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plunger
12-26-2010, 01:43 PM
Through necessity I am trying to make a worm and worm wheel.This is for my bandsaw.I bought a piece of v155 steel I hope this can be hardened.
My original worm was 29mm in diameter but I could not figure out its pitch. It was close to 4 tpi and close to 6 mm . But it was neither.I have decided to make my own pitch and used 6mm.
I have machined the shaft for the worm and put on the 6mm acme pitch. I call it acme but what I did is sharpen a tool using the original worm as a thread guage.
This is where I need some help.I want to cut relief into the worm ( made it longer than needed) but dont know how to go about this. Do I use a slitting saw or do I use a end mill . How many slits will it need and how do I relieve it .? I saw someone relieve a gear using a slit at an angle to the cutter. He claims it allows the free hobbing procsess to work better .Is this true. Will I need to harden the cutter for a one off job in phosper bronze and does the new worm need to be hardened or is it hard enough in its normal state.
I am mathamatically dislexic and am hoping that this will work even though I am not following making gears to the book .I just dont understand all these gear formulas and am hoping that a 6mm acme home made worm will work to drive a 21 tooth gear.(gear is also to be homemade) Can anyone see why it would not work
Does anyone know what v155 is similer too and is it a good piece of steel. Its all I could get as all the steel shops are closed this time of year and they had an offcut of this other wise I would have opted for drill rod
I really hope I can get this thing fixed
Regards Eugene

John Stevenson
12-26-2010, 01:53 PM
Eugene,
Although you say band saw I'm guessing this is the drive reduction ?

If so then altering the pitch of the worm will alter the centre distance of the worm and wheel.

If you are tied to a predetermined centre distance then you will have to sort a pitch out to keep the 21:1 reduction. I feel this need to be addressed before you go further.
Can't help on the steel grade as i have not come across this one in the UK

precisionmetal
12-26-2010, 02:23 PM
v155 = 4340

plunger
12-26-2010, 05:50 PM
Sir john it is from a 4x6 bandsaw .Cant get spares and a quote from 4 gear companies is the same as a new machine. The worm and wheel are machined in the casting with no adjustment capability. I measured the pitch as best as I could and set my machine on 4 tpi and followed the original worm but noticed it does not match up. The same as with 6 mm althougt both are close.I could not find anything that matches exactly and dont have the mathematical skill to work it out by doing fancy footwork with the change gears. Will it not work if I make the worm to 29mm as original and play with the pitch. I guess the relation of distances is important as its fixed and not adjustable but if i get close enought that it fits all together. Do you think I may have to change the no of teeth on my gear to perhaps make things work? I dont care if its a little faster or slower I just want to get it to go round. I am worried that by not applying the mathimatical equations first that I may get caught whereby the gears dont mesh. At worst case scenario is it possible that I could maybe rebore one of the casting bores bigger and make an eccentric bush for the bearings so that i have some form of adjustment.
If I can get this right it would give me a huge sence of acheivement
thanks eugene

John Stevenson
12-26-2010, 06:10 PM
Eugene,
Given where you live I can imagine the problems so can you answer a few questions?

I'll try to describe what's needed without a diagram but shout up is you need one.

Worm, need the diameter of the OD

Wheel, need diameter of OD as good as possible and the diameter of the bore.

Then push the worm into mesh with the wheel and measure from one side of the centre hole to the OD of the worm.
This will enable us to work out the pitch circle of the worm.

Lastly what pitches can you cut easily on your lathe around the original.

Doesn't matter if it's metric or TPI.

.

plunger
12-27-2010, 10:45 AM
tHANKS for trying to help me. It can be difficult at times and we definitly arnt spoilt for choice (no harbor freights)
I have already made the worm.It has a 6mm pitch as this is the closest to the original but it does run off the original on the last tooth over 30mm.I had no idea how deep to make the thread so I eyeballed it. The size of the worm is 29od (same as original)
The bore is 15mm
The gear is 47,6mm
When the worm and wheel are engaged They are 40mm This is the distance from the outside of the wheel to the inside of the worm bore.
I have made the hob but am stuck as to how to relieve it. It is designed to be held in a autoclark collet of 16 mm and is 50 long. I am not sure how to relieve it and if I need to harden it.
I have a dividing head but it will be a learning curve as I have only used the indexing on it and not the plates.Could I use the dividing head to allow the blank to free wheel rather than trying to make a spinning fixture?
The dividing head is a mecatechnica .Have no idea if its a quality dividing head. Feels good though.
Regards Eugene

John Stevenson
12-27-2010, 10:50 AM
Working on it.
Presumably using a vertical milling machine ?

plunger
12-27-2010, 11:02 AM
Its not a bridgeport..........:D
Its a iso 40 mitco I think they are badged but is a spanish machine called holke
Its a vertical

John Stevenson
12-27-2010, 11:17 AM
That's good I don't think a Bridgy is up to it :D

Ok we have all we need.

http://www.stevenson-engineers.co.uk/files/worm_and_wheel.jpg

Everything in black is what you have given me, worm OD of 29mm, wheel OD of 47.6, bore at 15mm and mesh of 40mm.

