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rack & pinion help

Hi all. In need of some help. To preface - I'm very, very stupid and I basically need babied for this. If that is not something you want to do, I suggest passing this thread by.

I have a rack and pinion that seems to be very non-standard.

Round rack.

~12mm OD.

Pinion gear

0.8750" OD

30 teeth

~.08" pitch

69mm travel on rack for full revolution of gear.

Pressure angle presumably 20*

Cannot find this for the life of me, and there also doesn't seem to be a lot of literature about rack and pinions online?

I can resign around this within a decent range.

Rack length is 269mm. Sorry for mixing metric and imperial btw.

Can use .5" OD rack because I presume it's more easily sourced. What other info am I missing to find the proper rack?

Thanks in advance. Any input is much appreciated
>>
>I have a rack and pinion that seems to be very non-standard.
Where, what is it in, and can you post a pic of what you actually have instead of stock imagery

>Cannot find this for the life of me, and there also doesn't seem to be a lot of literature about rack and pinions online?
Have you tried Machinery's Handbook?
>>
>>1665626
First off, gear racks are mostly bought from suppliers such as this one.

https://shop.sdp-si.com/catalog?cid=p502

Even the selection of gears and gear racks from large suppliers like McMaster-Carr will be pretty limited. Find the gear rack in the size, pressure angle, and length relevant to what you want to do. Then source a gear with the same pressure angle and pitch diameter that you want for the load and travel rate required.
>Round rack.
Do you mean a round driveshaft with a gear rack cut into it? Those aren't that common in the first place. And you're asking for a metric OD on one and then imperial measurements on the pinion gear.

>~.08" pitch
That's not a valid pitch number. See diagram
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>>1665626
stop panicking. the part is standard.
>>
It's close to their mod0.8, but when using their provided measurements, it's off by about .5mm

Still think that might be it?
>>
>>1665766
no. what the fuck part of "5 teeth in a cm" "2mm between teeth" looks like mod0.8!? you imbecile, did you hold it up against the picture ON YOUR FUCKING SCREEN
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>>1665839
please dont talk to me that way.
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>>1665839
Bruh this is op. Why are you on diy if you're so angry.

I printed it out and compared. The CLOSEST thing on this list is mod0.8

Tell me what I'm doing wrong?
>>
>>1665917
Does the scale in the lower right-hand corner match a ruler?
>>
>>1665921


Nearly. Close to 95% I think, lines were a bit thick. I checked ratios tho. It's about 10% off mod0.8 if my calipers are correct. I'm planning on just calling them in the morning
>>
>>1665703


The part is close to mod 0.8 and nothing else, but it doesn't match up to mod 0.8

Confused on why you're telling me it's standard. Am I missing something?
>>
pls help
>>
Do you need a replacement rack? What's this even for, what product did this assembly come out of?
I would assume you want a replacement but your original post is and you said you "need babied" for this one so I don't know.
>>
>>1666216

It's just a pre-existing custom assembly that has no documentation. I'm tasked with creating documentation/a BOM for it so that it can be re-created.

I do in fact want a replacement rack and I'm trying to get exactly what we have, but it seems ever so slightly non-standard (was probably made in Britain from sketchy parts suppliers)
>>
>>1666490
I'd bring the rack and pinion into a machine shop and ask if they could help with identifying the tooth pitch.
Looks like a custom machined part to me since it's roundish and has a few flats machined into it. This means just buying any rack from a hardware supplier won't be what you need, it's gotta be machined.
Does the tooth pitch have to be exact? If you're replacing parts why not also replace the spur gear?



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