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Another example of "Just because its shiny doesn't mean..."

John Conroy

Well-Known Member
Premium Member
#1
I bought an expensive Bostar brand 5c collet chuck on eBay from CDCO, the listing claims .0006" or less runout.

https://www.ebay.ca/itm/5C-Collet-C...h=item3f40a5e77d:g:incAAOSwt5hYalq4:rk:2:pf:0

The first thing I did was install it in my lathe spindle and check the runout of the collet taper in each of the 3 possible orientations of the D1-4 spindle mount. The best reading was .002" and the worst was .004". I checked my spindle and it has less than .0002" runout. If you want to see the measurement process I recorded it on video here.

https://johnconroy.smugmug.com/Bostar-5C-collet-chuck/n-rRw8Hg/i-TKCPnjf/A


I'm committed to keeping it as the return shipping would be pricey so I decided to try and fix it. It is manufactured in 2 halves and held together with 3 M6 cap screws and the orientation of the front and rear halves is indexed with 2 roll pins.



Taking it apart was easy, the machine work inside is a combination of good and horrible. The bores for the pinions look like they were done with a very dull drill bit but the rest is pretty OK looking. The pinions are on the bench above the chuck in this pic.



The pictures don't really show how rough the pinion bores are.



I removed the roll pins and tried orienting the 2 halves in all 3 positions and the original one is the best at .002" runout. Repeatable every time.

I tried leaving the cap screws slightly loose and tapping the front half with a dead blow hammer on the high spot to reduce the runout and got it down to .001".





That's where I left it for now but I'm going to try to get it down to .0005" and then drill 2 new holes to install the roll pins in different locations to hold it there. I'll post the results of that exercise here.
 
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PeterT

Ultra Member
Premium Member
#3
Bummer. I was going to suggest a hair brained fix, fix but I think you are already going down that path
- pre-drill new roll pin hole locations into rear half only
- slightly oversize drill the bolt holes if that's the next thing holding alignment back
- get some epoxy or retaining compound on the face between the two halves (gives you working time)
- sandwich together, mount in on spindle with bolts snug, no roll pins.
- tap-tap until its 0.0000000" allow glue to cure
- remove assembly, then drill through new roll pin holes into front body

I cant think of a good way to convert this into a Set-Tru type system. The adapter plate isn't the hard part, maybe a Gator or something. The question is how much work to modify the chuck rear to suit?
 

John Conroy

Well-Known Member
Premium Member
#5
I agree John. I will still be OK with it even if .001" is the best i can do for runnout. I don't think I'd buy a name brand one for $600-$1000. This one is plenty good enough for my needs.
 

John Conroy

Well-Known Member
Premium Member
#6
Bummer. I was going to suggest a hair brained fix, fix but I think you are already going down that path
- pre-drill new roll pin hole locations into rear half only
- slightly oversize drill the bolt holes if that's the next thing holding alignment back
- get some epoxy or retaining compound on the face between the two halves (gives you working time)
- sandwich together, mount in on spindle with bolts snug, no roll pins.
- tap-tap until its 0.0000000" allow glue to cure
- remove assembly, then drill through new roll pin holes into front body

I cant think of a good way to convert this into a Set-Tru type system. The adapter plate isn't the hard part, maybe a Gator or something. The question is how much work to modify the chuck rear to suit?

Peter, there is a register shoulder to center the 2 halves and i may have to increase the ID of the front half register by .001" to get enough movement to reduce the runnout any further. I think I'll just live with .001" rather than do that.
 

PeterT

Ultra Member
Premium Member
#7
Ah I see. Well to make you feel good, my Bison 5C direct mount has TIR of 0.001" in its best D1-4 orientation. That was out of the box, so looks like the going rate is 300$ per thou LOL.
In hindsight I would have bought a Set-Tru and I still might one day. But probably a Gator, Bison is nutty price. Like we were chatting before, its all about what you have to do. And then there is collets, same issue. Perfect chuck + bad collets = runout.

Here is an example of fussy work I'm doing with my 5C. These are bronze valve cages for the radial engine. The hole ID is 8mm (0.315") for reference. The valve stem is 3mm (0.118"). Every diameter has to be within a thou. OD to give me proper fit & Loctite annular gap within a mating hole in the aluminum head. The cup ID is reamed to give me reliable wall thickness starting point. Then the fun starts. The seat profile has 2 facets at 30-deg & 60-deg. Teeny tiny, maybe 20 thou long. Then finally, once set in the head (and no going back) the 45-deg seat is cut at the crown of the facet to ideally ~0.015-0.020" face width. So the issue is I cant do all these ops in one turning. I have to machine one end, then flip the part in the collet, then different ops on the other side. So concentricity & TIR repeatability comes into play. I cant use a 4-jaw & dial it true because there too little to hold onto & just the slightest of jaw pressure will distort the profile. Collets are much better grippers in that respect.

The aluminum block is just a practice mockup to get the issues sorted out. Its hard to photo at this scale but you can see where I blued the facets & cut the 45-deg seat (shiny band). Its varying so I'm still getting some distortion likely from the collet squeeze & stress relief, but getting in the ballpark. Then once assembled, these buggers need to be cross drilled into the cup for the induction/exhaust ports. Then counter bored & tapped holes. Ugh. Heads are complicated rascals. Once I get over this hump I think (hope) the other components will be easier.
 

