Straightedge V-way scraping

J

jshaugjord

Active User
Registered
Joined
Dec 26, 2012
Messages
63
Hi again guys,

I though it might be worth making a thread on the scraping of my friends straigthedge (will use this later in my milling machine resto project if he agrees, is not impatient..).

It was bought at an auction in Denmark and looked bot rusty and.. well, not good.
After a good clean-up I blued up to test and found it to be in need of attention.. 2 surfaces are also warped
There is a casting error on the "main" flat side, so I have used the surface for scraping training. Now, I will have to finish her up, though.

One thing I asked Richard of (this was prior to me taking his class, if I remember correctly) was if the angled section should be scraped 100% exact to the flat side (be it 40, 45, 50 or 60 degrees), so that it could be used into dovetails. If I understood him correctly, this was not neccessary, as it seldom is used this way. Also, dovetails are made to different angles.. Now, at this stage, there as been other threads on the topic, and an excellent YouTube video, also showing pull scraping.

One thing I learnt from this camelback scraping setup is that it is very important to have a sturdy base/mounting (pretty obvious!). Trying to use the power scraper, not having the casting bolted down or rigidly mounted (there is quite hefty weight difference to the milling machine casting, for which this is not a problem..) WILL produce chatter. This is induced because of the vibration and the harmonics you get between moving parts/table/casting etc.

So, another video
http://www.youtube.com/watch?v=TsQrri9Y4bw&feature=youtu.be

Will update you the progress.
 
First of all I want to thank you jan for sharing this to all. Like I teach "remove all ridges first" as you show on the top and it looks like a long ridge or burr. The small defect in the top left won't hurt anything. Just let it alone, or if you really want it to look better, you can mill it out and mach cast iron insert and use a press fit or fill it with aluminum plastic steel epoxy. The aluminum shines up like iron and the plastic steel gets black. but if it was me I would let it alone. Holding the straight edge is really important as you said or it jumps around. Remember we had the JoHansen 2 screw wood clamps we used in the class? his would be a great place to use 2 on the ends and setting on a wood table. You could also use 2 drill or mill vises. You could screw bolt or C-Clamp them down to the table. I would also scrape the angle side. But when you scrape them you will need to get the flat close ..say 12 points and flat to with-in .0002" then scrape the angle side to get it close, then hand it up with a rope fromthe ceiling and hit the straight-edge with a soft blow hammer or a wood club to"ring" it. It will vibrate like a tuning fork and this is a stress relieve method. The angle is unimportant as all machines have different angle, soyou tip it into the angle when rubbing it on the dovetail of the way. I sometimes use an old mill table that i tip backward about 45 deg and block it with wood and use the T slots and T bolts to fasten it to the table so it is super tight and won'y vibrate if you used it on V-ed out 4" x 4"s. The recent class I taught at Busch Precision that had a rotating angle table we mounted their straight edges to when we scraped the angle. I would also not try to get the back of the casting parallel to the angle. a waste of time, unless you want to for the fun of it. I would probaly ring the straight edge now as it may have been sitting for years and developed a twist. You can let it set on your big granite table for temp storage, but I would drill and tap a hole in one end and hang it up. Locate the center of weight on the end and that's where you drill your hole for an eye bolt. Rich

PS: Remember when i showed the class "tip" scraping? The top of your straight edge would be a great place to use it. The left end looks pretty even coverage from front to back and the right side is covering about 7/8 of the surface. You can scrpethe right side and eave the left side alone and as you scrape the one end it will tip in the middle. Less scraping to fill in the middle. Then whe it's flat or the middle comes in, then scrape both sides to get your bearing. The straight edge should be scraped .00005" flat nessand 45 to 42 PPI. or 40 on average. You can use it with only 20 ppi, but will need to be scraped more often.
 
I am behind on writing on the work progress, but managed to put together some more
(Seems a little narcissistic this "show-off", but the idea of this is of course to show other what an amateur like me is doing and for others hopefully to pick up some ideas, leave constructive comments/make corrections on my efforts so I can improve etc. I hope the videos are OK enough, but pls. give me some feedback if needed.. I won't mind! As long as you keep the the subject, not suggesting to hire a model to step in for "the old guy". Ha..ha..)

The camelback flat surface was high on the ends, one end having more contact than the other. You may get a flat surface by doing both ends, but since I learnt that there was no need for alignment (the 2 or 3 sides don't need to be parallel), I decided to tip scrape, because this should produce a flat surface faster/easier. My efforts on explaining this is as in the attached .pdf

I used a manual scraper for this, but thereafter changed to the BIAX (actually I have been swithcing back and forth. Seems OK to break it up like this)

A couple of videos showing some of the scraping on the flat way.
http://www.youtube.com/watch?v=4UkKYN6ZCDQ&feature=youtu.be
http://www.youtube.com/watch?v=f-1nFWUVSEo&feature=youtu.be


PS! Have by now also done the smaller flat, having "only" the "dovetail use" left. So we are nearing a finish here!
 
Last edited:
Sorry guys.. the 2nd video takes longer than anticipated to upload to YouTube. They give the adress quite early in the process and usually the timer is true (ie. how long until it is finished). This time not however..

Now it functions..
 
Last edited:
Hi guys,

Long time since I posted..

I finished the Camelback for my friend Ola and have now "delivered" to him. I hope he gets good use of it. For me, it has been rewarding both to be able to use it on the Schaublin mill (yes, there will be more on this later for those still interested) and as a learning experience (the learning will never stop, I am sure..)

This straightedge design is surely most versatile. I have others of different styles, but I found that the combination of a quite broad flat and the dovetail is very handy. It is also has good balance so it easily "tips in" so you get a sensitive "feel" when you mark up your part.

I made some videos again to document the scraping of the camelback:

http://www.youtube.com/watch?v=ie5PVdP-GiE
http://www.youtube.com/watch?v=6BKtsyxU4pg
http://www.youtube.com/watch?v=upYUQAo00-E

I made use of the yellow Canode "highlighter" on these last sessions. That gives a "gold'ish" look to the areas to be scraped.

This concludes this mini-series on the scraping "journey" needed to get this piece of "seasoned" iron from its' resting place in a damp barn in Denmark to a straightedge he can hopefully use to check and qualify the parts he wants to work on.

I also want to forward Richards greeting to you fellow members! He has been and still is a "goldmine" of expertize and help (indeed very willing to answer questions).
 
Last edited:
Good to hear from you. I'm exited to get to the Kansas City, Missouri class in late October. Then I can get to scraping some straight edges and machines too. Thanks for sharing your efforts, but don't give up on the model idea:))
 
You must log in or register to reply here.
Back
Top