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View Full Version : Options for D-shaft slot in handwheel



JoeBean
12-21-2010, 10:14 AM
Hi everyone,
I got some good deals last week and picked up a bunch of stuff from a guy on eBay (Interapid indicator, a couple different size surface gages, and a height gage). When I got the package the postal system had beaten it black and blue, but fortunately due to the good packaging the only thing broken was a plastic handwheel. I figure I'll probably machine a new one out of some 7075-T6 that I've got on hand, but what I'm unsure about is what to do for the slot for the D-shaft.

I glued the larger bits and pieces back together for the sake of a couple pictures, so this will give you an idea of what I'm dealing with:
http://i920.photobucket.com/albums/ad42/vagsrv/IMG_1617.jpg
http://i920.photobucket.com/albums/ad42/vagsrv/IMG_1618.jpg

As you can see the handwheel slides on to a D-shaft on the height gage, with a nut & washer holding it in place. The problem is how to machine the D-shaft slot. I don't have access to a shaper, only a CNC mill & lathe and other general shop equipment (50T press, mig & arc welders [no tig, unfortunately], etc.). I don't have access to a rotary broach either.

Here's a couple ideas I had thus far:
1. Drill or rough out the hole to remove as much material as possible, then use as small an endmill as reasonable (probably about 3/32" due to spindle speed limitations) to remove material at the corners of the flat to allow the shaft to fit. My biggest concern with this method is introducing slop, either initially or over time as things wear a bit, due to the unsupported spaces at both ends of the flat.
2. Machine the hole as though there were no flat, then machine a slot to hole a key so the long side of the key forms the flat. My concern, again, would be slop, though I think if I carefully machined the key myself I could eliminate that issue. There's also the fact that it looks kludgey.
3. Remove as much material from the hole as possible, form a broach from drill rod and use the press to finish the hole. I'm thinking the press because I don't know how much force is required to push the boach, having never used one before. I'm thinking a fair bit, though. Also, this would be the most "experimental" due to my lack of experience broaching.
4. Just make the hole round, make a "hub" that extends up past the surface a decent amount, drill an angled hole (as there wouldn't be room to get a drill in 90 degrees to the shaft) and install a set screw. Probably the most complicated option.

What do you guys think? Is there a simpler/easier way? Or would one of these methods work? If you've got any ideas/suggestions I'd appreciate them. I'm also open to the idea of just buying a replacement handle to fit (the dia of the shaft is .250" btw) if I could find one and the price was right, or a hub with the proper hole that I could insert into the handle. But I haven't been able to find either.

camdigger
12-21-2010, 10:31 AM
I vote for #4, but depending on how thick the web would be, it may be possible to drill into the central bore from the rim. A bit tricky, but IMHO, no worse than drilling and threading an angled hole.

TGTool
12-21-2010, 10:42 AM
I think #2 is the best solution. You can measure the edge of the slot that forms the flat to get it's position right. The backside doesn't matter because you can make the key thickness to fit. You say there's a washer so it will trap the key without further effort, or some Loctite would keep it there. This was done a lot in moldmaking with a former employer to fix the position of a round pin that had to be oriented correctly. Only the head of the pin needed a flat so the key intersected the counterbore on the back.

Benta
12-21-2010, 11:04 AM
I'd suggest an amended #2: instead of a key, use a piece of flat steel spring across the flat section. Curve it a bit towards the flat. If done right, this will eliminate slop.
This is done on knobs for stoves etc.

Benta.

tdmidget
12-21-2010, 11:48 AM
I don't see a problem. You have a cnc mill and a 3/32 end mill. Drill a starter hole and program the mill to cut the "D". At the intersection of the flat aand the circle cut a relief just large enough to remove the radius and allow the shaft to pass. The washer will cover it.

