CP gear cutters

[vintagengineerParticipant @vintagengineer]

Anyone know of a supplier for 1/4 CP gear cutters please?

[Nigel Graham 2Participant @nigelgraham2]

Have you tried looking by DP not CP?

That 1/4CP you use suggests your intended gear is of inch dimensions so starting there:

Gears and their cutters are normally designated by Diametral Pitch (DP, for inch sizes) and Module (Mod., for metric sizes).

If you need a DP-designated cutter, work out which you need by the pitch and the number of teeth (each cutter will make only a defined range of tooth-count), then search again by DP.

RDG tools sell both DP and Mod cutters, for a start.

As a guide, DP = pi / CP

So your 0.25″ CP gives 12.566.

The DP is normally a nice tidy integer so I think more likely your intended wheel is of 12DP; giving a CP actually of 0.262″.The value if of the number of teeth per inch of Pitch Diameter.

Did you try measuring it by an ordinary caliper across two teeth? That would likely not be very accurate. True pitch measuring needs special techniques or a Gear-tooth Caliper.

Better to use the Outside Diameter and Tooth Number (OD and N), noting that sometimes the tooth one “side” is opposite a gullet but the result should still be an integer:

DP = (N+2) / OD.

So if your intended wheel is to mate with existing ones, measure one of those, count its teeth and apply that formula to verify the DP.

If metric, Mod = 25.4 / DP. (in inches); or PD / N (in mm).

Formulae from:

Law, Ivan. Gears and Gear Cutting; ‘Workshop Practice Series No. 17’ (pub. Special Interest Model Books). TEE Publishing would be my first port of call for this comprehensive series.

NB (1) From that 1/4 you quote, I am assuming throughout your gears are to Inch sizes. Not metric.

 

 

[Nigel Graham 2]

On Nigel Graham 2 Said:

Have you tried looking by DP not CP?

Should we not take the original poster seriously and answer his question?

What is it that leads you to decide that what he has written is incorrect and instead answer a completely different question?

The 1/4″ CP (circular pitch) he uses suggests his intended gear is intended for linear movement of some sort or to mesh, perhaps, with a 4tpi leadscrew (yes I know that a spur gear will not mesh properly with a worm).

[JasonBModerator @jasonb]

There is someone with a selection on e-bay but you would need to look at each one to see if there is a 1/4 circular pitch and then the No you need.

Otherwise rather rare these days so a bit of a problem if you need to run it against existing gears

[vintagengineerParticipant @vintagengineer]

Definitely looking for CP cutters. Different from DP cutters.

[BazyleParticipant @bazyle]

Lots on ebay. Always annoys me that so many of the ones on ebay are CP not DP.. I guess when a company closes down the more canny machinists snaffle the DP cutters for their own workshop and leave teh CPs for the clearance bods.

[Pete RimmerParticipant @peterimmer30576]

A 2 mod cutter is so close to 1/4″ CP as to make no difference at all for a single-tooth-cutting tool. 0.2474″ as opposed to 0.2500″

Your biggest hurdle might be finding the desired pressure angle.

[DC31kParticipant @dc31k]

There is a number 3 one here:

https://www.ebay.co.uk/itm/266222160619

The person with the ‘selection’ (£25 each) does not have any 1/4″ CP listed, but would be worth contacting.

Home and Workshop Machinery would be worth a phone call.

These people could make you one:

Sheffield Cutting Tools Home Page

Someone reported here that the Tap and Die Company had been acquired by another company. They used to list involute cutters but would be expensive.

[HuubParticipant @huub]

Before buying a cutter, I would 3Dprint a gear to see if the module/dp  and pressure angle are correct.

[Michael GilliganParticipant @michaelgilligan61133]

May I just mention an “off-topic” issue, which might deserve investigation by the forum developers ?

The C. R.Tools video in DC31k’s post is covering the text which follows

… I glimpsed it as the page was loading

MichaelG.

[JasonBModerator @jasonb]

Michael, having looked at what is in both of DC31k’s posts I can’t see a video, there is a url link for CR Tools website but all the text in the reply box is what is also being displayed

[JasonB]

On JasonB Said:

Michael, having looked at what is in both of DC31k’s posts I can’t see a video, there is a url link for CR Tools website but all the text in the reply box is what is also being displayed

.

Must be Apple doing it’s cleverness then: rendering the hyperlink.

It’s probably just a ‘slideshow’ … but it certainly obscures some text.

.

.

MichaelG.

.

Edit: __ perhaps the ‘fix’ would be to dis-allow such rendering ?

[Pete RimmerParticipant @peterimmer30576]

One thing to consider: If you’re cutting a CP gear to mesh with a screw then the cutter should be as close as possible to the screw diameter to get the best engagement. If it’s meshing with a 4TPI rack then there’s no issue.

[Neil AParticipant @neila]

I don’t know what equipment the OP has, but has he considered making his own cutter.

On the “Clickspring” Website there are a series of videos on the production of “shop made gear cutters”

There is also a handy programme for calculating the sizes and positioning of the buttons used to produce the approximate profile of the involute. It’s only uses Module and DP inputs, but you can use 12.566 DP as the equivalent input, then you only have to know the pressure angle and number of teeth to get some numbers out.

I know this may not help, but it is interesting to see the processes involved.

Neil

[Author]

Posts