Jump to content
I Forge Iron

Hard Time Removing Belt Sander Marks


Recommended Posts

   Whenever I grind a knife I remove the scale and profile it with an 80 grit belt (the guard/casing on my craftsman 2x42 is to tight to put on a 40 grit belt) then sand at alternating angles with 120 and 240 grit belts, getting rid of all the previous scratches etc. After that when I go to hand sand it I have always found that if I try to use 220 or 320 grit paper it a lot of time and paper seems to do little so I have been doing the first step of hand sanding with 100 or 150 grit paper.

 

   Even when I use a fairly coarse grit the first grit after machine sanding always takes as long or longer than all the other grits up to 600. I was wondering if that is just the way it is or if I'm doing something wrong (pushing to hard on the sander, reusing old belts, etc.) or even if it would be worth it to get some higher grit belts and do all the sanding with a machine. Advice/ideas would be greatly appreciated.

Link to comment
Share on other sites

I have noticed similar variance between grades when under power or by hand. I have also noticed a difference between 120 grit aluminium oxide an 120 zirconium(zirconia?) even with both on angle grinder discs or both roll strip.

I guess the rule about doubling the grit number progressively can be followed slavishly if you stick to one form of abrasive process, but as you have found you could jump back a grade when you go hand finishing. Nobody is going to tell you off if you find a better process to reach your end result! If they do you have my aunty's permission to ignore them! :)

As to doing more finishing on the machine...every time! The guy that trained my furniture maker father said "always use the biggest tool you can get to the job" It saves so much time even if at first it is a bit scary that you will over do it.

I mentioned this on another thread recently, but it stands repeating...The thing about finishing that I remember from my school metalwork teacher and have worked to ever since, "the best way to get marks out of metal is not to put them in..." Extrapolate that out to all your working practice, material handling, hammer and anvil surfaces and abrasive grades it saves a lot of clearing up after....

Alan

Link to comment
Share on other sites

I found that I was using the belts too long. Not because they were worn but because the longer you stay on a grit the more scratches you are making. I try to do the absolute minimum with each grit. Get to the next higher grit as quickly as you possibly can to reduce the depth and number of scratches you are making and then having to sand back off.

I had a man who ended up being a good friend forge a knife in my shop. After watching him for 10 minutes I said to him "I have bigger hammers". He said "I know". 15 or so minutes later I asked  why he was not using a heavier hammer. He didn't miss a blow- and all he said was "Bigger hammer, bigger mistakes". I won't grind a blade with anything coarser than 50 grit. And I only use it to mark out my base grind. And I don't lean om my grinder at all. All I want to do, gently, is remove metal with the least damage as possible. Bigger grit, bigger scratches.

Most makers I have seen use pressure when they grind and it works well for them. Find what works for you.

Dave

Link to comment
Share on other sites

snip... "Bigger hammer, bigger mistakes".

snip...

Find what works for you.

Dave

 

I would argue against adopting the "bigger mistakes" attitude on so many levels.

 

If it were true power hammers would not have been invented.

 

I don't have such a snappy phrase in retort, maybe "bigger hammers, bigger profit"? and I am not just talking financial gain. Using a larger/ proper sized tool for the job can be a bit scary at first, but it is a classic mistake to think you are safe if you take a long time and many heats to make something. Or you just nibble around the edges.  But by a fairly logical extension he should be heating the workpiece with a candle, or he could  be certain he would not make any mistakes if he stayed in bed!

 

If you read David Pye's excellent books he talks of workmanship of risk and workmanship of certainty. Hand forging as the workmanship of risk using a smoothing plane to finish a plank with its regulated shaving size is workmanship of certainty.

 

You must commit to the process and take the risk of making a mistake in order to progress and develop your skills.

 

I have always described the power hammer as a brilliant amplifier of of my energy…but also an amplifier of mistakes.  But there are really good reasons for having one (or five, not boasting …just saying!) :)

 

I agree with your last statement, but "finding" it carries the corollary to spend your life looking for a better way. 

 

Alan 

 

I guess that is the first ten minutes of a few hours discussion about it!

 

Link to comment
Share on other sites

I did see you didnt mention what type of paper you are using.   If you are using Garnet or Aluminum Oxide ( ie Cheap sand paper)  it will take weeks to do what Silicon carbide can in an afternoon, and maybe wont do much of anything.  try reading the knife making post about  finishing your blade, and you will have less trouble.  If you cant get finer than 240 grit for your machine, its time to get a new machine, or modify the one you do have.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...