JoeBean
12-21-2010, 12:18 PM
I don't see a problem. You have a cnc mill and a 3/32 end mill. Drill a starter hole and program the mill to cut the "D". At the intersection of the flat aand the circle cut a relief just large enough to remove the radius and allow the shaft to pass. The washer will cover it.
That was my option #1. My biggest problem with it was that after darwing it & looking at the amount of unoccupied space left by the relief cuts, even with a 3/32" cutter, I was afraid it might be able to rotate off the flat, especially given that the pocket/hole is just over 1/2" deep(about 6x the cutter's dia). Although, thinking about it, it really wouldn't take much to hold it on as it's just a handwheel with light pressure required ( even just a bit of sleeve retainer and a drilled hole would probably hold). I may try it on some scrap, along with some of the other suggestions, to see what holds up.

Rex
12-21-2010, 12:19 PM
I think the keystock option is best.

Drill the hole to shaft size.
Use a broach to cut for an oversize key - up to the width of the shaft flat.
Thin a key to fit - mill or grinder
Silversolder or braze the key in place.
Face both sides to clean it up.

lynnl
12-21-2010, 02:00 PM
What I'd first try, is bore the hole out to about double the size of the round part of the D.
Then turn and knurl two pieces of brass suitable for press fit into that hole, with the correct size hole drilled/bored/reamed into one of those.
Then slice away the portion of the thru-holed piece where the flat is needed, and substitute in its place the right sized chunk taken from the other knurled piece.
And then... press the two pieces in simultaneously, as a unit.
...Viola! :)

Then after that didn't work .... :D

Kidding aside, I don't think it would be too difficult to get a pretty nice, neat appearance by doing that.
And you could leave a little flange on one end, and leave the length long enough to stand slightly proud when pressed in. Then when sandwiched between washers above and below, all should be locked firmly in place.

Of course there are plenty of places to buy such plastic knobs and wheels, e.g. Reidsupplyl.com, and Rockler Woodworking supply (I recently bought some from them), as well as McMaster Carr, etc. That'd be the most efficient solution, but where's the fun in that? ...eh?

macona
12-21-2010, 02:09 PM
Why not just make a one time use broach? Jut take a piece of drill rod, concave the cutting end, grind or mill the flat, harden and ten sharpen the end up. Ram it through. Might have to make a bushing to make it go straight.

Black_Moons
12-21-2010, 02:20 PM
How about a set screw? Either on its own, Or along with the 'key' to keep the slop out.

GadgetBuilder
12-21-2010, 02:37 PM
You've got the original hub which appears undamaged.

One possibility would be to make a stub arbor to fit this hub and machine the hub round (to remove the remaining broken pieces) . Then make a replacement handwheel with a hole to accept this hub and epoxy it in place. Make a nice large washer to hide the hub with a pocket to go over the hub and hide it completely.

John

alchymist
12-21-2010, 03:51 PM
You could look through a variety of knobs from appliances and electronic equipment to find a metal insert to fit and press fit it into your new knob.

JoeBean
12-21-2010, 05:10 PM
Why not just make a one time use broach? Jut take a piece of drill rod, concave the cutting end, grind or mill the flat, harden and ten sharpen the end up. Ram it through. Might have to make a bushing to make it go straight.
I was thinking of this but how much pressure do you think would be needed to push the broach through assuming most of the material was removed via the CNC (ie. there should basically only be the 2 corners to work with)?

JoeBean
12-21-2010, 05:15 PM
You've got the original hub which appears undamaged.

It looks OK in the picture, but the whole thing was actually shattered into pieces. It was basically snapped in half like a cookie, then one half was smashed into smaller bits. It's kind of holding together, but very lightly. It took a full 5 minutes of being clamped with superglue before it held at all.

Thanks everyone for your suggestions thus far, they've been some really helpful suggestions. I won't be going at this for about a week or so and am in the planning stage right now. These ideas sound really promising.

