finding involute gear cutter

[vic neweyParticipant @vicnewey60017]

Looking for 22 Dp number 8 involute cutter, seems they are hard to find, bore is 1/4″ and fits my MT1 drilling spindle.

[DC31kParticipant @dc31k]

Please say what pressure angle you require.

I think you will struggle to find one with that small bore.

RDG and eBay have 14.5 PA with 1″ bore.

[HuubParticipant @huub]

If it is for a single gear, try making a gear cutter (fly cutter). For this you only need a milling machine.  There are more examples on YouTube.

A number 8 cutter is intended for 12..13 tooth gear, quit small.
22 DP is about module 1.155, a non standard value.
Check the dimensions of the gear to be sure it is 22 DP.
Besides the DP you also need to know the pressure angle of the gear. Looking at the cutter it probably is 20°. Another standard value could be 14.5°
Use a CAD system (FreeCAD) and draw such a gear. Print it out and check if it matches the gear you want to make.

These type of gear cutters can be resharpened. Just grind the flat cutting edge a bit and they perform as new.

 

edit:

That number 8 gear cutter could also be for a 135 tooth gear, depending on the table you use.

[bernard towersParticipant @bernardtowers37738]

If its an older cutter its more likely to be 14.5 deg, single tooth (fly cutter) is probably the way to go deppending on howmany you need to make.

[Huub]

On Huub Said:

That number 8 gear cutter could also be for a 135 tooth gear, depending on the table you use.

It only depends upon whether the cutter is for imperial or metric. For imperial (DP) gears the number 8 cutter is used for 12 or 13 teeth. For metric (module) gears the cutters are numbered the other way round, so the number 8 cutter is for 135 teeth to a rack.

Julie

[vic neweyParticipant @vicnewey60017]

Thanks for the replies, I am just making a copies of a small gear on my vintage lathe as a project having not tried cutting gears before.
I have cut two in Aluminium that work perfectly. the gear connects to a worm to power the cross-slide. However I wanted to make one in steel as is the original but the cutter is now worn although it cuts aluminium with ease. The lathe has a dividing attachment so it’s all self contained

 

[DC31kParticipant @dc31k]

May I offer an observation?

If you count the visible teeth in the photograph and extrapolate to the full perimeter, it seems to total more than 13.

Clearly, the only person to give a definitive answer to the required tooth count is the OP, but it may be that a number 8 cutter is not the correct one.

[JasonBModerator @jasonb]

I’m also thinking the setup is wrong for a worm wheel.

The steel one has angled teeth and I would also hazard a guess they are cut with a hobbing action. Running a straight cut steel gear against your old worm may not do it a lot off good

 

Looks like the cutter spindle may be set at an angle but is being fed along the bed as I can’t see any sign of a compound slide. May even be why it is not cutting steel as the cutter is being fed slightly sideways.

[Dave HalfordParticipant @davehalford22513]

According to “Lathes” Pittler was 14.5 deg PA and most of the worms are multi start as seen on your shelf.

If the cutter is set straight along the bed it should cut steel, feeding just hard enough to produce chips and produce a straight cut spur gear for mating to other straight cut gears. Don’t mix these with the ones from your lathe.

[JasonB]

On JasonB Said:

Looks like the cutter spindle may be set at an angle but is being fed along the bed…

I do not know how sophisticated the Pittler is, but if the carriage feed were via the leadscrew AND the leadscrew is appropriately geared to the spindle*, the proper realtive motion necessary for a helical gear could be possible.

* in terms of screwcutting, it would be a super coarse pitch, with a tiny amount of spindle rotation producing a huge amount of longitudinal movement, hence why the leadscrew needs to be the driver (c.f. cutting the thread on a Quorn column).

[DC31k]

On DC31k Said:

On JasonB Said:

Looks like the cutter spindle may be set at an angle but is being fed along the bed…

I do not know how sophisticated the Pittler is, but if the carriage feed were via the leadscrew AND the leadscrew is appropriately geared to the spindle*, the proper realtive motion necessary for a helical gear could be possible.

* in terms of screwcutting, it would be a super coarse pitch, with a tiny amount of spindle rotation producing a huge amount of longitudinal movement, hence why the leadscrew needs to be the driver (c.f. cutting the thread on a Quorn column).

The machine is capable of a multitude of different tasks, over 200 in fact even though it’s dated to 1894. I am simply trying out gear cutting methods and in this photo with the spindle on top the angle can be adjusted and advanced by the cross slide. See the catalogue image of what this machine is capable of

I have an original equipment heavy drum  type cutter attachment I featured in another post this can swivel the cutter at any angle from horizontal to vertical and has it’s own slide for advancement
However I only have a number of plain cutters/ slitting saws etc and not prepared to spend £25 upwards for a cutter just to play around with.

I know I asked where I might find a cutter to fit the small drill spindle but will persevere with the cutter I have and make another one in aluminium.

