Chuck adapter machining

Just got back from Cabin Fever. Bought a new Bison "5, 4-jaw scroll chuck
and a threaded adapter plate (1-1/2" x8). Screw holes in the back of the
chuck. No holes in the adapter. I seem to recall a whole bunch of
discussions and a kind of FAQ on the most effective procedure for machining
the adapter and locating the holes. Can someone point me to that FAQ?
Boris
Reply to
Boris Beizer
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Boris
They make threaded center punches that you thread into the holes in the chuck. Be sure all is centered and tap lightly once. Then you will have the holes marked to drill as you please.
I have forgotten the exact name of the center punches.
Bob AZ
Reply to
Bob AZ
Heimann transfer screw sets? Not sure of the spelling but they come in sets of six with hexagonal metal tubes that serve as storage containers and "wrenches". Typically around $12-20 per set retail.
Reply to
Mike Henry
Think of them as very short transfer punches threaded on one end and pointed on the other. You screw the threads into the top piece with the pointed ends slightly proud of the surface. Then you line the two pieces up in the desired location (preferably perfectly centered) and rap the top piece with a hammer. I would be tempted to make some out of drill rod.
Bob Swinney
Reply to
Robert Swinney
The critical operations are fitting the backplate to your spindle and fitting the chuck to the backplate - or rather, the backplate to the chuck.
The screw holes aren't as critical, because they don't affect the accuracy of the chuck. Lay them out accurately or use transfer screws or a template. The screw holes can be slightly oversize to allow for any inaccuracies in their location.
John Martin
Reply to
John Martin
The screwholes aren't that big a deal. The key is to get the boss on the backplate dead center and normal to the spindle axis, and a very close fit to the chuck.
When I bought a Bison collet chuck from New England Brass, I called to ask if they might have any guidance about machining a backplate. I was fortunate enough to talk to Mr. Fowler Senior. He told me to carefully machine the backplate on the machine that it would fit. When I asked what sort of accuracy I should expect from the Bison collet chuck, he just said "it depends on how well you do your work."
I did as I was told. Spent most of a Sunday afternoon doing it, but I got it to barely a wiggle on a tenths indicator and a very slight interference fit with the collet chuck. I think I just winged the bolt holes. Well, not exactly, but I just laid out the bolt circle and drilled the holes, no big deal. All they do is allow bolts to pull the chuck up tight to the backplate, they don't locate anything.
Reply to
Don Foreman
That's where I bought mine.
I realize that now. Okay, lots of fiddly work on the boss. Time to get to work.
Thank you all... meanwhile, I did find the FAQ .. It is in the 3rd Beside Reader.
Boris
Reply to
Boris Beizer
Not really *that* fiddly. First check out the backplate as delivered.
It need to have a nice flat surface on the spindle side, because that surface determines angular runout, or wobble. Then look to see if the register diameter has been machined to a good fit for your particular spindle. It should be quite snug, as this determines radial runout.
If those are to your liking then mount the backplate (gently, there is hardly anything toughter to extract from a threaded spindle than an unmachined backplate that has been snapped on...) and take a skim cut on the face of the backplate. Then you need to machine the boss that fits into the chuck recess, with as small a clearance as you can achieve.
As mentioned some transfer screws can be used to mark the backplate for drilling, sometimes a long punch can work as well if it's a nice snug fit in the chuck. If the chuck is tapped then drill the holes to a generous size so the screws won't bind if a bit off.
You can also skim the exterior surface of the backplate, so it looks like it runs nice and true. Not required but it will keep you from looking at it each time you use it, and saying 'is that thing really on there right?'
Jim
Reply to
jim rozen
I looked in the very thin manual that came with the chuck (RTFM, of course, eventually) and behold, they had the bolt hole layout diameters documented. What is more, it was the same in both the English and German sections, so it must be right. I can just scribe around the edge at the difference between the backplate diameter and that diameter, then punch a point arbitrarily on that scribe line and swing the bolt hole diameter to locate the other two holes (assuming they are 120 degrees apart, that is).