JoeBean
12-21-2010, 05:19 PM
What I'd first try, is bore the hole out to about double the size of the round part of the D.
Then turn and knurl two pieces of brass suitable for press fit into that hole, with the correct size hole drilled/bored/reamed into one of those.
Then slice away the portion of the thru-holed piece where the flat is needed, and substitute in its place the right sized chunk taken from the other knurled piece.
And then... press the two pieces in simultaneously, as a unit.
...Viola! :)

Then after that didn't work .... :D

Kidding aside, I don't think it would be too difficult to get a pretty nice, neat appearance by doing that.
And you could leave a little flange on one end, and leave the length long enough to stand slightly proud when pressed in. Then when sandwiched between washers above and below, all should be locked firmly in place.

Of course there are plenty of places to buy such plastic knobs and wheels, e.g. Reidsupplyl.com, and Rockler Woodworking supply (I recently bought some from them), as well as McMaster Carr, etc. That'd be the most efficient solution, but where's the fun in that? ...eh?

That's an interesting idea - basically a split hub. I'll put that on my trial/experimental list to see how it works out.

I tried McMaster as I was fairly certain I'd seen some similar items before but despite them having a search entry for "hand wheels" there were no results. So I'm guessing my search term must be wrong. I'll give knob a try, as well as the other companies. Thanks!

Warren
12-21-2010, 05:27 PM
Another option would be lay out the hole and drill around the inside of the layout lines with a small teeny drill. Knock out the center with a small chisel or punch & finish to size with a small pattern file.

bollie7
12-21-2010, 05:34 PM
Can't you just use a "D" bit? LOL - sorry its been a long year, I couldn't resist.

have a great xmas everyone.

bollie7

firbikrhd1
12-21-2010, 06:31 PM
Rather than make a new piece why not attempt a strong repair of the knob/handle you have? In the past, on cracked "pot metal" pulleys I have cut discs of aluminum and used epoxy (JB Weld or Fasco product) to glue the disk to the original part on each side of the part thereby encapsulating the part in an aluminum "case" of sorts. It appears that the "D" shaped center you want to reproduce is in tact on the original part. By making four aluminum discs perhaps .060" or so thick, two for the depressed center area with holes for the boss where the original "D' shaped mounting hole is and two for the outer rim, and, using epoxy to attach them on each side of the original part you will have nearly encapsulated the part in aluminum and bridged the broken areas creating a much strengthened knob. The only drawback to this method might be that if the knob/handle is made of is polyethylene which epoxy doesn't like to stick to. In this case it appears that your knob/handle is made of either cast aluminum or zinc, neither of which should cause a problem with this method.

lynnl
12-21-2010, 07:03 PM
Another thought I've had, on the method I mentioned: machine out the inner hole FIRST, then mill away one side and silver braze the piece that will comprise the flat side of the D. And then AFTERWARD turn and knurl the complete insert for pressing in.

Another possiblility if you used the right kind of plastic: Make a steel D shaft and heat red hot, and use that to burn or melt a D shaped hole. Probably need to make a few trial pieces. ...and don't stay outta the fumes. :) (gotta get that safety caution in there.)

macona
12-21-2010, 07:09 PM
I was thinking of this but how much pressure do you think would be needed to push the broach through assuming most of the material was removed via the CNC (ie. there should basically only be the 2 corners to work with)?

Not any more than you could get out of a arbor press, or a mill quill if need be.

-Jerry

lynnl
12-21-2010, 07:26 PM
You could look through a variety of knobs from appliances and electronic equipment to find a metal insert to fit and press fit it into your new knob.

I like that idea too!
Probably the most practical of all. What comes immediately to mind are the pull off/push on control knobs for a kitchen electric range. Haven't measured, but just had mine off for cleaning coupla days ago, and they're right close to 1/4" shafts.

noah katz
12-21-2010, 10:55 PM
"the only thing broken was a plastic handwheel. I figure I'll probably machine a new one out of some 7075-T6"

If you're not doing it for the fun of it, you can get handwheels from Grizzly quite inexpensively.

