improvements. I'm not really that into end mill sharpening, mostly smaller diameter tooling. But I am intrigued by other ways to impart helical relief & other facet features. But I suspect the ER shank might have to be drilled further into the shaft to minimize stick out. Not sure if its hardened or viable. Smells like another rabbit hole like my 5C conversion idea.

Once I'm done my base level fixing I need to spend time focusing on grinding. These machines & tool grinding is a much deeper topic than I imagined.

 

[pontiac428]

That is an interesting observation. Last night I was using the 5C version on a metric shank countersink. It seemed like I was in between sizes. It was a bit tight on one collet, which you are not supposed to exceed nominal, but next smaller seemed like collet had to collapse quite a bit & required extra tightening. These are 1/64" increment so I figure I have the range covered. But that may not be entirely true. I have this same issue on occasion in my lathe where there are certain size gaps, typically on metric stock. I was almost warming up to getting a metric 5C set for that reason.

One of my ideas was to use an ER-16 shank with smaller nut & basically make my own spin work head from block of metal. I really could do no worse than the 'kit' I now have, in fact can visualize many improvements. I'm not really that into end mill sharpening, mostly smaller diameter tooling. But I am intrigued by other ways to impart helical relief & other facet features. But I suspect the ER shank might have to be drilled further into the shaft to minimize stick out. Not sure if its hardened or viable. Smells like another rabbit hole like my 5C conversion idea.

Once I'm done my base level fixing I need to spend time focusing on grinding. These machines & tool grinding is a much deeper topic than I imagined.

The industry has proven that Rego-fix ER is vastly superior to drawbar collets. You will have to find a way to shorten the stack height of the collet nut in order to have enough room to retract the tool tip to the yaw swing axis' center for forming radii. I do a lot of radius grinds like that. Hollow face grinds (like a rotary broach cutter) are another important capability that require the tool to be r distance away on the outboard side of the yaw axis. Make your carrier block so it sets the tool tip far enough back to do that.

 

[GeneT45]

I use an ER collet shank like you show, chucked in a 5C collet, to sharpen drills (4-facet grind). Works for me.

GsT

Edit: typo

 

[petertha]

The industry has proven that Rego-fix ER is vastly superior to drawbar collets. You will have to find a way to shorten the stack height of the collet nut in order to have enough room to retract the tool tip to the yaw swing axis' center for forming radii. I do a lot of radius grinds like that.

Yes that was my concern as well. In ER-16 for example, the type M nut is a bit smaller diameter (22mm x M19 thread) vs the hex nut type-A (28mm x M22 thread). But the nut lengths are 18 vs 17.5mm respectively & that factors into the minimum required stick-out of tool/bit for radii sweep as you say. I guess next level smaller is ER11. ER's accommodate diameter variations better but from stickout respect conventional collets still have merit I guess. But even there the face diameter of the collets are quite large diameter comparatively so even if the tool protruded 2mm you would probably hit the collet or housing.

 

[petertha]

I use an ER collet shank like you show, chucked in a 5C collet, to sharpen drills (4-facet grind). Works for me.

That's kind of direction I'd like to go. Particularly after watching th Stefan video, even though he did kind of a tertiary grinding step on conventional grinder, but I got the impression that was more tweaking or personal R&D vs a requirement above the 2-facet grind. The swing arm 'conventional drill sharpening' progressive helix relief involves that V-fixture. I get how it works but the 2-facet drills I have work better than my conventional drills & its basically axial feed & repeat at 180-deg rotation, all using the regular work head. My V-fixture looks like it was hammered out by blacksmith's - no offence to blacksmiths LOL

 

[C-Bag]

So I've kind of come full circle, burning cash along the way LOL

My garage is full of those cash burning circles. I personally had no use for the little Deckel collets with my imperial end mills of assorted sizes so pushed the R8 because I had a complete set. This was so I didn’t have to use a z eating drill chuck in my mill drill so thought I could solve the problem on the Checkel. It turned into a totally silly headache dealing with the outfit on eBay that I bought the Checkel from. I thought by careful research and through communication I could bypass the perceived pitfallls, once again FAIL.

There are many things that can only be learned directly and I thought I’d seldom if ever need the flute grinder. Then as usual it’s a weekend an deep into a project I need a 5/16” endmill. Turns out I have like 6 3/8” endmills and no 5/16. So I concoct the idea of making a 5/16 our of the 3/8. That’s where I find out the attachment has a ridiculous amount(I think) of play. So much I hold it over to one side and grind away and make my 5/16”. and it works perfectly and finish the project. But there’s a reason for the saying, “the devil is in the details”. IMHO the devil is details that only get me into deep yogurt and cost $$ for a solution who’s only problem was my quest for that elusive perfection that I don’t even understand because I’m not experienced.

My take away is no matter what the grit from grinding would mess up the works and cause it to drag and cause the grind to go schwangle. I should have left it the way it was because it pulled through smoothly and I got decent usable grinds.

 

[petertha]

I somehow feel better knowing there others like me in the universe LOL.

 

[C-Bag]

I’m certainly not proud of my OCD or hardheadedness. I only post hoping it becomes a warning to others staring into the rabbit hole abyss that is perfection.

 

[ddickey]

Yes that was my concern as well. In ER-16 for example, the type M nut is a bit smaller diameter (22mm x M19 thread) vs the hex nut type-A (28mm x M22 thread). But the nut lengths are 18 vs 17.5mm respectively & that factors into the minimum required stick-out of tool/bit for radii sweep as you say. I guess next level smaller is ER11. ER's accommodate diameter variations better but from stickout respect conventional collets still have merit I guess. But even there the face diameter of the collets are quite large diameter comparatively so even if the tool protruded 2mm you would probably hit the collet or housing.

You could make a new tool block that uses ER collets with a rear nut that pushes the collet forward on an ER taper. I made a collet block like that.