Understood. In this situation, it would be a mistake to make the holes extremely precise, because even if a thou off, it would cause the screws to bind and interfere with the boss's fit, which is what we depend on.
I was planning to do that for aesthetic reasons, but your psychological reasons are a more powerful incentive.
Boris
Reply to
Boris Beizer
Use Allen set screws. Get a hex wrench to fit, cut off the el handle. Chuck the remainder in the lathe and file a 45-degree point. Cut it off with about 1/4" of length, just enough to protrude from the screw with the point up. Make one for each screw, the same length Insert screws flush. Drop the points into the hexes. Place backplate, tap to mark each. Use a magnet to remove the points, then remove screws.
I would be tempted to locate the holes one at a time. Mark a hold, drill. Move to the 2nd location, use a bolt loosely through the first hole to locate it. Repeat.
Reply to
Rex B
make some out of drill rod.
Very clever. I was wondering how to get the damned things out , or in flush, for that matter. This is an elegant solution. It might even work. Going to try it ASAP. Gives me a good excuse to use my hex collets.
Boris
Reply to
Boris Beizer
If the recess is deep enough to allow it, make the points long enough to expose some of the straight section, so you could use pliers or a socket to remove them.
Reply to
Rex B
How many holes?? Never seen one with three. Also be aware that the folks who layed out the holes in the chuck might not be as precise as you are. Sometimes transfer screws really are best...
Sometimes you really do catch a chip under the mounting flat, and it will show, if you know to look for it. If the outer surface never does run flat, you won't ever look, it won't stand out. I guess now I call this the harold inspection...
The really tough part here is getting the register diameter to be snug. If they machined it right on the money, you are good to go. If they machined it large, that's too bad, but nothing that can be done about it.
If they didn't put a register diameter on the backplate, then it gets a bit sticky. You need to have that there for the packplate to mount up correctly. At this point you have to carefully mike the spindle, and mount the backplate backwards on the spindle, or hold it in a larger chuck. (when doing this, I never do have a larger chuck....) If you mount it backwards you then need to make a spacer ring so the front of the plate can come up square to the spindle face. It might help to make a dummy spindle gage, at the register diameter, if you are at all uncertain about ID/OD gaging.
Implicit in all this is the idea that the threads themselves in the backplate are loose enough that the ultimate fit of backplate to spindle is determined by only two things, face-to-face contact, and register diameter fit. You don't want the threads doing any alignment there, only pulling the assembly up.
Jim
Reply to
jim rozen
Bison. Polish. 4-jaw scroll chuck with three holes in the back.
Thaks for the tip. Just checked it. Put some screws in the holes and measured the distance between them. Forms an equilateral triangle with distances equal to within a half thou. Similarly for hole to lip edge distance. So the holes are probably correctly located to within a thou or so.
I'll do that anyhow. First problem, however, is that the mounting screws are metric and I don't stock metric set-screws. I'll have to go the hardware store and see if they have any. If not, I can still do it. Take the correct metric screw, cut off the head, drill a hole about 1/8" and somewhat deep. Then cut a screwdriver slot. Use a round point instead of a hex. Should work. Alternative (barbaric) is to use a 5/16 x 18 set screw with all but three threads ground off. Goes in nice for a few turns.
That's where I'm at.
I don't understand. Why mount it backward? I would have to do that only if the spindle mating surface was ratty.. It isn't. And even if it were, let's say it is hypothetically cocked to one side, by machining the front surface and the mating edge, everything is back in alignment again. Am I missing something here?
I'll put the backplate on a surface plate and check it. It looks very good and mounts really nice on the spindle. But doesn't hurt to check. Assuming that the back (the end against the spindle) is true, then all I need is to put the plate on the spindle and do a skim cut on the surface to get it absolutely true. Then I have to (very carefully) machine the step to the correct size. Once I have a good fit, I can put in the transfers screws, mark the holes and drill and counterbore them. Once that's done, I can attach the chuck to the backplate. Then I'll put in a mandrel and check the run-out. If it is excessive, I'll have to think about it. I do have an extra backplate of the right size. The final step will be to machine the edge of the backplate down to the chuck diameter (about 0.1 " to take off) and a cleanup cut on the back of the plate (not the spindle mating surface). Finally polish the lot -- and put in a registration mark on the edge.
