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Tool Tip #19: Hollow Chisel Motriser HCM Test run and Results

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Blog entry by robscastle posted 07-01-2015 06:20 AM 901 reads 0 times favorited 7 comments Add to Favorites Watch
« Part 18: Hollow Chisel Mortiser HCM Tune up More Preparation work Part 19 of Tool Tip series Part 20: Hollow Chisel Mortiser Tune Up Pt3 »

I conducted some tests using similar setup conditions

A piece of softwood and a piece of hardwod was used,
The gap between the auger and Hollow Chisel (HC) was 2.5mm in each test
A test instrument for automotive testing was used to measure temperature with a K type thermocouple
A luggage scale and chain was used for the force tests.

The test results are approximate only and are subject to human variations but I did my best to replicate identical conditions as much as possible.

So here we go.

Test 1 is with an unlapped and unpolished 3/8 HC
Test 2 is with a lapped and polished 3/8 HC

I used my phone to take the pictures as I ran the tests so they are all raw data shots so please bear with the blurring and framing.

Test 1 softwood

Two mortises were cut

The effort in kgs to do this varied from 9.5 kgs to 12 kgs
The temperature at the tip of the HC at completion was about 67deg C





Test 2 Softwood same material

Two mortices were cut

The effort in kgs to do this varied from 9.2 to 9.7 kgs
The temperature at the tip of the HC at completion was about 50deg C



Test 1 Hardwood

Only one mortise was completly cut due to the HC blocking with chips, To remove the chisel and reset everything was not considered worthwile

The effort in kgs to do this varied from 14.2 to 16 kgs
The temperature at the tip of the HC at completion of only one complete mortice was about 70.4 deg C



Test 2 Hardwood same material

Two mortises were cut

The effort in kgs to do this varied from 15.8 kgs to 17.4 kgs
The temperature at the tip of the HC at completion was about 59 deg C



Observations:

The effort to cut the mortices appeared to be less (by feel alone) however the results for hardwood show differently.
The effort to withdraw the HC was certainly improved to the extent no jambing in both materials at all occured after lapping the sides.

Apperance of the finished mortise.
As the mortices were individual cuts only this was not assessed.
Temperature: There is a measurable reduction in temperature after lapping.

Conclusion:

Was it all worthwile? I would say for somebody who does mortises on a regular basis most certainly.
For those of us which the use is less fequent I would also say yes, conditionally on how much pride you take in your work and maintenance of your tools.

I should try and get Mathias to rig up some proper test rigs to accurately validate the work, he would possibly get a real kick out of it too!

Enjoy

-- Regards Robert



7 comments so far

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1833 days


#1 posted 07-01-2015 01:21 PM

Very cool write-up. I’m in the process of sharpening/polishing my hollow chisels and found it an interesting read. Did you use a cone to sharpen the one chisel before lapping/polishing? If not, I’d be curious to know how that effects the results.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View Ocelot's profile

Ocelot

1470 posts in 2102 days


#2 posted 07-01-2015 03:27 PM

Good work there! Numbers rather than just opinions.

??? But what is an “HC”?

-Paul

View BinghamtonEd's profile

BinghamtonEd

2281 posts in 1833 days


#3 posted 07-01-2015 03:36 PM


??? But what is an “HC”?

Hollow chisel.

-- - The mightiest oak in the forest is just a little nut that held its ground.

View pintodeluxe's profile

pintodeluxe

4855 posts in 2277 days


#4 posted 07-01-2015 05:24 PM

I really enjoyed reading this. Especially with the large chisels (I have a 3/4” chisel) they need to be razor sharp on hardwoods.
I wonder how a sharpening cone would change your findings.
I use Lee Valley sharpening cones, which sell for $11 per pair. The set includes a coarse and fine cone.
http://www.leevalley.com/US/wood/page.aspx?p=41702&cat=1,180,42240,53317,41702

Thanks for posting this.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View stefang's profile

stefang

15512 posts in 2798 days


#5 posted 07-01-2015 05:55 PM

Great test and write-up Rob. Those LV cones look like the way to go for sharpening, so easy and quick.

-- Mike, an American living in Norway.

View robscastle's profile

robscastle

3392 posts in 1668 days


#6 posted 07-01-2015 09:26 PM

Thanks fellow LJs, some replies to address the questions:

BinghamtonEd

Ed
Yes a non diamond cone was used to sharpen all but the 5/8 and the “As bought” 3/8 tested in the unlapped condition.
It will get the same workover soon.

I need to add a Supplementary Information blog to the series as there is more interesting (if you have a HCM) to come.

Ocelot

Paul
When I decided to try and share the information I wondered just how I could provide any creditability to my findings.
So that is where the odd pieces of test equipment came into play.
Imagine if there were no photos at all, the results would be challengable to say the least. Its very crude but shows visual evidence to some extent.

I see Ed has provided the answer to my unvalidated abbreviations. I have also edited the text to explain what HC referes to in the first instance. Sorry about that, I sit here writing info and blissfully aware of what I am “on about” neglecting to consider that others may well not know exactly what I am thinking, is stems from time in the ARMY and their excessive use of Jargon, i.e. M60 for instance.

It can refer to a mine, a Tank, a machine Gun and an electric gatling gun, That I know of would you believe!!

pintodeluxe

Willie
I will have to see if Leevalley will ship to Australia as my attempts to locate a diamond cone here has been unsussesfull to date. I do have a “countersink type sharpener, and again its the addition information I need to add to complete the series.

stefang

Mike
Thanks for the comments, and agree locating a stone is certainly worthwile and an ongoing activity

-- Regards Robert

View Ocelot's profile

Ocelot

1470 posts in 2102 days


#7 posted 07-02-2015 03:44 PM


??? But what is an “HC”?

Hollow chisel.

- BinghamtonEd

Thanks. I was going to guess “holddown clamp”.

-Paul

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