D-bit grinder work head swap

[petertha]

I have an Accusize D-bit grinder with R-8 collet work head. Its ~3 years old now but I believe its still the same unit being sold & quite similar to other imports, typically with the U/Deckel style collets. Because I happen to have a full set of 5C collets, I decided to purchase the Shars 5C collet work head thinking (hoping) the parts would be essentially swappable. Turns out there are actually quite a few differences in the machines. The 5C head is bigger than R8, but not just due to the wider collet OD & spindle housing. Its beefier (and generally better built).

Anyways, even though the Shars dovetail slots are wider, I was able to mount the 5C head (blue) onto the Accumap existing lower compound swivel assembly (green) by utilizing the Shars base dovetail part & just making a new, thinner gib strip to marry them. There are specific sub-features between the base & work head that fit one another, so this was a better option.

I was quite happy with how things were coming together, but once it was all mounted up, it became obvious the new work head collet centerline will end up ~0.4" higher than than stock position. Hopefully my cut & paste pic shows what I mean. I'm actually not certain if this will makes an adverse difference grinding above the wheel center line, but it may make a difference in certain other orientations. Maybe limiting certain compound angle positions or swiveling movements. I have not gotten that far yet. It would also be the case for the other (endmill spin) fixture since I'm mounting on the same dovetail slide.

Note to the all considering a D-bit grinder purchase. These machines are definitely not created equal. I have a feeling the Shars is a more recent upgrade to the vintage of Accusize & similar machines. Possibly the spindle height is a bit taller? The Accusize spindle nose is 1:10 taper vs Shars is 1:5. I purchased Shars wheel adapters & re-machined them to fit my taper because they are made so much better than the single one that came with my unit. Nothing wrong with the R8 in itself, is actually quite compact. But there are differences in the mechanism & QC I'm finding.

Any comments appreciated.

 

[pontiac428]

The 5c workhead has bearings, so the centerline is higher. The centerline is of little relevance, since you swing the work across the wheel face in an arc. If you encounter a setup where you know the centerline needs to be lowered, just roll the head right or left and it will drop the centerline accordingly.

I agree that the Shars parts are nicer. I tried a 5C workhead from a non-shars China seller, and it was a total waste of my $90. I could have done better building from scratch for much less cost. It was unuseable with its daylight-showing clearances. Legos have literally two orders of magnitude tighter precision than whatever dimly-lit chinese basement sweatshop produced that eBay head.

 

[Winegrower]

Humm...you guys are causing me some concern. I just received a U3 5C collet head for my Deckel cutter/grinder clone (Kuming or such, seems quite well built) and at first glance seems like it will fit. I do like the grinder features, but to get wider capability I built a 5/16" square Deckel collet and a Accu-flex collet adapter that fits in a Deckel collet. But the 5C seemed like a good thing to have too, and a visual inspection looked quite good. Hope that's the case. Mr. Newman previously assured me the center height would not be a problem and he's not been wrong yet on my scorecard.

I also just finished a few sets of wheel hubs for the inexpensive diamond grinding wheels. So far so good.

 

[pontiac428]

Humm...you guys are causing me some concern. I just received a U3 5C collet head for my Deckel cutter/grinder clone (Kuming or such, seems quite well built) and at first glance seems like it will fit. I do like the grinder features, but to get wider capability I built a 5/16" square Deckel collet and a Accu-flex collet adapter that fits in a Deckel collet. But the 5C seemed like a good thing to have too, and a visual inspection looked quite good. Hope that's the case. Mr. Newman previously assured me the center height would not be a problem and he's not been wrong yet on my scorecard.

I also just finished a few sets of wheel hubs for the inexpensive diamond grinding wheels. So far so good.

You know what they say about broken clocks. I'm curious, about the name on your machine. Is it Kao Ming? That would be significant, they are a maker of grinding machinery in Taiwan that plays reduced budget competition to some major toolmakers like KO Lee and Cinci. Was it a new or used purchase?

 

[petertha]

The 5c workhead has bearings, so the centerline is higher. The centerline is of little relevance, since you swing the work across the wheel face in an arc. If you encounter a setup where you know the centerline needs to be lowered, just roll the head right or left and it will drop the centerline accordingly.