The two red circles are the base circle at 37.00mm and the theoretical pitch circle at 42.3mm.
The number of teeth is based on this diameter and the pitch so 42.3 x Pi /6 =22.14 so we will work on 22 teeth.

Your original was 21 but the pitch has altered.

Now looking to see what the steel grade is in a format I can understand in UK speak.

John Stevenson
12-27-2010, 12:32 PM
Ok steel is what we know as EN24 which is a thru hardening steel, ideal for a worm hob as it can be hardened with a torch.
First off you need to flute this to get some cutting edges, relieviing isn't needed for a simple one off like this.
You can use the dividing head with the indexing facility as you only need 4 flutes.

http://www.stevenson-engineers.co.uk/files/worm_hob.jpg

The idea is you remove 4 flutes with any size cutter and go just past the centre line so you have some cutting rake on the tool, repeat 4 times and you have a hob.
Three important things, you need the cutting rake, you need to leave enough to provide strength but if you leave too much you get rubbing.
Most importantly you need to work out the hand of the worm and cut the correct size. The one shown in the diagram is a RH worm, if you need LH then make the offset and tooth space the other side of centre.

That's the hob done, hardening is a matter of taking the hob gently to cheery red and quenching vertically down into a bath of oil.
make sure it goes straight into a fair quantity of oil so it cools as opposed to setting half the African continent on fire.
Oil is not as fierce as water for quenching and I have found that when cutting soft materials like bronze, brass and alloy that by he time you have ground the cutting edge the heat from grinding has taken the glass hard edge off and you can get away with tempering.

Many may not agree with this but it works foe me, I wouldn't do this on steel, in fact most time I get cutters professionally hardened as the hardening shop is literally across the road from me, but in Eugene's case this is not an option and he only has to do one wheel.

plunger
12-31-2010, 12:25 PM
I have completed my worm and wheel and have given myself a pat on the back. I think I can relate to making something to people getting a natural high from doing gym .A dose of endorphines I think its called. I just dont like getting tired so I make things.
I cant believe that it works . It came out real well. I really learnt from this.
I learnt about making a cutter and using my dividing head and hardening.
The best is I got my bandsaw back from the dead.
I still have some questions.
Should I have hardened the worm?
Can I use way oil for the lube in the gearbox?
THe one bored casting was a little tight . Without having to set an akward casting up in the mill to try to rebore a small amount out how could I do this while the machine is on its stand?

I think what I also learnt alot about is what decency there is in humans.
Here is a guy stuck on the other side of the world needing help and people have the caring and time to actually bother to help a hacker learn something.
Thanks to everyone who helped me especially to My mate Werner who just lurks here and to Sir John who helped me with the drawing and explanation.

At the same time this is a wonderfull site . I asked this question over at pm and my thread was banned. Can you believe it? I wasnt asking about a chineese bandsaw I was asking about how to make a worm and wheel.Maybe I have the wrong idea about what that site is all about.
I am a plumber by trade and love to teach what I know. I have taught two youngsters how to do the trade and they now run there own business.
I think its very sad to be stingy with what you know. When you die all that knowledge goes with you.Better to pass a bit on because you never know when you gonna kick the bucket Regards Eugene.

Carld
12-31-2010, 02:12 PM
PM is not a very friendly site, especially if you mention anything that could be related to Chinese stuff. He is a person that likes to start a thread and then chastise and belittle anyone that says anything he don't agree with. He is a person with a bad attitude and I doubt he even likes himself as he surely don't like anyone else.

I am glad you got your problem solved with help from here.

Benny Callaham
12-31-2010, 08:37 PM
Great job Plunger!

First an answer to your question about lubrication. Worm gear drives have a lot of sliding motion and for maximum life special lubrication is recommended. Below is a link about the subject:
http://www.machinerylubrication.com/Read/169/worm-gear-lubrication

I saw your post get banned on the PM site. A member mentioned a gear set on eBay that fits “most”. From that post the “Moderator” assumed that your saw was a low cost hobbyist model and locked the thread. Hobbyist and non-production topics are not very welcome there. The folks here are a lot friendlier.

Quote:
Originally Posted by nt1953
BRONZE GEAR FOR 4 x 6 METAL CUTTING BAND SAW-FITS MOST! - eBay (item 370467191659 end time Jan-15-11 07:15:59 PST)

Most of the time, someone is selling them on eBay
I suspected this thread was about one of those POS Chinese saws, now I know. The OP can thank you for having his thread locked.

Regards, Benny
In middle Tennessee, USA