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View Full Version : HOW MANY GEARS? HOWMANY TEETH ? BUT i DO NOT HAVE THAT MANY !



bitza500
7th Jan 2009, 11:25 AM
Hi guys this long winded rebuild is starting to get to me so PLEASE HELP.

I have just assembled the gearbox and have gone to fit the side gears from the gearbox to the tumblers But I am missing a gear Al in Canada who has 2 Hercus's both have 40tooth and a 56 tooth on the gearbox shaft and a 80 tooth as the Idler

Well I have a 56 and a 80 tooth but no 40 tooth
I have gone through all my downloads to find out what or why I am a 40 tooth gear missing but the hercus Book of Turning does not even tell you what size gears are standard

So can anybody enlighten me as to the reason I am missing a gear as I swore I had a twin gear on the gearbox ie 20 tooth& 56 tooth as a combination as I have a space were there should be something but the Book does not provide me with a very accurate picture or details as to the standard Factory Specs for a Model A lathe end gears

Also I am chasing the concentric and lever off the apron as due to having some of the parts plated to stop rust The smaller cast items just snap and was warned that some parts chrystalised when plated and break easy well this just fell in half and not from knocking the pin for the lever in as I had the complete apron finished picked it up and a piece fell on the floor so now I have to disassmble and find another

I have emailed Moyles but no response
Are they closed ???

all the best Derek

wannabe
7th Jan 2009, 11:55 AM
I think the 40 tooth gear your are referring to is for cutting 4tpi to 7 tpi threads. Mine is just bolted on the outside of the 56 tooth gear so it doesn't get lost. When you need to do 4 - 7 tpi you unbolt it off the shaft and replace the 20 tooth stud gear with the 40 tooth.

pipeclay
7th Jan 2009, 12:57 PM
Bit lost with what your asking in regards to your gear train,you are either missing the gear because you have lost it or it wasnt on the shaft to start with.
Unless you want to turn the 4 to 7 TPI threads just make a spacer of some type to stop the 56th gear moving on the shaft,even some washers would be ok.
I take it this is for a standard lathe and not the one you have riser blocks on.
The gears can be sourced so there is no problem getting them except perhaps for price.

bitza500
8th Jan 2009, 10:55 AM
hi Pipeclay, I am not sure that the setup on my lathe is original as every time I look at something it is either been remade or replaced and even after working all night trying to find the missing Gear I am still no better off
it looks like from what I can see is the 56 tooth is missing as I have a 40 on the gearbox as I know know that the gearbox had 2 gears 1 40 tooth and 1 56 tooth

This is only part of my problem as to just get it standard, then I have to work out how to connect the gears to the Headstock which is 2" higher as I was going 40, 80, 80, but then the top runs backwards (ON PAPER )

I have to run 3 gears of the same size??? to get it back running the right direction but will having 3 gears the same size give me the same gearbox settings ???

So far I have when stripping this lathe come across 2" and 3" nails instead of tapered pins the idler tumbler pulley is not a 20 Tooth and the gear on there looks like one of the Model A Apron ???

The spindle nuts were crushed in the vice to take up the wear????
the spindle has no thread on the end it has been cut off drilled and tapped plus it is to short

What I thought was a good old girl turns out to be a bad old girl and well mauled the rest seems ok it just looks like the previous owner did all his own repairs and patch ups

So all I am trying to do is get all the original parts so it is standard, so I can work out the gear train to the raised up Headstock so I have a gearbox that has the correct setup


I hope I can get some help with the gearing I will require to get this setup mobile as the rest is all done and assembled

Bar the raised tailstock as I am still looking for a taller and larger tailstock

So I have started with problems,then made more problems for myself in doing this conversion

I hope this makes sense

all the best Derek

aljunk
8th Jan 2009, 11:33 AM
Can't you just run the tumbler gear opposite to make it run the right way.

I'm glad you stopped into see the guys at Newmac, he thought mine was a "H" so we got that straightened out.
I ordered gear cutters today and I'm going to have a go at makin some gears for mine. I still did order the hercus gear 56 from them just to have it original equipment. First I'm going to make some out of Nylarod material to see how it will work, they say it has been engineered for a gear application so we'll see if it can handle the tooth loads.
I made a bevel gear out of this stuff for a taiwanese lathe I got for cheap cuz if was missing a nylon/plastic feed gear behind the apron and it sees to work great. The great thing about this stuff is u can make your own gear cutters out of steel and it cuts great.
I will edit some pics and post here in a bit just to show what can be done. I mean the thread is about gears right! lol

