Rack, pinion and gears.

Hi there

Maybe it’s not related to that forum but, alas,

I need to build a machine that revolve steel rod six times and at the same time advance it 9mm per one all revolution.

I sketch the machine but can’t put my head to calculate the gear.

I use hand drill for the rod revolving and I know that if I revolve the drill handle one all revelation and 5/8 of an all revelation the rod that attached to the drill will revolve six times.

I want to attach a Rack and pinion to it (to the drill gear) that will advance to rod: 6 x 9mm = 54mm.

It is to making screws.

Regards,

Ronen

Sorry, the question doesn't seem to make sense. Do you want 9mm advance per rev, or with 6 revs? In short, do you want to make a pitch of 1.5mm or 9mm? What do 1 and 5/8 have to do with it?

Ronen

just to confirm

do you want 9mm advance for 6 revolutions? Or 9mm advance per 1 revolution?

This.^^^^^^

For a rack and pinion to give 9mm travel per one revolution of the gear means that the PCD (Pitch Circle Diameter) of the gear is 9/pi = 2.86mm. That is a very small gear! Because you need 9mm of rack movement per revolution, it also means that the gear is not standard, so you would have to make the gear yourself, or pay a lot of money for somebody to make it for you.

You are looking at something like 0,2 Module (or 120DP Imperial) gears, with a non-standard PCD.

Good luck!

.

Taking this gently ... I think Ronen has a typical hand-drill with bevel gearing:

1 & 5/8 turns produces 6 revolutions of the chuck.

MichaelG.

.

Edit: Just as an aside ... this page features some unusual examples:

https://www.lowtechmagazine.com/2010/12/hand-powered-drilling-tools-and-machines.html

Edited By Michael Gilligan on 06/11/2020 10:58:05

It seems like you need to cut a thread of 9mm pitch.

Do you have access to a lathe, Ronen?

Martin.

Edited By blowlamp on 06/11/2020 10:49:45

Ronen needs to count the teeth on his drill's gear wheels to find the ratio.

Counted mine expecting a useful ratio and it is not. 56 teeth on the big wheel drive a 15 toothed gear . My hand-drill's ratio is a weird 56:15, I guess because the exact ratio on a drill doesn't matter. Propbably the designer goes for a decently strong pinion (15 teeth), and calculates a gear for the hand-crank that gives about 4:1 in the space available. One of the two gears is given an odd number of teeth to distribute wear.

So Ronen's plan to use a hand drill to cut a metric pitch may be too difficult. The hand-drill ratio is unhelpful compared with lathe change gears, The lathe's gears are mathematically chosen to produce screw-cutting ratios.

If I wanted to make a screwcutting machine, I'd look at something like an Electronic Leadscrew, but these don't appeal to the mechanically minded. Designing a gear based machine, I'd start from the cutting end, with a metric lead-screw rather than a rack (see Nigel's post for the reason), and calculate the gear ratio needed to synchronise cutter and job.

Although the sums are easier starting from the cutter end, gear ratio calculations make my head hurt! Ronen finds this difficult because it is!

Dave

I would go with a lead screw rather than a rack then all axis will be in the same alignment. Keeping it very basic if you use M10 x 1.5mm threaded rod as your lead screw you then just need a gear with six times as many teeth on the rotating work as you do on the leadscrew. 6 x 1.5 = 9mm .Toothed belt and pullies would also work instead of gears.

You could do it with a beam to lift the parts out of their initial location and advance the beam, then lower it. Or as has been said a helical thread form to advance, pitch doesn’t matter just a number of turns to advance distance. Or as initial question create a gear reduction to give required movement on rack.

9mm pitch screw the low tech way. Used for a long time to make the screw thread on presses for olive oil, wine, cider etc. Thread was marked on the wood then carved away as required to create the screw. For a 9mm pitch screw in steel I would be looking at thread milling, not an easy task to set a beginner trying to make something on the cheap.

Martin C

Edited By Martin Connelly on 06/11/2020 13:57:14

Cutting a 9 mm pitch thread is likely to pose a bit of a problem.

With a lathe with a 3 mm pitch Leadscrew, it will be rotating three times faster than the chuck, and so place quite a load on the gear train. Torque required at the cutting tool will be three times greater at the Mandrel.

Howard

For similar situations, it's usual to power the leadscrew and let the spindle follow.

Martin.

Hi everybody

Thanks so much for your reply, much appreciated.

I think I miss lead you somewhat. What I need is that:

I need to make a six revolution cork screw from 3mm music wire with 2.5mm inside diameter. It is for making rustic wine cork screw opener.

The Idea is attaching 2.5mm rod to hand drill and bends the wire around it six times. Now I have found that if I turn the drill handle 13/8 of revolution it will revolve the drill head six times. The trick is to advancing the wire while it revolves around the 2.5mm fixed rod, in steady travel distance. The pitch of the screw that I need is 9mm.

So I thought that I need to attach a pinion & rack mechanism to the drill and the rack will push the music wire in constant travel speed to give me the pitch I need.

I don’t know how to calculate the dimension of the P&R that revolves by the motion of the drill, so it will travel in the speed I needed.

Ideally I would like to make it on my lathe but too old to do the gears train calculation to give me screw / spring of 9mm pitch with 3mm wire and 2.5mm inside diameter.

Attached two photos that might help to understand what I am up to, the primitive way.

Thanks

Ronen

Ronen,

A simple solution is often the best. This I think will do what you want.

Wind a tight coil on your drill, don't worry about the spacing. Put on at least six turns, a few more won't matter. Then stretch the coil you have made to give you the pitch you are seeking.

Regards Brian

I applaud the shop-made approach but believe that, if expedient, it is possible to buy these "pigtails" ready made from firms dealing in turner's supplies.

As Brian said, keep it simple. It will just need a slightly larger diameter rod than the Ø2.5mm of the finished corkscrew.

Martin C

Thanks guys.

I think I will go to the simple / primitive approach and will give a go to the hand winding machine.

However to coil it tight and then pull it, pose a problem, as because its diameter (3mm) I sort of need to do it while it’s red hot and that make it difficult to evenly space the pitch.

Ronen

Hello again Ronen,

3 mm diameter music wire is pretty tough to bend anyway but might I suggest you wind the coil using a square bar with a 3.2 mm hole through it held in the lathe toolpost so that you can tension the wind, running the wire through a very hot flame immediately after the tool to get the wire red hot as you wind it on.

If you have a hand winding handle in the headstock spindle you can control the pace of operations and set up gearing as in screwcutting to give you a tight coil to keep the coils together

That way you can make a tight coil and then stretch it after winding to obtain your 9 mm pitch.

Regards Brian

Thanks Brian

And the rest of you guys. it is always plesent to post a Q on that forum.

Ronen