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dchristian
06-14-2006, 06:37 PM
I like to restore old cars for a hobby and needless to say I have to make a lot of my own parts. I recently purchased a bench top lath from Harbor Freight a model BV20 and a Northern Tools Bench top milling machine. I also subscribe to Home Machinist which I have learned a lot from but is way beyond my skills. I want to make parts that are not critical to safety like spindles or suspension parts. I have a book I purchased out of the magazine that gives some basics to machining. I also bought a 6 in chuck for my lath from Little Machine shop with an adaptor. When I try to cut the adaptor with a carbide bit I just get dust, not the usual shaving that I see with soft steel. Is this normal for some types steel? or am I doing something wrong? Also, could someone recommend a beginners book or video? Thanks for any help you can give.

tattoomike68
06-14-2006, 06:55 PM
It sound like you are cutting a cast iron adaptor. chips that are slivers and dusty is perfectly normal. cast iron is messy dirty stuff.

As far as books, years ago I went to the library and read all the ones they had.

SGW
06-14-2006, 07:55 PM
The main thing is patience...this hobby has a long learning curve.

You may want to try searching the achives; books have been recommended in the past. One I particularly like is "The Amateur's Lathe" by L.H. Sparey. It's now about 60 years old, and a bit dated, (and it's British), but it has a lot of good information, if you can find a copy.

But don't expect "a" book or "a" video to do it. Plan on multiple books/videos/magazines, and multiple years. I've been at this hobby about 30 years, and I'm still learning. I expect others would say the same.

wierdscience
06-14-2006, 08:06 PM
Yep,most back plates are either cast or semi-steel so they will make dust when machined.

If the dust coming off the machine gets bad get a dust mask,it's rough on the sinuses.

Magic9r
06-14-2006, 08:18 PM
What's your surface finish like after the cut?
Given that th finish is what you are looking for if it's good the job is good, only worry about how your chips come off if the finish is also poor,
Regards,
Nick

TECHSHOP
06-14-2006, 08:45 PM
Hope you can stick around, there is plenty to learn here and not just about machining, enjoy the fun.

If the "join date" block isn't on the blink, looks like you have been busy from the time you joined and your first post showed, and I thought I was a slow typist!

CCWKen
06-14-2006, 09:20 PM
I like to restore old cars for a hobby and needless to say I have to make a lot of my own parts. ... I want to make parts that are not critical to safety like spindles or suspension parts.

Welcome to forum. About time you come out of the closet. :D

Ditto on the cast iron. I will add that you should cover most of your lathe or use a vacuum during cutting cast iron. It gets all over the place and it's like throwing sand all over your equipment. (Read: grinding stone on the ways.)

I put the bold on your quote because this concerns me. I would classify spindles and suspension parts THE MOST CRITICAL safety items of any vehicle. One broken part can lead to a serious control problem. Most all spindles are forged steel and induction hardened. You may want to do your homework on metal types before making your own parts. Knowing the difference between cast iron and steel will be very helpful and much safer.

I'm not trying to rag on ya, just get you started in the right direction. ;)

Mcgyver
06-14-2006, 09:30 PM
I always tell noobs to get a copy of a grade 11 or 12 high school text. the give a good overview and touch upon most all basic tools & techniques and is intended for those without prior experience. I've ended up with a couple over the years and often look up the odd thing in them, there are many operations that you don't do often so its nice to have a couple reference texts handy

dchristian
06-15-2006, 12:45 AM
You are right, I would not attempt to make any critical part. Just simple things like a spacer or trim part or brackets. I made some axle's for my homemade welding cart but the biggest risk there is that it will fall on my foot. Yes, the part is cast metal but having never tried to cut cast metal before I was not sure I was doing it right. The cut is not all that good but I have a 1/4 in carbide bit, I have some 1/2 bits on the way. The bit is getting hot enough that it is getting discolored and the tip gets red at times. I asume that is not good. I am making a light feed, if I try to go heavier it bogs down the lath. I think I may be turning at to high a speed. Any way thanks for the help and I will keep at it.

Mark Hockett
06-15-2006, 01:34 AM
dchristian,
It sounds like you were turning it too fast or your cutter is very dull. Cutting cast iron with HSS tooling should be done at around 70 ft/min. If your using carbide it should be between 300 and 800 ft/min. The way you calculate the RPM is ft/min times 3.82 divided by the diameter of the part. So if you are using carbide a good starting point would be 300 X 3.82 = 1146 divided by 6.0" = 191 RPM. This only works if your setup is rigid (not with a 1/4" cutter) and your cutting tools are sharp. The RPM for HSS tooling would be about 45.
I would recommend finding a copy of the Machinery's Handbook. It lists cutting speeds and feeds for most metals.

You should have tons of fun with that lathe and mill.

Mark Hockett
Island Tech Enterprises
Clinton, WA
360-914-6026

More chip less lip

dchristian
06-15-2006, 09:14 AM
WOW! What a difference and a lesson in lath speed! Slowed down the lath to 300, sharpened the bit and it cut like a champ. A nice smooth cut too. Thanks to everyone, this is fun! I just wish I had tried this years ago

dchristian
06-15-2006, 09:44 AM
Wow! What a difference. Slowed the speed down to 300, sharpened the bit and it cut great! That was a good lesson learned in the inportance of proper lath speed. It make me feel good when thinks go right. Thanks for the help and I will get the the book you recommended!

ASparky
06-15-2006, 07:05 PM
I found the same thing with stainless (304 and 316). Was totally amazed at how much better when slowed down a lot.

Model Maker
06-16-2006, 09:35 AM
What's your surface finish like after the cut?
Given that th finish is what you are looking for if it's good the job is good, only worry about how your chips come off if the finish is also poor,
Regards,
Nick


That is not completely true. You can get a good finish and have chips that are coming off the tool way too hot which indicates that your part is hot. Now what you are doing is putting undo stress on the metal. One is not more important than the other. That is a common mistake that I see. Someone puts all their eggs into the finish basket, chip basket or recommended speeds and feeds basket. All of these things deserve your attention because the combination of all of these plus a few more is what makes a quality part!

Millman
06-16-2006, 09:53 AM
{You can get a good finish and have chips that are coming off the tool way too hot which indicates that your part is hot. Now what you are doing is putting undo stress on the metal. One is not more important than the other. That is a common mistake that I see. Someone puts all their eggs into the finish basket, chip basket or recommended speeds and feeds basket. All of these things deserve your attention because the combination of all of these} Model Maker, now that is a very common sense way of putting it, and most of the time, that is all it takes; common sense. See, you didn't even have to get into Astrophysics to give an intelligent answer. Keep up the good work.