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View Full Version : Ideas fixturing flanged hubless timing pulley in lathe



bigmoose
12-16-2017, 08:54 AM
Could use a few ideas how to fixture a small (around 1 inch diameter) flanged and hubless timing pulley in the lathe for boring. Flanges are rather fragile and there is no hub to clamp down on. I've scratched my bald head for a while on this one, and figure there will be a good idea from those more experienced.

BCRider
12-16-2017, 09:28 AM
Does it have a hole which would allow you to turn a mandrel and push fit the pulley? Or if it face mounts onto the end of a cam with screws then turn a slug to match the end of the cam?

Otherwise I'd say that a picture of your pulley is worth at least 1000 words and would avoid a bucket load of misunderstanding.

metalmagpie
12-16-2017, 09:29 AM
This sounds like a case for one of those low-melting-point compounds like cerrobend.

Alan Smith
12-16-2017, 09:41 AM
Generally would use a collet to hold very small flanged pulleys (up to 1.75" DIA) You could use soft jaws in a 3 jaw chuck or make your own collet with a slug of ally bored to your diameter, deep enough to take both flanges, then put a single slit in it with a saw and remount in the chuck as it was oriented previously.

Watch the flange rims are concentric with the pulley rim surface, they aren't always.

tmc_31
12-16-2017, 10:08 AM
Cut out some pieces of aluminum beer can to wrap around your chuck jaws to cushion the pulley.

A.K. Boomer
12-16-2017, 10:11 AM
if you install a section of used timing belt around the diameter of the engagement cogs does it stick out further than the flange?

Bob La Londe
12-16-2017, 10:23 AM
Bore and turn a piece of aluminum (or whatever you have) into a ring with ID that matches the OD of the belt surface of the pulley. Cut it in half with a saw. Deburr it. Mount in adapter you just made and bore. Done.

Or...

Mount your face plate. Center pulley on face plate with a center in the tail stock. Clamp pulley in place with whatever clamps are necessary. Back off tail stock and bore. Done.

754
12-16-2017, 10:29 AM
Make 3 or 4 pins the right length to fit between flanges. Bigger than the groove is fine, you need it to go past the flange.
Then Chuck in a good 3 jaw or 4 jaw ..depends on tooth number.

Stepside
12-16-2017, 10:31 AM
Assuming that you have a 4 jaw chuck there are a couple of possibilities.

1) As metalmagpie says and use some Cerrobend and cast it in a mold. When done place the part with the Cerrobend in some near to boiling water and the Cerrobend will melt off the pulley. I have bought Cerrobend on Amazon Prime.

2) Two equal length and width pieces of material. The thickness equal or just under the distance between the flanges. Sandwich a piece of thin material between the two blocks and center in the lathe. The center aligned to the shim/thin material. Bore to match the pulley diameter and remove from lathe. Discard the shim and replace with the pulley. Use the four jaws to center the existing bore and then bore to desired diameter.

3) Put your location in case one of is your neighbor.

Have fun
Pete

oxford
12-16-2017, 12:03 PM
If it is a standard pulley for a timing belt, those flanges are usually just stamped sheet metal and pressed on to the pulley. They can be removed and then reinstalled. You could then just chuck up on the tooth section.

Willy
12-16-2017, 12:11 PM
Have you got a faceplate. I've fixtured a very wide variety of oddly shaped work to this often overlooked option.

lakeside53
12-16-2017, 12:12 PM
If you have soft-jaws just make room for the flanges and grip on the main pulley. Only takes a minute or two.

ODgreenK5
12-16-2017, 12:20 PM
I've used dowel pins before to chuck pulleys and gears. That way I was grabbing on the pitch diameter, not the OD.

Sent from my LGLS775 using Tapatalk

754
12-16-2017, 12:58 PM
Exactly, center the bore on the teeth m not the pressed on, stamped flanges. .
Unless you want intentional runout, or want to chance it not running true.

If part ofvthe pins stick out from the chucks you can then check with a dial indicator.

danlb
12-16-2017, 01:16 PM
I searched for flanged hubless timing pulley and don't see any that don't have a center hole for mounting on a shaft. That makes a mandrel the obvious choice for most uses.