Both the Accusize R8 & Shars 5C workheads have bearings, so that is common between them. This picture isn't the best but shows them side by side. The (blue) 5C is wider & taller in cross section. Some of that might be due to larger 5C diameter translating to spindle tube. But its also beefier. Also its dovetail base is vertically a bit thicker & wider than Accusize. Because I am using the Shars base, the cobined sandwich centerline ends up being a bit more elevated.

You are probably right about the issue being a non issue. After playing with it on the machine I realized I can just alter the fore/aft nod & als fore /aft dovetail slide so the axis presents to the wheel quite similar.

 

[petertha]

I just received a U3 5C collet head for my Deckel cutter/grinder clone (Kuming or such, seems quite well built) and at first glance seems like it will fit. I do like the grinder features, but to get wider capability I built a 5/16" square Deckel collet and a Accu-flex collet adapter that fits in a Deckel collet. But the 5C seemed like a good thing to have too, and a visual inspection looked quite good.

I can take some better pictures of the 5C dovetail base (black chunk) & how it integrates with the work head. But the thing to know is there are some inter-related components between base & work head that you would have to replicate. It could of course be machined & adapted to a different machine, but just for discussion purposes:
- dovetail size & gib strip & adjuster set screws & position lock bolt/handle
- fore-aft adjustment mechanism. It involves a threaded cylinder thingy nut that resides inside a hole in the dovetail block & lock screw
- lateral adjustment mechanism (relative to the scale you see). It involves a leadscrew type cross bolt threaded into a cylindrical nut in the center of dovetail.

Collectively this is why I thought easier to just use the Shars base & mount it to the lower existing swivel parts.

 

[petertha]

Unfortunately Shars only sells the work head assembly as shown (blue). But the pivot post was different size than my Accusize. So I managed to marry yellow shade (work head + dovetail block) to my machine (starting with green shade) with a bit of dovetail gib strip futzing.

The

 

[petertha]

I haven't talked about the spin/slide 'end mill' accessory yet but it shares the same collet type as work head & mounts to the same dovetail base. Again, the Shars was a nicer build & also beefier. My R8 is ok, but one think I don't like is how they went skinny on the taper nose (cad sketch). Most of the collet nose sticks out proud so its not getting the benefit of the seat support/tightening the way normal taper sockets work. It also omits the topside T-slot Shars has for the finger following apparatus & basically has a single threaded hole.

I was going to make a new block from scratch using ER-16 shank/collet & I still may. That's what got me thinking, maybe just retrofit with Shars. Well, I'm into it this deep, may as well keep plugging away & see where it goes. Hopefully when I settle into grinding instead of machine Frankenstein-ing I will enjoy it a bit more.

 

[C-Bag]

My Checkel came with R8 also and while crude, it’s repeatable and turns out good grinds. The R8 being proud of the nose is of no consequence. I fell down the rabbit hole of trying to improve the flute grinding attachment because it was so ludicrously loose. I ended up sleeving the old housing and made a nice slip fit. FAIL. I was warned the only good flute grinding attachment is an air bearing and i found out the hard way it’s totally true. There is a reason the P&W, KO Lee, Gorton, CutterMaster and Cinci all have air bearing attachments. Not only is it frictionless it keeps the abrasive out of the slide. I admitted defeat after even trying seals and found an old KO Lee air bearing head on CL and there is just no comparison.

 

[petertha]

That is an interesting comment C-Bag. I was kind of wondering same thing. It slips & slides with nice coating of oil but I can't see how long that would last with abrasive dust starting to cling to it. I imagine aluminum oxide type wheel would be worse buildup that debris vs. diamond or CBN but abrasive is abrasive. I think Renzetti made some special wipers for ends of the sliding casting to protect his new shaft, but I didn't see any similar mods for sealing the rotating spindles of work heads themselves. There just isn't a hood spot to put anything there, at least the main indexing work head.

Actually this whole 5C vs R8 may be a self inflicted rabbit hole for me. Either collet system only grabs within a small increment of the nominal size, which is (my understanding) how these D-bit grinders came about to begin with dating back to Deckel. I believe you only ever got a handful of collets because the intent was to grind tools with nominal shank sizes, not a full range of incremental drill bits for example. I happen to have a 1/64" 5C set for regular machining so it seemed silly not to utilize that. When the Deckel collets became scarce & expensive, before the Asian reproduction clones came about, they 'North-Americanized' the work heads to more common 5C & R8. I ended up buying a set of metric R8's because they would serve dual use on my mill. They grip stock perfectly fine. So I've kind of come full circle, burning cash along the way LOL