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Form building & dowel pin placement.......


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#1 BambooBeginner

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Posted 03 April 2015 - 09:18 AM

I am planning to make another set of planing forms - the first set I made were done following the Thomas Penrose layout and I have been pretty happy with the forms overall.

 

Reviewing the details to refresh my memory I looked at the Waldron layout which has the dowel pins close to the push/pull bolts rather than centred between them as in the Penrose layout. Sometimes I have noticed a slight binding of the dowel pins when making large adjustments such as setting out the butt side and wondered if the Waldron layout might reduce this at all?

It is not surprising really given that the forms are flexing slightly between stations - and with the pins bang in the middle of the "flex" at times this is what must cause the slight "creaky" binding of the pins.

 

Is there a preference for dowel pin positioning or is it just down to personal preference?

 

The forms I am planning will be at 6 inch centres as I have a lot of old English tapers which are all given at 6 inch centres and figure a second set of forms will reduce the "faffing" involved in interpreting these tapers for 5 inch centre forms.

I also like making stuff so it will be fun as well.

 

Cheers

Steve


As inward love breeds outward talk, The hound some praise, and some the hawk; Some, better pleased with private sport, Use tennis; some a mistress court: But these delights I neither wish Nor envy, while I freely fish.

#2 JW Healy

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Posted 03 April 2015 - 09:54 PM

Steve,

 

When I started, I too made a Penrose planning form but eventually found the limitations caused by to my filing errors, tapping errors, etc. so bought a Bellinger. It too has the dowel pins halfway between the stations. The binding of the dowel pins seems to be likely caused by the kind of minor errors I made.


JW

#3 Galt

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Posted 03 April 2015 - 10:58 PM

Steve,

 

In order for the bars to remain in good planer alignment, the bars and pins must have a snug sliding fit. For there to be no theoretical binding, the bars must move parallel to one another. Since we rarely experience this condition when setting tapers, there will always be some bind in the fit. By placing the pins near the adjusting bolts, the mechanical advantage of the threads will easily overcome the perceived binding.

 

Galt


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#4 BambooBeginner

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Posted 04 April 2015 - 08:37 AM

Steve,

 

When I started, I too made a Penrose planning form but eventually found the limitations caused by to my filing errors, tapping errors, etc. so bought a Bellinger. It too has the dowel pins halfway between the stations. The binding of the dowel pins seems to be likely caused by the kind of minor errors I made.

Hi JW, I would be the first to acknowledge my forms certainly must have errors, but the strips they produce fit together accurately without gaps etc so are good enough for my needs - If only I had the money to afford a set of Bellingers plus shipping to the UK :-)  When I talk about "binding" I suppose I should clarify - what I mean is that I can feel a little gentle resistance when setting a steep taper rather than anything severe. It was only when I looked at the Waldron design that I really thought about the stresses that must be placed on pins between stations in these circumstances and that even pins which are perfectly aligned when the bars are parallel cannot be perfectly aligned when the bars are flexed between stations when set to a taper and therefore subject to extra pressure/wear.

 

Steve,

 

In order for the bars to remain in good planer alignment, the bars and pins must have a snug sliding fit. For there to be no theoretical binding, the bars must move parallel to one another. Since we rarely experience this condition when setting tapers, there will always be some bind in the fit. By placing the pins near the adjusting bolts, the mechanical advantage of the threads will easily overcome the perceived binding.

 

Galt

Hi Galt - yes I think this is what I was realising when comparing the two designs... it seems to make more mechanical sense to place the pins near to the adjusting bolts to keep the bars as close to parallel as possible where the pins go through them. I guess it seems there is no strong convention here as I notice Larry Swearingen is using this design but Bellinger by the sound of it are between stations.

 

I'm probably guilty of over-analysis but thought it was an interesting design difference worth exploring.

Thank you both for your responses.

 

Tight lines

Steve


As inward love breeds outward talk, The hound some praise, and some the hawk; Some, better pleased with private sport, Use tennis; some a mistress court: But these delights I neither wish Nor envy, while I freely fish.

#5 Mike McGuire

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Posted 04 April 2015 - 06:39 PM

You might want to take a look at my approach to filing your groove. It's a considerable improvement over the Penrose approach. Instead of having to recalculate and readjust the spacing as you file to avoid rocking it, I set it just once using a more accurate method than Pernrose's dial caliper, and use an adjustable depth file setup.

 

Mike


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#6 canerodscom

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Posted 05 April 2015 - 07:11 AM

I agree that Mike's method of setting the forms is going to be easier and more accurate.  I first saw the adjustable plane and file tools in Don Schneider's article here:  http://www.bamboorod...ning_forms.html  Don gives a few more details on how to make the tools for cutting the groove.  And though his article focused on making wooden forms, the concepts apply equally as well to making steel forms.

 

Harry


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#7 BambooBeginner

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Posted 05 April 2015 - 02:29 PM

Mike/Harry thanks for your input regarding cutting the groove - I can see how that would be a preferable way to do it, having done it the other way - trying to keep track of which station had been adjusted etc!

 

Harry - does the Don Schneider file plane use the adjuster bolt as a depth stop to set the depth of the file carrier - and is the file carrier free to drop down when the file plane is lifted up? I think it must work that way but it's nice to check with someone who knows.

 

Thanks again

Steve


As inward love breeds outward talk, The hound some praise, and some the hawk; Some, better pleased with private sport, Use tennis; some a mistress court: But these delights I neither wish Nor envy, while I freely fish.

#8 canerodscom

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Posted 06 April 2015 - 07:44 AM

Yes to both questions.  I own one of each tool actually built by Don.  Not sure where they are at the moment.  I have loaned them to folks all over the world and can't remember who borrowed them last... but they have not come home.

 


Harry - does the Don Schneider file plane use the adjuster bolt as a depth stop to set the depth of the file carrier - and is the file carrier free to drop down when the file plane is lifted up? I think it must work that way but it's nice to check with someone who knows.

Harry Boyd
[email protected]
http://www.canerods.com
Heat Treating Fixtures and Ovens
(318)435-5476 home phone
(318)282-1825 Shop/cell phone



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