Author Topic: Tried to mill teeth into welded sprocket  (Read 2939 times)

Offline PekkaNF

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Tried to mill teeth into welded sprocket
« on: August 12, 2013, 10:58:25 PM »
My father bought a well used potato elevator for 30. Elevator chain wheels were worn out pretty badly and he decided to fix then by welding some more material. Then chucked them to me "You have a milling machine, mill some teeths". Also gave some measurement that looked reasonable and I manged to mill the teeths that more or less followed the welded contour. All's well?

Suspicious as I am, I asked more measurements on the chain itself - something did not add up. PCD was about 27 mm too big. I should be 150 mm. I called back and asked how much did he weld to make up the worn part? Two full packages of welding rods!

I tried to plunge slot drill into them....Broke two slot drills with rotab. Then bolted the sprocket wheel onto mill table, only with a spacer and next slot drill broke when went into weld about 0,5 mm. Good only knows how many times that poor wheel was welded before and with what. Part of the weld is like chewing gum and part is pretty hard and work hardening.

I'm asking a local water/laser cutting company how much it would cost to cut them from 16 mm steel plate. I can't afford using slot drills at this rate. And spend allready three days of my making a fixtures/arbors and reducing it's heft by turning it smaller.

Alternative plan is to drill bottom of the teeth with hsco drill and offer an angle grinder to that bugger.

And I don't have very good idea of the actual tooth form, because it's not a classical chain wheel but a very agricultural view of it.

This is going to a character building experience.

PekkaNF

Offline NeoTech

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Re: Tried to mill teeth into welded sprocket
« Reply #1 on: August 13, 2013, 01:41:21 AM »
This is going to a character building experience.

 :lol: :lol: :lol:   We have a saying at my work when these kinda problems occurs.. "just put your head through the wall"..  :bang:
Machinery: Optimum D320x920, Optimum BF20L, Aciera F3. -- I have not failed. I've just found 10,000 ways that won't work. http://www.roughedge.se/blogg/

Offline Anzaniste

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Re: Tried to mill teeth into welded sprocket
« Reply #2 on: September 01, 2013, 02:46:33 AM »
I'm not sure what you mean by a classical chain wheel but roller chain is a fairly standard item. Simple plate wheels either with or without bosses are usually available off the shelf from engineering supply houses (usually bearing supply houses in the UK).
All you need to know is the pitch of the rollers and the number of teeth.
Scrooby, 1 mile south of Gods own County.

Offline PekkaNF

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Re: Tried to mill teeth into welded sprocket
« Reply #3 on: September 01, 2013, 02:10:15 PM »
Nope. This is a potato elevator and the "chain" is pretty far from standard roller chain. After googling enough, I got anecdotal evidence that the sprocket shape is not very conventional roller chain sprocket shape, nor gear wheel...

I got sick of breaking slot drills, asked one friend to draw wheels and bosses. Send DXF out on one local company and they said they would cut them out of 16 mm steel, when they have real order on works...waiting that to materialize.

Pekka

Offline PekkaNF

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Re: Tried to mill teeth into welded sprocket
« Reply #4 on: September 12, 2013, 03:14:30 PM »
A little step forward - I think!

Got the parts plasma cut from 16 mm steel plate. At first they looked good, but cut was a whole lot lower quality I'm used to.

Biggest problems are holes, that taper too small....I need to open them up from 9 mm to 10.5 mm. It's a pain.

20 years ago if we needed to tap a hole into plasma cut plate, we made a recess with a bigger than thread OD with sharpened masonry drill and then drilled and tapped with HSS. But I have never opened a plasma cut hole bigger.

Any suggestions?

PekkaNF