Boris
Reply to
Boris Beizer
< SNIP>
Finished the job yesterday, with only a little bit of blood on the work. Note, a pinky does not make a good cushion to prevent the chuck from banging on the ways ... and as I never seem to learn, you can't depend on hands for keeping things from running away from you on the drill press. Did the hex wrench trick. As I said earlier, I didn't have metric set screws of that size, so I went the barbarian route with 5/16 x18 set screws with all but two threads ground off. But I had only two of these, so I could only make two, instead of three, sets of locating points. Not a problem, If two points are located, set your dividers to the distance between the two points (after center punching them) and swing that distance from both points. The intersection MUST be the location of the third point .. well, almost ... so a little bit of judicious work with a rat-tail file to fix the third hole. Whacked my left middle finger when the counterbore grabbed. No real problem cutting the step and getting a really close fit. I haven't checked the run-out yet, but it looks quite good. I'll put that off until I have to. That's one of those things you really don't want to know. Biggest problem was today. Reminded me again of why I hate machining cast iron. Dirty! dirty! dirty! Spent the last three hours cleaning up the lathe, the bay in which the lathe sits, the drill press, work benches, etc. Anyhow, that job's done. Also fitted the BXA toolpost I bought at auction at Cabin Fever. Chinese, but it came with 8 tool holders. It is at about the limit for my 12" Clausing. It's okay with 1/2" toolbits, but with 5/8" tool bits, you have to fiddle to get the tool on center and the adjusting nut is at the limit. Still, compared with the AXA size, it is massively rigid. If you have a 12" or bigger lathe, you should certainly opt for the BXA size because tool holders on the used market are far more plentiful than AXA and also much cheaper. I'll have more to say about Cabin Fever after I get my check from them for the stuff I auctioned off.
Boris
Reply to
Boris Beizer
I ran into the opposite problem with the BXA on my 14" lathe-- the toolpost was too far below center, so I ccouldn't use the smaller toolbits without running out of adjusting room at the top of the post. I fixed that by putting a piece of 1/4" plate under it. Probably should have gotten the CXA. Regardless, I'm very happy with it... --Glenn Lyford
Reply to
glyford
Why are you using 5/8 toolbits? Seems way overkill for a 12 inch lathe. I rarely use anything bigger than 3/8 and I prefer 5/16 because they are faster to grind.
Reply to
Chuck Sherwood
Boris
Also fitted the BXA toolpost I bought at auction at Cabin Fever. Chinese, but it came with 8 tool holders.
Also fitted the BXA toolpost I bought at auction at Cabin Fever. Chinese, but it came with 8 tool holders.
I have the BXA toolpost and also the one that camme with my lathe. I also have a bunch of 1/16" metal spacers to adjust the height of my tool bits should the need arise. With this I am able to use from 5/16" to 1" tool bits.
Bob AZ
Reply to
Bob AZ
According to Boris Beizer :
[ ... ]
:-)
Hmm ... My 12x24" Clausing has no problems with 5/8" bits -- mostly insert tooling which has the insert precisely in line with the top of the shank.
Now -- in taking some insert tooling with 3/4" shanks and adapting it to 5/8", I would probably have problems if I took off the top of the shank, but I always remove the material from the bottom of the shank instead, so the height remains correct.
I used to use a small surface grinder to remove the material from the bottom of the shanks, but I have discovered that a wide conventional milling cutter in the Nichols horizontal does an excellent job of removing the necessary 1/8" of rather tough metal.
Absolutely. (Of course, if you want a tool holder which inspires feeding frenzys on eBay, you may have to do what I did and buy new instead. In particular, this was necessary for the BXA-16N holder, which holds directly two triangular inserts, one for turning and one for facing.
O.K.
Enjoy, DoN.
Reply to
DoN. Nichols
According to Chuck Sherwood :
I don't know about him, but I use the 5/8" shank holders for insert tooling -- and I get less chatter than I do with 1/2" shank tooling.
Enjoy, DoN.
Reply to
DoN. Nichols

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