[vic neweyParticipant @vicnewey60017]

As a point of interest this machine is able to cut any of the examples in this catalogue image, with the correct cutters of course

[John HaineParticipant @johnhaine32865]

Home

Might sharpen you cutter

[vic neweyParticipant @vicnewey60017]

I’ve done another one which is better than the original and it works perfectly.  I repositioned the spindle and set it on the top of the cross slide and advanced the tool via it’s handle, the slide being slightly askew from the main lathe bed

The previous owner made the little gear as the original was lost but had nothing to copy, I note that the teeth are quite narrow at the tip although the worm is coarse. I made a very short video of me testing it using a drill.
Normally it works off a universal joint but as I have the lathe set up for indexing the headstock drive belt is slackened off.

I am now going to try making one in Bronze as I still think steel is going to struggle. The only problem with Aluminium is the grub screw on such a short thread, the gear itself has 20 teeth although I am told the cutter is  for 12-13 tpi but nevertheless it works like a dream

https://youtu.be/1DqqcUi8DRo?si=fg5E8JE5LjBgUdjV

 

[HuubParticipant @huub]

The only problem with Aluminium is the grub screw on such a short thread

Make the shaft thicker or use a smaller grub screw having a finer pitch.
Seem to work OK.

[Huub]

On Huub Said:

The only problem with Aluminium is the grub screw on such a short thread

Make the shaft thicker or use a smaller grub screw having a finer pitch.
Seem to work OK.

 

Barely enough room to make it thicker though as it’s level with the bottom of the teeth. l think l will make one in Bronze as it will be easier on the cutter than steel and l have a suitable piece to use

[John HaineParticipant @johnhaine32865]

As I suggested above, you might ask PP Thornton if they could sharpen your cutter as it’s quite small.  Though they generally sharpen cycloidal cutters, either type only needs grinding on the front face of the teeth so the tooth shape is irrelevant.

[Michael GilliganParticipant @michaelgilligan61133]

FWIW

The mighty Google directed me to this page:

Making spur gears using a dividing head

See the notes on Brown & Sharpe cutters for small gears

… and also to this useful video:

.

MichaelG.

[BazyleParticipant @bazyle]

It should be possible to make a simple guide in hard plastic that enables you to touch up the teeth with a diamond file. To avoid clogging the file design the guide so that the guide faces bear on the file ends which are wrapped in Sellotape.
3D printing for the guide comes to mind.

[Michael Gilligan]

On Michael Gilligan Said:

FWIW

The mighty Google directed me to this page:

Making spur gears using a dividing head

See the notes on Brown & Sharpe cutters for small gears

… and also to this useful video:

.

MichaelG.

An interesting video for sure, it explains things very clearly. The problem is that with my current set up milling spindle the bore is only 1/4″ I have an original equipment drilling spindle that is much more robust but it only takes collets. My other original equipment multi angle drum type milling attachment with a geared head and it’s own cross slide takes 25mm bore which cutters are around £25 each from RDG so just to experiment with gear cutting it’s a bit much unless I had something I actually needed to make, repair or replace something missing etc.

I’m not sure if sending the cutter off for sharpening is worthwhile either as it will probably cost half the price of a new 1″ cutter so I am going to look for a more reasonable 25mm cutter

 

[JuddyParticipant @juddy]

Try Home and workshop for cutters: https://www.homeandworkshop.co.uk/stock-item/dp-gear-cutters/246/

 

[Juddy]

On Juddy Said:

Try Home and workshop for cutters: https://www.homeandworkshop.co.uk/stock-item/dp-gear-cutters/246/

 

They have a huge selection there ! but no mention of bore size as I can see on RDG there are 22mm and 16mm as well as 1″
Those are £20 each and not sure if VAT is included so with shipping they would end up similar to RDG £25 inc post

[Michael GilliganParticipant @michaelgilligan61133]

I suspect that you need to make a difficult choice, Vic

The [original Pittler-supplied?] cutter has a 1/4” bore, but Horological cutters have 7mm … so not only is it a rare item but it might be difficult to get professionally sharpened … £££

I wish you success with whatever approach you take.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

I suspect that you need to make a difficult choice, Vic

The [original Pittler-supplied?] cutter has a 1/4” bore, but Horological cutters have 7mm … so not only is it a rare item but it might be difficult to get professionally sharpened … £££

I wish you success with whatever approach you take.

MichaelG.

Thanks Michael, the one I just used was made by Potts, UK 1930’s era so not a Pittler one, I have several cutters with 1/4″ bore and a number of MT1 mandrels to fit them, they came with another smaller Pittler lathe I have. Not really a problem as I already pointed out I am just enjoying trying out some of the things the machine is capable of so now will try something different I think

[Michael GilliganParticipant @michaelgilligan61133]

Just for the record … here is Brown’s patent:

https://worldwide.espacenet.com/patent/search?q=pn%3DUS45294A

MichaelG.

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