However... It all depends on which surface you are going to work on. Facing will use one fixture, boring will use another, truing up the teeth (working surface) yet another. :)

Dan

RichR
12-16-2017, 01:34 PM
I searched for flanged hubless timing pulley and don't see any that don't have a center hole for mounting on a shaft. That makes a mandrel the obvious choice for most uses.

However... It all depends on which surface you are going to work on. Facing will use one fixture, boring will use another, truing up the teeth (working surface) yet another. :)

Dan

Well since he said:

Could use a few ideas how to fixture a small (around 1 inch diameter) flanged and hubless timing pulley in the lathe for boring. Flanges are rather fragile and there is no hub to clamp down on. I've scratched my bald head for a while on this one, and figure there will be a good idea from those more experienced.
I'm going to go out on a limb and suggest that plugging the hole with a mandrel might be counterproductive.:rolleyes:

MrFluffy
12-16-2017, 01:41 PM
Ive used pins to grip sprockets, but also I've used soft jaws bored to the od of a timing pulley and it came out just fine. I just popped the flanges off, but I didnt need them so I left them off.

danlb
12-16-2017, 02:18 PM
Thanks for pointing that out Rich. I read that part twice and missed it. Maybe it was because I already had a vision in my head of all the parts of a pulley that can be turned or bored. Like this...

http://www.3dcontentcentral.com/showmodels/CONTENTCENTRAL/POLIA%205V-203-3%20BORNE/POLIA%205V-203-3%20BORNE.JPG


It seems obvious that the OP wants to bore it for a new shaft.

Toolguy
12-16-2017, 05:48 PM
Push the pulley up against the chuck jaws with a live center. Turn the OD of the flanges both same diam. just enough to cleanup concentric. Put in chuck or collet and bore.

Old School
12-16-2017, 07:48 PM
Doesn't it seem odd that we have another poster that for some reason doesn't get back to anyone as to how this helped or worked out? Seems like a lot of good ideas went his or her way that could have been used to solve their problem. Sorry just thinking out loud !!!!

ikdor
12-17-2017, 04:47 AM
It doesn’t seem odd to me. He posted yesterday and maybe he has a day job.

Bob La Londe
12-17-2017, 09:27 AM
It doesn’t seem odd to me. He posted yesterday and maybe he has a day job.


Odd? No not really. Happens all the time. The reason you state is common, but quite often folks get the answer they need and then just move on. I kind of try to make it a point to atleast come back and say thanks or let people know what worked out for me, but because so often newbie questions seem to get ignored on forums full of "experts." Its sometimes hard to come back and check them all. I have found on two forums I visit newbie questions or specific genre questions either seem to get ignored or criticized. Other times the "experts" go off to attack or offer tangential advice on aspects of the project that were not the question. They were just information posted for background.

I asked recently about welding up (in a welding group) a tube frame table and how to minimize weld distortion in the setup and process. I detailed my materials, welders, and materials for background. Not one person actually addressed my question. Oh, well. I'll proceed and see what happens, but the only reason I'll go back to that group and say what happened is for those folks who might have wondered the same things I did and were to afraid to say anything.

Generally this forum tends to be better than that, but unless you have been here a while or visit it often you don't know that. Its just one more forum in the noise.

J Tiers
12-17-2017, 10:58 AM
....... Other times the "experts" go off to attack or offer tangential advice on aspects of the project that were not the question. They were just information posted for background.

.......

Happens too often, and is really annoying, because usually some tiny subgroup is extremely vocal about attacking that side issue, and will NOT shut up even when the side issue is firmly stated to be not the point or not even valid, by others. It's one thing if the main point has been handled, which can be the case, that is not really a problem, even if perhaps silly. It is another thing if it is just pounded into the thread in the middle of useful help.

CCWKen
12-17-2017, 12:13 PM
Sounds like no one has actually done it before. I've re-bored many flimsy or delicate pulleys. Some plastic but mostly thin die cast. You don't need to smash the things to hold them. Light pressure is all that's needed. Especially if all you're doing is boring and it's toward the head. Light cuts, no hogging is the method to use.