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Tom Kitta

Active Member
#9
Wow just around $200 CAD for it - you should not complain about accuracy - 0.001 for that money is great!

I wish they had D6 for say $250 - I would get one right away.

I never saw them so cheap even from China.
 

John Conroy

Well-Known Member
Premium Member
#11
I èmailed the vendor and complained about the runnout and explàined that because return shipping would be expenxive I am going to try and fix it. He thanked me and refunded me $30 USD. I'm happy with the deal and with the vendor.
 

PeterT

Ultra Member
Premium Member
#12
Just for the future reference file, I stumbled on this Shars 5C collet chuck with what I think is a set-tru equivalent body & matching D backplate. Not as cheap as the ebay find, OTOH it gives you a fighting chance to dial it into the spindle by the adjustability. By 0.0006" TIR repeat, I assume they are talking about the collet face grind accuracy.

Now what is going on with Shars = $265 and USA Brand = $383? It has to be one of those tricky marketing things where its really made offshore but the line name has 'USA' in there as bait for the unsuspecting. The only USA names I can think of might be something like Royal & they are super spendy like probably 2-3X Bison/TMX.

John.C did you get some 5C collet blocks?
 

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Dabbler

Well-Known Member
#13
I have the ER40 6 sided version only. I decided I'd go ER40. I do have a 5C end mill sharpening block, though. (no 5C collets for it).
 

John Conroy

Well-Known Member
Premium Member
#14
I bought a set of collet blocks from KBC. I'm sure they are made in China but I spent quite a lot of time measuring them on my surface plate and found no dimensional errors greater than .0005". The price is almost as low as anything I found on eBay.

https://www.kbctools.ca/products/WORK HOLDING/COLLET CHUCKS @@26 COLLETS/COLLET CHUCKS/5C COLLET CHUCKS @@26 FIXTURES/839.aspx

I also picked up a 15 piece set of collets from All Industrial Tool Supply for $100 CDN shipped which are also very good with runout numbers under .001".

I've been using the square collet block and the 1/2" collet to make up a batch of parts that I sell and found that it saves me quite a bit of set up time over using using my homebuilt rapid indexer and with better accuracy. I'm able to easily repeat dimensions to within + - .001" with the collet block in the mill vise. Screenshot_20181231-000340.png
 
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John Conroy

Well-Known Member
Premium Member
#15
So I'm into this 5C collet thing for about $450. The quality of all the stuff I got suits the kind of work I do for not a great deal of money.
 

PeterT

Ultra Member
Premium Member
#16
Sorry about that. More than one John.C on the forum. Just like more than one PT. Anyways, good to know what you have too, Dabbler.
 

PeterT

Ultra Member
Premium Member
#17
From Amazon review (not me!). So remember boys & girls, even though its shiny gold Titanium Nitride coated (so we are told), doesn't mean the drill can actually function with the relief angle ground the opposite way, or different between the 2 opposing flutes. Sheesh.

I bought some bulk pack Crappy Tire un-coated drills many moons ago. Seemed like a good deal in a nice plastic container. But obviously factory duds with botched up edges, unequal flutes, you name it. Like the Amazon guy said, they stood a better chance of burning a hole in wood due to friction than actually cutting anything. Pathetic rip off. I kept them around to drill out crusted glue bottle tips & they even failed at that task. And I wonder why sh*tty tools give me a rash LOL.
 

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Tom Kitta

Active Member
#18
Long time ago I bought 2 packs of 100 drill bits or so at crappy tire - like a decade ago - before I was interested in tooling. They were like $10 each. Gave them to my dad. Many are simply crooked - problem with tampering. Some are sizes off.

Even if sizes are OK you may get bad stuff - like 5 years ago I got some stuff from Niko tools - again dad has them.

Or a set of all letter number drills... dad has them.

You can see a pattern now - dad gets a lot of free drill bits ;)

If I was the guy with these bad drill bits I would try to re-sharpen them - if they are straight they may work in wood / construction well.
 

DPittman

Active Member
#19
From Amazon review (not me!). So remember boys & girls, even though its shiny gold Titanium Nitride coated (so we are told), doesn't mean the drill can actually function with the relief angle ground the opposite way, or different between the 2 opposing flutes. Sheesh.

I bought some bulk pack Crappy Tire un-coated drills many moons ago. Seemed like a good deal in a nice plastic container. But obviously factory duds with botched up edges, unequal flutes, you name it. Like the Amazon guy said, they stood a better chance of burning a hole in wood due to friction than actually cutting anything. Pathetic rip off. I kept them around to drill out crusted glue bottle tips & they even failed at that task. And I wonder why sh*tty tools give me a rash LOL.
Any chance these would be salvageable with a simple sharpening with a drill doctor?
 

Tom Kitta

Active Member
#20
The only way to somehow salvage them is to find the ones that are more or less straight and sharpen them for mostly wood work. Some that are a bit off can be broken and used as sharpened stubs - if you want to bother with such a thing.

Other uses involve just treating them as piece of metal of round stock shape.

If you work somewhere where tools get stolen by you coworkers it may be a good bite tool.

They can be given away for free as part of incentive to buy something else.

You can practice sharpening on them.

Stock for making custom tools - say custom counter bore - hopefully to be used in something soft.

I am sure there are plenty of other uses.