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Powder Coating Experiment (Calgary)

YYCHM

YYCHM

(Craig)
Premium Member
Well..... I'm still chasing the down feed slop in my mini-mill.

Seems the mesh between the down feed rack, and the rack pinion gear are the biggest culprits, followed by the helical gear and handle seat mesh. I want to see if a liberal application of powder coating to those parts tightens things up.

As such, I need a volunteer with a powder coating gun and oven big enough to accommodate the 13.5" long rack. I'll supply the paint.

Any takers?
 
H

historicalarms

Ultra Member
You already know where I live...and I've got both, a gun & a full sized kitchen range in the shop to use for PC.

that being said I'm not convinced that PC is a solution to your problem Craig. PC is tough for a single use situation such as what I use it for (bullet coating) but I think the constant pressure and re-use exerted in your application would quickly erode it down to nothing.

I think a better solution might be a machine shop that has iron filings that they blow into a torch flame directed at a metal object that needs a few thou build-up instead of a much more aggressive arc build-up.
 
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Tom O

Ultra Member
Couldn’t you shim them to fit? I would think that powdercoating would be a temporary fix at best. I have some shim stock and my sons powdercoating gun we haven’t fired up yet.
 
YYCHM

YYCHM

(Craig)
Premium Member
I agree that PCing would probably just end up being a temporary fix.

This is my niggle.

In order to raise the tool off the work piece requires a full 0.055" reversal of the fine feed dial. That's almost a full turn.

Today I shimmed the gear rack out 0.02" and that reduced the play to 0.04" A good 0.02 of that is the mesh between the helical gear and handle seat teeth. I can actually poke the tip of a x-acto blade into the gap present between the teeth of helical gear and handle seat teeth, so there should be some gain by tightening that up. One solution offered up on the web is to peen the tooth faces thus raising the metal some. That's where PCing the teeth came to mind and I attempted that once already but with not having a PC gun the coverage was poor.

MESH.JPG


I would be happy getting this down to 0.02".

I'm open to suggestions.
 
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Tom O

Ultra Member
Could you wrap a piece of shim over the cog tightening it up? Or perhaps make another?
Or a dab of liquid steel when fitting?
 
P

PeterT

Ultra Member
Premium Member
Is the issue you are trying to solve basically annoyance with backlash, or is the spindle floating & you cant hold a depth setting milling? My RF-45 mill down feed was reasonably tight & smooth but the depth indicator was completely out to lunch. I attached various DRO's over the years, least expensive of which was a re purposed digital vernier. As long as I locked the spindle during milling it held fine was reasonably accurate for progressive depth cuts. Even in drill press mode the backlash will taken up one way or another when the cogs mate once it sees resistance from the work, as long as depth can be zeroed & measured with some independent indicator.

What is the purpose of the cogs to begin with do you think? I wonder why it couldn't be a single slot keyway for example?
 
YYCHM

YYCHM

(Craig)
Premium Member
Spent the entire afternoon analyzing this thing.

0.015" can be attributed to the rack and pinion mesh.

0.015" can be attributed to the worm gear and helical gear mesh.

0.01" can be attributed to the helical gear and handle seat mesh.

Member janger has offered to PC for me, so I think I will attempt coating the handle seat-helical gear-worm gear and see where that takes me.

Got nothing to lose by trying.

Just need to find the time to T up with john now.
 
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historicalarms

Ultra Member
I would try the liquid steel suggestion , JB weld comes to mind or, I think Loctite sells a product to repair splines & shafts that have wore loose.

I would clean one of the gear bodies very clean of anything other than very bare metal and very lightly cover the other gear with a release agent ( I have use Johnsons furniture wax ), smear a liberal amount of whatever compound you choose on the clean gear and carefully join the two pieces, metal to metal on one gear face and metal to compound on the other.
 
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