Everyone says; "you can make small parts on a big lathe". This is your chance to prove it. :cool:

nickel-city-fab
12-17-2017, 12:55 PM
I would just crazy-glue it to the end of a aluminum bar and have at it. Gently heat breaks the glue.

Bob La Londe
12-17-2017, 12:59 PM
Sounds like no one has actually done it before. I've re-bored many flimsy or delicate pulleys. Some plastic but mostly thin die cast. You don't need to smash the things to hold them. Light pressure is all that's needed. Especially if all you're doing is boring and it's toward the head. Light cuts, no hogging is the method to use.

Everyone says; "you can make small parts on a big lathe". This is your chance to prove it. :cool:

Why does it sound to you like nobody has actually done it before?

I've bored out many pulleys including flanged timing pulleys. I've done it on my lathe and before I had a decent lathe I would do it using spiral interpolation on my CNC mill. If I didn't have a CNC mill I would have done it with a boring head. The reason I do not reference off the flanges is it often doesn't give me a true center. My big mill can easily get me under .001 for size and concentricity. Better if I take two passes and measure in between.

I just prefer a better setup and fewer passes. You can do a lot with a poor or flimsy setup with light passes, but it isn't easier, and it doesn't save you any time in the end.

Paul Alciatore
12-17-2017, 04:01 PM
This seems much ado for a one-off job. I would make a bushing with a bored hole that will fit over both flanges. The OD would be about 0.5" larger. Slit it in half. Now use that bushing to hold the pulley centered in your four jaw chuck and have at it. With uniform pressure all around you can grip the pulley quite firmly without crushing those flanges. You can dial it in on the existing bore hole in the pulley.

bigmoose
12-17-2017, 06:13 PM
Gents I haven't forgotten you... just spent two long days in the shop trying to catch up on other commitments. Please know that I am sincerely appreciative for your advice!

The pulley is anodized aluminum, I want to preserve the anodize for potential wear protection. The flanges are aluminum and appear fragile, as they have a very tenuous crimp connection to the pulley. I could TIG them back on, but it would damage the anodize.

You gents came up with, to me at least, three great recommendations:

1) Bore and turn a piece of aluminum (or whatever you have) into a ring with ID that matches the OD of the belt surface of the pulley. Cut it in half with a saw. Deburr it. Mount in adapter you just made and bore. Done.


2) As metalmagpie says and use some Cerrobend and cast it in a mold. When done place the part with the Cerrobend in some near to boiling water and the Cerrobend will melt off the pulley.

3) I've used dowel pins before to chuck pulleys and gears. That way I was grabbing on the pitch diameter, not the OD.

I am an old guy (65), but self taught over those years, it is easy to get stumped :) working alone. To me recommendation 3 might be the most precise as it registers on the pitch diameter, followed by number 2 which would register on the bore diameter, and number 1 would be pretty close, if I take care with the boring and the OD runs true with the pitch diameter.

I need to check my store of short dowel pins, and test the chuck set up. I have a 3 jaw a 4 jaw and 4C collets for my 4913 Clausing.

Thanks again gents for the tips! I have to look up and learn about Cerrobend, it is a material that is completely new to me.

oxford
12-17-2017, 06:51 PM
I would think on a timing pulley the OD would run true with the pitch diameter, the belt is seeing contact there unlike a sprocket for a chain where the chain isn't seeing contact with the OD.

RichR
12-17-2017, 09:15 PM
... I need to check my store of short dowel pins, ...

You could turn some pins to any size you need. It's not like they need to be hardened, you're using them to grab aluminum.

Gary Paine
12-17-2017, 09:47 PM
1) Bore and turn a piece of aluminum (or whatever you have) into a ring with ID that matches the OD of the belt surface of the pulley. Cut it in half with a saw. Deburr it. Mount in adapter you just made and bore. Done.

I would use this idea modified such that you are creating a donut with ID matching your timing gear OD and thickness to fit inside the flanges. Split it. The OD should be bigger than the flange diameter. Just put donut halves on the gear, chuck it up and dial it in with a 4 jaw for best accuracy.