Brush machining ( for biax)

I have a new to me Biax scraper and earlier this week talked with Matt at Dapra. Matt was very helpful. My scraper, a 4/EASL, was made in 1965. The scraper was doing fine- but I wanted to findout what I could. Matt cautioned be to not "push" this scaper too hard in roughing, as it had a phenolic spiral gear which could be stripped- and they had no replacements for. He also suggested I check the brushes. They do not have those either- but indicated something close could be fitted.

About 2 hours of use (after I talked with Matt) the scraper quit- and I belive I reached the end of the line with the brushes. I found some at the hardware store which are OK in width, but thick by .025. I was planning to mill then down to the correct thickness. I do not know how long the origninals are- and the spring, wire and end on the new ones are different also. I was going to try and unsoder the old end and put the old spring and end on the new brush.

Is there any way to determine how long the new brush should be? What I have left is .160 past the spring, and the new one is .550 long

Any suggestions on how to hold the brush to mill it? I assume it is brittle. Would I be better off to try and sand it or file it down?
I have not done anything like this before.

I modified brushes to fit a spindle tach with a file. I held the brush in my fingers and stroked it carefully against the file. Still working 6-7 yrs later. For length, I'd just make sure the spring works OK, and keep it as long as possible.

I agree with Mudflap, a file and maybe wet&dry is the way to go, have fun getting the black out of your hands!

Take care. Sami.

Thanks guys- I am back to scraping!

I used a file and it cut down easily. I did have to switch the direction of the cut as I was working to keep it cutting parallel.

Turns out I did not need to switch the spring to get it to fit- but did need to clip down the end.

All in all it was much easier than I thought it was going to be.

If it was too easy try it again in the dark, while its raining, onehanded, and drunk.

Hint, too late this time, but maybe next time. Keep your dial caliper handy when sanding. The sandpapper or file whatever always cuts more at the leading edge. WWQ

I was using the calipers.

I did not word it well- but my comment about having to switch the direction of the cut was because of the greater cut on the leading edge.

At least- that is how it was cutting in this care. I also wondered if it was related to how I was holding it- which was by hand. It they are not very large and there was not much to hold on to.

I got an E-mail asking what brushes I used.

The store had several self serve drawers with various brushes. I brought along my calipers and the tool so i could measure things on the spot if needed.

The brushes I was replacing were .247 by .155.
The slot they fit in was .250 by - as I recall, .157

What I purchased was from Serv-a-lite products Incoporated
CB-34-617
Replacement carbon brushes for Skil Power Tools.

I did need to bend out and clip off the 4 wings on the brass endcap (? correct term). This was more work than filing down the carbon.

Next time I will pay more attend to the endcap fit and less to the carbon, as the carbon shapes easily.

I have had to adapt brushes on several ocasions and always used sandpaper not emery/wet-or-dry. The brush manufacturer I was able to ask told me this was the way to go, use figure 8 lapping and make sure the brush material is as close as possible to the original. The tone of coppery colour (if any), the darkness of the carbon and its texture all being indicators of similarity or not. Ther is a wide difference in brush hardness which can relate to comutator wear.