aljunk
8th Jan 2009, 11:56 AM
Here's a link to some pics of a gear I made last summer. I found an old washer that was 7mm thick and about 50mm round sorta did a freehand of the tooth profile in the lathe and used a Zip cut grinder to cut 4 'teeth' in it filed a bit of relief angle and voila!
This gear was missing a few teeth and the feed would stop when it got to the stripped gears. It's what they call a sacrificial gear, it's supposed to strip if the feed gets jammed up but since the machine is 17 yrs old they no longer make parts for them, it's a Goodway made in Taiwan. I contacted the factory and they said parts were obsolete but actually emailed me the blueprints for the gear (and all the rest of the apron parts) I was amazed that they would do that! It works great too by the way, very smooth and quiet.
http://photoshare.shaw.ca/messages/viewthumb/5965349580-1231374522-70015/parm/page/1/15/

aljunk
8th Jan 2009, 12:06 PM
What is the norm down there metric or imperial? We're kinda both here, used to be only imperial but in 1970 or so they started the switch to metric here. All goods being imported for sale must have metric labeling now etc, and all goods sold must be in metric quantities.

jmk89
8th Jan 2009, 12:22 PM
What is the norm down there metric or imperial? We're kinda both here, used to be only imperial but in 1970 or so they started the switch to metric here. All goods being imported for sale must have metric labeling now etc, and all goods sold must be in metric quantities.

I don't know what is standard, but the 127 tooth and 63 tooth gears are often used to get a metric approximation. The other good system is the Myford two 21 tooth gear conversions (works well for a 8 tpi leadscrew). If you want I can (when I get home from holidays) give you the Myford table

pipeclay
8th Jan 2009, 03:11 PM
The majority ofNew mechanical items in Australia are Metric,still a lot of older Imperial things being used,and some new stuff from the States is a combination of both(more so when the manufactureing of items is spread globally).

pipeclay
8th Jan 2009, 03:14 PM
Dereck do you just want to get the gearbox to work so that you can use the feeds or do you want to screw cut as well.

pipeclay
8th Jan 2009, 04:24 PM
Another thing to have a look at is where the banjo bracket hits on the gearbox,I dont think you will have clearance to be able to raise the bracket your 2" without it hitting the box.

billrule
8th Jan 2009, 05:56 PM
Yeah Aljunk; most of us are bilingual down under, especially the older guys. Absolutely nothing unusual in a timberyard for someone to want an 8 x 2; 3.6metres long:U

bitza500
12th Jan 2009, 11:19 PM
Hi Guys, what I need is to make sure that on the Gearbox shaft there is 2 gears 1 is a 40 and the other is a 56 tooth and the idler gear is a 80 tooth
Is this the standard for a Imperial setup???
And I am hopefully get 2 matching gears to run of the idler onto the tumbler so I still have the same ratio ???

As If I use 2 x 32 teeth gears from the 80 tooth will the ratio still be the same
Will the ratios still be the same if the 2 extra matching gears 32 tooth are use so as to connect the gearbox to the tumbler assembly

I am a bit lost in ratio but if you use 2 gears the same size the ratio should should not change ?????

Can anybody who has some more Grey matter upstairs tell me if this will work ????

all the best Derek

bitza500
12th Jan 2009, 11:30 PM
Dereck do you just want to get the gearbox to work so that you can use the feeds or do you want to screw cut as well.

Hi Pipeclay, I want to be able to use the gearbox eventually for screwcutting but working out the extra pulleys I need is my main problem
My brain tells me that if I connect 2 matching size gears to get the exta height all I will have to di is use the tumblers back to front as Aljunk said that it should work but I am chasing opinions on the adding a Matching pair of gears onto the 80 tooth Idler so as to connect to the 20 tooth on the Tumbler assembly and still have the gearbox running at the same speed and the same ratios ???

all the best Derek

pipeclay
13th Jan 2009, 02:00 AM
On paper it appears to be ok with either 2x32 or 2x40 gears.
Have you checked to see if the banjo bracket will clear the gearbox.

bitza500
13th Jan 2009, 07:09 AM
Hi Pipeclay, I originally had it set up as 40,80,80 to the 20 tooth tumbler,but this just did not seem right as the 80 is just a IDLER and after a bit of reading and Al in Canada advising
All I had to do was have from Standard on the gearbox 56 tooth Idler 80 Tooth and then a pair of matching gears so as to not put the ratio out, just give me my extra height

I do not know if the pictures in My Black and blue Beauty shows the setup as all the gears were painted black and I was short 1 gear as I was chasing 2 40 tooth gears but had to settle for the 32 as I had 2 of them