Evan
12-22-2010, 01:13 AM
Just make a small hub with a wide, thin flange and a round hole and a setscrew to engage the flat. Mount whatever you want to the flange with three screws.

Like this:

http://ixian.ca/pics8/handwheel1.jpg

metalmagpie
12-22-2010, 01:30 PM
My idea is a little different: go ahead and make your wheel with a round hole. Put the wheel in the vise so the axis is horizontal, then clamp flat plates wrapped in wax paper on each side of the hole, so they just cover the bottom of the hole, but deep enough. Now you have a nice mold. Next you need to precisely (within 1%) measure the density of some JB Weld or other epoxy. Then measure your original D hole and figure out the weight of epoxy to make up the flat part of the hole. Then use a gram scale to weigh out some JB Weld and then goob it into the hole between your flat plates. The JB Weld is fluid enough to run down to the bottom just by the force of gravity. Let it dry 24 hours then unclamp the side plates and crack them off. The epoxy should have formed a really nice flat right on the bottom of the hole.

This wouldn't hold up to say a machine gearbox, but for a handwheel that has little force on it, it should work fine. Gram scales are available very inexpensively in small plastic versions, just a few bucks. I bought one at a tobacco shop near a university when I needed to weigh out a precise amount of grease to inject into the bearings of a grinder spindle I was rebuilding.

metalmagpie

Alistair Hosie
12-22-2010, 01:52 PM
The market is floded with these handwheels for a few dollars new why worry,if it were me for the small sum of money involved I would buy a new one.Alistair

JoeBean
12-23-2010, 02:01 PM
The market is floded with these handwheels for a few dollars new why worry,if it were me for the small sum of money involved I would buy a new one.Alistair
I actually did just order 2 for $8 from ebay, with setscrews to hold. I mainly boyght them as they have an aluminum hub that the setscrews are in which I figure I can reuse similar to how Evan et. al. have suggested going about it.

I know everyone keeps saying that these are available everywhere for pennies, but I haven't been able to find anywhere that a) have 1/4" D shaped through hole to be held as the original is, and b) are anywhere near as large in diameter as the original (approx 3.5"). It's complicated further by the fact that I'm in Canada, so for anyone who won't ship here I need to ship to a relative and have them forward it.

But negating shipping costs, Most of the sites mentioned that sell handwheels have 1/2"+ bores where I'd still have to make the hub, and with shipping it is actually cheaper for me just to mill out the hand wheel myself. The only places I've found with something that might be workable (aside from the aforementioned fluke of a find on ebay) are mouser and digikey, electronics suppliers for any who aren't familiar. Digikey have a nice aluminum unit, but with a 1/4" hole with setscrew and not the D through hole, and it's only about 2" in diameter. That might be fine, though, as it doesn't require much force to operate the gage anyway. The cost, though, is almost $30 shipped. The other option is from Mouser. All phenolic knob with a set screw, just over 2" in dia. Shipped for about $12. I may have bought that if I hadn't stumbled across the other one. In either case, though, it's not close to an exact replacement, more like an "it'll do" kludge.

BTW I found a thread on PM yesterday that lead to a manufacturer of D-shaft broaches - around $400-500! :eek: So if someone finds this thread later if it's for a 1-off a shop-made broach, or one of the other suggestions above, is probably your best bet.

Mcgyver
12-23-2010, 02:59 PM
I suppose this is too late if you've ordered one, but unless you get a good match i'd make one....its off a height gauge so it it has to be about the right size and look half decent....not something a typical machine handles could take the place of.

The D shaft is easily made through a fabrication - you make a D shaped insert. Bore the ID, mill away the right amount, solder a piece across where you milled then turn the OD. loctite into the work piece. this pic gives the general idea

http://i20.photobucket.com/albums/b201/michael0100/upt/uptsmalltapheadhandle.jpg