How to increase tightness between splined pieces?

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JohnnyK81
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How to increase tightness between splined pieces?

Post by JohnnyK81 » Thu Jul 30, 2020 1:54 pm

Hi guys,

First post with my new email, as my old email is long gone and my account didn't seem to work (although nobody would recognize my old username, so it's moot. hah!)

Anyways I'm working on a project that involves a bar in torsion, and receiving plate, but unfortunately the closest match I could find (The receiving plate is the existing piece) is a 3/4-36 spline steering shaft. And while it's close, there is a fair bit of play between the two parts.


I cannot find a place to machine the bar with those little splines on it around here (I have tried, believe me.) so 'off the shelf' is what I am forced to try.

Any thoughts on how to "add tightness"? This bar will see approximately 150-200ft-lb of torque, is my best guess. The parts DO catch each other, the spline count is correct, and I know 150-200 lbs it not much, but I would like a fair bit more tighteness.

My two thoughts are, a thick, strong coating (Which I wouldn't attempt if there were dynamic forces involved, but I'm almost thinking it could work in this case? Although I could very well be wrong!)

And my backup plan, which I do not like, is cutting a tiny slit and pushing the receiving plate together and rewelding. But I may lose a spline (And hence, no fitty anymore), or the fitment may be wonky, or I may just blow off a few splines with my weld! (A set screw is not accessible, either)

Any thoughts?

Thanks guys!

Spline Fit.jpg
Spline Fit 2.jpg

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JohnR
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Re: How to increase tightness between splined pieces?

Post by JohnR » Thu Jul 30, 2020 2:57 pm

What is your current clearance between both components?
What is your maximum runout between components ?
What is the maximum rpm that will be seen?

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liveaboard
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Re: How to increase tightness between splined pieces?

Post by liveaboard » Thu Jul 30, 2020 3:48 pm

To me, that looks way, way off. I think you need a different solution.
Here is a shaft and collar I made that is subjected to high torque [an 8 ton hydraulic ram pushes on the lever].
I drilled + tapped, then cut the screw heads on the lathe to fit the drilled holes tightly.
tapping.jpg
pivot plate and lever.jpg
Last edited by liveaboard on Thu Jul 30, 2020 4:16 pm, edited 1 time in total.

John Evans
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Re: How to increase tightness between splined pieces?

Post by John Evans » Thu Jul 30, 2020 3:52 pm

If once assembled there is no slip movement required one of the Loc-tite products may answer. Like the Green sleeve and bearing retainer compound.
www.chaski.com

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Bill Shields
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Re: How to increase tightness between splined pieces?

Post by Bill Shields » Thu Jul 30, 2020 5:22 pm

i think i would pass on the loc-tite for his application since your clearances may be greater than what loc-tite can handle.

The shaft collar will do the job if you have the room to put it in.

Machining splines is an art and very difficult to do for the intermediate (and smaller) size you are dealing with....generally they are broached (internally) using standard sizes.

these are companys that I have used a couple of times.

http://www.avongear.com/

http://www.team-ind.com/

My guess is that it would be cheaper for you to reuse the shaft and make a new holder with a rough pilot bore and let them broach the spline to fit the shaft.
Too many things going on to bother listing them.

JohnnyK81
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Re: How to increase tightness between splined pieces?

Post by JohnnyK81 » Thu Jul 30, 2020 8:25 pm

Thanks for the responses. I will check sizes/clearances accurately and report back.

(JohnR and Liveabroad, there is no RPM or runout. See below. The purposes of these splines is to hold 150lbs-ft, everytime the door is operated (90 degrees, approximately. I suppose for that 90 degrees it would be at approximately 60rpm ballpark).

I can calculate what I 'need' in a spline, but what I can't calculate is if what I have here will handle what I need ( If that makes sense. And unfortunately, this off the shelf component mishmash is my best shot at fabrication.)

There is no RPM for this application. I will be using a torsion spring to replace a torsion bar, so this spline would be seeing the reaction forces to that spring (as mentioned, I believe max 150-200lb-ft). 90 degree of travel.

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mcostello
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Re: How to increase tightness between splined pieces?

Post by mcostello » Thu Jul 30, 2020 8:47 pm

Could You slit the plate and press it a little smaller?

JohnnyK81
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Re: How to increase tightness between splined pieces?

Post by JohnnyK81 » Thu Jul 30, 2020 9:28 pm

That was one of my thoughts but then I'm afraid of 'losing a spline' and them not mating?

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Rich_Carlstedt
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Re: How to increase tightness between splined pieces?

Post by Rich_Carlstedt » Thu Jul 30, 2020 9:45 pm

Lots of questions to ask which can affect the approach
Does it have to be removable ?
Do you want the spline to move linearly when in use ( at all ?)?
Is it for anti-backlash that you want fill
Is it for power transmission
How close alignment is required
How much $$$ do you want to spend ( Is it fix at any cost ie)

Some solutions depending on any of the above
Cadillac version 1.... have a new spline cut $$$
Cadillac version 2....Have the spline "Electroless " Nickel plated ( Chrome will not work ) Called EN ..Thickness to fit $$
Both above will allow a sliding fit

Shop repairs possible without part modification and subject to desired objectives
1.Silver solder the assembly -permanently
2.Tin the surfaces with soft solder and "Broach" the surface - Takes up play and allows movement, but longevity and strength are unknown ?
3.Place female on a flat steel sheet . place heat melt glue in cavity , play flame under sheet to melt glue while placing heated spline into cavity
Glue will extrude upward, providing same cavity filling as Loctite
4. Use Loctite application called "Quick Metal" . It is different than normal Loctite products . You may lube the mating part to allow disassembly
It is made for loose splines
https://www.travers.com/6608482-quick-m ... 5%7CC%3A60

Rich

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NP317
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Re: How to increase tightness between splined pieces?

Post by NP317 » Thu Jul 30, 2020 10:28 pm

If removal is not required, use JB Weld to fill the spaces. Use the slow setting type which is the strongest.

Depending on the material that the female spline plate is made from, consider heating it to red and press it flat to forge it around the male spline (inserted after the heating is done.) The goal it to deform/shrink it to fit the shaft. The setup might be a challenge.
I've seen that done with an hydraulic press to shrink a hole in a heated bar.
RussN

choprboy
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Re: How to increase tightness between splined pieces?

Post by choprboy » Fri Jul 31, 2020 12:49 am

mcostello wrote:
Thu Jul 30, 2020 8:47 pm
Could You slit the plate and press it a little smaller?
I had a similar thought, but slightly different manner. Could you heat shrink the bracket, either by quickly heating to high temp and cooling, or running several weld bead around the circumference of the bore on both side (possibly you could TIG it without any filler). But how much it would shrink would depend on what material the bracket is made from.

I agree with the other comments here though, try to fill the gap with locktite/etc is unlikely to succeed long term.

epanzella
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Re: How to increase tightness between splined pieces?

Post by epanzella » Sat Aug 01, 2020 8:38 am

The female is a simple part. Replace them both with a common spline size.
Ed P
SAVE A COW, EAT A DEER

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