Thread: Taiwanese bandsaw parts

Originally Posted by Ueee

Thats right Andre, You just make a Worm out of a bit of steel (silver or even MS id you just cutting bronze). Then cut in some flutes, add some relief and cut your gear. The best way i have seen to cut the gear is in the lathe, with a dummy spindle on the cross slide to mount the gear blank on and the hob in the lathe. Does that make sense?
here is a link that may be of some help: Making Wormgears

Ewan

Ewan,

Correct me if I am wrong, but wouldn't you need to be able to cut either a module thread or a DP thread, depending on which system the original worm is, to make a correct cutter to match an existing design of worm wheel which the original worm would mesh with? You would probably need the correct match to preserve correct centre distances and operating speeds.

Who knows what Modulum Threads are? - The Home Shop Machinist & Machinist's Workshop Magazine's BBS has some discussion on module and DP threads.

Some lathes are set up to be able to do this, but a close approximation to Pi/2 can be arrived at on loose change gear lathes by incorporating a 55/35 compound gear in the gear train to allow usable module or DP threads to be cut. The other change gears in the train would need to be calculated for the Mod or DP thread being cut. Don't forget, too, that many worms have multi-start threads. Also, commercial worm threads are not usually 55 or 60 degrees like a normal tap, but something closer to an Acme thread shape.

Frank.

Originally Posted by franco

Ewan,

Correct me if I am wrong, but wouldn't you need to be able to cut either a module thread or a DP thread, depending on which system the original worm is, to make a correct cutter to match an existing design of worm wheel which the original worm would mesh with? You would probably need the correct match to preserve correct centre distances and operating speeds.

Who knows what Modulum Threads are? - The Home Shop Machinist & Machinist's Workshop Magazine's BBS has some discussion on module and DP threads.

Some lathes are set up to be able to do this, but a close approximation to Pi/2 can be arrived at on loose change gear lathes by incorporating a 55/35 compound gear in the gear train to allow usable module or DP threads to be cut. The other change gears in the train would need to be calculated for the Mod or DP thread being cut. Don't forget, too, that many worms have multi-start threads.

Frank.

Yes you are right Frank, but i figured that Andre would be able to work out the pitch required and gear his machine to suit. I cannot remember of hand what lathe he has, but he also has access to lathes at his work that may cut module and DP worms. Looking at the gear's angle i would guess it to be single lead, although if it is a twin then all the more to learn.

Ewan

I am unsure of how to measure the worm or the gear.I don't have a lathe that can cut module threads,I was planing to make a new worm and gear with a 14.5 degree angle and cut to the closest tpi I can get on my lathe.

Originally Posted by welder

I am unsure of how to measure the worm or the gear.I don't have a lathe that can cut module threads,I was planing to make a new worm and gear with a 14.5 degree angle and cut to the closest tpi I can get on my lathe.

Andre,

This chart might help to identify the Mod or DP thread of your worm:
Pitch conversion charts

If it is 1 mod (single start) it will have a pitch of 3.1416 mm, or 0.1237 in. = 8.084 TPI
If it is 0.8 mod (single start) pitch will be 2.5133 mm or 0.1047 in. = 10.11 TPI, and so on if I am reading the chart correctly.

Unfortunately there are not many mod or DP threads which are reasonably close to common metric pitches or TPI numbers. In the case of mod 1 above you might get away with 8 TPI, and in the 0.8 mod example with 2.5 mm pitch or 10 TPI for a while, but they would not really mesh correctly, and, I suspect, would not last long in use - just my opinion - someone else with more experience with worm drives might like to comment.

Regards,

Frank.

Well I finally fixed the band saw.I rang Hare and Forbes and they had a replacment gear instock for $65 so I bought it. I also had to remake the drive shaft the gear goes on and that took 2 attempts to get right as I had to wind out the compound to compensate for the taper the lathe turns.I now have everything installed and the saw cuts again

Good to see you got it sorted.

I've been thinking about buying a small horizontal metal bandsaw for quite a while now. I have a need to cut quite a bit of light gauge square section steel post soon.

What are people's thoughts on these units and what to watch out for? Eg. is gearbox trouble common ?

I considered a second hand Paramount Browns one on Gumtree for $200 a while back (near new) but was too slow making my mind up.

Rob