As for fitting it is avery tight fit and would have prefered 2 x 40 tooth gears but I am unable to find any cheap gears as (YES) on paper it sounds and looks good but I have to bore the gears out to setup the gear train

As I have alredy bored 1 x 32 tooth I found that on the Model a Apron there is a 40 tooth gear but with a larger diameter bore

This does not bother me as I have to make the sleeves as I only have sleeves suitable for 2 gears so I could make them to suit it just means I am missing 2 x 40 tooth gears for 2 Model A Aprons

But as I have no concentric to operate the direction of the feed as they broke on the flat solid section as they (I have been told ) crystalise and go brittle any old cast items seem to have this problem as I have had a few items I have found broken in the box of bits just from other parts sitting on them

Unless you have some spare gears or a old Model A Apron ?????

will find out tonight as I am going to my mates to make the sleeve/collar to fit inside the gear and also give me Clearance

But as it is only going to be 37 C today I doubt I will get finished

all the best Derek

blackfrancis
13th Jan 2009, 11:39 AM
Hi Derek

Just put any gears you like on the banjo. As long as you don't use compound gears on the banjo, i.e. two gears joined together such as the 72/18, and you leave the ratio of the gear on the tumbler divided by the gear at the end of the quick change box unchanged, the ratio will be the same. In other words use any idler gears you want, it doesn't matter. If you use two idler gears they don't have to be the same size, you can use an 80 and a 40 rather than a pair of 80s.

If you aren't sure set the gear box to cut 8 tpi. Spin the chuck around by hand. If the leadscrew is turning at the exact same speed as the chuck all is ok. Spin the chuck a dozen times and see that the leadscrew does the same.

Cheers
Steve

bitza500
14th Jan 2009, 11:33 AM
Hi Derek

Just put any gears you like on the banjo. As long as you don't use compound gears on the banjo, i.e. two gears joined together such as the 72/18, and you leave the ratio of the gear on the tumbler divided by the gear at the end of the quick change box unchanged, the ratio will be the same. In other words use any idler gears you want, it doesn't matter. If you use two idler gears they don't have to be the same size, you can use an 80 and a 40 rather than a pair of 80s.

If you aren't sure set the gear box to cut 8 tpi. Spin the chuck around by hand. If the leadscrew is turning at the exact same speed as the chuck all is ok. Spin the chuck a dozen times and see that the leadscrew does the same.

Cheers
Steve



Hi Steve, so what you are saying is so long as the teeth on the 2 idler gears do not equal 100 ?? I can use any gears to set up the tumblers to run correctly ???
As I always thought that the standard 56/80 tooth gears are standard and to keep the RATIO ??? correct I would need to have 2 matching gears so as to not change the ratio as I am having FUN????? trying to work this out as the system I want to use as Pipeclay suggested is either 2 x 32 or 2 x 40 teeth gears as how the setup will end up as
56 tooth gearbox 80 tooth Idler 40 tooth idler and another 40 tooth as another idler as YES this is for the lathe with the 2" riser block so as Geometrically (Big word) speaking I was under the opinion that to keep the ratio correct from the original 56/80 gears I would have to use 2 matching 40 tooth as Idlers

As I have to use 3 idlers to raise the idler bracket so every thing mates and I am VERY CONFUSED as to the way the Ratio system now works ?????

Thanks Steve I will try that out first the 8TPI system as you suggested ,but am sure using 3 idler gears 2 must match ????

all the best Derek

blackfrancis
14th Jan 2009, 03:13 PM
Hi Derek

Perhaps a simple example for how to do stuff on a model C lathe will make things clear. So I assume you have no compound gears on the banjo. E.g. a 72/18 gear as used on the model B & C is a compound gear not an idler.

Lets say we want to cut an 8TPI thread on a model C with three idlers. Lets say we put a 32 gear on both the tumbler and the lead screw, with the first idler having 40 teeth, the second 50 and the third 60. Now to cut 8TPI the spindle and the lead screw need to turn at the same speed. The gear on the tumbler spins at the same speed as the spindle. Lets use the symbol S for the spindle speed. The speed of the lead screw will be given by

S x 32 / 40 x 40 / 50 x 50 / 60 x 60 / 32 = S

So despite the crazy combination of idler gears it still cuts 8TPI. Thats why they call them idler gears, they don't do anything.

Now, all you need to do/know: Grab a calculator and take the number of teeth on the gear you have on the tumbler and divide it by the number of teeth on the gear on the lead screw. If this ratio is the same as the ratio for the gears that were there originally then all will work properly. If it is different you are in trouble. That's all there is too it.

Cheers
Steve